Systems, apparatuses, and methods for interacting with spin-stored quantum information

Abstract

This application relates to systems, apparatuses, and methods for interacting with spin-stored quantum information. A quantum information processing apparatus includes a semiconductor substrate. An optical resonator is coupled to the substrate. The optical resonator supports a first photonic mode having a first resonator frequency. The quantum information processing apparatus includes a non-gaseous chalcogenide donor atom disposed within the semiconductor substrate and optically coupled to the optical resonator. The donor atom has a transition frequency that resonates with the resonator frequency. Also disclosed herein are systems, apparatuses, articles, and methods having practical applications in quantum information processing including one or more deep impurities in a silicon substrate optically coupled to an optical structure or associated with the one or more deep impurities.

Description

[0001] Related Application Data

[0002] This application is a divisional application of Chinese Patent Application No. 201680080209.0, filed on November 25, 2016, entitled "SYSTEMS, DEVICES, AND METHODS FOR INTERACTING WITH QUANTUM INFORMATION STORED IN SPINS."

[0003] Cross Reference To Related Applications

[0004] This application is a nonprovisional of U.S. Patent Application No. 62 / 260,391, filed on November 27, 2015, entitled "SYSTEMS, DEVICES, AND METHODS FOR INTERACTING WITH QUANTUM INFORMATION STORED IN SPINS," which is incorporated by reference herein in its entirety, and claims priority to the U.S. Patent Application. TECHNICAL FIELD

[0005] The present invention relates generally to the field of quantum computing and quantum information. BACKGROUND

[0006] Quantum devices are manufactured articles or structures in which quantum mechanical effects are significant and / or dominant. Quantum devices, such as superconducting circuits and spintronic circuits, include circuits in which current transport is dominated by quantum mechanisms. Superconducting circuits use quantum physics phenomena, such as tunneling and flux quantization. Spintronic circuits use physical properties of spin, such as electron spin, as resources to receive, process, store, transmit, or output information. Quantum devices can be used in measurement instruments, in computing machines, and the like. Examples of computing machines include components of conventional computers and quantum computers.

[0007] Proposed technologies for implementing quantum computers describe electronic devices in which information is encoded in the nuclear spins of donor atoms, specifically phosphorus-31, placed in silicon substrates. The donor atoms are placed at a shallow depth, e.g., 20 nanometers, in the silicon substrate and are spaced apart with precision of one unit cell, e.g., with about 20 nanometers. Logic or computational operations are performed on individual spins using externally applied electromagnetic fields, and spin measurements are made using spin-dependent charge transfer, and spin measurements are detected using highly sensitive electrometers. The proposed technologies have not been fully implemented. SUMMARY

[0008] A technique for implementing a quantum computer involves a quantum information processing device. The quantum information processing device includes a semiconductor substrate. Deep impurities (e.g., non-gaseous chalcogen donor atoms) are disposed within the semiconductor substrate. Each of the deep impurities (e.g., non-gaseous chalcogen donor atoms) is characterized by a plurality of quantum states corresponding to different electronic or nuclear spin states of the deep impurity and representing qubit information. The quantum information processing device further includes a first optical resonator having a first photonic mode with a first resonator frequency and optical states representing resonator information. The first optical resonator optically couples the qubit information and the resonator information.

[0009] An operational method for a quantum information processor. The quantum information processor includes an optical structure coupled to a semiconductor substrate. A plurality of deep impurities are disposed in the semiconductor substrate. Each of the deep impurities is characterized by a plurality of quantum states corresponding to different electronic and nuclear spin states of a donor atom, information represented by the quantum states of the deep impurities (e.g., donor atoms). The method includes initializing a first deep impurity of the plurality of deep impurities to a first reference state and initializing a second deep impurity of the plurality of deep impurities to the first reference state. The method further involves causing an optical resonator proximate to a first donor atom and a second donor atom to resonate with the first donor atom and the second donor atom and measuring an optical state of the optical resonator as a measure of the information represented by the quantum states of the first donor atom and the second donor atom.

[0010] Another operational method is for a quantum information processor including donor atoms implanted in a semiconductor substrate. The method includes initializing the donor atoms to a reference state and applying a pulsed magnetic field to a first donor atom to change state, causing an optical resonator proximate to the donor atoms to resonate with the donor atoms, and measuring whether a photon is present or not present in the optical resonator.

[0011] Another operational method is for a quantum information processor including non-gaseous chalcogen donor atoms disposed in a semiconductor substrate. The non-gaseous chalcogen donor atoms are characterized as having one or more different quantum states representing information. In one aspect, the method includes receiving a photon having a first quantum state at an optical resonator optically coupled to the non-gaseous chalcogen donor atoms and forming a second quantum state in the non-gaseous chalcogen donor atom corresponding to the first quantum state at the optical resonator.

[0012] In another aspect, the method includes forming a first quantum state in the non-gaseous chalcogen donor atom in the semiconductor substrate; and optically coupling the non-gaseous chalcogen donor atom to an optical resonator. The method also includes forming a photon having a second quantum state at the optical resonator, the second quantum state corresponding to the first quantum state in the non-gaseous chalcogen donor atom.

[0013] A system including a digital computer and an analog computer is substantially described and illustrated herein.

[0014] A system including a quantum information processor is substantially described and illustrated herein. The quantum information processor includes a semiconductor substrate, a first non-gaseous donor atom implanted in the substrate, a second non-gaseous donor atom implanted in the substrate, and an optical structure defined in the substrate, and is substantially otherwise described and illustrated herein.

[0015] A quantum information processor is substantially described and illustrated herein.

[0016] A quantum information storage device is substantially described and illustrated herein.

[0017] A method of operation for a system including a digital computer and an analog computer is substantially described and illustrated herein.

[0018] A method of operation for a quantum information processor is substantially described and illustrated herein. BRIEF DESCRIPTION OF DRAWINGS

[0019] The systems, devices, articles, and methods are described in more detail herein with reference to the following drawings, in which:

[0020] Figure 1 is a schematic diagram illustrating a portion of a system including a quantum information processor;

[0021] Figure 2 is a schematic diagram illustrating an exemplary donor atom and resonator;

[0022] Figure 3 is a schematic diagram illustrating an exemplary portion of a quantum information processor;

[0023] Figure 4 is a schematic diagram illustrating an exemplary portion of a quantum information processor including a pair of donor atoms;

[0024] Figure 5 is a schematic diagram illustrating an exemplary portion of a quantum information processor;

[0025] Figure 6is a schematic diagram illustrating an exemplary portion of a quantum information processor including a pair of optical resonators and a pair of impurity atoms;

[0026] Figure 7 is a schematic diagram illustrating an exemplary portion of a quantum information processor including an optical readout device;

[0027] Figure 8 is a graph illustrating energy levels of a contrast magnetic field plot of an impurity electron-nuclear system;

[0028] Figure 9 is a flowchart illustrating an embodiment of a method of operation in a quantum information processor;

[0029] Figure 10 is a flowchart illustrating an embodiment of a method to prepare one or more qubits in an initial state;

[0030] Figure 11 is a flowchart illustrating an embodiment of a method to couple two or more qubits;

[0031] Figure 12 is a flowchart illustrating an embodiment of a method to read out at least one qubit;

[0032] Figure 13A and 13B is a flowchart illustrating a method for interconversion of flying qubits and stationary qubits;

[0033] Figure 14 schematically illustrates a plurality of energy levels of a coupled system including deep impurities and optical structures; and

[0034] Figure 15 is a schematic diagram illustrating a section of a quantum information processing device including a plurality of deep impurities optically coupled to a waveguide. DETAILED DESCRIPTION

[0035] Systems, devices, articles, and methods having practical applications in quantum information processing (e.g., quantum computing and quantum communication) are disclosed herein. Some embodiments of the inventive systems, devices, articles, and methods include or are characterized by two or more of the following aspects of a quantum computer: well-defined qubits, reliable state preparation, low decoherence rates, accurate quantum gate operations, multi-qubit coupling, and strong quantum measurements. Systems, devices, articles, and methods having practical applications in quantum communication and quantum computing can interconvert states in stationary qubits (e.g., solid state) and flying qubits (e.g., photons).

[0036] Figure 1A computer system 100 including specialized apparatus to process information is diagrammatically illustrated. The system 100 includes a digital computer 102 that includes a control subsystem 104. The control subsystem 104 includes at least one processor 105. The digital computer 102 includes a bus 106 coupled to the control subsystem 104. The system 100 includes at least one non-transitory computer- and processor-readable storage device 108 and a network interface subsystem 110, both of which are communicatively coupled to the bus 106. The digital computer 102 includes an input subsystem 112 and an output subsystem 114 communicatively coupled to the bus 106. The digital computer 102 includes an analog computer interface subsystem 116 coupled to the bus 106. In various implementations, the bus 106 communicatively couples several pairs or all of the subsystems in the computer 102. In some implementations, some of the subsystems of the system 100 are omitted or combined.

[0037] The at least one processor 105 can be any logic processing unit, such as one or more digital processors, microprocessors, central processing units (CPUs), graphics processing units (GPUs), application-specific integrated circuits (ASICs), programmable gate arrays (PGAs), programmable logic units (PLUs), digital signal processors (DSPs), network processors (NPs), and the like.

[0038] The network interface subsystem 110 includes communication circuitry to support bidirectional communications of processor-readable data and processor-executable instructions. The network interface subsystem 110 employs communication protocols to exchange processor-readable data and processor-executable instructions via a network or non-network communication channel (not shown) (e.g., the Internet, a serial connection, a parallel connection, a wireless connection, a fiber optic connection, a combination of the foregoing, and the like) with one or more other digital computers or analog computers.

[0039] The input subsystem 112 includes one or more user interface devices, such as a keyboard, a pointing device, a numeric keypad, a touchscreen. In some implementations, the input subsystem 112 includes one or more sensors for the digital computer 102 or the analog computer 150. The one or more sensors provide information characterizing or representing an environment or internal state of the digital computer 102 and / or the analog computer 150. The output subsystem 114 includes one or more user interface devices, such as a display, a light, a speaker, and a printer.

[0040] The storage device 108 is at least one non-transitory or tangible storage device. For example, the storage device 108 can include one or more volatile read-and-write memory (RAM) devices, and one or more non-volatile read-only memory (ROM) devices, such as flash memory, magnetic hard disks, optical disks, solid-state disks (SSDs), and the like. Those skilled in the art will appreciate that a memory device can be implemented in various ways, such as read-only memory (ROM), random access memory (RAM), hard drives (HDDs), network drives, flash memory, other forms of computer- and processor-readable storage media, and / or combinations thereof. A memory device can be read-only or read-write. Further, modern computer systems incorporate volatile memory devices and non-volatile memory devices, such as cache memory, solid-state hard drives, in-memory databases, and the like.

[0041] The storage device 108 includes or stores processor-executable instructions and / or processor-readable data 120 associated with the operation of the system 100. Execution of the processor-executable instructions and / or data 120 causes the at least one processor 105 and / or the control subsystem 104, for example, to perform various methods and actions through the network interface subsystem 110 or the analog computer interface subsystem 116. The processor 105 can cause the system 100 to perform methods and actions. For example, the processor-executable instructions and / or processor-readable data 120 can include a basic input / output system (BIOS) (not shown), an operating system 122, peripheral drivers (not shown), server instructions 124, application instructions 126, calibration instructions 128, quantum information processor control instructions 130, environmental control instructions 132, and processor-readable data 134.

[0042] The exemplary operating system 122 can include The server instructions 124 include processor-executable instructions and / or processor-readable data to interact with computers external to the system 100 via the network interface subsystem across a network. In some embodiments, the processor-executable server instructions 124 include processor-executable instructions and / or processor-readable data that, when executed by a processor, schedule work of the digital computer 102 or the analog computer 150. The application instructions 126 include processor-executable instructions that, when executed, cause the system 100 to perform at an application, such as to perform computations on the digital computer 102 or the analog computer 150.

[0043] Calibration instructions 128 include processor-executable instructions that, when executed by a processor (e.g., processor 105), cause the processor to calibrate and store calibrated values for analog computer 150. Components included in or on analog computer 150 can have inter-component variations in operational parameters. Calibration instructions 128, when executed by a processor, allow for testing and correction of these inter-component variations and / or variations from expected or ideal component parameters.

[0044] Quantum information processor control instructions 130 include processor-executable instructions that, when executed by a processor (e.g., processor 105), cause the processor to control, initialize, write, manipulate, read out, and / or otherwise send data to / from analog computer 150. Quantum information processor control instructions 130 implement, in part, the methods described herein.

[0045] Environment control instructions 132 include processor-executable instructions and / or processor-readable data that, when executed by a processor (e.g., processor 105), cause the processor to control and monitor aspects of the specified and possibly specialized environment for portions or all of analog computer 150. Examples of such instructions 132 include instructions to monitor and control temperature and magnetic fields that affect the quantum information processor. Environment control instructions 132 implement, in part, the methods described herein, including those in Figure 10 and with respect to Figure 10 those methods, etc.

[0046] Data 134 includes data used or obtained through operation of system 100. For example, one or more logs from digital computer 102 and analog computer 150. Data 134 includes data associated with (e.g., created by, referenced by, altered by) a processor executing processor-executable instructions (e.g., server instructions 124, application instructions 126, calibration instructions 128, quantum information processor control instructions 130, and environment control instructions 132).

[0047] Analog computer interface (ACI) subsystem 116 includes communication circuitry that supports bidirectional communication between digital computer 102 and analog computer 150. In some embodiments, analog computer interface subsystem 116 interacts with environment subsystem 152 of analog computer 150. In some embodiments, analog computer interface subsystem 116 interacts with quantum information processor 154 via one or more subsystems of analog computer 150 (e.g., subsystems 156 and 158). In various embodiments, ACI subsystem 116 includes a waveform digitizer such as an ALAZAR TECH ATS9440, 4-channel, 14-bit, 125 MS / s card or an ALAZAR TECH ATS9360, 1-channel, 12-bit, 1.8 GS / s PCI card, cards from Alazar Technologies Inc. of Pointe-Claire, QC, CA.

[0048] Analog computer 150 includes an environment subsystem 152 that provides a prescribed environment for quantum information processor 154. For example, aspects of the prescribed environment can include one or more of humidity, air pressure, vibration, magnetic field, temperature, and electromagnetic field. In some embodiments, environment subsystem 152 provides a low magnetic field around quantum information processor 154. In some embodiments, environment subsystem 152 provides a time-invariant magnetic field around quantum information processor 154. In some embodiments, environment subsystem 152 provides a time-varying or pulsed magnetic field. In some embodiments, environment subsystem 152 maintains quantum information processor 154 at cryogenic temperatures via one or more cryogenic units and / or cold sources. For example, quantum information processor 154 can be maintained at approximately 4K. Other useful temperatures for quantum information processor 154 include temperatures in the range from approximately 100 mK to approximately 77 K. In some embodiments, environment subsystem 152 maintains an environment around quantum information processor 154 having a temperature of approximately 290 K. In some embodiments, environment subsystem 152 includes vibration isolation including dampers in the cryogenic units. In some embodiments, environment subsystem 152 provides quantum information processor 154 with a low humidity and constant air pressure (e.g., stable mild vacuum) environment.

[0049] The quantum information processor 154 includes one or more qubits. A qubit (or quantum bit) is a logical building block of a quantum computer that can be compared to a binary digit in a conventional digital computer. A qubit is conventionally a defined physical system that has two or more discrete states called computational states or basis states. The basis states are logically analogous to binary states. These states can be labeled |0> and |1>. In some implementations, these states are eigenstates of the Sigma-Z operator (Pauli matrix operator) of a physical system. Such qubits are said to be in the Z diagonal basis. A qubit can be in a state superposition (e.g., a|0> + β|1>). The coefficients a and β can be complex numbers. One or more logical operations can be performed on one or more qubits. These operations can occur at a specified time (e.g., at a designated time) or at a specified period at a frequency.

[0050] In some implementations, the quantum information processor 154 includes one or more devices or subsystems to perform one or more types of single-qubit operations on one or more qubits. Examples of single-qubit operations include a Sigma-X or bit-flip operation that can be compared to a conventional "NOT" gate. A Sigma-X operation implements a rotation of a quantum state of a Bloch sphere around an X axis. When the rotation is π radians, the state |0> maps to |1> and vice versa, i.e., a complete bit flip. In some examples, the quantum information processor 154 can perform a Sigma-Y operation on one or more qubits without a conventional binary counterpart. A Sigma-Y operation implements a rotation around a Y axis. If the rotation is π radians, the operation maps the state |0> to i|1> and the state |1> to -i|0>. The Sigma-Y operation is sometimes called a Pauli-Y operation or gate. In some examples, the quantum information processor 154 can perform a Sigma-Z or phase operation on one or more qubits without a conventional counterpart. A Sigma-Z operation implements a rotation around a Z axis. If the rotation is π radians, the operation maps |0> to |0> and |1> to -|1>. The Sigma-Z operation is sometimes called a phase flip or bias operation or gate.

[0051] In some implementations, the quantum information processor 154 includes one or more couplers that can couple qubits. A two-qubit coupling operation can be a selective operation. The two-qubit coupling operation can be performed on a first and a second qubit. An example of a two-qubit coupling operation is a CNOT gate, where two qubits are treated as inputs and the output state of the first qubit is the "not" of the input state of the first qubit (conditional on the state of the input state of the second qubit). Other examples of two-qubit coupling operations are Ising coupling, diagonal coupling, or Sigma-Z Sigma-Z coupling. In the quantum information processor 154, qubits can be communicatively coupled to each other by several structures and devices. In some implementations, qubit-qubit interactions are mediated via a single coupler included in the quantum information processor 154. In some implementations, qubit-qubit interactions are mediated via multiple couplers. In some implementations, the quantum information processor 154 couples three or more qubits. The quantum information processor 154 includes one or more optical structures as couplers. The quantum information processor 154 can include one or more optical resonators and / or one or more waveguides as couplers.

[0052] The analog computer 150 includes a quantum input subsystem 156 to write and manipulate the quantum information processor 154. In some implementations, the quantum input subsystem 156 includes a digital-to-analog converter. In some implementations, the quantum input subsystem 156 includes a light source to apply narrow or broad spectrum light to a portion of the quantum information processor 154. In some implementations, the quantum input subsystem 156 includes an electromagnet to provide a magnetic field to a portion or all of the quantum information processor 154. In some implementations, the quantum input subsystem 156 includes one or more emitters (e.g., wires, antennas, coils) to selectively provide one or more time, duration, and frequency control pulses to the quantum information processor 154. An example of a pulse generator is a PSPL 10070A available from Tektronix, Inc. of Beaverton, OR, US. TM In some implementations, the emitters are on the quantum information processor 154. In some implementations, the emitters are proximate to the quantum information processor 154 and coupled to a device on it. Microwave, RF, and / or electromagnetic control pulses can be used. In some implementations, the quantum input subsystem 156 is used in conjunction with the control subsystem 104 to perform electron paramagnetic resonance (EPR) and / or nuclear magnetic resonance (NMR) on the electronic and / or nuclear spins in the quantum input subsystem 156. In some implementations, a bulk EPR or NMR cavity encloses the quantum information processor 154.

[0053] In some implementations, the quantum input subsystem 156 includes wires electrically (e.g., galvanically) coupled to one or more electrodes or pairs of electrodes included in the quantum information processor 154. In some implementations, the quantum input subsystem 156 applies DC and AC currents from the quantum input subsystem 156 to electrically bias and control the quantum information processor 154. For example, the quantum input subsystem 156 can inject or remove carriers (e.g., electrons and holes) from one or more portions of the quantum information processor 154. Alternatively, in some examples, a static or oscillating electric or magnetic field is provided. DC currents and voltages can be provided by a low-noise power supply, such as a battery-powered voltage source. The currents and voltages can be applied through a resistive voltage divider / voltage combiner. AC currents and voltages can be applied to portions of the quantum information processor 154 using an arbitrary waveform generator or signal generator, such as a TELEDYNE LECROY ARB STUDIO 1104 TM ) available from Teledyne Technologies, Inc. of Thousand Oaks, CA, US. AC currents and voltages for electron spin resonance (ESR) can be applied to portions of the quantum information processor 154 using a signal generator, such as an AGILENT E8257D TM microwave analog signal generator available from Agilent Technologies of Santa Clara, CA, US. Lines leading from and / or to the quantum information processor 154, including those shown in FIG. 1, can include filters, such as low-pass, band-pass, and high-pass filters. Figure 1

[0054] ​Analog computer 150 includes a quantum output subsystem 158 to manipulate and read quantum information processor 154 from. In some implementations, quantum output subsystem 158 includes an analog-to-digital converter. In some implementations, quantum output subsystem 158 includes one or several optical readout devices. An optical readout device detects photons produced by or in quantum information processor 154 or measures a state of an optical structure included on or in quantum information processor 154. An optical structure, such as a resonator, supports one or more photonic modes. Examples of optical structures are described herein. In some implementations, an optical readout device distinguishes between the presence or absence of one or more photons in an optical resonator. In some examples, an optical readout device detects a frequency shift of one or more photonic modes of an optical structure. One optical readout device can read the state of one or more optical resonators. The state of an optical structure can depend on the state of a deep impurity (e.g., a donor atom) coupled to the optical structure. Examples of deep impurities are described herein.

[0055] In some implementations, digital computer 102 uses quantum output subsystem 158 to perform logical operations on information in quantum information processor 154. For example, quantum output subsystem 158 can be used to perform measurements on quantum information processor 154. In some implementations that include a strong quantum measurement device (e.g., at least with respect to the examples described herein), measurements can replace one or more quantum operations. Universal quantum computation can be achieved using only local and non-local (e.g., parity) measurements. Figure 7

[0056] In some implementations, quantum output subsystem 158 performs single-shot readout of the state of components in quantum information processor 154. In some implementations, quantum output subsystem 158 performs readout of the state of components in quantum information processor 154 at gigahertz speeds.

[0057] In some implementations, analog computer 150 is communicatively coupled to quantum information channel 170. Quantum information channel 170 can be used to send quantum information to and from quantum information processor 154. In some implementations, portions of digital computer 102 and analog computer 150 are omitted to form a smaller information processing device that includes quantum information processor 154 and quantum information channel 170.

[0058] Figure 2 is a schematic diagram illustrating a portion of quantum information processor 200. The illustrated portion of quantum information processor 200 includes a substrate of semiconductor material 202, an exemplary donor atom 204 placed (e.g., implanted) within semiconductor material 202, and an optical resonator 206 communicatively coupled to exemplary donor atom 204.​

[0059] In some implementations, the semiconductor material 202 is silicon. In some implementations, the semiconductor material 202 is natural silicon. In some implementations, the semiconductor material 202 is purified non-paramagnetic silicon. The semiconductor material 202 includes silicon carbide or silicon germanium. One way to increase a performance metric of a physical system, such as a longer coherence time of a system such as the quantum information processor 200, is to use a semiconductor material with a large fraction of non-paramagnetic nuclei. Natural silicon is composed of approximately 95% non-paramagnetic nuclei (92.2% silicon-28 and 3.1% silicon-30) and can be purified to remove some to almost all non-zero nuclear spin isotopes, such as silicon-29.

[0060] These stable isotopes can be separated by forming silicon tetrafluoride (SiF4) gas and then applying centrifuge or elutriation based techniques to separate the isotopes. Using isotopically purified silicon tetrafluoride and / or isotopically purified silane (SiH4) produced from silicon tetrafluoride, wafers and crystals of isotopically purified silicon can be formed using molecular beam epitaxy (MBE), chemical vapor deposition (CVD), and others. Suitable semiconductor material 202 can be purchased from Isoflex USA Isotopes Supply Company of San Francisco, CA, US.

[0061] The donor atoms 204 are disposed within a bulk of the semiconductor material 202. In some implementations, the donor atoms 204 are implanted, deposited, or placed deep within a bulk or mass of the semiconductor material 202. In at least one implementation, the placement is shallow. For example, a plurality of interfaces (e.g., faces, sides, or edges) bound the extent of the semiconductor material 202. In some implementations, the donor atoms 204 are disposed at a distance greater than 10 nanometers from each of the plurality of interfaces. In some implementations, the donor atoms 204 are evanescently coupled to an optical structure (e.g., resonator, waveguide, lens) and positioned at a shallow depth (e.g., a few nanometers) within the semiconductor material 202. In some implementations, the donor atoms 204 are disposed at a distance greater than 20 nanometers from each of the plurality of interfaces. In some implementations, the donor atoms 204 are disposed at a distance greater than 30 nanometers from each of the plurality of interfaces. In some implementations, the donor atoms 204 are disposed at a distance between 30 nanometers and 500 nanometers from each of the plurality of interfaces. In some implementations, the donor atoms 204 are disposed at a distance between 10 nanometers and 2 micrometers from each of the plurality of interfaces. In some implementations, the donor atoms 204 are disposed at a distance between 30 nanometers and 1 micrometer from each of the plurality of interfaces. The deeper the location, the farther the donor is from charges that can reside on the interfaces.

[0062] The donor type and implantation method vary with the embodiment. Ion implantation, a standard technique in the semiconductor industry, can be used to implant donor atoms 204 into semiconductor material 202 in a controlled manner. One implantation process is described in U.S. Patent 3,434,894. In some embodiments, donor atoms 204 are stable, non-gaseous chalcogen atoms. That is, long-lived metal and non-metal group 16 atoms with substitutional, two-donor electronic structure in silicon. Examples include sulfur, selenium, and tellurium. In some embodiments, specific isotopes are used. Examples include sulfur-33, selenium-77, tellurium-123, and tellurium-125. Suitable isotopes are available from IsoFluor, Inc. of USA. In some embodiments, donor atoms 204 are ions with ionization energy substantially greater than thermal energy kT B "deep level impurities" or "deep level donors" with ionization energy substantially greater than thermal energy kT at room temperature (about 293 K). The energy of shallow donors can be comparable to thermal energy at room temperature. Herein, "shallow" and "deep" are used in two senses: one, to qualify the energy of one or more donor atoms; and two, to qualify the spatial location of one or more donor atoms. These different meanings will be apparent to one of skill in the art, especially in view of the context, at each individual occurrence, e.g., "energy," "energy level," "spectrum" versus "position," "placement," "location," etc. B is the Boltzmann constant and temperature T is room temperature (about 293 K). The energy of shallow donors can be comparable to thermal energy at room temperature. Herein, "shallow" and "deep" are used in two senses: one, to qualify the energy of one or more donor atoms; and two, to qualify the spatial location of one or more donor atoms. These different meanings will be apparent to one of skill in the art, especially in view of the context, at each individual occurrence, e.g., "energy," "energy level," "spectrum" versus "position," "placement," "location," etc.

[0063] Donor atoms 204 in semiconductor material 202 define part or all of a qubit. In some embodiments, donor atoms 204 in semiconductor material 202 include two states with different magnetic spin values. In some embodiments, donor atoms 204 have a first state corresponding to spin down |↓>. In some embodiments, this is labeled |0>, a logical state of a qubit that can be comparable to "0" in a classical bit. In some embodiments, donor atoms 204 have a second state corresponding to spin up |↑>. This can be labeled |1>, a logical state of a qubit that can be comparable to "1" in a classical bit. Herein, at least in the context of a qubit, "0" and "1" are used to refer to the logical states of a qubit, not to the physical states of a qubit. Figure 8 Examples of quantum states of donor atoms are shown and described at 10 or 14.

[0064] In some embodiments, donor atoms operate up to about 100 gigahertz. That is, manipulation of donor electrons or nuclear spins can be accomplished using driving frequencies corresponding to a splitting of the energy of these states, which are frequencies up to about 100 gigahertz. In some embodiments, a Hamiltonian describing donor atoms 204 includes a transverse single-qubit term (e.g., a Σ-X term) with a magnitude related to a frequency up to about 100 gigahertz. The transverse single-qubit term is a bit flip, i.e., operating on a first state to produce a second state and vice versa.

[0065] In some implementations, the donor atom 204 has spin-selective transitions. In some implementations, the donor atom 204 has an optical electric transition dipole moment (μ) of about 1 Debye (or about 3 x 10 -30 C m) which is a stronger transition dipole value than some free-space atoms. The transition dipole moment μ of an atom placed within a matching optical structure (e.g., the resonator 206) with a local electric field E (an aligned portion of the electric field E) causes a resonator coupling strength proportional to the product of the transition dipole moment and the aligned portion electric field. In some implementations, the donor atom 204 has one or more transitions in a convenient wavelength corresponding to wavelengths of commercially available optical emitters, lasers, detectors, mirrors, and the like. In some implementations, the wavelength corresponds to a mid-IR wavelength. In some implementations, the donor atom 204 does not exhibit significant photonic sidebands and / or two-photon induced photoionization.

[0066] The quantum information processor 200 includes an optical resonator 206. A resonator, optical resonator, optical cavity, or cavity is an arrangement of refracting and reflecting material interfaces that allows light waves to form standing waves. The geometry of the resonator 206 allows the resonator 206 to store energy as particular standing waves, photonic modes, or modes. Various modes can have a characteristic wavelength where the characteristic length of the resonator (e.g., a one-dimensional cavity) is equal to an integer multiple of one-quarter of the characteristic wavelength. Modes of a resonator have frequencies. In some implementations, the modes correspond to optical wavelengths (frequencies). An exemplary resonator 206 is schematically shown as two concave mirrors 206-1 and 206-2. The mirrors are separated by a characteristic length 208. In some implementations, the characteristic length 208 is between 1 micrometer and 10 micrometers and includes 1 micrometer and 10 micrometers. In some implementations, the characteristic length 208 is between 100 nanometers and 1 millimeter and includes 100 nanometers and 1 millimeter.

[0067] In some implementations, the resonator 206 is defined by features (e.g., voids and protrusions). In some implementations, the resonator 206 is defined by voids (e.g., pores, cavities, recesses, grooves, holes, notches, pockets, depressions, or slots) on or as part of one or more interfaces of the semiconductor material 202. For example, a void can be defined by an interface that is recessed from surrounding interfaces. In some implementations, the resonator 206 is defined by protrusions (e.g., bumps, pillars, ridges, blades) on or protruding from one or more interfaces of the semiconductor material 202. In some implementations, the features are spaced apart from each other by about 100 nanometers. In some implementations, the voids and protrusions are spaced apart from each other by about 500 nanometers or approximately 800 nanometers. In some implementations, the features are spaced apart by between 300 nanometers and 3 micrometers and include 300 nanometers and 3 micrometers.

[0068] The resonator 206 is optically (e.g., evanescently) coupled to the donor atom 204. That is, the electric field associated with the optical mode in the resonator 206 overlaps with the electron wave function of the donor atom 204. In some implementations, the mode of the resonator 206 has a frequency that matches (i.e., resonates with) a transition in the donor atom 204, the resonator frequency. That is, the two frequencies are the same, or approximately the same. Here, "approximately" is used in the sense of plus or minus 10% of the target frequency. In some implementations, two frequencies that are approximately the same result in weaker communication between the two systems. In some implementations, the resonator 206 has a resonator frequency that is close to one or more of the optical transition frequencies of the donor atom 204. An example of optical coupling is evanescent coupling. Evanescently coupling (or near-field interaction) includes placing two refractive bodies sufficiently close to each other such that an electric field wave that is expected to reflect internally in the first body propagates into the proximity of the second body.

[0069] Examples of optical resonators include structures defined in silicon-on-insulator materials. In some implementations, an optical resonator, such as the resonator 206, has a quality factor of 10 4 In some implementations, an optical resonator has a quality factor of more than 10 3 In some implementations, an optical resonator, such as the resonator 206, occupies a space that is proportional to (λ / n) 3 where λ is the photonic mode wavelength and n is the refractive index of the material included in the resonator.

[0070] A donor atom in a semiconductor material can be coupled to an optical resonator, such as the donor atom 204 and the resonator 206. For example, an optical resonator formed from a silicon-on-insulator material can have a cavity mode wavelength of close to 2.9 microns, a quality factor of more than 10 4 The atom-resonator coupling strength can be determined by the cavity mode volume, the placement of the atom relative to the resonator, and the orientation of the provided magnetic field (e.g., provided by the quantum input subsystem 156). The resonator 206 is coupled to the donor atom 204 via resonance (matching or close to matching) of a pair of frequencies: the cavity or mode frequency in the resonator 206, and the transition frequency in the donor atom 204. Herein, the transition frequency or the like in the donor atom 204 can be referred to as the first transition frequency, the second transition frequency, and so on for purposes of enumeration and identification, and not to suggest that it is the lowest, the second lowest, and so on.

[0071] Figure 3 is a schematic diagram illustrating an exemplary portion of a quantum information processor 300. The quantum information processor 300 includes a plurality of donor atoms 204 and a plurality of resonators 206. The donor atoms 204 are coupled to the resonators 206 via a pair of frequencies: the cavity or mode frequency in the resonator 206, and the transition frequency in the donor atom 204. Herein, the transition frequency or the like in the donor atom 204 can be referred to as the first transition frequency, the second transition frequency, and so on for purposes of enumeration and identification, and not to suggest that it is the lowest, the second lowest, and so on. Figure 3One interpretation of the schematic in FIG. 2A is a plan view of a semiconducting chip containing donor atoms 204 and resonators 206.

[0072] Quantum information processor 300 contains a plurality of donor atoms spaced apart, including atoms 204A, 204B, and 204C. The plurality of donor atoms including atoms 204 are associated with a plurality of resonators spaced apart, including resonators 206A, 206B, and 206C. In the illustrated example, each donor atom in the plurality of donor atoms 204 is aligned with an associated resonator in resonators 206 along at least one axis. In various implementations, the required precision of the spacing between donor atoms is low.

[0073] In some implementations, quantum information processor 300 contains a quantum register comprising two or more donor atoms 204 and one or more resonators 206. In some implementations, quantum information processor 300 contains one or more single electrodes proximate to two or more donor atoms 204 and one or more resonators 206. The electrodes can be overlying semiconductor material 202. In some implementations, quantum information processor 300 contains one or more pairs of electrodes proximate to and straddling two or more donor atoms 204 and one or more resonators 206. Straddling includes placement across and astride.

[0074] In some implementations, resonators 206A, 206B, and 206C are part of a larger arrangement of resonators. For example, the larger arrangement is a two-dimensional tiling. Resonator 206A is spaced apart from resonator 206B by a distance 302. Resonator 206B is spaced apart from resonator 206C by a distance 304. Resonator 206C is spaced apart from resonator 206A by a distance 306. In some implementations, the staggering of resonators is regular and two or more of distances 302, 304, and 306 are the same.

[0075] In the illustrated example, distances 302, 304, and 306 are on the order of a characteristic decay length λ / n, where λ is a photonic mode wavelength and n is the refractive index of the material separating resonators 206A, 206B, and 206C. For example, λ can be an average wavelength associated with a dominant photonic mode in resonators 206A, 206B, and 206C. In some implementations, the distance between resonators is ten times the characteristic decay length. In some implementations, the characteristic wavelength is a wavelength in the medium or media separating resonators 206A, 206B, and 206C. For example, in silicon, the wavelength is reduced by a factor of approximately 3, i.e., n(λ) ~ 3.45 for some wavelengths λ.

[0076] In some implementations, the quantum information processor 300 includes multiple couplers, where each coupler includes two resonators. For example, resonators 206A and 206B are a coupler for the emitter atoms 204A and 204B.

[0077] In some implementations, the resonators 206A, 206B, and 206C are coupled by waveguides. In some implementations, the distances 302, 304, and 306 can be as small as a micron and as long as several meters. In some implementations, the resonators 206A, 206B, and 206C are on different semiconductor substrates and coupled by waveguides or optical fibers. In some implementations, a first plurality of emitter atoms and resonators included with a first semiconductor substrate are optically coupled to a second plurality of emitter atoms and resonators included with a second semiconductor substrate. In some implementations, a remote substrate is coupled by one or more waveguides included in a Type II quantum computer (a smaller quantum system coupled by lossy or conventional channels).

[0078] Figure 4 is a schematic diagram illustrating an exemplary portion of a quantum information processor 400 including a pair of emitter atoms 204D and 204E. Each emitter atom in the pair is associated with a resonator (e.g., resonators 206D and 206E). The resonators 206D and 206E can be defined within a semiconducting structure that is recessed from a substrate. In some implementations, the resonators 206D and 206E protrude from the substrate and are primarily separated by free space (e.g., vacuum or air). In some implementations, the resonators are primarily separated by a cladding material such as silicon nitride. A distance 402 between the resonators 206D and 206E is on the order of a characteristic wavelength of the pair of resonators. In some embodiments, the characteristic wavelength is a wavelength in one or more media that separates the pair of resonators. The contrast between free space and intervening solid material between the pair of resonators allows for a larger distance between the resonators or an equivalent distance with a larger coupling strength.

[0079] Figure 5 is a schematic diagram illustrating an exemplary portion of a quantum information processor 500. The quantum information processor 500 includes a plurality of emitter atoms 504-0, 504-1, 504-2, 504-3, and 504-4, collectively 504. The quantum information processor 500 includes a plurality of resonators 506-1, 506-2, 506-3, and 506-4, collectively 506. A resonator can be interposed between a first emitter atom and a second emitter atom. For example, resonator 506-1 is interposed between emitter atom 504-0 and emitter atom 504-1. As Figure 5As illustrated in the middle, both the apparent center of mass and the principal axis (e.g., the longitudinal axis) of resonator 506-1 coincide with donor atom 504-0 and donor atom 504-1. However, if the resonator is coupled to first and second donor atoms that are then "interposed therebetween," neither the center of mass nor the principal axis of the resonator need coincide with the first and second donor atoms.

[0080] Each donor atom is associated with and communicatively coupled to a plurality of resonators. In this way, donor atoms can be communicatively coupled via shared resonators. Resonators 506 can be constructed in the same way that resonators 206 can be constructed.

[0081] Exemplary portions of quantum information processor 500 can extend. In some implementations, resonators 506 and donor atoms 504 are part of a larger resonator and donor atom arrangement. For example, the larger arrangement is a two-dimensional tiling, i.e., a plurality of donor atoms 504-0, 504-2, and 504-3 and resonators 506 form a repeatable sub-portion of an exemplary quantum information processor. The repeatable sub-portion can be tiled over a larger area.

[0082] In various implementations, the required precision with respect to inter-donor atom spacing is low. Donor atoms 504 can have a given interlacing, but also have a dispersion (i.e., a distance from a given position) of up to 50 nm or up to and including 100 nm. This tolerance advantageously compares with the precision of implantation techniques.

[0083] In some implementations, quantum information processor 500 includes a plurality of couplers, where each coupler includes a resonator. For example, resonator 506-1 is a coupler for donor atoms 204A and 204B. Herein, at least with respect to Figure 12 Operation of a coupler is described.

[0084] Figure 6 is a schematic diagram illustrating an exemplary portion of quantum information processor 600 including a pair of optical resonators and a pair of donor atoms. The exemplary portion of quantum information processor 600 includes a photonic crystal defined in a semiconductor substrate 602.

[0085] A photonic crystal is a periodic optical structure that affects the motion of photons within and across the structure. That is, it strongly confines light. A photonic crystal is characterized by a bandgap or stopband. A bandgap is a range of photon frequencies for which no photons can be transmitted through a material (e.g., semiconductor substrate 602) if tunneling effects are ignored. Methods of fabrication of photonic crystals depend on the number of dimensions in which the photonic bandgap must exist.

[0086] In some implementations, fabrication of the one or more quantum information processors includes using semiconductor fabrication facilities, machines, and procedures for CMOS wafers. In some implementations, fabrication of the quantum information processors includes thin film deposition, patterning, and etching. Unless otherwise required by the specific context, throughout this specification, terms like "deposit" and "deposition" are used to encompass any method of material deposition, including but not limited to physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma-enhanced PVD, plasma-enhanced CVD, and atomic layer deposition (ALD). Unless otherwise required by the specific context, throughout this specification, terms like "patterning" and "patterned" are used to encompass any method of forming a material on, in, and over a substrate in a specific shape or pattern, or of forming the substrate, by applying and processing a mask material (e.g., resist), and defining in the mask material in several geometric shapes via exposure to radiation (e.g., light or electrons). Etching removes a layer of material, e.g., a substrate, a semiconductor layer, a dielectric layer, an oxide layer, an electrically insulating layer, and / or a metal layer, according to a desired pattern determined by a photoresist or other mask. Exemplary etching techniques are wet chemical etching, dry chemical etching, plasma etching, physical etching, and reactive ion etching.

[0087] The quantum information processor 600 includes a semiconductor substrate 602. The semiconductor substrate 602 includes or supports one or more resonators. A generally periodic optical structure including two or more features (e.g., voids and protrusions) is defined within or on the semiconductor substrate 602. As Figure 6 As illustrated in FIG. 6B, a lattice of features (lattice 604) is defined in or on the semiconductor substrate 602.

[0088] In some implementations, the characteristic lattice 604 is a hole (e.g., a cylinder, a recess, a hole, a notch, or a void) defined in the semiconductor substrate 602. The lattice 604 can be regular, e.g., an equilateral triangular lattice. In the case of an equilateral triangular lattice, two parameters define the regular triangular lattice. The lattice constant defines the distance between the holes (center to center). The radius defines the size of the holes (e.g., hole 603) in the lattice 604. The latter can be expressed as a fraction of the former. In some implementations, the interior (or cavity) of the resonator is defined by one or more interruptions in the lattice. In some implementations, the interruptions are features that are missing from the lattice or displaced within the lattice. For example, the absence of a feature results in an interruption in the pattern of features. Another example is a feature that is present but laterally displaced from the regular position. As shown in 600, multiple holes are missing from the lattice 604. These include lattice interruptions 606-1 and 606-2. The lattice interruption 606-1 defines the interior (or cavity) of a one-dimensional resonator. Each lattice interruption is characterized or described by a principal axis and a spatial extent or length L (line segment 610) along or parallel to the principal axis.

[0089] The quantum information processor 600 includes optical resonator 608-1 and optical resonator 608-2. The optical resonator 608-1 (608-2) includes a portion of the semiconductor substrate 602 and the lattice 604, as well as the lattice interruption 606-1 (606-2). The electric field inside the resonator (e.g., optical resonator 608-1) can be designed to leak out.

[0090] The quantum information processor 600 includes multiple donor atoms. An exemplary donor atom 612 is placed in the optical resonator 608-2. In some implementations, the donor atoms are placed at an antinode of the photonic mode of the optical resonator. An antinode includes a region of maximum amplitude between nodes. For example, the donor atom 612 is placed approximately at the midpoint of the optical resonator 608-2. In some implementations, the donor atoms are placed away from the center of the resonator. For example, the donor atom 613 is placed towards a corner of the optical resonator 608-1. The donor atom 613 can be coupled to a different mode of the resonator or have a smaller coupling strength.

[0091] The quantum information processor 600 includes an optical structure 614 in communication with the optical resonator 608-1 and the optical resonator 608-2. The optical structure 614 can be a waveguide that supports one or more propagating modes, or a resonator that supports one or more resonant modes.

[0092] Figure 7is a schematic diagram illustrating an exemplary portion of a quantum information processor 700 including an optical resonator 706 and a waveguide 708 (e.g., an optical fiber). A spin 704 is coupled to the optical resonator 706. The state of the spin 704 is read out via interaction of the optical resonator 706 with the waveguide 708.

[0093] The quantum information processor 700 includes a semiconductor substrate 702 in which a spin 704 is implanted in the semiconductor substrate 702. The spin 704 is coupled to an optical resonator 706 defined on or in the semiconductor substrate 702. The optical resonator 706 is communicatively coupled to a waveguide 708 separated by a distance 714. In some implementations, the waveguide 708 is an on-chip photonic waveguide. In some implementations, an optical fiber is used.

[0094] A light source 710 sends light along the waveguide 708 to interact with the optical resonator 706, and the light is measured at a detector 712. The optical resonator 706 is coupled to the spin 704. The state of the spin 704 affects the state (e.g., frequency) of the optical resonator 706. In some implementations, the transmission of light from the light source 710 through the waveguide 708 and into the detector 712 will vary depending on the frequency of the optical resonator 706. For example, for a particular waveguide-resonator separation 714, if the light source frequency matches the frequency of the optical resonator 706, then the transmission to the detector 712 will be less than if the light source frequency is different from the resonator frequency. Similarly, the light reflection back to the light source will be reduced when the light source frequency matches the resonator frequency. The wavelength-dependent transmission of the optical channel between the light source 710 and the detector 712 reveals any coupling to a number of nearby spin. If the optical resonator 706 is coupled to a spin-selective subset of optical transitions, then this wavelength-dependent transmission reveals the spin state of the coupled spin. In some implementations, the optical detector includes a combination of electrical and optical elements to detect changes in a property of the light in the waveguide 708 (e.g., optical polarization, number of photons, optical intensity, relative indistinguishability of multiple photons, optical frequency, detection time, spatial distribution of light, or the like) that can be used to infer the state of the optical resonator 706 and the coupled deep impurity (e.g., spin 704).

[0095] Figure 8is a graph 800 illustrating energy plotted against background magnetic field strength. Graph 800 includes energy of eigenstates (i.e., allowed steady states) plotted against magnetic field for a coupled nuclear spin-½, electron spin-½ impurity system. In graph 800, the nuclear spin splitting is artificially exaggerated to illustrate certain features. Graph 800 includes energy on a first axis 802 and transverse magnetic field on axis 804. A series of energy levels 806 for nuclear spin (N) and electron spin (E) are plotted. Transitions 810 include between the 1s:A ground state (labeled with singlet and triplet states) and the 1s:Γ7 excited state. These electron-nuclear spin states are good quantum numbers in, for example, high field limits above 1 Tesla. In some implementations, instead of a nuclear spin-½ isotope such as selenium-77, a nuclear isotope with spin-0 or spin-3 / 2 (e.g., sulfur-34 and sulfur-33, respectively) is used, which correspondingly changes the energy level structure.

[0096] For a given electron-nuclear spin-½ system with a given electron-nuclear coupling, there is a particular magnetic field 808, called the "clock transition," where the derivative of the transition frequency of the nuclear spin state is zero. In some implementations, this magnetic field is used to further extend the nuclear spin coherence time by reducing its sensitivity to magnetic field fluctuations. As the magnetic field increases, the energies of the different states diverge. In some implementations, higher nuclear spin systems additionally possess an electron spin clock transition, where the derivative of the transition frequency of the electron spin state is zero.

[0097] The computational states of quantum computation and quantum information processing vary with implementation. In some implementations, the computational states are based on the nuclear spin of a deep impurity (e.g., a donor atom). An example encoding is |0> = |↓> n and |1> = |↑> n In some implementations, the computational states are based on the electron spin of the impurity. An example encoding is |0> = |↓> e and |1> = |↑> e In some implementations, the computational states are based on both the electron spin and the nuclear spin of the impurity. These are singlet / triplet qubits, where the singlet is spin-0 and the triplet is a triply degenerate spin-1 state. For example, |0> ∝ |↑↓> - |↓↑> and |1> ∝ |↑↓> + |↓↑>, |1> = |↓↓>, and |1> = |↑↑>. The first spin can be the electron spin and the second spin is the nuclear spin. In some implementations, the |0> and |1> qubit states are defined by a ground state (e.g., the energy level labeled 1s:A) and an optically excited state (e.g., the energy level labeled 1s:T2).

[0098] It is described that in the presence of a magnetic field (e.g., The Hamiltonian for the spin interaction of the electron spin with the nuclear spin via the isolated deep impurity (e.g., donor atom 204) in the case of a magnetic field applied along the transverse direction H = h

[0099]

[0100] The first two terms are the Zeeman terms for the electron and nuclear spins, while the third term is the hyperfine interaction. Here, μ B is the Bohr magneton, μ n is the nuclear magneton, and g e and g n are the electron and nuclear g-factors. and are the z-components of the complete spin operators (e.g., s ). B is the magnetic field defined above; and A is a material dependent constant, i.e., the hyperfine constant. When the magnetic field is strong, the following are good labels for the system, |en> = { |↓↓>, |↓↑>, |↑↓>, |↑↑>}. In the absence of excitation, e.g., at low temperatures, the electron spin has a lower energy state. The nuclear spin states differ by an energy corresponding to the nuclear resonance frequency By applying a magnetic pulse along the transverse direction the spins oscillate at the nuclear resonance frequency. In this example of a Sigma-X operation, the spins can be flipped, put in a spin superposition, etc. This is magnetic resonance control of multiple deep impurities, e.g., NMR and ESR. Optical excitation of an excited state of an impurity near resonance with the optical transition frequency can also be used to control the spin qubit ground state. One spin associated with a first deep impurity can be selected from a plurality of spins by applying a voltage to an electrode capacitively coupled to the first deep impurity. That is, the voltage of a capacitor containing the first deep impurity is varied. The magnetic resonance frequency as well as the optical transition frequency of the deep impurity changes. For a positive charge on the electrode, the magnetic resonance frequency drops, ω'0 < ω0. Now, one impurity (the target impurity) can be addressed from a plurality of impurities using optical or magnetic resonance control. A quantum input subsystem can form a similar frequency shift by straining a semiconductor substrate proximate to the target donor atom.

[0101] Figure 9 FIG. 13 illustrates an example method 1300 for operation of a quantum information processor. For the method 1300, as with the other methods taught herein, various acts can be performed in an order different than illustrated and described. In addition, methods can omit some acts, and / or employ additional acts. One or more acts of the method 1300 can be performed by or via one or more circuits, such as one or more hardware processors. In some implementations, the method 1300 is performed by a controller, such as the control subsystem 104 of the system 100.

[0102] Method 900 generally begins with a call from a controller. At 902, the controller causes preparation of one or more qubits. In some examples, the controller causes initialization of one or more impurities (e.g., donor atoms) and one or more optical structures (e.g., optical resonators or waveguides).

[0103] At 904, the controller optionally causes performance of single-qubit manipulations in the one or more qubits. In some implementations, the controller causes the quantum input subsystem to apply magnetic resonance pulses and / or mechanical pulses and / or electrical pulses and / or optical pulses to the one or more deep impurities and / or the one or more optical structures. In some implementations, the single-qubit manipulations include application of Sigma-X operations.

[0104] In some implementations, spin qubits can be manipulated using magnetic resonance. In some implementations, spin qubits can be manipulated using optical pulses. These magnetic or optical control fields can be applied to individual deep impurities, individual optical structures, multiple deep impurities, and / or multiple optical structures. In some implementations, the properties (e.g., frequency and coupling strength) of individual deep impurities and optical structures can be externally controlled using, for example, magnetic field gradients, strain, or electric fields. This allows global control fields to selectively act on subsets of deep impurities and optical structures.

[0105] In some implementations, the controller performs one of actions 906, 908, and 910. At 906, the controller causes the analog computer to convert photonic or flying qubit states to spin qubit states and / or vice versa. In some implementations, the controller causes the quantum input subsystem and / or the quantum output subsystem to convert photonic qubit states to spin qubit states or to convert qubit states to photonic qubit states. At 908, the controller causes coupling of two or more deep impurities via one or more optical structures. At 910, the controller causes readout of the one or more deep impurities and / or the one or more optical structures. Method 900 ends until it is called again.

[0106] Figure 10 An example method 1000 for operation of a quantum information processor is illustrated. Method 1000 is an implementation of action 902. For method 1000, as with other methods taught herein, various actions can be performed in an order different than illustrated and described. In addition, methods can omit some actions, and / or take additional actions. One or more actions of method 1000 can be performed by or via one or more circuits, such as one or more hardware processors. In some implementations, method 1000 is performed by a controller (e.g., control subsystem 104 of system 100).

[0107] Method 1000 generally begins with a call from a controller. At 1002, the controller causes the analog computer and / or environmental subsystem to prepare an isolated environment for a quantum information processor to provide an environment for one or more impurities and / or optical structures. For example, the quantum information processor can include one or more deep impurities (e.g., donor atoms) and one or more optical structures (e.g., resonators).

[0108] At 1004, the controller causes the analog computer 150 and / or quantum input subsystem 156 to prepare one or more impurities (e.g., donor atoms) in a selected charge state (e.g., a singly ionized state). For example, a donor atom (e.g., donor atom 204, i.e., a stable, non-gaseous chalcogen atom) is an atom disposed in a semiconductor material 202. In operating a quantum information processor according to method 1000, such donor atoms can be singly ionized. Two electrons are bound to a chalcogen donor atom in its electrically neutral state, making it a helium-like or double donor. The binding energy of the first electron of a chalcogen donor atom is much smaller than that of the second electron, e.g., a factor of 2 smaller. Using various methods, one electron is stripped from the donor atom, making it hydrogen-like. That is, the double donor can be singly ionized. One method of preparing a hydrogen-like donor atom includes photoionization: applying light with an energy greater than the natural donor atom binding energy. A second method involves electrically biasing the device with nearby electrodes. In some embodiments, the quantum information processor includes acceptor sites within the semiconductor material to receive free electrons. One material suitable for acceptor sites is boron. Acceptors can include those from Group III (13), e.g., boron, aluminum, gallium, and indium.

[0109] At 1006, the controller causes one or more optical structures (e.g., optical resonators or waveguides) to be initialized. For example, after a long time and at low temperature, one or more optical resonators will not have a residual photon. That is, in a particular environment (e.g., low temperature), the optical resonator will be unthermalized (i.e., zero photons) and thus initialized by equilibration with the environment.

[0110] At 1008, the controller causes the analog computer 150 and / or the quantum input subsystem 156 to prepare one or more impurities and / or optical structures to be in a reference state. The reference state depends on the computational state used by the quantum information processor. In some embodiments, one or more qubits are in the state |0>. Several techniques exist for initializing the spin state of the impurity. In some embodiments, the application of a specific optical frequency can be used to drive the spin of the impurity to a predetermined initial state. In some embodiments, it is possible to measure the spin and, if necessary, manipulate each qubit to the desired state using magnetic resonance (e.g., EPR, NMR) or pulsed optics techniques. That is, at the start of computation, each qubit in the quantum information processor is initialized such that it has a known and well-defined computational (logical) state, such as a nuclear spin state, an electron spin state, or a combination thereof. This can be achieved by reading out each qubit. When the measured state of a qubit is incorrect, the controller manipulates the state of the qubit to align with the correct initial state. In some embodiments, the qubit is a nuclear spin. In some embodiments, the qubit is an electron spin. In some implementations, for example using a near-zero magnetic field, the electron-nuclear spin qubit is described as a singlet / triple qubit. The same techniques described for individual electron-nuclear spin cases can also be used to initialize the singlet / triple state. In some implementations, combinations of the above qubits are employed simultaneously.

[0111] Figure 11 This diagram illustrates method 1100, an example operation for a quantum information processor. Method 1100 is... Figure 9 The implementation of action 908. For method 1100, as with other methods taught herein, various actions may be performed in a different order than those illustrated and described. Additionally, some actions may be omitted, and / or additional actions may be employed. One or more actions of method 1100 may be performed by or via one or more circuits (e.g., one or more hardware processors). In some implementations, method 1100 is performed by a controller (e.g., control subsystem 104 of system 100).

[0112] Donor atoms in semiconductor materials can be communicatively coupled to each other through several methods compatible with the systems and devices described herein. In some embodiments, donor atoms will be coupled via a single optical structure and / or multiple optical structures and / or flying photons. Figure 5 An example of an optical structure that couples two deep impurities is shown. Figure 3 Examples of two optical structures coupled with two deep impurities are presented. Methods for interconverting photons and qubits are demonstrated in this paper.

[0113] Method 1100 shows three actions 1102, 1104, and 1106, but in some implementations only one action is performed. In some implementations, the plurality of coupled qubits includes a plurality of donor atoms having a plurality of transition frequencies. The plurality of qubits is coupled when each qubit is near-resonant with each other qubit and one or more optical structures, and when each qubit is proximate (e.g., within a distance comparable to a characteristic distance) to each optical structure.

[0114] Method 1100 generally begins with a call from a controller. At 1102, the controller causes an analog computer and / or a quantum input subsystem to tune an optical structure (e.g., an optical resonator).

[0115] Different tuning methods are suitable for (de)modulating optical structures for control or calibration purposes, e.g., coupling donor atoms to the optical structures, or overcoming variations in resonant frequencies between a plurality of optical structures. In some implementations, the control subsystem injects electrical carriers via electrodes proximate the optical structure. For example, the electrodes are in electrical contact with a substrate, e.g., semiconductor material 202, and are disposed on either side of the optical structure.

[0116] In some implementations, the quantum information processor includes a device to strain a bulk of semiconductor material. In some implementations, the strain is applied to semiconductor material that includes an optical structure. The control subsystem can cause compression or stretching (generally, strain) of a region of the semiconductor material that includes one or more optical structures and / or one or more donor atoms. When the strain changes a characteristic dimension (e.g., a resonator geometry) and / or a property of the optical structure, there is a change in the frequency (e.g., the resonator frequency) of the optical structure. Strain can also be used to change the optical transition frequency of a donor atom. Strain in a semiconductor substrate (e.g., strain along one direction) is a mechanical force that has a small effect on the 1s:A ground state but changes the energy levels of the 1s:Γ7 excited states and thus the energy difference between these states. See Figure 8 transition 810 in

[0117] In some implementations, the device to strain the semiconductor material includes a piezoelectric material, e.g., lead zirconate titanate, barium titanate, or strontium titanate, electrically coupled to a power source via two electrodes. The controller varies the current passing between the two electrodes and through the piezoelectric material, and strains the semiconductor material. In some implementations, the device includes a microelectromechanical system (MEMS) to strain a bulk of semiconductor included in the optical structure.

[0118] In some implementations, the quantum information processor includes static strain in a bulk of semiconductor. Residual film stress gradients in the layers of the structure induce a strain gradient. The static strain can be offset or enhanced by piezoelectric and / or MEMS.

[0119] At 1104, the controller causes the analog computer and / or quantum input subsystem to tune a first set of impurities (e.g., donor atoms) in the semiconducting material. In some implementations, the first set includes one donor atom. In some implementations, the first set includes multiple donor atoms. In some implementations, the controller causes a strain in the semiconductor material via the input subsystem to change the optical transition frequency of the donor atoms. In some implementations, the controller causes the input subsystem to apply a magnetic field to change the optical transition frequency of the multiple donor atoms. In some implementations, the controller causes the input subsystem to manipulate the spin state of the multiple donor atoms to change their optical transition frequency.

[0120] At 1106, the controller causes the analog computer and / or quantum input subsystem to tune a second set of impurities (e.g., donor atoms) in the semiconducting material. The set can be one or more donor atoms. The controller can achieve the tuning via strain and / or magnetic field. By using a magnetic field with a spatial gradient, the controller can select and tune a particular donor atom.

[0121] At 1108, after a suitable period, the controller causes the analog computer and / or quantum input subsystem to detune one or more of the first set of impurities that are not resonant, the second set of impurities, and one or more optical structures. The period determines the coupling. In an example, if the first and second set of donor atoms includes one donor atom, the interaction between the multiple qubits is a product of a time-varying coefficient and a multi-qubit diagonal term. For example, in the case of two qubits, the coupling term can have the form:

[0122]

[0123] where H C is the Hamiltonian operator of the interaction, J(t) is a time-varying coefficient, and denotes the tensor product between the z-component of the spin operator of the first donor atom (i.e., the Sigma-Z operator) and the z-component of the spin operator of the second donor atom.

[0124] Figure 12 is a flowchart illustrating an example implementation of a method 1200 to read out the state of a donor atom. The method 1200 is an implementation of the method 910 of Figure 9 as described herein. For the method 1200, as with other methods taught herein, the various actions can be performed in an order different than illustrated and described. In addition, the method can omit some actions, and / or employ additional actions. One or more actions of the method 1200 can be performed by or via one or more circuits, such as one or more hardware processors. In some implementations, the method 1200 is performed by a controller, such as the control subsystem 104 of the system 100.

[0125] At 1202, the controller receives information indicative of a nonzero likelihood that an optical structure (e.g., optical resonator) optically coupled to an impurity (e.g., donor atom) can have received a photon. For example, the optical resonator is coupled to a donor atom included in a computation. After 1202, the controller can perform action 1204 or action 1206.

[0126] At 1204, the controller counts the number of photons in the optical structure (e.g., optical resonator) via the quantum output subsystem. The state of the donor atom coupled to the optical structure can be inferred.

[0127] At 1206, the controller infers the spin state of the donor atom via the quantum output subsystem by measuring the optical frequency or other optical characteristic of the communicatively coupled optical structure (e.g., optical resonator). In some implementations, the parity of the spin states of multiple donor atoms can be inferred by measuring the optical frequency or other optical characteristic of the communicatively coupled optical structure.

[0128] The state of the donor atom affects the state (e.g., frequency) of the optical structure. By causing light to be transmitted onto the optical structure and observing the reflection and / or absorption of the light, the state of any one or more donor atoms coupled to the optical structure can be inferred. The light can be blackbody light with a nontrivial spectral density at the resonances of the optical resonator. The light can be narrow-spectrum light that matches one or more resonances of the donor atom and / or the resonator. If the source frequency matches the resonator frequency, then the light will be absorbed and otherwise reflected. If the state of the coupled donor atom affects the resonances of the resonator, then the state of the donor atom can be inferred from the absorption and reflection data. In various implementations, a single photon can be used to infer the spin qubit state. In various implementations, multiple photons can be used to infer the spin qubit state.

[0129] At 1208, the controller returns the results of the photon counting or frequency shift. In some implementations, the controller stores the results of the photon counting or frequency shift.

[0130] In some implementations, the readout device and coupler are used to implement a quantum error correction code on a quantum information processor. Quantum error correction codes can be used to improve the performance of a quantum computer. Recently, the surface code has emerged as a useful method. These have a high tolerance to errors in the physical qubits. The surface code has a fault tolerance threshold of about 1%. That is, if the probability of an error per time step in a gate modality quantum computation is less than 1%, then it is arbitrarily believed that long computations are possible. That is, the code will correct for any errors. Typically, in a surface code implementation, each physical qubit is coupled to its nearest neighbors, forming a two-dimensional lattice, with half being qubits for storing quantum information, logical qubits, and half being qubits used as ancilla qubits to perform error correction. However, the surface code can be used with logically proximate qubits if two qubits are coupled via a resonator or via a waveguide but not in proximity to each other.

[0131] Figure 13A FIG. 13A is a flow diagram illustrating an implementation of a method 1300 to convert a state of a flying qubit (i.e., a photon) to a state of a stationary qubit.

[0132] At 1302, the quantum information processor receives a photon at an optical structure (e.g., a resonator). The photon can be in a waveguide, e.g., a qubit intercoupler, or a quantum communication channel, e.g., channel 170 of system 100. The optical structure is optically coupled to a donor atom in a semiconductor substrate. In some implementations, the photon has a first quantum state.

[0133] At 1304, the quantum information processor forms a second quantum state in the donor atom in the semiconductor substrate. In some implementations, the photon has a second quantum state that depends on the first quantum state (e.g., is the same as the mapping between states, corresponds to the mapping). That is, the quantum information processor is a photon memory. Here, corresponds means that the first state and the second state differ in the underlying state but align in the amplitude of the respective underlying state.

[0134] Figure 13B FIG. 13B is a flow diagram illustrating an implementation of a method 1350 to convert a state of a stationary qubit to a state in a flying qubit.

[0135] At 1352, the quantum information processor forms a first quantum state in a donor atom in a semiconductor substrate. The donor atom is optically coupled to an optical structure, e.g., a waveguide.

[0136] At 1354, the quantum information processor forms a second quantum state in a photon that exits the optical structure. In some embodiments, the photon has a second quantum state that depends on the first quantum state. That is, the quantum information processor can form a flying qubit. In some embodiments, the photon enters an optical structure, such as a waveguide, a lens, or a resonator.

[0137] Donor atoms can be used to emit photons that are communicatively coupled to a waveguide. In some embodiments, the emission of the photon can be electrically triggered. In some embodiments, the emission of the photon can be optically triggered. In some embodiments, the emitted photon will be quantum entangled with a plurality of donor atom qubits. In some embodiments, the photon will not be entangled with any donor atom qubits.

[0138] Single-ionized chalcogen donor atoms have multiple electronic orbital excited states, labeled approximately bare hydrogen atoms. These energy levels include Is, 2s, and 2p. When in a silicon lattice with six equivalent conduction band valleys, the Is energy level further splits into twelve energy levels. Listed in decreasing binding energy, these energy levels are: two for Is: A ground state; two for Is: T2(Γ7) energy level; four for Is: T2(Γ8) energy level; and four for Is: E energy level. In some embodiments, the donor atom and thus the electron with hydrogen-like orbitals can be pumped into a higher excited state, such as 2p. Depending on this excited state, the electron undergoes a cascade process down to Is: T2(Γ7), from which it emits a photon to reach the ground state Is: A. In this way, the donor atom can act as a deterministic single-photon source. In some embodiments, the donor atom is pumped directly into Is: T2(Γ7) and then, after some characteristic delay, the donor will emit a photon. In some embodiments, the donor atom is directly coupled to a waveguide. In some embodiments, the donor atom is coupled to a resonator, which in turn is coupled to a waveguide. In some embodiments, the coupled photon structure matches multiple transition frequencies. In some embodiments, the emitted photon qubit will have an overlying frequency, polarization, and / or spatial mode whose state is quantum entangled with the donor atom.

[0139] Spin-to-photon conversion:There are four electronic transitions from 1s:A to 1s:T2 (Γ7). Two of these transitions are linearly polarized along the direction of the applied magnetic field, and the other two are negative and positive circularly polarized. In some embodiments, the donor atomic spin qubit is placed into a linearly polarized optical cavity. The input spin superposition can then be transferred into a photon by exciting the atom. Once pumped into an excited state, it will later emit a photon in a frequency superposition that matches the input spin state superposition. In some embodiments, information encoded in a spin qubit is transferred into a spatial mode by placing the donor atom into a chiral photonic component (e.g., a chiral waveguide), which directs the oppositely circularly polarized photons into opposite spatial directions. The photons are then emitted into path superpositions that correspond to the input superposition spin states. In some embodiments, the spin qubit superposition shifts the frequency of an optical resonator near the path of the incoming photon, which in turn directs, reflects, or phase shifts the incoming photon so that its state becomes entangled with the state of the spin qubit. In some embodiments, frequency-matched photons are incident on a donor atom in a photonic structure, where resonant photons are absorbed and later re-emitted, and only non-resonant photons are reflected. The output photons are then time-bin entangled with the spin state of the qubit.

[0140] Photon-to-spin conversion: In some embodiments, photon-to-spin conversion can occur by populating an optical structure (e.g., a resonator) with a single photon. When a photon is present in an optical resonator, the available optical frequencies of a deep impurity (e.g., a donor atom) change according to the Jaynes-Cummings model. This means that a geometric operation can be performed selectively on an electron spin when a photon is present in the optical resonator, permitting photon-to-spin qubit conversion. In some embodiments, photon-to-spin conversion can occur by strong non-resonant driving ("virtual" process). If the frequency of a single photon differs from the energy separation of the electron spin by exactly the energy of the strong pump beam, then the single photon can be used to flip the electron spin (conditional on the frequency of the single input photon). In some embodiments, an incoming photon qubit can undergo quantum teleportation into a spin qubit state. Quantum teleportation can be implemented by performing an oddity measurement on the incoming photon and a secondary photon that is entangled with the donor spin qubit.

[0141] Purcell loss:By coupling the optical structure (e.g., resonator) to a subset of the two spin ground states (e.g., one of the two), one avoids the Purcell loss due to the optical structure or resonator. The state of a quantum device including a qubit will eventually decay within a characteristic time period. Two common decay mechanisms are the relaxation of the amplitude or excitation with an associated Tl time. The second is a phase disturbance with an associated dephasing or T2 time. A longer characteristic time allows for information to be stored longer or more quantum operations to be performed. Several factors can contribute to the decay mechanisms. For a deep impurity in a semiconductor substrate, the substrate itself can be one source of de-coherence. Resonant modes with frequencies close to the frequency of the qubit can cause the qubit to decay. This is called Purcell loss.

[0142] As previously mentioned, a deep impurity (e.g., a donor atom) can be used to emit a photon communicatively coupled to a waveguide. Again consider the system 100 in Figure 1 The quantum information processor 154 can emit photons into the quantum information channel 170 (an example of a waveguide). Once emitted by an impurity or optical structure included in the quantum information processor 154, the photons can be collected and transmitted by the quantum information channel 170. Examples of quantum information channels 170 include optical fibers (also known as fiber optics) and free space.

[0143] The reverse process can occur. In some implementations, a frequency-matched photon incident on a deep impurity in an optical structure is absorbed. For example, a photon traveling via the quantum information channel 170 can be emitted and directed to the quantum information processor 154. A photon emitted from the quantum information channel 170 can be collected by a deep impurity or optical structure included in or on the quantum information processor 154.

[0144] The quantum information processor 154 can be optically coupled to the quantum information channel 170 in different ways. For example, the optical coupling can be evanescently coupled. Consider Figure 7 The light source 710 sends light along the waveguide 708 to interact with the optical resonator 706. One or more portions of one or more surfaces of the quantum information processor 154 or the quantum information channel 170 can include an anti-reflective coating or film to more efficiently collect or transmit one or more photons. A portion of the optical fiber can be coated with an anti-reflective film, e.g., the extent of the fiber's entrance / exit pupil. A lens can be disposed between the quantum information channel 170 and the quantum information processor 154. In some implementations, the photons moving between the quantum information processor 154 and the quantum information channel 170 can be focused or directed by the lens.

[0145] The quantum information processor 154 and other portions of the system 100 can be used as a single photon source. The deep impurities in the quantum information processor 154 can act as a deterministic single photon source. The single photon source can be part of a salable item, can be a salable item, or produces a salable item, i.e., a photon. In some implementations, the deep impurities included in the quantum information processor 154 are pumped directly into the ls:T2(Γ7) state by a light source (e.g., included in the quantum input subsystem 156) and after some characteristic delay the impurities will emit a photon.

[0146] The single photon source can be in an optical quantum cryptography system (QCS), where, for example, a sender and a receiver create a common secret information. When the system 100 is operated as a QCS, the sender transmits a stream of single photons to the receiver via a quantum information channel 170. For example, the system 100 sends photons to another device. Each photon will encode an information bit. An eavesdropper intercepting the stream will interact with one or more photons. The state of these intercepted photons will change as will the information encoded by the photons. Thus, the sender and the receiver can determine if their communication has been intercepted, and if not, use the communication to create a common secret information.

[0147] Portions of the system 100 can use the common secret information to create information used in the operation of machines, e.g., computing machines and communication machines. For example, the system 100 can be associated with a sender and create a cryptographic key, e.g., a one-time pad, by using the communication as a seed to a generator of a pad. For example, the system 100 can be associated with a receiver and execute processor executable instructions that define a key generation method, e.g., a Blum Blum Shub method, a Yarrow method, etc. Portions of the system 100 and counterpart systems (not shown in the figure) can use the common secret information in a key agreement protocol of a virtual private network. The application program instructions 126 include processor executable instructions that, when executed, cause the system 100 to use portions of the system 100 as a communication device to generate seeds, keys, nonces, hashes, etc. Figure 1

[0148] ​The portions of the system 100, the single-photon source, can be used as a random number generator. The random number generator can be used to seed a pseudo-random number generator to form an initialization vector, a parameter for a hash function, a nonce, an encryption salt, or a key, among others. The digital computer 102 can interact with the quantum information processor 154 via the quantum input subsystem 156 and the quantum output subsystem 158 to form one or more random numbers. The digital computer 102 can generate a signal that includes information representing the one or more random numbers. The digital computer 102, via the control subsystem 104, can cause the information representing the one or more random numbers to be transmitted via the network interface subsystem 110 and a network or non-network communication channel (not shown). The information representing the one or more random numbers can be sent via the quantum information channel 170. The digital computer 102, via the control subsystem 104, can cause the information representing the one or more random numbers to be stored as processor-readable information on the at least one non-transitory computer- and processor-readable storage device 108.

[0149] The portions of the system 100 that include or operate as a single-photon source can be used beyond the realm of random numbers and cryptography. A single-photon source can be a low-noise source of optics, spectroscopy, and metrology. Many light sources emit photons at a rate that randomly fluctuates, limiting their utility. This uncertainty is called jitter. A single-photon source that produces photons at regular time intervals can have reduced jitter.

[0150] Consistent with the exemplary systems, devices, methods, and articles of manufacture herein, a processor can cause information to be transmitted through a communication channel (e.g., an optical fiber, a fiber, a network or non-network communication channel). In cases of longer separations between a sender and a receiver or in cases of networked communication channels, it is useful to operate the portions of the system 100 as a quantum repeater. In some implementations, a quantum repeater provides a photon-to-atom qubit interconversion. At least in Figure 9 Examples of methods to interconvert stationary qubits (e.g., solid state) and flying qubits (e.g., photons) are described at 13. In the operation of a quantum repeater, the state of a flying qubit (i.e., a photon) is converted to the state of a stationary qubit. For example, see the method 1300 illustrated in Figure 13A The state of the stationary qubit is then converted to the state of a flying qubit. For example, see the method 1350 illustrated in Figure 13B

[0151] ​The exemplary systems and devices described herein can be operated or guided according to methods developed in the field of cavity quantum electrodynamics (cavity QED). Cavity QED involves the interaction of a single atom with a single electromagnetic field mode or multiple thereof. Consider a two-level atom interacting with a single electromagnetic field mode. The system can be modeled as a Hamiltonian for the interaction of two-level atoms, electromagnetic field modes, coupling thereof to the environment. Using well-known approximations (e.g., dipole and rotating wave), the Jaynes-Cummings Hamiltonian is analytically solvable. Further, the states of the Hamiltonian can be restricted to four (4) states: the ground or excited state of the atom, and the electromagnetic field mode containing n or n+1 photons. Interactions with the environment can occur via spontaneous emission from the atom or electromagnetic field mode. When the associated decay rates are less than the single-photon Rabi frequency, then coherent evolution can occur. Some quantum computers utilize coherent evolution as a computational resource.

[0152] Consider Figure 2 an exemplary donor atom 204. The donor atom 204 can include a singly ionized donor 77Se+and a single electron bound to the singly ionized donor. At zero magnetic field, the hyperfine interaction splits the donor atom 204 ground state spin levels into electron-nuclear spin singlet and triplet states. See Figure 8 Among many optical transitions available for the donor atom, excitation to the lowest excited state 1s: T2: Γ7has suitable properties. See discussion herein at least at FIG. 13. In some implementations, the semiconductor material 202 extends several millimeters to several tens of millimeters along three directions and includes 28Si: 77Se+, where the residual 29Si is 75 parts per million and the donor density of 77Se is 5 x 10 -21 m -3 This sample exhibits a 2.9 μιη transition 1s: A to / from 1s: Γ7(optical transition) and has been well characterized to a linewidth of at most 0.007 cm -1 In some implementations, the information processor 200 can be modeled as a strong coupling between the donor atom 204 and the optical resonator 206. For example, the donor atom 204 is a 77Se+ion placed at a mode maximum of the optical resonator 206 with a resonant frequency matching the 1s: A to / from 1s: Γ7transition of the donor atom 204.

[0153] An environment subsystem, such as the environment subsystem 152, can apply a magnetic field with a maximum strength and direction to maximize the strength of the coupling between the donor atom 204 and the optical resonator 206. For an information processor, such as the information processor 200, the transition frequencies between multiple ground and excited states are generally different from one another and shifted according to the applied magnetic field. Thus, the donor atom 204 and the optical resonator 206 can be selectively coupled or decoupled depending on the spin state of the atom.

[0154] When a magnetic field is applied, the spin ground state and excited states split with different rates of divergence. See Figure 8 and note how the singlet and triplet states of 1s: T2(Γ7) split with different energy levels of the applied magnetic field represented on axis 804 (with different energies shown on axis 802).

[0155] For an information processor, such as information processor 200, the transition frequencies between multiple ground states and excited states are generally different from one another and shifted according to an applied magnetic field. Thus, the donor atom 204 and optical resonator 206 can be selectively coupled or decoupled depending on the spin state of the atom.

[0156] The resonance and selective coupling of deep impurities and optical structures (e.g., donor atom 204 and optical resonator 206) can be dynamically adjusted by the application of an electric field, a magnetic field, or a mechanical strain. The properties (e.g., their frequencies and coupling strengths) of individual impurities or optical structures or the interactions of individual impurities or optical structures can be controlled with a magnetic field, an electric field, or a mechanical strain.

[0157] In some implementations, a quantum information processor includes one or more donor atoms with optical transitions. Exemplary donors are non-gaseous stable chalcogen atoms. The donors can have non-zero nuclear spin, for example, some chalcogen nuclear isotopes have non-zero spin, such as33S (spin -3 / 2),77Se (spin -1 / 2), and123Te and125Te (both spin -1 / 2). The ground states of these donor atoms have the same spin Hamiltonian as Group V (15) donors, but with much larger hyperfine constants A of approximately 312 MHz, 1.66 GHz, 2.90 GHz, and 3.50 GHz, respectively.

[0158] In some implementations, a deep impurity and electron can thus have a hydrogen-like orbital, i.e., a '1s' hydrogen-like manifold of28Si:77Se+. When in a silicon lattice with six equivalent conduction band valleys, the 1s energy level is further split into twelve energy levels.

[0159] In some implementations, a quantum information processor includes one or more donor atoms, i.e., a bi-donor. When singly ionized, a bi-donor has even greater binding energy (614 meV for S+, 593 meV for Se+, and 411 meV for Te+) and a hydrogen-like (or He+) orbital structure with optical transitions in the mid-infrared ('mid-IR'). In28Si:77Se+, the optical transition between the spin ground state and the lowest excited state is sufficiently narrow to be spin-selective even at very low or zero magnetic field. Examples of non-gaseous stable chalcogen atoms include neutral, ionized, and doubly ionized atoms, for example, S 0 (approximately 300 meV), Se 0(about 300 meV), Te 0 (about 300 meV), Se + (593 meV), S + (614 meV), Se + (593 meV), Te + (411 meV), S ++ , Se ++ , and Te ++ As with the single-ionized charge states of deep donors, the neutral (e.g., uncharged) doubly- ionized charge states of deep acceptors also admit suitably narrow optical transitions to excited states, and these transitions are similarly able to be strongly coupled to optical structures. Doubly-ionized atoms can be employed as nuclear spin qubits and proximate to optical structures can interact with the doubly-ionized charge states. In some embodiments, only one particular charge state is used to define a qubit. In some embodiments, multiple charge states are used to define a qubit.

[0160] Examples of deep impurities include metal clusters, e.g., clusters of four atoms, e.g., Cu4 (1014 meV), Cu3Ag (944 meV), Cu2Ag2 (867 meV), Cu3Pt (884 meV), Cu3Pt (882.36 meV), Cu2LiPt (850.1 meV), CuLi2Pt (827.6 meV), Li3Pt (814.9 meV), Ag4 (778 meV), Li3Au (765.3 meV), CuLi2Au (746.7 meV), Cu3Au (735 meV), and Cu2LiAu (735.2 meV). Examples of deep impurities include metal clusters, e.g., clusters of five atoms, e.g., CuLi3(Au) (1090.2 meV), Cu4Au (1066 meV), Cu3LiAu (1052.7 meV), CuLi2Ag (909.9 meV), Cu4Pt (777 meV), Cu2Li2Pt (694.6 meV), Cu3LiPt (725.6 meV), and CuLi3Pt (671.6 meV). Examples of deep impurities include metal atoms or metal clusters selected from transition metals, e.g., clusters including copper, silver, gold, or platinum. In some embodiments, the transition metal is a metal from the d-block or Groups 3-12 on the periodic table. In some embodiments, the transition metal includes a metal selected from the f-block or lanthanides and actinides.

[0161] Examples of deep impurities include Group I and II (1 and 2) atoms or clusters, e.g., Group 2 double acceptors (e.g., Mg + (256.5 meV), Mg 0(107.5 meV) and Be) or Group I dopants (e.g., Li 0 and Li + ). Examples of dopants include compounds and clusters, including those described above. Examples of dopants include sulfur and copper, for example, so-called S A (968 meV) and S B (812 meV) centers.

[0162] As described herein, deep impurities, such as dopant atoms 204, can have transitions in convenient wavelengths corresponding to wavelengths of commercially available optical emitters, lasers, detectors, mirrors, etc. In some embodiments, the wavelengths correspond to mid-IR wavelengths. Various embodiments can include and utilize lasers that can emit light at wavelengths at or near optical transitions of impurities included in the semiconductor substrate. For example, quantum input subsystem 156 includes a light source. Various embodiments can include and utilize lasers with variable or fixed wavelengths. Suitable lasers for various embodiments include the following types and wavelengths: AlGaInP (0.63 to 0.9 μιη), vertical cavity surface emitting laser (VCSEL) (GaAs-AlGaAs) (0.6 to 1.3 μιη), Nd:YAG (1.064 to 1.064 μιη), VCSEL (0.85 to 1.5 μιη), Cr:Mg2Si04(1.23 to 1.27 μιη), InGaAs (1.1 to 1.7 μιη), Raman (1 to 2 μιη), InGaAsP (1 to 2.1 μιη), AlGaIn / AsSb (about 2 μιη), dye Raman shifted (0.9 to 4.5 μιη), HF chemicals (2.7 to 2.9 μιη), Cr:ZnSe / S (1.9 to 2.6 μιη), XeHe (2 to 4 μιη), quantum cascade laser (2.63 to 250 μιη), lead salts (3 to 20 μιη), hybrid silicon (3 to 30 μιη), GaInAsSb (3 to 30 μιη), optical parametric oscillator (OPO) (3 to 1000 μιη), and CO (doubled) (4.6 to 5.8 μιη).

[0163] In some embodiments, optical readout reads information stored in the state of a deep impurity. Different electronic states (including different spin states) of a deep impurity in an electric field are associated with different spin or charge distributions in the semiconductor substrate. These different distributions affect the properties of the proximal optical structure. Optical measurements on the proximal optical structure (e.g., as described herein at least in Figure 7

[0164] Figure 14 Various embodiments of the present invention illustratively depict energy levels 1400. Energy levels 1400 are plotted against an axis of energy 1402. Along the axis of energy 1402, energy levels 1400 are plotted at energy levels 1404.​Figure 14 The horizontal direction plots a series of excited states. The multiple energy levels 1400 include a Jaynes-Cummings ladder 1404 of the coupled system, including the deep impurity and the optical structure. In the Jaynes-Cummings ladder 1404, the number of photons in the optical structure is plotted. Note that the energy levels continue after n = 2. In the Jaynes-Cummings ladder 1404, the energy level of one photon in the optical structure and two photons in the optical structure differ by the resonance frequency, ω C .

[0165] The Jaynes-Cummings ladder 1404 allows for a resonant transition between the 1s:A ground state and the 1s:Γ7 excited state with aligned energy levels. That is, if no effective magnetic field is applied to the deep impurity, there is zero hyperfine interaction to split the ground state (e.g., the atom is a nuclear spin-zero isotope). The transition is approximately the same energy. This constitutes a dressed state mixing generation. See, for example, the energy level of n = 2 in the Jaynes-Cummings ladder 1404 and the 1s:Γ7 excited state 1406. These match or substantially match for the resonant transition.

[0166] The controller can apply a magnetic field to the deep impurity via the input subsystem. When a magnetic field is applied to the deep impurity, the states in the Jaynes-Cummings ladder 1404 split into up and down spin states, e.g., the down spin state 1410. The spin ground and excited states split with different g factors. See the length scale for the 1s:A and 1s:Γ7 states at n = 2, where one split is one-half of the other. In selenium-77, the ground state splits by g A ≈ 2.01 and the excited state 1s:Γ7 splits by g Γ7 ≈ 0.64. In Figure 14 In the Jaynes-Cummings ladder 1404, the energy level of the 1s:Γ7 excited state 1406 is represented by a long dash followed by two dots, indicating a split and / or shifted energy level under a magnetic field. The application of a magnetic field moves the energy level of the state. The energy levels in the ground and excited states no longer match or substantially match. For example, the energy of the state 1412 does not match the energy of the state 1414.

[0167] The controller can tune the energy level of the excited state via the input subsystem. The controller can shift the energy level by Δω, see shift 1416. The controller can shift the energy level for an excited state (e.g., the 1s:Γ7 state) by applying and / or varying an electric field and / or strain to the semiconductor substrate. Devices to apply an electric field or strain to one or more portions of a semiconductor substrate are described herein, at least with respect to Figure 1 , 2 and 8. In Figure 14In some embodiments, a long dash followed by a dot indicates an energy level that is shifted under an electric field or strain. Here, after a shift of Δω, the energy levels are aligned. See, for example, energy level 1418. In some embodiments, the controller can shift the energy levels to the excited state to account for a mismatch between the transition frequency of the deep impurity and the resonance frequency of the optical structure. Figure 14 In some embodiments, while a downward state is exhibited in resonance (see set of energy levels 1418), an upward state can be made to be in resonance. The controller can shift the energy levels to the excited state to account for a mismatch between the transition frequency of the deep impurity and the resonance frequency of the optical structure.

[0168] The resulting strong coupling condition is spin dependent for energy level 1408. Spin dependent cavity coupling allows the controller to perform single spin readout near or above 4.2 K via the output system. Spin dependent optical structure coupling allows readout without optical excitation of the impurity. For example, in some embodiments, if the electron spin of the deep impurity is in the uncoupled ground state (e.g., upward), the optical structure will transmit any light-resonance light that matches the resonance frequency of the optical structure, here ω C . Conversely, if the electron spin is in the coupled ground state (e.g., downward), the nanocavity will reflect the resonance light at frequency ω C , as that frequency is no longer resonant in this system configuration. Transitions 1420 and 1422 illustrate part of the process. Transition 1420 is coupled. Transition 1422 is uncoupled.

[0169] In some embodiments, when the electron spin of the deep impurity is in the uncoupled ground state, the optical structure will reflect the resonance light. Conversely, the resonance light is transmitted when the electron spin is in the coupled ground state. A large number of photons can be used to infer the response of the optical structure without exciting the deep impurity system or non-resonant transitions in the coupled optical structure-deep impurity system.

[0170] Figure 15is a schematic diagram illustrating a section of an exemplary portion of a quantum information processing device 1500 including a plurality of deep impurities 1504 and a waveguide 1506. The quantum information device 1500 includes a semiconductor substrate 1502. The plurality of deep impurities 1504-1, 1504-2, 1504-3, and 1504-4 (collectively 1504) are disposed within the semiconductor substrate 1502. The waveguide 1506 (an example of an optical structure) supports a propagation mode capable of supporting a plurality of propagation mode frequencies. The plurality of deep impurities 1504 are optically coupled to the waveguide 1506 via the propagation mode. In the illustrated example, the distances 1508-1 and 1508-2 are on the order of the wavelength λ of the waveguide's mode. Each deep impurity of the plurality of deep impurities 1504 can be placed at or near an antinode of the propagation mode in the waveguide 1506. The waveguide 1506 is a device that confines or guides electromagnetic waves along a path defined by its physical structure. The waveguide 1516 can be defined within or on the substrate 1502. Light can propagate through the waveguide 1516 and couple to the plurality of deep impurities 1504-1, 1504-2, 1504-3, and 1504-4.

[0171] Further implementations are summarized in the following examples.

[0172] Example 1: A quantum information processing device comprising: a semiconductor substrate; one or more deep impurities disposed within the semiconductor substrate, wherein each of the deep impurities is characterized by a plurality of quantum states corresponding to different electronic or nuclear spin states of the deep impurity and representing qubit information; one or more optical structures integrated with or coupled to the semiconductor substrate, each optical structure having a characteristic modal frequency and an optical state representing optical structure information; and a first deep impurity optically coupled to a first optical structure, the first deep impurity having a first transition frequency between a first pair of the plurality of quantum states, the first transition frequency matching a first characteristic modal frequency of the first optical structure, wherein the first optical structure optically couples the qubit information and the optical structure information.

[0173] Example 2: The device of example 1, wherein the characteristic modal frequency of the optical structure is a resonant modal frequency.

[0174] Example 3: The device of example 1, wherein the characteristic modal frequency of the first optical structure is a propagating modal frequency.

[0175] Example 4: The device of any of examples 1-2, wherein the first optical structure is a first optical resonator having a first photonic mode, the first photonic mode having the characteristic modal frequency as a first resonator frequency.

[0176] Example 5: The apparatus of any one of Examples 1-4, wherein the first pair of the plurality of quantum states includes a first quantum state and a second quantum state, and the first transition frequency corresponds to an optical transition between the first quantum state and the second quantum state of the plurality of quantum states.

[0177] Example 6: The apparatus of any one of Examples 1-5, wherein the deep impurity is a non-gaseous chalcogen atom.

[0178] Example 7: The apparatus of any one of Examples 1-6, further comprising: a second optical structure having a second mode with a second characteristic modal frequency; and a second deep impurity coupled to the second optical structure, the second deep impurity having a second transition frequency between a second pair of energy levels, and the second transition frequency matching the second characteristic modal frequency.

[0179] Example 8: The apparatus of Example 7, wherein the second optical structure is at a distance from the first optical resonator that is less than about twenty times a characteristic decay length λ / n, where λ is a first photonic mode wavelength and n is a refractive index of the semiconductor substrate.

[0180] Example 9: The apparatus of any one of Examples 7 and 8, wherein: at least a portion of the second optical structure is interposed between the first deep impurity and the second deep impurity, or the first deep impurity and the second deep impurity are disposed within the second optical structure.

[0181] Example 10: The apparatus of any one of Examples 1-9, further comprising a pair of electrodes positioned to apply an electric field to the first optical structure straddling the first optical structure.

[0182] Example 11: The apparatus of any one of Examples 1-10, further comprising a waveguide optically coupled to the first optical structure to optically probe an optical state of the first optical structure.

[0183] Example 12: A method of operation for a quantum information processor, the quantum information processor including one or more optical structures integrated with a semiconductor substrate, a plurality of deep impurities disposed in the semiconductor substrate, and wherein each of the deep impurities is characterized by a plurality of quantum states corresponding to different electronic or nuclear spin states of the deep impurities and representing quantum information, the method comprising: initializing a first deep impurity of the plurality of deep impurities to a first reference state; initializing a second deep impurity of the plurality of deep impurities to the first reference state; causing an optical structure proximate to the first deep impurity and the second deep impurity to resonate with the first deep impurity and the second deep impurity; and measuring an optical state of the optical structure as a measure of the information represented by the quantum states of the first deep impurity and the second deep impurity.

[0184] Example 13: The method of example 12, wherein the first deep impurity is a double donor, and the method further comprises ionizing the first deep impurity to a singly ionized state.

[0185] Example 14: The method of any of examples 12 and 13, wherein initializing the first deep impurity of the plurality of deep impurities further comprises initializing the first deep impurity of the plurality of deep impurities to at least one of: a nuclear spin state as a second reference state of the first deep impurity; an electronic spin state as a third reference state of the first deep impurity; and a combined electronic spin and nuclear spin state as a fourth reference state of the first deep impurity.

[0186] Example 15: The method of any of examples 12-14, wherein the optical structure is a first optical resonator having a first photonic mode with a first resonator frequency.

[0187] Example 16: The method of any of examples 12-15, wherein the optical structure is an optical waveguide having one or more propagating modes and frequencies carrying quantum information.

[0188] Example 17: The method of any of examples 12-16, wherein another optical structure is proximate to the second deep impurity, the method further comprising: tuning the other optical structure to resonate with the optical structure, the first deep impurity, and the second deep impurity.

[0189] Example 18: The method of any of examples 12-17, wherein causing the optical structure proximate to the first deep impurity and the second deep impurity to resonate with the first deep impurity and the second deep impurity further comprises: tuning the first deep impurity toward a transition frequency that matches a resonant frequency of the optical structure.

[0190] Example 19: The method of any one of Examples 12-18, wherein causing the optical structure proximate to the first deep impurity and the second deep impurity to resonate with the first deep impurity and the second deep impurity further comprises: applying a magnetic field with a spatial gradient to the first deep impurity and the second deep impurity, wherein the magnetic field has a first value at the first deep impurity and a second value at the second deep impurity.

[0191] Example 20: The method of any one of Examples 12-19, wherein causing the optical structure proximate to the first deep impurity and the second deep impurity to resonate with the first deep impurity and the second deep impurity further comprises: applying a force to the semiconductor substrate to modify a strain in the semiconductor substrate proximate to the optical structure.

[0192] Example 21 : The method of any one of Examples 12-20, wherein causing the optical structure proximate to the first deep impurity and the second deep impurity to resonate with the first deep impurity and the second deep impurity further comprises: injecting a plurality of carriers into the semiconductor substrate proximate to the optical structure to electronically couple the first deep impurity and the second deep impurity.

[0193] Example 22: The method of any one of Examples 12-21, further comprising: applying a pulsed magnetic field to the first deep impurity to change a state of the first deep impurity.

[0194] Example 23: The method of any one of Examples 12-22, wherein measuring the state of the optical structure further comprises: measuring a presence or absence of a photon in the optical structure.

[0195] Example 24: The method of any one of Examples 12-22, wherein measuring the state of the optical structure further comprises: measuring a frequency shift in a resonant frequency of the optical structure.

[0196] Example 25: A method of operation for a quantum information processor comprising an impurity atom implanted in a semiconductor substrate, the method comprising: initializing the impurity atom to a reference state; applying a pulsed electromagnetic field to change a state of the first impurity atom; causing an optical structure proximate to the impurity atom to optically resonate with the impurity atom; and measuring a state of the optical structure.

[0197] Example 26: The method of Example 25, wherein the impurity atom is a double impurity, the method further comprising: ionizing the impurity atom to form a single ionized impurity atom.

[0198] Example 27: The method of example 25 or 26, further comprising: applying a positive voltage to an electrode overlying the semiconductor substrate and the donor atoms to change a state of the donor atoms.

[0199] Example 28: The method of examples 25-27, wherein the first donor atom has a transition frequency, and causing the optical structure proximate to the donor atom to optically resonate with the first donor atom further comprises: tuning the transition frequency of the first donor atom toward a frequency that matches a resonance frequency of the optical structure.

[0200] Example 29: The method of any of examples 25-28, wherein causing the optical structure proximate to the donor atom to optically resonate with the first donor atom further comprises: applying a force to the semiconductor substrate to modify a resonance geometry of the optical structure or a transition frequency of the first donor atom.

[0201] Example 30: The method of any of examples 25-29, wherein causing the optical structure proximate to the donor atom to optically resonate with the first donor atom comprises: injecting a plurality of carriers into the semiconductor substrate proximate to the optical structure to modify a resonance frequency in the optical structure.

[0202] Example 31 : The method of any of examples 25-30, wherein measuring the state of the optical structure further comprises: measuring a presence or absence of a photon in the optical structure, or measuring a frequency shift in a resonance frequency of the optical structure.

[0203] Example 32: A method for operation of a quantum information processor including a deep impurity disposed in a semiconductor substrate, wherein the deep impurity has two or more different quantum states representing information. The method comprises: receiving a first photon having a first quantum state at an optical structure optically coupled to the deep impurity; and forming a second quantum state in the deep impurity depending on the first quantum state at the optical structure.

[0204] Example 33: The method of example 32, further comprising: forming a second photon having a third quantum state at the optical structure depending on the second quantum state in the deep impurity; and causing emission of the second photon having the third quantum state.

[0205] Example 34: The method of example 33, wherein causing emission of the second photon having the third quantum state further comprises: optically or electrically triggering emission of the second photon.

[0206] Example 35: The method of example 32, wherein the quantum information processor is a photonic memory.

[0207] Example 36: A method for operating a quantum information processor comprising a deep impurity disposed in a semiconductor substrate, wherein the deep impurity has two or more different quantum states representing information, the method comprising: forming a first quantum state of the deep impurity in the semiconductor substrate; optically coupling the deep impurity to an optical structure; and causing a photon having a second quantum state to be formed at the optical structure in dependence on the first quantum state in the deep impurity.

[0208] Example 37: The method of example 36, further comprising: optically coupling the optical structure to a waveguide; and causing the photon having the second quantum state to be emitted into the waveguide at the optical structure.

[0209] Example 38: The method of example 37, wherein causing the photon having the second quantum state to be emitted into the waveguide further comprises: optically or electrically triggering emission of the second photon.

[0210] Example 39: The method of any one of examples 37 or 38, wherein the quantum information processor is a single-photon source.

[0211] Example 40: A quantum information processing system comprising: a processor-based device including at least one processor; a quantum information processor, wherein the quantum information processor includes a semiconductor substrate, a plurality of non-gaseous chalcogen donor atoms disposed within the semiconductor substrate, wherein a first respective donor atom of the plurality of non-gaseous chalcogen donor atoms has a first transition having a first transition frequency, and a plurality of optical resonators physically coupled to the semiconductor substrate, wherein a first respective optical resonator of the plurality of optical resonators is selectively coupled to the first respective donor atom of the plurality of non-gaseous chalcogen donor atoms; and a plurality of communication lines providing communication between the processor-based device and the quantum information processor.

[0212] Example 41: The system of example 40, wherein: the plurality of non-gaseous chalcogen donor atoms includes a second respective donor atom; the first respective optical resonator of the plurality of optical resonators has a first resonator frequency; the second respective donor atom of the plurality of non-gaseous chalcogen donor atoms is selectively coupled to the first respective optical resonator and has a second transition having a second transition frequency; and the first resonator frequency matches the first transition frequency and the second transition frequency.

[0213] Example 42: The system of Example 40 or 41, wherein: the plurality of optical resonators further includes a second respective optical resonator having a second resonator frequency; the second respective optical resonator is selectively coupled to the second respective donor atom of the plurality of non-gaseous chalcogen donor atoms; the second transition frequency matches the second resonator frequency; and the first resonator frequency matches the second resonator frequency.

[0214] Example 43: The system of any one of Examples 40-42, wherein the first respective donor atom of the plurality of non-gaseous chalcogen donor atoms is disposed at a depth greater than ten nanometers in the semiconductor substrate.

[0215] Example 44: The system of any one of Examples 40-43, wherein the first respective donor atom of the plurality of non-gaseous chalcogen donor atoms is a deep level donor having a thermal energy kT at room temperature substantially greater than an ionization energy of T. B

[0216] Example 45: The system of any one of Examples 40-44, further comprising an environment subsystem that controls parameters of an environment in which the quantum information processor operates, the parameters including one or more of humidity, air pressure, vibration, magnetic field, temperature, and electromagnetic field.

[0217] Example 46: The system of any one of Examples 40-45, further comprising: at least one legacy communication channel in communication with the at least one processor; and a network interface subsystem that, when in operation, supports bidirectional communication of processor-readable data over the at least one legacy communication channel.

[0218] Example 47: The system of any one of Examples 40-46, further comprising: a waveguide optically coupled to the first respective non-gaseous chalcogen donor atom of the plurality of non-gaseous chalcogen donor atoms disposed within the semiconductor substrate.

[0219] Example 48: The system of any one of Examples 40-47, wherein the first respective non-gaseous chalcogen donor atom of the plurality of non-gaseous chalcogen donor atoms has a plurality of energy levels or states identified as electronic spin states, nuclear spin states, and combined electronic and nuclear spin states, and wherein a selected pair of the plurality of energy levels or states is designated as a pair of computational states of the first respective non-gaseous chalcogen donor atom.

[0220] ​Example 49: The system of any one of Examples 40-48, wherein: the first respective non-gaseous chalcogen donor atom of the plurality of non-gaseous chalcogen donor atoms comprises a pair of computational states; and the pair of computational states is selected from the group consisting of: a first value of a nuclear spin state of the first respective non-gaseous chalcogen donor atom and a second value of the nuclear spin state of the first respective non-gaseous chalcogen donor atom; a first value of an electron spin state of the first respective non-gaseous chalcogen donor atom and a second value of the electron spin state of the first respective non-gaseous chalcogen donor atom; and a first value of a nuclear spin and an electron spin of the first respective non-gaseous chalcogen donor atom, and a plurality of values of the nuclear spin and the electron spin of the first respective non-gaseous chalcogen donor atom, wherein the first value of the nuclear spin and the electron spin is a singlet, and the plurality of values of the nuclear spin and the electron spin of the respective non-gaseous chalcogen donor atom is a triplet.

[0221] Example 50: The system of any one of Examples 40-49, further comprising a quantum input subsystem in communication with the at least one processor and a quantum information processor.

[0222] Example 51 : The system of Example 50, wherein the quantum input subsystem includes a pair of electrodes proximate to the first respective non-gaseous chalcogen donor atom disposed within the semiconductor substrate; and wherein the at least one processor causes the quantum input subsystem to apply an electric field to the first respective non-gaseous chalcogen donor atom disposed within the semiconductor substrate via the plurality of communication lines and the pair of electrodes.

[0223] Example 52: The system of any one of Examples 50-51, wherein the quantum input subsystem includes: a pair of electrodes disposed proximate to one or more portions of a quantum information processor; and wherein the at least one processor causes the quantum input subsystem to change a number of electrical carriers to one or more portions of a quantum information processor via the plurality of communication lines and the pair of electrodes.

[0224] Example 53: The system of any one of Examples 50-52, wherein the one or more portions of a quantum information processor include the first respective optical resonator of the plurality of optical resonators.

[0225] Example 54: The system of any one of Examples 50-53, wherein the one or more portions of a quantum information processor include the first respective non-gaseous chalcogen donor atom of the plurality of non-gaseous chalcogen donor atoms disposed within the semiconductor substrate.

[0226] Example 55: The system of any one of Examples 50-54, wherein the quantum input subsystem includes an electromagnet proximate to the quantum information processor; and wherein the at least one processor, via the plurality of communication lines, causes the quantum input subsystem to apply a magnetic field to one or more portions of a quantum information processor via the plurality of communication lines and the electromagnet.

[0227] Example 56: The system of any one of Examples 40-55, wherein: the one or more portions of a quantum information processor include the plurality of non-gaseous chalcogen donor atoms disposed within the semiconductor substrate; and the magnetic field includes a spatial gradient within a spatial extent of the plurality of non-gaseous chalcogen donor atoms.

[0228] Example 57: The system of Example 56, wherein the magnetic field changes the first transition and the first transition frequency of the first respective donor atom of the plurality of non-gaseous chalcogen donor atoms.

[0229] Example 58: The system of any one of Examples 40-57, wherein: the plurality of non-gaseous chalcogen donor atoms includes a plurality of nuclear spins; the first respective non-gaseous chalcogen donor atom of the plurality of non-gaseous chalcogen donor atoms includes a first respective nuclear spin of the plurality of nuclear spins; the first respective nuclear spin includes a first nuclear resonance frequency; and the magnetic field is applied along a transverse direction to cause the first respective nuclear spin of the plurality of nuclear spins to have a sinusoidal temporal oscillation at a rate corresponding to the nuclear resonance frequency.

[0230] Example 59: The system of any one of Examples 40-58, further comprising: a variable length device embedded in the semiconductor substrate, wherein the at least one processor, via the quantum input subsystem and the plurality of communication lines, causes the variable length device to change a length to affect a strain on a proximate region of the semiconductor substrate.

[0231] Example 60: The system of any one of Examples 40-59, wherein the proximate region of the semiconductor substrate includes at least one of: the first respective non-gaseous chalcogen donor atom of the plurality of non-gaseous chalcogen donor atoms disposed within the semiconductor substrate; and the first respective optical resonator of the plurality of optical resonators selectively coupled to the first respective donor atom of the plurality of non-gaseous chalcogen donor atoms.

[0232] Example 61: The system of any one of Examples 40-60, wherein the variable length device is a piezoelectric material device or a microelectromechanical system.

[0233] Example 62: The system of any one of Examples 40-61, wherein the at least one processor causes the quantum input subsystem to apply one or more magnetic resonance control operations to one or more of the plurality of non-gaseous chalcogen donor atoms disposed within the semiconductor substrate.

[0234] Example 63: The system of any one of Examples 40-62, wherein the one or more magnetic resonance control operations include one or more of: an electron spin resonance operation; a nuclear magnetic resonance operation; a single-qubit operation; and a multi-qubit operation.

[0235] Example 64: The system of any one of Examples 40-63, further comprising a quantum output subsystem in communication with the at least one processor.

[0236] Example 65: The system of any one of Examples 40-64, wherein the at least one processor causes the quantum output subsystem to measure a state of one or more of the plurality of non-gaseous chalcogen donor atoms disposed within the semiconductor substrate.

[0237] Example 66: The system of any one of Examples 40-65, wherein the quantum output subsystem includes an optical measurement device, and the at least one processor causes the optical measurement device to measure a state of the first respective optical resonator of the plurality of optical resonators physically coupled to the semiconductor substrate.

[0238] Example 67: The system of any one of Examples 40-66, wherein the optical measurement device measures a frequency shift of the first resonator frequency of the first respective optical resonator of the plurality of optical resonators physically coupled to the semiconductor substrate.

[0239] Example 68: The system of any one of Examples 40-67, wherein the optical measurement device measures a presence or absence of a photon in the first respective optical resonator of the plurality of optical resonators physically coupled to the semiconductor substrate.

[0240] Example 69: An information processing device comprising: a semiconductor substrate; a first deep impurity disposed within the semiconductor substrate, wherein the first deep impurity has a first ground state, a second ground state, and an optical transition between the first ground state and the second ground state; and a first optical structure physically coupled to the semiconductor substrate optically coupled to the first deep impurity.

[0241] Example 70: The device of Example 69, wherein the deep impurity has a substantially greater thermal energy kB Ionization energy of T.

[0242] Example 71 : The device of Example 69 or 70, wherein the deep impurity is a stable, non-gaseous chalcogen atom.

[0243] Example 72: The device of Example 71, wherein the stable, non-gaseous chalcogen atom is a sulfur atom, a selenium atom, or a tellurium atom.

[0244] Example 73: The device of any of Examples 69-72, wherein the deep level donor is a metal atom or a metal cluster.

[0245] Example 74: The device of Example 73, wherein the metal atom is a transition metal element.

[0246] Example 75: The device of Example 73, wherein the metal atom is a lithium atom, a beryllium atom, or a magnesium atom.

[0247] Example 76: The device of Example 73, wherein the metal cluster consists essentially of four atoms or five atoms.

[0248] Example 77: The device of any of Examples 73 or 76, wherein the metal cluster includes one or more atoms selected from the group consisting of copper, silver, gold, and platinum.

[0249] Example 78: The device of any of Examples 69-73, 76, or 77, wherein the deep impurity includes copper and sulfur.

[0250] Example 79: The device of any of Examples 69-73, 76, 77, or 78, wherein the deep impurity is S A center or S B center.

[0251] Example 80: The device of any of Examples 69-79, wherein the semiconductor substrate is made of silicon that includes more than 95% non-paramagnetic silicon isotopes.

[0252] Example 81 : The device of any of Examples 69-80, wherein the semiconductor substrate includes silicon carbide or silicon germanium.

[0253] Example 82: The device of any of Examples 69-81, wherein the first base state or the second base state is an electron spin state, a nuclear spin state, and a combined electron and nuclear spin state.

[0254] Example 83: The device of any of Examples 69-82, further comprising an acceptor disposed with the semiconductor substrate.

[0255] Example 84: The device of Example 83, wherein the acceptor is boron, aluminum, gallium, or indium.

[0256] The term about modifying a numerical quantity means plus or minus ten percent (10%), unless otherwise stated herein or unless context clearly indicates otherwise. Between two numerals, is to be interpreted as between, and including, the two numerals, unless otherwise indicated or unless context clearly indicates otherwise.

[0257] In the foregoing description, some specific details are included to provide an understanding of various disclosed implementations. One skilled in the relevant art, however, will recognize that implementations can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In some instances, well-known structures associated with semiconductor and / or optical devices and / or quantum computing and / or quantum information processing, such as targets, substrates, lenses, waveguides, shields, filters, lasers, processor-executable instructions (e.g., BIOS, drivers), are not shown or described in detail in order to avoid unnecessarily obscuring descriptions of the described implementations.

[0258] In this specification and the appended claims, "a," "an," or "another" applied to "one embodiment," "one example," or "one implementation" are used in the sense of at least one of the referenced embodiment, example, or implementation. Thus, for example, the phrase "in one embodiment," "in an embodiment," or "another embodiment" does not necessarily refer to the same embodiment, example, or implementation. Furthermore, the particular features, structures, or characteristics can be combined in any suitable manner in one or more embodiments, examples, or implementations.

[0259] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates otherwise. It should also be noted that the term "or" is generally employed in its sense including "and / or" unless the context clearly dictates otherwise.

[0260] Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise," "comprising," and the like are to be construed in an open, non- limiting sense, as meaning "including, but not limited to."

[0261] All of the U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications, and non-patent publications referred to in this specification or in any application data sheet including U.S. Provisional Application No. 62 / 260,391 (filed November 27, 2015) are incorporated herein by reference in their entireties for all purposes.

[0262] While certain features of the described embodiments and implementations have been illustrated, it will now be apparent to those persons skilled in the art that many modifications, substitutions, changes, and equivalents can be made to the embodiments and implementations described without departing from the scope of the described embodiments and implementations. It is therefore intended that the appended claims be construed to cover all such modifications and changes as fall within the true scope of the described embodiments and implementations.

Claims

1. An information processing device comprising: a semiconductor substrate; a deep impurity disposed within the semiconductor substrate, the deep impurity having a plurality of spin-selective optical transitions; an optical structure coupled to the semiconductor substrate and having one or more photonic modes; a controller configured to manipulate a quantum state of the deep impurity by applying at least one of a magnetic field, an electric field, or a mechanical strain to the semiconductor substrate to cause a subset of the spin-selective optical transitions of the deep impurity to couple to a first one of the photonic modes of the optical structure; an optical detector; and a quantum information channel arranged to collect photons from the optical structure and carry the photons to the optical detector, wherein the optical detector is configured to determine a number of photons received from the quantum information channel and infer the quantum state of the deep impurity based on the number of photons.

2. The information processing device of claim 1, wherein the deep impurity has a quantum state comprising a superposition of a first quantum ground state and a second quantum ground state, wherein the first and second quantum ground states comprise distinct first and second spin ground states of the deep impurity, respectively, each having a non-zero electron spin, wherein the deep impurity has an excited state and the spin-selective optical transitions are transitions between the spin ground states to the excited state.

3. The information processing device of claim 1, wherein the optical detector is configured to infer the quantum state of the deep impurity based on an optical intensity of the photons.

4. The information processing device of claim 1, wherein the quantum information channel includes a chiral waveguide that directs oppositely circularly polarized photons into opposite spatial directions such that the photons are emitted into a path superposition corresponding to a superposition spin state of the deep impurity.

5. The information processing device of claim 1, wherein the photonic modes of the optical structure depend on the quantum state of the deep impurity.

6. The information processing device of any one of claims 1-5, comprising a light source configured to direct photons into the optical structure.

7. The information processing device of claim 6, wherein a frequency of the photons from the light source matches the frequency of the photonic modes of the optical structure.

8. The information processing device of claim 7, wherein the deep impurity is operable to absorb and later re-emit resonant photons and non-resonant photons are reflected such that after a frequency-matched photon interacts with the deep impurity, an output photon is entangled with a spin state of the deep impurity in time.

9. The information processing device of claim 1, wherein the optical detector is configured to infer the quantum state of the photons received from the quantum information channel by detecting a change in a property of the photons. ​ 10. The information processing apparatus of claim 9, wherein the property of the photon comprises at least one of: optical polarization, number of photons, optical intensity, relative indistinguishability of multiple photons, optical frequency, detection time, and spatial distribution of photons.

11. The information processing apparatus of claim 1, comprising two or more of the deep impurities optically coupled to the optical structure, wherein the controller is configured to infer the parity of the spin state of the two or more deep impurities by measuring an optical frequency or other optical characteristic of the optical structure.

12. The information processing device of any one of claims 1-5, comprising two or more of the deep impurities optically coupled to the optical structure, wherein each of the deep impurities is characterized by a plurality of quantum states corresponding to different electronic or nuclear spin states of the deep impurity, and the controller is configured to initialize a first one of the deep impurities to a first reference state; initializing a second of the deep impurities to the first reference state; causing the optical structure to resonate with the first and second of the deep impurities; and measuring an optical state of the optical structure as a measurement of information represented by the quantum state of the first and second of the deep impurities.

13. The information processing apparatus of any one of claims 1-5, wherein the controller is configured to cause a light source to transmit light onto the optical structure and infer a quantum state of the deep impurities based on data related to reflection and / or absorption of the transmitted light.

14. The information processing apparatus of claim 13, wherein the light source is operable to emit blackbody light having a non-trivial spectral density at a resonance of the optical structure.

15. The information processing apparatus of any one of claims 1-5, comprising one or more electrodes proximate to the optical structure and the deep impurities and a control subsystem operable to modulate the deep impurities via injection of electrical carriers through electrodes proximate to the optical structure.

16. The information processing apparatus according to any one of Claims 1-5, wherein the deep impurity has an ionization energy substantially greater than the thermal energy k B T, where k B is the Boltzmann constant and T is room temperature.

17. The information processing apparatus of any one of claims 1-5, wherein the deep impurities are located at an anti-node of the photonic mode of the optical structure.

18. The information processing apparatus of any one of claims 1-5, wherein the semiconductor substrate comprises silicon carbide or silicon germanium.

19. The information processing apparatus of any one of claims 1-5, wherein the semiconductor substrate is made of silicon comprising more than 95% of non-paramagnetic silicon isotopes.

20. The information processing apparatus of any one of claims 1-5, comprising a subsystem operable to electrically or optically trigger the deep impurities to emit photons.

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