Method and apparatus for multi-purpose light collection for remotely entangling atomic quantum computers in a multi-core architecture

Abstract

Aspects of the present disclosure generally relate to systems and methods for use in the implementation and / or operation of a quantum information processing (QIP) system, and more particularly, to receiving a readout beam associated with the state of a first qubit of an array of trapped ions, receiving an interconnect beam configured to entangle a second qubit of the array with an external qubit of an external array, receiving an addressing beam configured to control the state of a third qubit of the array from an addressing unit, directing, via at least one switch, the addressing beam from the addressing unit towards the third qubit, directing, via at least one switch, the readout beam towards a photodetector, and directing, via at least one switch, the interconnect beam towards an interconnect unit optically coupled to the external array.

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 366,874, filed on June 23, 2022, the entire content of which is incorporated herein by reference.

[0002] Aspects of the present disclosure generally relate to systems and methods for use in the implementation and / or operation of quantum information processing (QIP) systems, and more specifically, to the operation of multiple QIP systems.

Background Art

[0003] Trapped atoms are one of the major implementations of quantum information processing or quantum computing. Atom - based qubits can be used as quantum memories, as quantum gates in quantum computers and simulators, and can act as nodes for quantum communication networks. Qubits based on trapped atomic ions enjoy a combination of rare attributes. For example, qubits based on trapped atomic ions have very good coherence properties, can be prepared and measured with nearly 100% efficiency, and can easily become entangled with each other by modulating their Coulomb interactions with a suitable external control field such as an optical field or a microwave field. These attributes make atom - based qubits attractive for extended quantum operations such as quantum computing or quantum simulation.

[0004] Therefore, it is important to develop new technologies to improve the design, manufacture, implementation, and / or control of various QIP systems used as quantum computers or quantum simulators, especially QIP systems that process operations based on atom - based qubits.

Summary of the Invention

[0005] The following presents a simplified overview of one or more aspects to provide a basic understanding of such aspects. This overview is not an extensive overview of all contemplated aspects, nor is it intended to identify key or critical elements of all aspects or to delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that follows.

[0006] In some aspects of the present disclosure, switches / interconnections can be used to implement remote entangling of qubits. The interconnect beam used to entangle remote qubits can traverse substantially the same path as the readout beam and / or the addressing beam. The switch / interconnection can be used to separate the readout beam, the interconnect beam, and / or the addressing beam and direct them towards different optical components. The readout beam can be directed towards a readout device. The interconnect beam can be directed towards a remote qubit.

[0007] Aspects of the present disclosure include a system and method for receiving a readout beam associated with the state of a first qubit of an array of trapped ions, receiving an interconnect beam configured to entangle a second qubit of the array with an external qubit of an external array, receiving an addressing beam configured to control the state of a third qubit of the array from an addressing unit, directing the addressing beam from the addressing unit towards the third qubit via at least one switch, directing the readout beam towards a photodetector via at least one switch, and directing the interconnect beam towards an interconnect unit optically coupled to the external array via at least one switch.

[0008] To achieve the foregoing and related purposes, one or more aspects include features that are fully described hereinafter in this specification and particularly pointed out in the claims. The following description and the accompanying drawings set forth in detail certain illustrative features of one or more aspects. However, these features are only a part of the various ways in which the principles of the various aspects can be utilized, and this description is intended to include all such aspects and their equivalents.

Brief Description of the Drawings

[0009] The disclosed aspects are described hereinafter in this specification in conjunction with the accompanying drawings, which are for the purpose of illustrating the disclosed aspects and not for the purpose of limitation, and like reference numerals indicate like elements.

[0010]

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Mode for Carrying Out the Invention

[0011] The detailed description set forth below in connection with the appended drawings or figures is intended as a description of various configurations or implementations and is not intended to represent the only configuration or implementation in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details or with variations of these specific details. In some instances, well - known components are shown in block diagram form, and some blocks may represent one or more well - known components.

[0012] Quantum computing (QC) is a method for processing information that uses quantum two-level systems or qubits (quantum bits) as the basic unit of information storage. QC further exploits the entanglement between qubits that is natively generated in many QC platforms to perform calculations with fewer resources (e.g., computational time, number of bits, etc.) than classical computing schemes. Within a quantum computer, a quantum processing unit (QPU) can be allocated by a subset of qubits, deterministically generate entanglement among them, and thereby directly execute quantum gates. Building large-scale QPUs can be a difficult task involving many technical obstacles specific to the particular quantum system used as the platform for computing. An alternative approach to scaling QC is to interconnect multiple small-scale QPUs, each of which has limited computational power individually but, when linked, has the computational power of a much larger device.

[0013] The technical challenges for scaling QC are closely related to the computational platform on which the qubits are encoded. In atomic systems, the qubits are essentially identical, and many systems naturally have good connectivity between the qubits within a QPU. The main difficulty in scaling these platforms is the technical overhead associated with increasing the QPU size while maintaining the performance of the QPU, and most notably, the gate fidelity and gate time. Thus, there is a lack of technical implementations that enable QC in atomic systems.

[0014] A modular approach for scaling QC in atomic systems avoids the need for a large number of qubits in a single QPU by connecting smaller QPUs. One exemplary aspect involves using optical interconnects, also known as photonic links, to herald entanglement between distant QPUs.

[0015] Exemplary aspects of the present disclosure include optical hardware configured to implement a multi-QPU approach to atomic QC. Three basic operations in a multi-QPU approach to atomic QC can utilize high-NA optical access to atoms, including one or more of (1) individual addressing of optical qubits, (2) spatially resolved qubit readout, and / or (3) fluorescence collection for heralding remote entanglement as in optical interconnects. Given the limitations on optical access to atoms within a vacuum chamber, it may be advantageous to perform all of these three operations via a single high-NA viewport.

[0016] Aspects of the present disclosure include the design of an optical system that enables optical paths for the operations shown above while maintaining the independence of the degrees of freedom necessary for their functions (e.g., wavelength, polarization). Another aspect includes several means for separating these optical paths that utilize any of the temporal, spatial, or frequency degrees of freedom of light.

[0017] Solutions to the above problems are described in more detail in connection with FIGS. 1-15, and FIGS. 1-3 provide a general configuration of a QIP system or quantum computer, more specifically an atom-based QIP system or quantum computer.

[0018] FIG. 1 shown below depicts a diagram 100 having a plurality of atomic ions 106 (e.g., atomic ions 106a, 106b, …, 106c, and 106d) trapped in a linear crystal or linear chain 110 using a trap (the trap can be within a vacuum chamber as shown in FIG. 2). The trap may also be referred to as an ion trap. The ion trap shown can be constructed or fabricated on a semiconductor substrate, a dielectric substrate, or a glass die or wafer (also referred to as a glass substrate). The atomic ions 106 can be provided to the trap as atomic species for ionization and confinement to the chain 110.

[0019] In the example shown in FIG. 1, the trap includes electrodes for trapping or confining a plurality of atomic ions within the chain 110 that is laser cooled to be nearly stationary. The number of atomic ions (N) to be trapped can be set, and more or fewer atomic ions can be trapped. The atomic ions can be, for example, ytterbium ions (e.g., 171 Yb + ions). The atomic ions are irradiated with laser (light) radiation tuned to the 171 Yb + resonance, and the fluorescence of the atomic ions is imaged onto a camera or some other type of detection device. In this example, the atomic ions may be separated from each other by about 5 micrometers (μm), but the separation may be smaller or larger than 5 μm. The separation of the atomic ions is determined by the balance between the external confinement force and the Coulomb repulsive force and need not be uniform. Further, in addition to ytterbium atomic ions, neutral atoms, rubidium atoms, different atomic ions, or different atomic ion species may also be used. The trap may be a linear RF Paul trap, but other types of confinement including optical confinement may also be used. Thus, the confinement device may be based on different technologies and may hold ions and / or neutral atoms. For example, an ion trap is an example of such a confinement device. The ion trap may be, for example, a surface trap.

[0020] FIG. 2 shown below is a block diagram showing an example of a QIP system 200 according to various aspects of the present disclosure. The QIP system 200 may also be referred to as a quantum computing system, a quantum computer, a computer device, a trapped ion system, etc. The QIP system 200 may be part of a hybrid computing system that includes a classical computer for the classical computer (computation) and operations that the QIP system 200 is used to perform quantum computing and operations.

[0021] Shown in FIG. 2 is a general-purpose controller 205 configured to execute various control operations of the QIP system 200. Instructions regarding the control operations may be stored in a memory (not shown) within the general-purpose controller 205, or may be updated over time via a communication interface (not shown). The general-purpose controller 205 is shown separately from the QIP system 200, but the general-purpose controller 205 may be integrated with the QIP system 200 or may be a part of the QIP system 200. The general-purpose controller 205 may include an automation and calibration controller 280 configured to execute various calibration, inspection, and automation operations related to the QIP system 200.

[0022] The QIP system 200 may include an algorithm component 210 that can operate with other parts of the QIP system 200 to execute a quantum algorithm or quantum operation, including a stack or sequence of combinations of single-qubit operations and / or multi-qubit operations (e.g., two-qubit operations), as well as extended quantum computing. Thus, the algorithm component 210 can provide instructions to various components of the QIP system 200 (e.g., the optical and trap controller 220) to enable the implementation of a quantum algorithm or quantum operation. The algorithm component 210 may receive information resulting from the implementation of a quantum algorithm or quantum operation, may process the information, and / or may transfer the information to another component of the QIP system 200 or to another device for further processing.

[0023] The QIP system 200 may include an optical and trap controller 220 that includes generating signals for controlling trap 270. The optical and trap controller 220 controls various aspects of trap 270 within chamber 250 and controls the operation of a laser and optical system that provides an optical beam that interacts with atoms or ions within the trap. When used to confine or trap ions, trap 270 may sometimes be referred to as an ion trap. However, trap 270 can also be used to trap neutral atoms, Rydberg atoms, different atomic ions, or different species of atomic ions. The laser and optical system may be at least partially disposed within the optical and trap controller 220, and / or within chamber 250. For example, the optical system within chamber 250 may refer to an optical component or an optical assembly.

[0024] The QIP system 200 may include an imaging system 230. The imaging system 230 may include a high-resolution imager (e.g., a CCD camera) or other type of detection device (e.g., a photomultiplier tube or PMT) for observing atomic ions while and / or after the atomic ions are provided to trap 270. In one aspect, the imaging system 230 may be implemented separately from the optical and trap controller 220, but may need to be coordinated with the optical and trap controller 220 if fluorescence is used to detect, identify, and label atomic ions using image processing algorithms.

[0025] In addition to the above components, the QIP system 200 may include a source 260 that provides a species of atoms (e.g., a plume or flux of neutral atoms) to a chamber 250 having a trap 270. If atomic ions are the basis for quantum operations, the trap 270 confines the once-ionized (e.g., photo-ionized) species of atoms. The trap 270 can be part of or a processing portion of the processor of the QIP system 200. That is, the trap 270 can be considered to be at the core of the processing operation of the QIP system 200 for holding the atom-based qubits used to perform quantum operations or simulations. At least a portion of the source 260 may be implemented separately from the chamber 250.

[0026] It should be understood that the various components of the QIP system 200 described in FIG. 2 are described at a high level for ease of understanding. Such components may include one or more sub-components, the details of which may be provided below as needed to better understand particular aspects of the present disclosure.

[0027] Referring now to FIG. 3 shown below, an example of a computer system or device 300 according to an aspect of the present disclosure is shown. The computer device 300 can represent, for example, a single computing device, multiple computing devices, or a distributed computing system. The computer device 300 may be configured as a quantum computer (e.g., a QIP system), as a classical computer, or to perform a combination of quantum computing functions and classical computing functions, sometimes referred to as hybrid functionality or operation. For example, the computer device 300 can be used to process information using quantum algorithms, classical computer data processing operations, or a combination of both. In some cases, the results from one set of operations (e.g., quantum algorithms) are shared with another set of operations (e.g., classical computer data processing). A general example of the computer device 300 implemented as a QIP system capable of performing quantum computing and simulation is, for example, the QIP system 200 shown in FIG. 2.

[0028] The computer device 300 may include a processor 310 for executing processing functions related to one or more of the features described herein. The processor 310 may include a single or a set of multiple processors, or a multi-core processor. Further, the processor 310 may be implemented as an integrated processing system and / or a distributed processing system. The processor 310 may include one or more central processing units (CPUs) 310a, one or more graphics processing units (GPUs) 310b, one or more quantum processing units (QPUs) 310c, one or more intelligent processing units (IPUs) 310d (e.g., artificial intelligence or AI processors), or a combination of some or all of these types of processors. In one aspect, the processor 310 may refer to a general-purpose processor of the computer device 300, and the computer device may also include an additional processor 310 for executing more specific functions (e.g., functions including controlling the operation of the computer device 300).

[0029] The computer device 300 may include a memory 320 for storing instructions executable by the processor 310 to perform operations. The memory 320 may also store data for processing by the processor 310 and / or data obtained from processing by the processor 310. In one embodiment, for example, the memory 320 may correspond to a computer-readable storage medium storing code or instructions for performing one or more functions or operations. Similar to the processor 310, the memory 320 may refer to the general memory of the computer device 300, which may also include additional memory 320 for storing instructions and / or data for more specific functions.

[0030] Processor 310 and memory 320 may be used in connection with different operations, which may include, but are not limited to, operations such as computing, calculating, simulating, controlling, calibrating, system management, and any other operations of computer device 300 described herein, including any method or process described herein.

[0031] Furthermore, computer device 300 may include a communication component 330 that provides for establishing and maintaining communication with one or more parties that utilize hardware, software, and services. Communication component 330 may also be used to transmit communication between components on computer device 300, as well as between computer device 300 and external devices such as devices disposed via a communication network and / or devices continuously or locally connected to computer device 300. For example, communication component 330 may include one or more buses and may further include a transmit chain component and a receive chain component respectively associated with a transmitter and a receiver operable to interface with an external device. Communication component 330 may be used to receive update information regarding the operation or functionality of computer device 300.

[0032] Additionally, computer device 300 may include a data store 340, which may be any suitable combination of hardware and / or software, and which provides mass storage of information, databases, and programs related to the operation of computer device 300 and / or any method or process described herein. For example, data store 340 may be a data repository for an operating system 360 (e.g., a classical OS, or a quantum OS, or both). In one embodiment, data store 340 may include memory 320. In one embodiment, processor 310 may execute an operating system 360 and / or an application or program, and memory 320 or data store 340 may store them.

[0033] The computer device 300 may also include a user interface component 350 configured to receive input from a user of the computer device 300 and further configured to generate output for presentation to the user or for providing (directly or indirectly) to a different system. The user interface component 350 may include one or more input devices, which may include, but are not limited to, a keyboard, a numeric keypad, a mouse, a touch sensor display, a digitizer, navigation keys, function keys, a microphone, a voice recognition component, any other mechanism capable of receiving input from a user, or any combination thereof. Further, the user interface component 350 may include one or more output devices, which may include, but are not limited to, a display, a speaker, a tactile feedback mechanism, a printer, any other mechanism capable of presenting output to a user, or any combination thereof. In one embodiment, the user interface component 350 may send and / or receive messages corresponding to the operation of the operating system 360. When the computer device 300 is implemented as part of a cloud-based infrastructure solution, the user interface component 350 may be used to enable a user of the cloud-based infrastructure solution to interact remotely with the computer device 300.

[0034] In connection with the systems described in FIGS. 1 - 3, aspects of the present disclosure include an interconnect system configured to couple a plurality of QPUs disposed remotely from each other. The systems described in FIGS. 2 - 3 may be used to control various aspects of the interconnect system as described below.

[0035] FIG. 4 shows an example of a QPU network 400 according to an aspect of the present disclosure. Individual atoms confined in a one - or multi - dimensional array within a vacuum chamber can provide a promising platform for QC that is also suitable for an interconnected QPU network. Proposals for interconnecting atomic qubits probabilistically herald entanglement between "distant" atoms (i.e., atoms that do not directly interact) upon detection of photons emitted from each atom. Thus, in the interconnection operation in a multi - QPU QC architecture, attempts at interconnection may be repeated.

[0036] In some aspects, the QPU network 400 may include a first vacuum chamber 402 having a first processor QPU1 and a second processor QPU2. The QPU network 400 may include a second vacuum chamber 404 having a third processor QPU3 and a fourth vacuum chamber 406 having a fourth processor QPU4. Other numbers of vacuum chambers and / or processors may also be implemented. The QPU network 400 may include an optical switch 410 configured to provide one or more paths for entangling qubits within the processors QPU1, QPU2, QPU3, QPU4, as described below.

[0037] FIG. 5 shows an example of a viewport 500 according to some aspects of the present disclosure. As shown, the viewport shows an exemplary ion chain, such as the ion chain 110 above, as a straight row of ions 510 in FIG. 5. The optical system used to collect photons for the interconnect operation advantageously does not interfere with other functions of the QC. Aspects of the present disclosure include a light collection apparatus (LCA) for an atomic quantum computing platform, which enables highly efficient light collection for the interconnect operation and at the same time enables the readout of qubit states for the gate operation and the addressing of individual qubits through the same viewport of the vacuum system. Readout, addressing, and interconnect operations are three functions of a multi-QPU atomic quantum computer that rely on high numerical aperture optical access. Aspects of the present disclosure facilitate these operations while utilizing a single viewport for the atoms. In addition, aspects of the present disclosure enable any-to-any connectivity between any QPUs within a quantum network using a switch that can operate on the same principle as the discrete components in the LCA.

[0038] FIGS. 6A - C show exemplary configurations of trapped ions within a QPU, such as the QPUs 1 - 4 above, according to some aspects of the present disclosure. An atomic quantum computer is composed of an array of atoms trapped within a vacuum chamber. The size and dimensions of the atomic array may vary, but the spacing between atoms within a single cluster can be in the range of 1 - 10 μm. At these spacings, the physical interactions between atoms are significant and can be used to directly generate entanglement between pairs or multiple atoms within the array. In the configuration shown in FIG. 6C, the ions can be shuffled, enabling dynamic placement.

[0039] FIG. 7 shows an example of the state of trapped ions in a QPU according to an aspect of the present disclosure. In one aspect, the two energy levels of each atom in the QPU can be assigned to be the "zero" state and the "one" state of a qubit. Light of a particular optical frequency is used to drive gates of single and multiple qubits. This light is often focused to a spot narrower than the typical distance between atoms, thereby implementing individual addressing of qubits. Ideally, the addressing light should have a uniform intensity distribution across the region where atoms can move within the trap and be focused so as to have no crosstalk with adjacent atoms. These requirements can be achieved by an optical system with a high numerical aperture.

[0040] In some aspects, readout of qubit states in an atomic (e.g., trapped ion) quantum computer is typically achieved by driving one of the qubit states (e.g., state "1") with a strong transition, collecting fluorescence with a detector, and imaging. For high-fidelity readout of computations, the optical system for collecting fluorescence photons for qubit readout can have high collection efficiency and good spatial resolution, so that the image of the atoms generated at the detection surface has no large spatial overlap. A high-efficiency imaging system with good spatial resolution may require an optical system with a high numerical aperture for access to the atoms.

[0041] In a particular aspect, implementation of remote entanglement across a QPU in an atomic quantum computer may require collecting fluorescence photons from atoms in separate QPUs that are not necessarily in the same vacuum chamber (as shown in FIG. 1). The frequencies of these photons may or may not match the frequencies of the photons collected for qubit readout. For high-speed and high-fidelity interconnect operation, high-efficiency photon collection into an optical fiber or another photonic waveguide is required. When coupling fluorescence from multiple atoms into different optical fibers, the optical system may be required to have high spatial resolution so as to minimize crosstalk between adjacent channels.

[0042] To flexibly interconnect different QPUs, photons collected for the interconnection operation can be appropriately routed to create appropriate links. The linked QPUs may be in the same vacuum chamber or in separate chambers. In either scenario, the switch can determine which QPUs to optically connect to enable remote entanglement.

[0043] FIG. 8 shows an example of an interconnection system 800 according to an aspect of the present disclosure. In some aspects, the interconnection system 800 may include one or more atomic arrays 802 containing a plurality of trapped ions, such as the chamber 250 described above with respect to FIG. 2 (not shown), within a vacuum chamber (not shown). The one or more atomic arrays 802 may include one or more QPUs. The states of the plurality of trapped ions may be used to implement the qubit states of a QPU (not shown). The interconnection system 800 may include a vacuum chamber viewport 804 (e.g., viewport 500) configured to provide an optical path to the one or more atomic arrays 802 while maintaining the pressure within the vacuum chamber (not shown). The viewport 804 may include one or more glass plates. The interconnection system 800 may include an optical component 810 (e.g., a microscope objective). The optical component 810 may be a multi-lens optical system that is achromatic over a wavelength range spanning the interconnection, readout, and addressing operations (e.g., a range from near-infrared (IR) to near-ultraviolet (UV)). The optical component 810 may be configured to correct for distortions introduced by the viewport 804.

[0044] In some aspects, the light for each major function may be separated by two consecutive components before being directed to units specific to each operation. The interconnection and readout units are intended as output paths for collecting fluorescence, while the addressing unit provides optical access to individual qubits for light directed to the QPU.

[0045] In certain embodiments, the interconnect system 800 may include a first switch 820 configured to separate an addressing beam, a readout beam, and an interconnect beam from the addressing unit 822. In particular, the first switch 820 may be configured to direct the addressing beam from the addressing unit 822 towards the optical components 810 and the one or more atomic arrays 802. The first switch 820 may be configured to direct the readout beam and the interconnect beam from the optical components 810 and the one or more atomic arrays 802 towards a second switch 830.

[0046] In some embodiments, the interconnect system 800 may include a second switch 830 configured to separate the readout beam and the interconnect beam. The second switch 830 may be able to direct the interconnect beam towards the interconnect unit 840 and the readout beam towards the readout unit 850. The interconnect unit 840 may be coupled to one or more waveguide arrays associated with one or more QPUs. The readout unit 850 may be coupled to one or more photodetectors (e.g., the imaging system 230) configured to capture the readout beam.

[0047] In certain embodiments, the interconnect beam may be directed towards one or more QPUs, or another switch, to enable entanglement across multiple QPUs.

[0048] FIG. 9 shows a functional diagram of an interconnect system 800 according to an embodiment of the present disclosure. In some embodiments of the present disclosure, one or more atomic arrays 802 within a vacuum chamber are characterized by their overall extent S and the qubit separation d within the QPU. S, including the distance between QPUs within the same chamber, determines the required field of view of the LAC, while d specifies the required resolution of the LAC.

[0049] In some embodiments, the optical component 810 can be characterized by its numerical aperture (NA), its field of view (FOV), its point-spread function (PSF), and / or its effective focal length (f eff ) For imaging qubits, the FOV must be at least as large as S. For individually addressing qubits, the PSF of the objective lens across the FOV must exhibit a resolution better than d (i.e., the distance between the first zeros of the Airy function image of a point source anywhere within the FOV must be smaller than d). The NA sets the solid angle from which fluorescence can be collected from the atoms. The NA is basically limited by the diameter of the viewport D4, as well as the minimum working distance which is the sum of D1, D2, and D3. Here, the optical component 810 may be a microscope objective lens considered to be in an infinite conjugate configuration.

[0050] In one aspect of the present disclosure, the first switch 820 may include a dichroic mirror in an exemplary embodiment. The addressing beam may be separated from the readout beam and the interconnect beam by the dichroic mirror. The wavelength λ of the light used to address the qubits add may be near-infrared (near-IR). The λ which is the fluorescence collected for readout and interconnect operations int、read may be in the near-ultraviolet (near-UV) or visible region. This separation of tens to hundreds of nanometers is sufficient for the thin-film interference of the dichroic mirror to efficiently separate the addressing light.

[0051] In some embodiments, the addressing unit 822 is an average magnification M adjustable by δM which is an amount that maps the imaging of atoms onto an array of laser beams generated by a diffractive optical element (not shown) and input to the addressing ports of the LAC a aIt may include a variable magnification telescope. According to an exemplary aspect, the magnification is determined by the requirement that each addressing beam significantly overlaps with only one atom. Since the typical movement of atoms is very small, this condition is mainly set by the separation d. The size of the input beam and the separation of the addressing beams can be measured offline, but the separation between atoms is typically unknown until the system is built. Therefore, the flexibility to optimize this mapping is provided by an adjustable magnification. In some aspects, a variable telescope design, such as a variable telescope that only requires moving internal lenses to change the magnification, can provide the required magnification and adjustment range. In some embodiments, the external dimensions of the addressing unit remain fixed while the magnification is being adjusted.

[0052] In certain aspects of the present disclosure, the second switch 830 may be configured to separate the readout beam and the interconnect beam using one or more schemes suitable for implementing entanglement. Examples of the schemes include frequency division multiplexing, spatial division multiplexing, and / or time division multiplexing. These solutions can be implemented individually or in combination in a given architecture. This scheme will be described in more detail below.

[0053] In some aspects of the present disclosure, the interconnect unit 840 may include one or more of a fiber-coupled lens and / or a waveguide array for collecting fluorescence for implementing remote entanglement from trapped ions of one or more atomic arrays 802. An exemplary embodiment of the waveguide array includes a bundle of single-mode fibers and a rigid waveguide channel having micro-optics. The imaging magnification of the fiber-coupled lens (M i ) is set to maximize the overlap between the imaging of the atoms and the mode field diameter of the waveguide (P i ). This sets the requirements regarding the spacing between waveguide channels, taking into account the atomic configuration intended for the interconnect operation (as shown in FIG. 12).

[0054] In certain embodiments, the readout unit 850 may include one or more variable magnification telescopes with an average magnification M adjustable by an amount δM r . r

[0055] In some embodiments, one or more photodetectors 860 may be configured to capture a readout beam associated with the state of trapped ions within one or more atomic arrays 802. The one or more photodetectors 860 may be able to capture fluorescence within the readout beam associated with the trapped ions. The one or more photodetectors 860 may be able to analyze the characteristics of the fluorescence to determine the state of the trapped ions. The one or more photodetectors 860 may include one or more devices (e.g., charge coupled devices, avalanche photodiodes, etc.) characterized by an effective aperture (A r ), a pixel size (P r ), and a desired number of pixels used (N r ). The magnification M r is determined by the desired size of the image on the photodetector, and the size of the image can be set by conditions such that the imaging of adjacent atoms has negligible overlap while minimizing the number of pixels used (as shown in FIG. 11). The target size of the atoms within the trap may be smaller than the resolution of the microscope objective lens, and thus this magnification can be specified using the PSF of the microscope objective lens. As described above, the adjustable magnification enables optimization of the imaging size for varying the distance d between qubits.

[0056] In some aspects of the present disclosure, a single switch can be used to modulate the addressing beam, the readout beam, and the interconnect beam. The single switch may use a combination of frequency division multiplexing, time division multiplexing, and / or spatial division multiplexing to modulate the beam.

[0057] Figures 10A - C show examples of schemes for multiplexing beams according to aspects of the present disclosure. Referring to FIGS. 9 and 10A - C, the second switch 830 may be configured to implement one or more of frequency - division multiplexing, space - division multiplexing, and / or time - division multiplexing. FIG. 10A shows an example of frequency - division multiplexing. The read beam and the interconnect beam can collide with the first mirror 1002 as a combined beam. Based on the frequency difference between the read beam (λ read ) and the interconnect beam (λ int ), the first mirror 1002 can direct the read beam in a first direction (e.g., towards the read unit 850) and the interconnect beam in a second direction (e.g., towards the interconnect unit 840).

[0058] FIG. 10B shows an example of space - division multiplexing according to aspects of the present disclosure. The read beam and the interconnect beam can be directed by the first lens 1004, the second mirror 1006, and / or an optional second lens 1008 to achieve space - division multiplexing. The first lens 1004 can refract the read beam and the interconnect beam towards different spatial positions. For example, the first lens 1004 can refract the interconnect beam towards the second mirror 1006 and the read beam towards an optional second lens 1008. The second mirror 1006 can reflect the interconnect beam in a second direction (e.g., towards the interconnect unit 840). The optional second lens 1008 can refract the read beam in a first direction (e.g., towards the read unit 850). In an alternative embodiment, the first lens 1004 can refract the interconnect beam and the read beam towards the second mirror 1006. The second mirror 1006 can reflect the read beam in a first direction and the interconnect beam in a second direction. Other configurations may also be implemented.

[0059] FIG. 10C shows an example of time-division multiplexing according to an aspect of the present disclosure. The read beam and the interconnect beam can be directed by a third mirror 1008 at different times to implement time-division multiplexing. For example, the interconnect beam can impinge on the third mirror 1008 at a first time. The third mirror 1008 can reflect the interconnect beam in a second direction (at the first time). The read beam can impinge on the third mirror 1008 at a second time different from the first time. Prior to the second time, the third mirror 1008 can be spatially shifted and / or rotated so that when the read beam impinges on the third mirror 1008, the third mirror 1008 can reflect the read beam in a first direction. Other configurations may also be implemented.

[0060] FIG. 13 shows an example of an operation for routing an interconnect beam by a second switch 830 according to an aspect of the present disclosure. Referring to FIGS. 8-10, the second switch 830 can enable routing of fluorescent photons collected via the interconnect unit 840 of the interconnect system 800 to a unit implementing remote entanglement between QPUs (not shown). These QPUs may be present in the same vacuum chamber or in separate chambers. The second switch 830 may be composed of a chip / tilt mirror similar to that described for separating the light intended for read and interconnect operations. Alternatively or additionally, the second switch 830 may be a photonic quantum computer that uses Mach-Zehnder interferometers etched in silicon waveguides to route photons along different paths. After routing, these photons are then sent to a unit implementing remote entanglement by interfering pairs of photons with a 50 / 50 beam splitter, thereby erasing the information of either path. Examples of implementations of these units are shown in FIGS. 14A-B for photons entangled in polarization and the degrees of freedom of occupancy, but are not limited thereto.

[0061] Refer to FIGS. 14A - B showing an example of a unit for predicting remote entanglement. The beam splitter interferes fluorescent photons and erases the information of either path. Then, depending on which degree of freedom of the photon is used for entanglement, the photon is detected either in the setup (a) or the simultaneous detection (b) of a Bell state analyzer.

[0062] FIG. 15 shows a method 1500 for implementing remote entanglement according to an aspect of the present disclosure. The method 1500 can be executed by one or more of the QIP system 200, the computer device 300, and / or the interconnection system 800, and / or one or more of their sub - components.

[0063] At 1505, the method 1500 can receive a read - out beam associated with the state of the first qubit of an array of trapped ions. For example, the optical component 810, the first switch 820, the second switch 830, and / or the interconnection system 800 can receive a read - out beam from one or more atomic arrays 802.

[0064] At 1510, the method 1500 can receive an interconnection beam configured to entangle the second qubit of the array with an external qubit of an external array. For example, the optical component 810, the first switch 820, the second switch 830, and / or the interconnection system 800 can receive an interconnection beam configured to entangle the qubits of one or more atomic arrays 802 with qubits in another QPU.

[0065] At 1515, the method 1500 can receive an addressing beam from an addressing unit configured to control the state of the third qubit of the array. For example, the first switch 820, the second switch 830, and / or the interconnection system 800 can receive an addressing beam from the addressing unit 822.

[0066] At 1520, method 1500 can direct the addressing beam from the addressing unit towards the third qubit via at least one switch. For example, the general-purpose controller 205, the optical and trap controller 220, the QIP system 200, the processor 310, the memory 320, the user interface 350, the operating system 360, the computer device 300, the switch 820, the second switch 830, and / or the interconnection system 800 can direct the addressing beam towards one or more atomic arrays 802.

[0067] At 1525, method 1500 can direct the readout beam towards the photodetector via at least one switch. For example, the general-purpose controller 205, the optical and trap controller 220, the QIP system 200, the processor 310, the memory 320, the user interface 350, the operating system 360, the computer device 300, the switch 820, the second switch 830, and / or the interconnection system 800 can direct the readout beam towards the readout unit 850 and / or one or more photodetectors 860.

[0068] At 1530, method 1500 can direct the interconnection beam towards an interconnection unit optically coupled to an external array via at least one switch. For example, the general-purpose controller 205, the optical and trap controller 220, the QIP system 200, the processor 310, the memory 320, the user interface 350, the operating system 360, the computer device 300, the switch 820, the second switch 830, and / or the interconnection system 800 can direct the interconnection beam towards the interconnection unit 840.

[0069] Aspects of the present disclosure are methods for receiving a readout beam associated with the state of a first qubit of an array of trapped ions, including receiving an interconnect beam configured to entangle a second qubit of the array with an external qubit of an external array, receiving an addressing beam from an addressing unit configured to control the state of a third qubit of the array, directing the addressing beam from the addressing unit towards the third qubit via at least one switch, directing the readout beam towards a photodetector via at least one switch, and directing the interconnect beam towards an interconnect unit optically coupled to the external array via at least one switch.

[0070] Aspects of the present disclosure include the above method further comprising receiving the readout beam and the interconnect beam via a viewport.

[0071] Aspects of the present disclosure include any of the above methods further comprising multiplexing the addressing beam with a combination of the readout beam and the interconnect beam via frequency division multiplexing.

[0072] Aspects of the present disclosure include any of the above methods further comprising multiplexing the readout beam and the interconnect beam via frequency division multiplexing.

[0073] Aspects of the present disclosure include any of the above methods further comprising multiplexing the readout beam and the interconnect beam via time division multiplexing.

[0074] Aspects of the present disclosure include any of the above methods further comprising multiplexing the readout beam and the interconnect beam via spatial division multiplexing.

[0075] The foregoing description of the disclosure is provided to enable a person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the common principles defined herein may be applied to other variations without departing from the scope of the disclosure. Further, although the elements of the described embodiments may be described or claimed in the singular, the plural is contemplated unless explicitly stated to the contrary. Additionally, unless otherwise stated, all or part of any embodiment may be used in conjunction with all or part of any other embodiment. Accordingly, the disclosure is not to be limited to the examples and designs described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

Claim 1 A method for remotely entangling a quantum processing unit (QPU), comprising: receiving, via a first switch, a readout beam associated with the state of a first qubit of an array of trapped ions; receiving, via the first switch, an interconnect beam configured to entangle a second qubit of the array with an external qubit of an external array; receiving, via the first switch, an addressing beam from an addressing unit configured to control the state of a third qubit of the array; multiplexing, via the first switch, the addressing beam with a combination of the readout beam and the interconnect beam; directing, via the first switch, the addressing beam from the addressing unit towards the third qubit, wherein the first switch is configured to direct a combination of the readout beam and the interconnect beam towards a second switch different from the first switch; separating, via the second switch, the combination of the readout beam and the interconnect beam received from the first switch; directing, via the second switch, the readout beam towards a photodetector; directing, via the second switch, the interconnect beam towards an interconnect unit optically coupled to the external array A method comprising the above steps. Claim 2 The method according to claim 1, further comprising receiving, via the first switch, the readout beam and the interconnect beam via a viewport. Claim 3 The method according to claim 1, further comprising multiplexing, via the second switch, the addressing beam with a combination of the readout beam and the interconnect beam via frequency division multiplexing. Claim 4 The method according to claim 1, further comprising multiplexing, via the second switch, the readout beam and the interconnect beam via frequency division multiplexing. Claim 5 The method according to claim 1, further comprising multiplexing the read beam and the interconnect beam via time-division multiplexing through the second switch.

6. The method according to claim 1, further comprising multiplexing the read beam and the interconnect beam via space-division multiplexing through the second switch.

7. An interconnect system for remotely entangling a quantum processing unit (QPU), an array of trapped ions, an addressing unit configured to transmit an addressing beam, receiving a read beam associated with the state of a first qubit of the array of trapped ions, receiving an interconnect beam configured to entangle a second qubit of the array with an external qubit of an external array, separating the addressing beam from the addressing unit configured to control the state of a third qubit of the array, multiplexing the addressing beam with a combination of the read beam and the interconnect beam, directing the addressing beam from the addressing unit towards the third qubit a first switch configured to, separating the read beam and the interconnect beam, directing the read beam from the first switch towards a photodetector, a second switch configured to direct the interconnect beam from the first switch towards an interconnect unit, comprising: wherein the second switch is different from the first switch, the interconnect unit is configured to be optically coupled to the external array, and the photodetector is configured to capture light emitted from the read beam. Interconnect system.

8. The interconnect system according to claim 7, further comprising a vacuum chamber, wherein the array of trapped ions is disposed within the vacuum chamber.

9. The interconnect system according to claim 8, further comprising a viewport disposed between the array of trapped ions and the first switch.

10. The interconnect system according to claim 9, further comprising an optical component disposed between the viewport and the first switch.

11. The interconnect system according to claim 10, wherein the optical component includes a microscope objective lens.

12. The interconnect system according to claim 7, wherein the addressing unit includes a variable magnification telescope.

13. The interconnect system according to claim 7, further comprising a readout unit disposed between the second switch and the photodetector.

14. The interconnect system according to claim 13, wherein the readout unit includes a variable magnification telescope.

15. The interconnect system according to claim 7, wherein the photodetector includes a charge coupled device or an avalanche photodiode.

16. The interconnect system according to claim 7, wherein the first switch is further configured to multiplex the addressing beam and the combination of the readout beam and the interconnect beam via a first mirror.

17. The interconnect system according to claim 16, wherein the second switch includes a second mirror configured to multiplex the readout beam and the interconnect beam.

18. The interconnect system according to claim 16, wherein the second switch includes a movable mirror and a lens, and the second switch is configured to multiplex the readout beam and the interconnect beam via the movable mirror and the lens.

19. The interconnect system according to claim 16, wherein the second switch is further configured to receive the combination of the readout beam and the interconnect beam, the second switch includes a rotatable mirror and a lens, and the second switch is configured to multiplex the readout beam and the interconnect beam via the rotatable mirror and the lens.

20. The interconnect system according to claim 7, wherein the interconnect unit includes one or more of a waveguide, a fiber coupling lens, or a fiber.

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