Advanced processing elements and systems

Abstract

A processing element for a quantum processing device is disclosed. The processing element comprises: a silicon substrate; a dielectric material, wherein the silicon substrate and the dielectric material form an interface; an electrode formed on the dielectric material for isolating one or more electrons in the silicon substrate to form a quantum dot; a group IV atom having a nuclear spin located in a wave function of the one or more electrons, the nuclear spin of the group IV atom being entangled with the one or more electrons; and a control arrangement for controlling quantum properties of the quantum dot and / or the nuclear spin to operate as a qubit.

Description

Technical Field

[0001] This disclosure relates to a processing element for an advanced processing system, and particularly, but not exclusively, to a quantum processing system and a processing element for a quantum processing system. Background Technology

[0002] The developments described in this section are known to the inventors. However, unless otherwise indicated, they should not be assumed to be prior art or known to those skilled in the art simply because any of the developments described in this section is included in this section.

[0003] Large-scale quantum processing systems hold the promise of a technological revolution, offering the potential to solve problems that classical machines cannot. To date, many different structures, materials, and architectures have been proposed to realize quantum processing systems and fabricate their fundamental information units (or qubits).

[0004] For example, one way to manufacture qubits is by using silicon quantum dots. In this case, the quantum dots are made using... 28 An interface is formed between the Si substrate and the dielectric material. A confining arrangement is used to confine one or more electrons in the silicon substrate to form a quantum dot, and a control arrangement (e.g., a gate) is formed on the dielectric material to control the confined electrons (e.g., by applying a voltage to tune the electron spin resonance frequency of the confined electrons). A technique for fabricating such quantum dots and a processing system utilizing these quantum dots are described in international patent applications PCT / AU2014 / 000596 and PCT / AU2016 / 050713, both of which are incorporated herein by reference in their entirety.

[0005] When multiple such quantum dots are fabricated at appropriate distances from each other, quantum information can move through the quantum dot array via electron spin shuttle or exchange-mediated coupling.

[0006] Spin-based qubits exhibit high control fidelity and can be fabricated using existing techniques to create metal-oxide-semiconductor field-effect transistors (MOSFETs), making them a popular choice for semiconductor-based qubits. However, they can be affected by short coherence times.

[0007] Therefore, an improvement is desired. Summary of the Invention

[0008] According to an aspect of this disclosure, a processing element for a quantum processing device is provided, the processing element comprising: a silicon substrate; a dielectric material, wherein the silicon substrate and the dielectric material form an interface; an electrode formed on the dielectric material for isolating one or more electrons in the silicon substrate to form a quantum dot; a group IV atom whose nuclear spin is located in the wavefunction of one or more electrons, wherein the nuclear spin of the group IV atom is entangled with one or more electrons; and a control arrangement for controlling the quantum properties of the quantum dot and / or the nuclear spin of the group IV atom for qubit operation.

[0009] In some embodiments, the atom can be 29 Si atoms. In other embodiments, the atom may be an atom of a group IV isotope having nuclear spin. For example, the atom may be germanium-73 with a spin of 9 / 2. 73 Ge atom. In other examples, the atom can be carbon-13 (Ge). 13 C) Atoms, Tin-115 ( 115 Sn), Tin-117 117 Sn) or Tin-119 119 Sn) atoms.

[0010] In some embodiments where the atoms are silicon-29 atoms, the silicon substrate is isotopically enriched. 28 Si substrate. In some embodiments, isotope enriched... 28 The Si substrate contains less than or equal to 800 ppm 29 Si atoms. It will be recognized that... 29 Si atoms can exist naturally in isotope-rich environments. 28 In Si substrate, or 29 Si atoms can be designed to be pure 28 In the Si substrate—that is, within the wave function of the quantum dot electrons.

[0011] Furthermore, the diameter of the quantum dot electronic wavefunction of the processing element can be less than or approximately 50 nm. In some preferred embodiments, the diameter can be less than or approximately 15 nm.

[0012] It will be recognized that the nuclear spin of group IV atoms can become entangled with the electrons of quantum dots through a variety of mechanisms. One such mechanism is the hyperfine interaction between the electron and the nuclear spin. The strength of the hyperfine interaction can vary depending on the size of the electron waveform diameter and the position of the group IV atom within the waveform. In some embodiments, the hyperfine interaction between the electron and the group IV atom is between approximately 100 kHz and 1 MHz.

[0013] According to another aspect of this disclosure, a method for operating a plurality of quantum processing elements is provided, each quantum processing element comprising: a silicon substrate; a dielectric material, wherein the silicon substrate and the dielectric material form an interface; an electrode formed on the dielectric material for isolating one or more electrons in the silicon substrate to form a quantum dot; a group IV atom whose nuclear spin is located in the wave function of one or more electrons, the nuclear spin of the group IV atom being entangled with the one or more electrons; and a control arrangement for controlling the quantum properties and / or nuclear spin of the quantum dot to operate as a qubit. The method includes the step of: applying a signal via the control arrangement to control the state of the qubits in the quantum processing element.

[0014] In some embodiments, the method further includes: applying a signal via a controlled arrangement to store information in a qubit. This may include: applying a signal to store information in the electron spin of the quantum dot; and swapping that information from the electron spin to... 29 The nuclear spin of a Si atom.

[0015] In some embodiments, the method further includes: transferring information from a first processing element of a plurality of processing elements to a second processing element of a plurality of processing elements. This includes: exchanging information from the nuclear spins of group IV atoms of the first processing element to the electron spins of the first processing element; transferring the electron spins from the first processing element to a quantum dot of the second processing element; entanglement of the transferred electron spins with the nuclear spins of group IV atoms of the second processing element; and exchanging quantum information from the transferred electron spins to the nuclear spins of group IV atoms of the second processing element.

[0016] According to another embodiment, a method for manufacturing an advanced processing device is disclosed. The method includes the steps of: manufacturing a plurality of processing elements by: providing... 28 A silicon substrate with a Si layer; so that the dielectric layer and 28 A dielectric layer is formed by forming an interface with a Si layer; multiple electrodes are formed, which are adapted to isolate one or more electrons around the interface to define multiple quantum dots; one or more group IV atoms are positioned such that the nuclear spins of the one or more group IV atoms are entangled with the electrons of the quantum dots, such that the quantum dots and the nuclear spin pairs operate as qubits; multiple control components, including switches, are formed, which are arranged to interact with the multiple electrodes; and multiple control lines are formed; each control line is connected to one or more control components to enable simultaneous operation of multiple processing elements; wherein the multiple electrodes, control components, and control lines are formed using a silicon metal-oxide-semiconductor (SiMOS) fabrication process.

[0017] A quantum processing device is also disclosed, comprising: a plurality of quantum processing elements arranged in a matrix, each processing element including: a silicon substrate forming an interface and a dielectric material; an electrode arrangement adapted to confine one or more electrons in silicon to form a quantum dot, and nuclear spins entangled with one or more electrons; a plurality of control components disposed around the processing elements; each control component including one or more switches arranged to interact with the electrode arrangement to perform quantum operations using the processing elements; and a plurality of control lines; each control line connected to the plurality of control components to enable simultaneous operation of the plurality of processing elements. Attached Figure Description

[0018] Figure 1A This is a plan view of a processing element according to some aspects of this disclosure.

[0019] Figure 1B yes Figure 1A A cross-sectional view of the processing element.

[0020] Figure 2A This is a cross-sectional view of a quantum device according to some aspects of this disclosure.

[0021] Figure 2B yes Figure 2A A plan view of a quantum device.

[0022] Figure 3 This is a schematic circuit representation illustrating the transmission of quantum information.

[0023] Figure 4A This is a graph illustrating the stability of a dual quantum dot, showing the charge state of each quantum dot in relation to the gate bias.

[0024] Figure 4B It is a graph showing the nuclear spin readout bias sequence.

[0025] Figure 5 This is a graph showing the frequency scans used for nuclear spin readout.

[0026] Figure 6A This is a reservoir-based readout graph showing the electron spin-up probability for five frequency scans.

[0027] Figure 6B This is a graph showing the electron spin-up probability measured for a frequency scan after subtracting the average of the two resonance peaks.

[0028] Figure 7A This is a diagram illustrating the Rabi oscillations of nuclear spin.

[0029] Figure 7B It is the Rabi chevron pattern for unloaded quantum dots.

[0030] Figure 7C It is a Rabi V-shaped pattern in which spin-down electrons are loaded into a quantum dot.

[0031] Figure 8A This illustrates nuclear spin T2 for different charge configurations of two quantum dots. * and T2 Hahn Measured charts.

[0032] Figure 8B It shows from Figure 8A The table contains the measured values ​​of coherence time and decay exponent for nuclear spin extracted from the measurements.

[0033] Figure 9 This is a schematic diagram illustrating example entanglement sequences for entanglement of electron and nuclear spins according to some embodiments of the present disclosure.

[0034] Figure 10A-10F The state tomography of the Bell state is shown.

[0035] While the invention is open to various modifications and alternatives, specific embodiments are illustrated by way of example and described in detail in the accompanying drawings. However, it should be understood that the drawings and detailed descriptions are not intended to limit the invention to the specific forms disclosed. The invention is to be covered by all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. Detailed Implementation

[0036] Typically, the surface silicon layer in which the gate-based quantum dots are formed isotopically enriched to primarily contain 28 Si atoms, known 28 Si atoms do not have their own nuclear spin, and therefore allow for long coherence times in the resulting quantum dots. Even isotopically enriched silicon typically contains small amounts of... 29 Si atoms. These 29 Si atoms have nuclear spin, which can sometimes affect the coherence time of quantum dots.

[0037] However, the inventors of this application have discovered that, 29 The nuclear spin of a Si atom can interact closely with nearby quantum dots, especially with the electron spin of nearby quantum dots (e.g., via hyperfine coupling), so that pairs of nuclear spin and quantum dots can form qubits.

[0038] Electron spins typically have poor information storage capacity (e.g., electron spins can usually store information for 5-10 microseconds), but they are highly mobile and can be used to move information around in quantum processing systems. On the other hand, nuclear spins have good storage capacity (e.g., nuclear spins can typically store information for 5-10 milliseconds), but nuclear spins are fixed in the crystal lattice and cannot move, and are generally not suitable for transmitting information.

[0039] In this disclosure, by combining quantum dots with 29 Combining silicon atoms allows them to utilize the properties of electrons and nuclear spins to form processing elements, resulting in elements with high information storage capacity and high mobility. In one example, quantum information can be stored in nuclear spins until it is ready for manipulation, at which point it is exchanged back for electrons in the quantum dot.

[0040] To form such processing devices, quantum dots need to be small enough, and 29 The density of Si atoms needs to be high enough so that the electron spin of the quantum dot is similar to that of the surrounding atoms. 29 There is strong hyperfine coupling between Si atoms (relative to the electron spin resonance linewidth). In some embodiments, the wavefunction diameter of the electrons in the quantum dot is less than 50 nm, and in some preferred embodiments, the diameter is about 15 nm or less (e.g., between 8-15 nm). In this case, the silicon substrate... 29 The density of Si atoms can be between 50 and 800 ppm.

[0041] It will be recognized that, in certain situations, for example, when 29 When the density of Si atoms is low or they are naturally absent in the silicon substrate (e.g., if the silicon substrate is pure...) 28 Si substrate), 29 Si atoms can be precisely placed within the wavefunction of (multiple) electrons of a quantum dot (e.g., via ion implantation), making it possible to... 29 Si atoms are entangled with (multiple) electrons.

[0042] The strength of the hyperfine interaction between electrons and nuclear spins is determined by the magnitude of the wavefunction of the electron in the quantum dot and 29 The position of the Si atom within this wavefunction determines its orientation. The more strongly the quantum dot is confined (i.e., the smaller the quantum dot), the smaller its electron wavefunction, and the greater the hyperfine coupling between the electron and the nuclear spin located within the electron wavefunction.

[0043] Therefore, it will be recognized that if the quantum dot is too large, its wavefunction will be large, resulting in a smaller hyperfine interaction between the electron and the nuclear spin located in the electron's wavefunction. Similarly, if29 The high density of Si leads to a large amount of 29 Si atoms can be located in the wave function of electrons, these 29 Si atoms can be used as background noise and to reduce the coherence time of quantum dots. Alternatively, if 29 Since Si has a low density and its quantum dots are very small, 29 Si atoms may not be located in the small wavefunction of electrons, and therefore may not be entangled with the electron spins of the quantum dot. Therefore, the size of the quantum dot and... 29 The balance between Si atomic densities is important.

[0044] In order to allow 29 Entanglement between the Si nuclear spin and the quantum dot electron spin states, and manipulating this pair as qubits, requires a specific operating frequency. Furthermore, for qubits to transmit information along the quantum processing system, the hyperfine coupling between the electron and the qubit's nuclear spin should allow quantum information to move through the quantum dot array via spin shuttle or exchange-mediated coupling. For example, the hyperfine coupling between electron and nuclear spin may be weaker than the coupling between quantum dots.

[0045] It will be recognized that the resulting qubits can be used to form quantum processing systems based on nuclear spin or electron spin. Furthermore, the resulting devices can function as memory devices for storing quantum information, as information processing devices, or both.

[0046] Referring to FIG1, a plan view of the processing element 100 according to an embodiment of the present disclosure is shown. Figure 1A ) and side section view ( Figure 1B As shown in the diagram. Processing element 100 can be implemented as a qubit for a quantum computer that processes multiple of these processing elements.

[0047] In this embodiment, the processing element 100 includes a silicon substrate 102 and a dielectric 104. The silicon substrate 102 in this example is isotopically enriched silicon with a dielectric constant of less than or equal to 800 ppm. 29 The silicon atomic density is high, and the dielectric 104 is silicon dioxide. Isotopically enriched silicon can be an epitaxial layer grown on a conventional silicon substrate. It will be appreciated that, in other examples, the silicon substrate... 29 The density of Si atoms can vary and may fall outside this range. For example, in some cases, silicon substrates can have a density below 50 ppm, and 29 Si atoms can be designed or fabricated into silicon substrates, enabling 29 Si atoms are located in and around the wave function of (multiple) electrons in a quantum dot.

[0048] A gate electrode 106 is provided, and the gate electrode 106 is operable to form a quantum dot close to the Si / SiO2 interface. The gate electrode 106 is also arranged to modify the quantum properties of the quantum dot. In one example, the quantum dot comprises one or more electrons 108, and the gate electrode 106 is configured to control the effective g-factor of the electrons 108. Throughout this specification, the term "effective g-factor" is used broadly to indicate the ratio between the spin resonant frequency of a spin system and a DC magnetic field.

[0049] In addition to controlling the quantum properties of quantum dots, the gate electrode 106 can also be used to directly control the spin of electrons 108 using an AC electric field or magnetic field.

[0050] In order to form electrons 108 in the quantum dot, a sufficiently positive voltage is applied to the gate electrode 106. This results in the region below the gate 106 (see...) Figure 1B Electrons in region 122 are isolated. Figure 1B This illustrates how a single electron is isolated in region 122, thus forming an isolated quantum dot. The processing element 100 also includes elements located within the wavefunction of electron 108. 29 Si atoms 110, making 29 The nuclear spin of the Si atom is entangled with the electron 108 of the quantum dot. Therefore, a single quantum bit can be encoded in the spin of the isolated electron 108 and / or the entangled nuclear spin 110.

[0051] It will be recognized that the gate electrode 106 is also used for control. 29 The quantum properties of Si atoms and / or the control of nuclear spin. Additionally, the gate electrode 106 can be used to control... 29 The spin of the Si nucleus (e.g., using techniques similar to those used for electron spin resonance) exchanges quantum information between the nucleus and electron and / or between two such processing elements.

[0052] Figure 2 shows a cross-sectional view of a quantum device 200 according to an embodiment of the present disclosure. Figure 2A ) and plan view ( Figure 2B Device 200 may be a quantum memory, a quantum processor, or a combination of a quantum memory and a processor for storing information.

[0053] Quantum device 200 includes an isotope-enriched dielectric layer 204 on top. 28 Si layer 202. Gate electrodes 206A-206P are formed on dielectric layer 204. When a sufficiently large positive voltage is applied via the gate electrodes 206, one or more electrons 208 are isolated in the region below each gate electrode 206. These isolated electrodes 208 then interact with one or more of the wavefunctions located in each of the electrons 208. 29Si atoms are entangled to form entangled electrons and nuclear spins, in which quantum dots and 29 Each combination of Si atoms can be used to encode a qubit.

[0054] In the example shown, a 4×4 qubit array can be encoded in quantum device 200. In this case, an electromagnetic field can be applied to gate electrode 206 to control the inter-quantum dot coupling and the hyperfine coupling between electrons and nuclear spins in a particular processing element.

[0055] In some embodiments, the gate electrode 206, and therefore the quantum dot location, can be photolithographically defined anywhere on the quantum device 200, thus providing flexibility in device design. However, typically, a quantum device design fabricated on top of an 800 ppm isotope-enriched silicon substrate with a gate width less than 30 nm, separated by high-quality thermally grown oxide, will meet the requirements for forming such a processing element (i.e., optimal dot size and...). 29 (Si atomic density, and the trade-off between hyperfine coupling and point-to-point coupling).

[0056] Entanglement of nuclear and electron spins

[0057] The electron spin resonance (ESR) frequency (f) of entangled nuclei and electron spins ESR )for-

[0058] When the nuclear spin is up, f ESR =|γ e B|+A / 2,

[0059] When the nuclear spin is down, f ESR =|γ e B|-A / 2

[0060] Where, γ e A is the electron gyromagnetic ratio, B is the electron-nuclear hyperfine interaction, and C is the DC magnetic field. Furthermore, spin-up can be defined as a spin parallel to or aligned with the DC magnetic field (B), while spin-down can be defined as an antiparallel or oppositely aligned with the DC magnetic field.

[0061] A two-qubit operation known as the controlled-NOT (CNOT) gate was achieved by performing spin reversal using pi pulses at one of these frequencies, which can be used to generate entanglement.

[0062] Figure 6A This is a graph showing the nuclear magnetic resonance (NMR)-pi pulses (i.e., nuclear spin rotations) between five spin-inversion repetitions. Specifically, Figure 6AThe reservoir-based readout of electron spin-up probabilities for five frequency scans is shown. The nuclear spin rotates between each frequency scan, causing the ESR frequency to jump between two distinct values.

[0063] Figure 6B This is a graph showing the electron spin-up probability measured for a frequency sweep after subtracting the average of the two resonance peaks. The relative frequencies show the hyperfine coupling at approximately 450 kHz.

[0064] Figure 9 An example entanglement sequence for entanglement of electron and nuclear spins is shown. Specifically, the figure illustrates the sequence of gates used for entanglement. As shown, state preparation (i.e., the first stage) is performed with pi / 2(x) for the nuclear spin, followed by a CNOT gate (X) for the electron spin. State projection and readout can be performed via a series of pi / 2 gates for both electron and nuclear spins with different phases. A detailed example of generating electron-nuclear entanglement via conditional spins is described in Dehollain, JP et al.'s "Bell's inequality violation with spins in silicon" (Nat Nano 11, 242-246), and is incorporated herein in its entirety.

[0065] nuclear spin control

[0066] As previously noted, the gate electrode can be used for control. 29 The nuclear spin of Si atoms. In particular, the nuclear spin can be controlled via an AC magnetic field in the same way as the electron spin resonance of electrons in quantum dots.

[0067] Depending on whether the quantum dot is loaded with electrons, the resonance frequency will be

[0068] When no electrons are loaded, |γ_N B|

[0069] When electrons are loaded with spin down, |γ_N B|+A / 2

[0070] When electrons are loaded with spin-up, |γ_N B|-A / 2

[0071] Typical achievable rotating Rabi frequencies are between 1 and 10 kHz.

[0072] Figure 7A The graph shows the Rabi oscillations of nuclear spin, demonstrating nuclear spin control with a very high readout fidelity of >99%.

[0073] Figure 7BThis is a graph showing the Rabi V-shaped pattern for an unloaded quantum dot (i.e., no electrons are loaded into the quantum dot). The graph illustrates the detuning of the Rabi oscillations at the frequency.

[0074] Figure 7C This is a diagram illustrating the Rabi V-shaped pattern of a quantum dot with spin-down electrons loaded into it. The shift in resonant frequency gives a hyperfine coupling of 448.5 ± 0.1 kHz.

[0075] Storing quantum information

[0076] As previously noted, nuclear spins have a longer quantum memory storage capacity than electron spins. To take advantage of this, the processing elements of Figures 1 and 2 can be used to store quantum information in nuclear spins until the processing function requires that quantum information.

[0077] Therefore, once quantum information is encoded on the electron spin of a quantum dot using the mechanisms described in international patent applications PCT / AU2014 / 000596 and PCT / AU2016 / 050713, memory operations are performed to map the qubit information encoded in the electron spin state onto the nuclear spin state.

[0078] This operation, known as the SWAP operation, can be implemented using three controlled spins and typically includes three phases—initialization, transfer, and recovery. In one embodiment, nuclear initialization in a spin-up state is achieved using a sequence of microwave and / or RF pulses. Starting with a spin-down electronic state and an unknown nuclear spin state, the microwave pulse flips the electron to a spin-up state only if the nucleus is also in a spin-up state. In this case, the subsequent RF pulse detunes the nucleus and places it in the target spin-up state. Conversely, if the nucleus is initially spin-down, the microwave pulse detunes the electron, and the subsequent RF pulse flips the nucleus from a spin-down state to a spin-up state. With another electron readout / initialization step, the system is unconditionally prepared such that the electron is in a spin-down state and the nucleus is in a spin-up state.

[0079] During the transfer phase, to transfer quantum information from the electron to the nucleus, the first RF pulse conditionally transfers the spin-down component of the electron's spin state to the spin-down component of the nucleus, thus creating bi-quantum coherence between the electron and the nucleus if the electron has a spin-up component, or between the electron and the nucleus if the electron is spin-up or spin-down. Subsequent microwave pulses, conditioned on the nucleus's spin-up subspace, convert the spin-up electron and nucleus components to an electron-spin-down, nucleus-spin-up state, thereby placing the nucleus and electron spins, which contain all quantum information, in a spin-down eigenstate. The memory protocol's "transfer" operation is now complete, and the quantum information may remain in the nucleus state for the desired waiting time before the pulse order is reversed (the "restore" sequence) to bring the quantum information back to the electron state.

[0080] Nuclear spin state readout

[0081] As previously noted, in addition to isolated electrons, electrical signals can be applied to electrodes 106 / 206 to perform selected operations on the processing element and / or read out the quantum state of the processing element.

[0082] In some embodiments, electron spin resonance (ESR) can be performed on the electrons of a quantum dot using, for example, microwave pulses to perform nuclear spin state readout. In one example, these microwave pulses can be delivered by an on-chip broadband planar transmission line (not shown).

[0083] In response to a microwave pulse, the system will exhibit two possible ESR frequencies depending on the nuclear spin state—that is, for spin-up, the processing element will exhibit an ESR frequency equal to the ESR frequency of the hyperfine interaction plus half the frequency of the γ pulse. e B+A / 2), and for nuclear spin down, the processing element will exhibit an ESR frequency that is half that of the hyperfine interaction (γ). e (BA / 2). Therefore, depending on the detected ESR, the state of the nuclear spin can be determined.

[0084] Figure 4A A stability plot of the two quantum dots is shown, which illustrates the charge state of each point in relation to the bias applied through the gate electrode. Figure 4A The diagram shows the bias configurations for different stages of nuclear spin readout, where N indicates the nuclear magnetic resonance (RF) signal, E indicates the electron spin resonance (EMR) microwave signal, and R indicates the readout point.

[0085] also, Figure 4B The nuclear spin readout bias sequence is shown, which illustrates the nuclear magnetic resonance RF signal (N), the electron spin resonance microwave signal (E), and the readout point (R).

[0086] Figure 5This is a frequency scan, which shows the resonance observed when an 11.908 MHz radio frequency signal and a 1.42 T magnetic field are applied, thus giving a gyromagnetic ratio of |γ|. N |=8.83MHz / T, which is consistent with 29 Si is consistent.

[0087] Mobile Information

[0088] As previously noted, the nucleus is generally immobile, and therefore the nuclear spin is generally immobile, while the electron is very mobile, and therefore the electron spin is very mobile, and can shuttle along the quantum device 200 to transmit information to other circuit nodes. Figure 3 This is a schematic circuit representation showing the shuttle between a quantum dot and a single electron 302, which are used for the exchange coupling of quantum information.

[0089] Typically, in donor-electron spin systems, the nuclear coherence of the donor is disrupted when an electron is unloaded from the donor. This is because the ionization rate of the unloaded electron is relatively slow compared to the typical hyperfine coupling between the donor and electron, which causes the nuclear spin state to undergo random phase shifts depending on the random time it takes for the electron to be ionized.

[0090] However, because electrons can tunnel between two adjacent quantum dots via spin shuttle or exchange-mediated coupling in the currently disclosed systems, the tunneling rate for unloading electrons from the quantum dots is much higher than the ionization rate in electron donor systems. Therefore, nuclear spin coherence can be maintained during electron unloading in the currently disclosed systems.

[0091] This is important when electrons are used as the medium for entanglement between nuclear spins in different quantum dots. For this purpose, electron 302 can first become entangled with nuclear spin 304 in the first quantum dot 306. Electron 302 is then transferred to the second quantum dot 308, where it can become entangled with the second nuclear spin 310. If the state of the electron spin in the second quantum dot is measured at this point, it will be determined that both nuclear spins 304 and 310 are projected into an entangled state, even if the two nuclear spins do not interact directly. In this way, information can travel across the quantum device 200 from one quantum dot to the next.

[0092] Figure 8 shows 29 The nuclear spin coherence property of Si atoms. In particular, Figure 8A This illustrates nuclear spin T2 with different charge configurations for two points. * and T2 Hahn The measured graph (offset 1 for each trajectory). Each point is loaded with either 1 or 0 electrons.

[0093] Figure 8BThis is a table showing the measured values ​​of coherence time and decay exponent for nuclear spin extracted from the measurements in Figure 8a.

[0094] Figure 10 includes multiple graphs, each showing a state tomography scan of a Bell state. Specifically, graphs 10A-10C show state tomography scans of Bell states with spin-down initialization, and graphs 10D-10F show state tomography scans of Bell states with spin-up initialization. Correlation / anti-correlation is observed on the basis of XX, YY, and ZZ. The fidelity estimate for spin-down initialization is F = 72 ± 3%, and for spin-up initialization, it is F = 80 ± 3%.

[0095] It will be recognized that the architecture described in the above embodiments utilizes the properties of quantum dots. 29 Electrons entangled with the Si atom nucleus. In other embodiments, the quantum dot can be configured to confine holes instead of electrons, and the holes can be... 29 Si atoms are entangled.

[0096] Other Group IV elements

[0097] In some embodiments, with use 29 In contrast to using Si atoms and entangled their nuclear spins with nearby quantum dots, any other (stable) group IV atom with nuclear spin (e.g., carbon, germanium, tin, or lead) can be used. In one example, carbon-13 (…) could be used. 13 C) Isotopes. In another example, germanium-73 can be used. 73 Tin has many stable isotopes with nuclear spin, such as tin-115 (Ge). 115 Sn), Tin-117 117 Sn), Tin-119 119 Sn), and can utilize any of these isotopes of tin instead of 29 Si atoms.

[0098] One or more atoms of these elements can be injected with low energy to place them at shallow depths, thus within the wavefunction of nearby quantum dots (similar to the above). 29 (In the manner described by the Si atom). Then, the nuclear spin of the atom can become entangled with the electron spins of nearby quantum dots via hyperfine coupling.

[0099] Carbon and tin isotopes have a spin of 1 / 2 (similar to...) 29 Si), therefore with 29The silicon atom functions in the same way. Germanium isotopes have a spin of 9 / 2. This means that the germanium nucleus has 10 states that can be used for quantum computing, whereas silicon, carbon, and tin atoms only have 2 states available.

[0100] An example method for artificially introducing one or more Group IV atoms into a silicon substrate is described in U.S. Patent No. 7,002,166, entitled “Method and System for Single Ion Implantation,” which is incorporated herein by reference in its entirety. Although the implantation technique is described with respect to phosphorus atoms in that patent, these techniques (with slight modifications) can be used to precisely implant carbon, silicon, germanium, or tin atoms into a silicon substrate.

[0101] The term “include” (and its grammatical variations) as used in this article is used in the inclusive sense of “having” or “containing”, rather than in the sense of “consisting of only”.

[0102] Those skilled in the art will recognize that many changes and / or modifications can be made to the invention as illustrated in the specific embodiments without departing from the spirit or scope of the invention as broadly described. Therefore, the embodiments of the invention are to be considered illustrative rather than restrictive in all respects.

Claims

1. A processing element for a quantum processing device, the processing element comprising: silicon substrate; A dielectric material, wherein the silicon substrate and the dielectric material form an interface; One or more electrodes formed on the dielectric material are used to isolate one or more electrons in the silicon substrate to form quantum dots; Group IV atoms, whose nuclear spins lie in the wavefunction of one or more electrons, and whose nuclear spins are entangled with the one or more electrons; and The control arrangement includes one or more electrodes for controlling the quantum properties of the quantum dot and the nuclear spin to operate the qubit.

2. The processing element according to claim 1, wherein, The control arrangement is configured to control the spin of one or more electrons in the quantum dot.

3. The processing element according to claim 2, wherein, The control arrangement is configured to operate pairs of quantum dot electron spins and nuclear spins of the group IV atoms as the qubits.

4. The processing element according to claim 3, wherein, The control arrangement is configured to apply an AC electromagnetic field to control the nuclear spin of at least the group IV atoms.

5. The processing element according to claim 4, wherein, The control arrangement is configured to apply the AC electromagnetic field using the one or more electrodes.

6. The processing element according to claim 1, wherein, The group IV atom is silicon-29.

7. The processing element according to claim 6, wherein, The silicon substrate is isotopically enriched. 28 Si substrate.

8. The processing element according to claim 7, wherein, The isotope enrichment 28 The Si substrate contains less than or equal to 800 ppm of 29 Si atoms.

9. The processing element according to claim 1, wherein, The group IV atoms are isotopes of group IV elements that have nuclear spin.

10. The processing element according to claim 9, wherein, The atom in question is germanium-73.

11. The processing element according to claim 9 or 10, wherein, The group IV atoms are implanted into the silicon substrate.

12. The processing element according to any one of claims 1-11, wherein, The diameter of the quantum dot electron wave function is less than 50 nm.

13. The processing element according to any one of claims 1-12, wherein, The diameter of the quantum dot electron wavefunction is less than or equal to 15 nm.

14. The processing element according to any one of claims 1-13, wherein, The nuclear spins of the group IV atoms are entangled with the electrons of the quantum dot via hyperfine interactions, wherein the strength of the hyperfine interactions is controlled relative to the electron spin resonance linewidth of the quantum dot.

15. The processing element according to claim 7, wherein, The intensity of the hyperfine interaction is controlled by the position of the group IV atoms in the substrate.

16. The processing element according to claim 14, wherein, The hyperfine interaction between the electron and the group IV atom occurs between 100 kHz and 1 MHz.

17. A method for operating a plurality of quantum processing elements, each processing element comprising: silicon substrate; A dielectric material, wherein a silicon substrate and the dielectric material form an interface; one or more electrodes formed on the dielectric material for isolating one or more electrons in the silicon substrate to form a quantum dot; a group IV atom whose nuclear spin is located in the wave function of the one or more electrons, the nuclear spin of the group IV atom being entangled with the one or more electrons; and a control arrangement including the one or more electrodes for controlling the quantum properties of the quantum dot and the nuclear spin to operate the quantum dot and / or the nuclear spin as qubits, the method comprising the following steps: Signals are applied via the control arrangement to control the state of the qubits.

18. The method of claim 17, further comprising: Signals are applied via the control arrangement to store information in the qubits.

19. The method according to claim 18, wherein, Storing information in the qubits includes: Apply the signal to store information in the electron spin of the quantum dot; and This information is exchanged from the electron spin to the nuclear spin of the group IV atom.

20. The method of claim 19, further comprising: Quantum information is transferred from a first processing element to a second processing element among the plurality of processing elements.

21. The method according to claim 20, wherein, Transmitting information from the first processing element to the second processing element includes: The quantum information is exchanged from the nuclear spin of a group IV atom in the first processing element to the electron spin of the first processing element; and The quantum dot that transfers the electron spin from the first processing element to the second processing element; To entangle the delivered electron spin with the nuclear spin of the group IV atoms of the second processing element; and The quantum information is exchanged from the delivered electron spin to the nuclear spin of a group IV atom in the second processing element.

22. The method according to claim 21, wherein, The electron spin of the first processing element is transferred to the quantum dot of the second processing element via spin shuttle or exchange-mediated coupling between the quantum dots of the first processing element and the second processing element.

23. A method for manufacturing an advanced processing device, comprising the following steps: Multiple processing elements are manufactured through the following operations: Provides including 28 Silicon substrate with Si layer; So that the dielectric layer and 28 The dielectric layer is formed by forming an interface with the Si layer; Multiple electrodes are formed, the multiple electrodes being configured to isolate one or more electrons around the interface to define multiple quantum dots; Position one or more group IV atoms, the nuclear spins of the one or more group IV atoms in the wave function of the one or more electrons, such that the nuclear spins of the one or more group IV atoms are entangled with the electrons of the quantum dot, such that the quantum dot and the nuclear spin pair are operated as qubits. A plurality of control components including switches are formed, the switches being arranged to interact with the plurality of electrodes, at least one of the plurality of electrodes being configured to control the nuclear spin; as well as Multiple control lines are formed, each connecting to one or more control components to enable simultaneous operation of the multiple processing elements. The plurality of electrodes, control components and control lines are formed using a silicon metal oxide semiconductor manufacturing process.

24. The method for manufacturing according to claim 23, wherein, At least one of the group IV atoms is a silicon-29 atom.

25. The method for manufacturing according to claim 23, wherein, Providing the silicon substrate includes providing isotope enrichment. 28 Si substrate.

26. The method for manufacturing according to claim 25, wherein, The isotope enrichment 28 The Si substrate contains less than or equal to 800 ppm of 29 Si atoms.

27. The method for manufacturing according to claim 23, wherein, At least one of the group IV atoms is a germanium 73 atom.

28. The method for manufacturing according to any one of claims 23, 24 or 27, wherein, One or more Group IV atoms are implanted into the silicon substrate.

29. The method for manufacturing according to any one of claims 23-28, wherein, The wave function diameter of the electrons in each quantum dot is less than 50 nm.

30. The method for manufacturing according to claim 29, wherein, The wavefunction diameter of at least one electron in at least one of the quantum dots is less than or equal to 15 nm.

31. The method for manufacturing according to any one of claims 23-30, wherein, The nuclear spins of the group IV atoms become entangled with the electrons of the quantum dots via hyperfine interactions.

32. The method for manufacturing according to claim 31, wherein, The hyperfine interaction between electrons and atoms occurs between 100 kHz and 1 MHz.

33. A quantum processing device, comprising: Multiple quantum processing elements arranged in a matrix, each processing element being the processing element according to claim 1; Multiple control units are disposed around the processing element; each control unit includes one or more switches arranged to interact with the processing element to perform quantum operations using one or more of the multiple processing elements. as well as Multiple control lines; Each control line connects to multiple control components to enable the simultaneous operation of one or more of the multiple processing elements.

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