Quantum computing system with reconfigurable quantum processing units

Abstract

A quantum computing system comprising a reconfigurable quantum processing unit optically coupled to a photon source and a photon detector and having a plurality of Mach-Zehnder interferometers (MZIs); and a controller communicatively coupled to the plurality of MZIs and configured to generate a control signal to alter a phase setting of at least one of the plurality of MZIs, and the plurality of MZIs configured to alter a phase of one or more photons passing through the plurality of MZIs. Further, the quantum computing system comprises a quantum memory array having a plurality of quantum memories optically coupled to the plurality of MZIs, wherein each quantum memory is configured to absorb a photon received by the quantum memory comprising quantum information and release a photon comprising quantum information of the received photon into the reconfigurable quantum processing unit.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Application Serial No. 63 / 044,615, filed June 26, 2020, pursuant to 35 U.SC §119, and is based on the content of that provisional application, the content of which is incorporated herein by reference in its entirety. Technical Field

[0003] This specification generally relates to quantum computing systems. More specifically, this disclosure relates to quantum computing systems having reconfigurable quantum processing units for performing linear optical quantum computing. Background Technology

[0004] Linear optical quantum computing is the physical realization of a universal quantum computer using quantum gates and qubits. Currently, unitary operations can be performed on dual-track encoded photons using beam splitters and phase shifters. The simplicity and low decoherence of optical components make linear optical realizations more attractive than superconducting realizations of quantum computing. However, linear optical quantum computing uses probabilistic two-qubit and multi-qubit linear optical gates. Therefore, the output of a linear optical quantum computer may be incorrect. Thus, techniques and designs to reduce the error probability of linear optical quantum computers are desired.

[0005] An example linear computing system is described in E. Knill, R. Laflamme, and G. Milburn's "Efficient Linear Optics Quantum Computation" (arXiv:quant-ph / 0006088 (2000)), which discusses linear optical quantum computing based on beam splitters, phase shifters, and teleportation protocols for creating near-deterministic multi-qubit transitions. However, this protocol requires a large number of linear optical components to form the optical quantum computer, which raises scalability and qubit synchronization problems. Another example linear computing system is described in J. Carolan et al.'s "Universal linear optics" in Science 349, 6249, 711-716 (2015), which utilizes reconfigurable Mach-Zehnder interferometers (MZIs) to perform unitary operations. In this scheme, the total number of MZIs required for a given computational task will depend on the number of qubits and computational steps required to complete the task. Therefore, increasingly complex computational tasks require a corresponding increase in the number of MZIs, which also raises scalability and qubit synchronization issues.

[0006] Therefore, there is a need for improved, scalable quantum computing systems that can handle increasingly complex computational tasks. Summary of the Invention

[0007] According to a first aspect of this disclosure, a quantum computing system includes a reconfigurable quantum processing unit optically coupled to a photon source and a photon detector, the reconfigurable quantum processing unit having a plurality of Mach-Zehnder interferometers (MZIs), and a controller communicatively coupled to the plurality of MZIs. The controller is configured to generate control signals to change the phase setting of at least one of the plurality of MZIs, and the plurality of MZIs are configured to change the phase of one or more photons passing through the plurality of MZIs. Furthermore, the quantum computing system includes a quantum memory array having a plurality of quantum memories optically coupled to the plurality of MZIs, wherein each quantum memory is configured to absorb photons including quantum information received by the quantum memory from the reconfigurable quantum processing unit and release photons including the quantum information of the received photons into the reconfigurable quantum processing unit.

[0008] The second aspect includes the quantum computing system of the first aspect, wherein a plurality of MZIs are arranged in an MZI lattice, the MZI lattice including a first boundary MZI column disposed along a first end of a reconfigurable quantum processing unit, a second boundary MZI column disposed along a second end of a reconfigurable quantum processing unit, and one or more inner MZI columns positioned between the first boundary MZI column and the second boundary MZI column.

[0009] The third aspect includes the quantum computing system of the second aspect, wherein the first boundary MZI column is optically coupled to the adjacent inner MZI column with an offset orientation, and the second boundary MZI column is optically coupled to the adjacent inner MZI column with an offset orientation.

[0010] The fourth aspect includes the quantum computing system of the third aspect, wherein one or more internal MZI columns comprise multiple columns of internal MZI, and the internal MZI of adjacent columns are optically coupled to each other with an offset orientation.

[0011] The fifth aspect includes a quantum computing system of any one of the second to fourth aspects, wherein each first boundary MZI is optically coupled to at least one quantum memory in a quantum memory array, such that photons guided from each first boundary MZI are received by at least one quantum memory.

[0012] The sixth aspect includes a quantum computing system of any of the foregoing aspects, wherein each MZI includes an uplink path, a downlink path, a first beam splitter and a second beam splitter of the optically coupled uplink path and downlink path, a first phase shifter arranged along the uplink path or the downlink path, and a second phase shifter arranged along the uplink path or the downlink path.

[0013] The seventh aspect includes the quantum computing system of the sixth aspect, wherein the controller is configured to generate control signals to change the phase settings of the first phase shifter, the second phase shifter, or both the first phase shifter and the second phase shifter.

[0014] The eighth aspect includes the quantum computing system of the sixth or seventh aspect, wherein the controller is configured to generate control signals to change the coupling ratio of the first beam splitter, the second beam splitter, or both the first beam splitter and the second beam splitter.

[0015] The ninth aspect includes a quantum computing system comprising any one of the sixth to eighth aspects, wherein the uplink path includes a first upper link, an upper intermediate link, and a second upper link, the downlink path includes a first lower link, a lower intermediate link, and a second lower link, the first upper link and the first lower link are optically coupled to a first beam splitter, the upper intermediate link and the lower intermediate link extend between the first beam splitter and the second beam splitter and are optically coupled to the first beam splitter and the second beam splitter, the second upper link and the second lower link are optically coupled to a second beam splitter, a first phase shifter is disposed on one of the upper intermediate link and the lower intermediate link, and a second phase shifter is disposed on one of the second upper link and the second lower link.

[0016] The tenth aspect includes the quantum computing system of the ninth aspect, wherein the first upper link and the first lower link, the second upper link and the second lower link, as well as the upper middle link and the lower middle link are each optical waveguides.

[0017] The eleventh aspect includes a quantum computing system comprising any one of the sixth to tenth aspects, wherein the first beam splitter and the second beam splitter each have a coupling ratio of 50:50.

[0018] The twelfth aspect includes a quantum computing system of any of the preceding aspects, wherein a photon source and a photon detector are each part of an optical node, and the optical node further includes an optical switch located between and optically coupled to the photon source and the photon detector.

[0019] The thirteenth aspect includes the quantum computing system of the twelfth aspect, wherein an optical node is disposed between a first end of a reconfigurable quantum processing unit and a quantum memory array, the optical node further including a detection path extending between a photon source and a photon detector and through an optical switch, and a processing path extending through the optical switch non-parallel to the detection path, wherein the processing path is optically coupled to at least one MZI and at least one quantum memory in the quantum memory array.

[0020] The fourteenth aspect includes the quantum computing system of the twelfth or thirteenth aspect, wherein optical nodes are arranged in an optical node array comprising a plurality of optical nodes disposed between a first end of a reconfigurable quantum processing unit and a quantum memory array and optically coupled to the first end of the reconfigurable quantum processing unit and the quantum memory array.

[0021] The fifteenth aspect includes a quantum computing system of any of the preceding aspects, wherein the photon source is a single-photon source and the photon detector is a single-photon detector.

[0022] The sixteenth aspect includes a quantum computing system of any of the preceding aspects, wherein the quantum memory array includes a first quantum memory array, the quantum computing system further includes a second quantum memory array, and a reconfigurable quantum processing unit is positioned between and optically coupled to the first and second quantum memory arrays.

[0023] The seventeenth aspect includes the quantum computing system of the sixteenth aspect, wherein each quantum memory in the first quantum memory array and the second quantum memory array is configured to emit photons by reverse emission, such that the photons emitted by both the first quantum memory array and the second quantum memory array are directed toward a reconfigurable quantum processing unit.

[0024] The eighteenth aspect includes the quantum computing system of the sixteenth or seventeenth aspect, wherein a photon source and a photon detector are each part of an optical node, the optical node further including an optical switch positioned between and optically coupled to the photon source and the photon detector, the optical node being a separate optical node in an optical node array, and the optical node array being disposed between a reconfigurable quantum processing unit and a first quantum memory array, such that photons propagating from the reconfigurable quantum processing unit to the first quantum memory array pass through the optical switches of the respective optical nodes in the optical node array.

[0025] The nineteenth aspect includes the quantum computing system of the eighteenth aspect, wherein the optical switches of the respective optical nodes in the optical node array are configured to selectively direct photons toward a first quantum memory array, a reconfigurable quantum processing unit, and respective photon detectors of the respective optical nodes.

[0026] The twentieth aspect includes a quantum computing system comprising any one of the first to sixteenth aspects, wherein each quantum memory in the quantum memory array is configured to release photons by forward emission, such that photons directed from a first end of a reconfigurable quantum processing unit to a first end of the quantum memory are released from a second end of the quantum memory into a bypass optical path optically coupled to the second end of the reconfigurable quantum processing unit.

[0027] According to a twenty-first aspect of this disclosure, a method of performing a computational task includes: directing one or more photons into a reconfigurable quantum processing unit having a plurality of Mach-Zehnder interferometers (MZIs) such that at least one of the one or more photons passes through the reconfigurable quantum processing unit; using a quantum memory in a quantum memory array to absorb photons received from the reconfigurable quantum processing unit by the quantum memory, the received photons comprising quantum information, wherein the quantum memory array includes a plurality of quantum memories optically coupled to the plurality of MZIs of the reconfigurable quantum processing unit; generating a control signal using a controller communicatively coupled to the plurality of MZIs of the reconfigurable quantum processing unit, the control signal changing the phase setting of at least one of the plurality of MZIs; releasing photons from the quantum memory into the reconfigurable quantum processing unit such that the released photons pass through the reconfigurable quantum processing unit, wherein the released photons comprise quantum information of the absorbed photons; and using a photon detector to measure the quantum properties of the one or more released photons, wherein the quantum properties correspond to at least a portion of the computational task.

[0028] The twenty-second aspect includes the method of the twenty-first aspect, wherein the quantum properties include at least one of linear polarization, circular polarization, elliptic polarization, translational displacement, orbital angular momentum, and phase.

[0029] The twenty-third aspect includes the method of the twenty-first or twenty-second aspect, wherein directing one or more photons to a reconfigurable quantum processing unit includes emitting one or more photons from one or more photon sources and directing one or more photons to a reconfigurable quantum processing unit.

[0030] The twenty-fourth aspect includes the method of the twenty-first or twenty-second aspect, wherein directing one or more photons to a reconfigurable quantum processing unit comprises: emitting one or more photons from one or more photon sources; directing one or more photons to a quantum memory array such that one or more quantum memories in the quantum memory array absorb one or more photons; and releasing one or more photons from one or more quantum memories in the quantum memory array to the reconfigurable quantum processing unit such that the released photons include quantum information of the corresponding absorbed photons.

[0031] The twenty-fifth aspect includes the method of the twenty-fourth aspect, wherein the released photons arrive synchronously at a reconfigurable quantum processing unit.

[0032] The twenty-sixth aspect includes a method of any one of the twenty-first to twenty-fifth aspects, wherein absorbing a photon received by a quantum memory excites the atomic ensemble state of the quantum memory from a first energy state to a second energy state, and when the atomic ensemble state of the quantum memory returns to the first energy state, a release of a photon carrying the quantum information of the absorbed photon occurs.

[0033] The twenty-seventh aspect includes the method of the twenty-sixth aspect, wherein the ensemble state of the atoms of the quantum memory returns to the first energy state in response to a control signal received from the controller.

[0034] The twenty-eighth aspect includes a method of any one of the twenty-first to twenty-seventh aspects, wherein computational steps involve performing a computational task on one or more photons by passing them through a reconfigurable quantum processing unit.

[0035] The twenty-ninth aspect includes a method comprising any one of the twenty-first to twenty-eighth aspects, wherein the quantum memory array includes a first quantum memory array, a reconfigurable quantum processing unit is positioned between and optically coupled to the first and second quantum memory arrays, a photon detector is part of an optical node, the optical node further includes an optical switch positioned between and optically coupled to the photon source and the photon detector, the optical nodes are separate optical nodes in an optical node array, and the optical node array is disposed between the reconfigurable quantum processing unit and the first quantum memory array, such that photons propagating from the reconfigurable quantum processing unit to the first quantum memory array pass through the optical switches of the separate optical nodes in the optical node array.

[0036] The thirtieth aspect includes the method of the twenty-ninth aspect, wherein each quantum memory in the first quantum memory array and the second quantum memory array is configured to release photons by reverse emission, such that the photons released by both the first quantum memory array and the second quantum memory array are directed toward a reconfigurable quantum processing unit.

[0037] The thirty-first aspect includes the method of the twenty-ninth or thirtieth aspect, wherein measuring the quantum properties of one or more emitted photons includes using optical switches to direct photons toward a photon detector, wherein the optical switches of each respective optical node are configured to selectively direct photons toward a first quantum memory array, a reconfigurable quantum processing unit, and a photon detector of the respective optical node.

[0038] According to a thirty-second aspect of this disclosure, a quantum computing system includes a reconfigurable quantum processing unit having a first end, a second end, and a plurality of Mach-Zehnder interferometers (MZIs) disposed between the first and second ends, wherein the reconfigurable quantum processing unit is disposed between a first quantum memory array and a second quantum memory array. The quantum computing system also includes an optical node array having a plurality of optical nodes, wherein each optical node includes a photon source, a photon detector, and an optical switch positioned between and optically coupled to the photon source and the photon detector, and the optical node array is disposed between the first end of the reconfigurable quantum processing unit and the first quantum memory array, such that photons propagating from the first end of the reconfigurable quantum processing unit to the respective quantum memories in the first quantum memory array pass through the optical switch. Furthermore, the quantum computing system includes a controller communicatively coupled to a plurality of MZIs, wherein the controller is configured to generate control signals to change the phase setting of at least one of the plurality of MZIs, and the plurality of MZIs are configured to change the phase of one or more photons output by a photon source, and each quantum memory in a first quantum memory array and a second quantum memory array is configured to absorb photons including quantum information received from a reconfigurable quantum processing unit, and release photons including the quantum information of the received photons into the reconfigurable quantum processing unit.

[0039] The thirty-third aspect includes the quantum computing system of the thirty-second aspect, wherein a plurality of MZIs are arranged in an MZI lattice, the MZI lattice including a first boundary MZI column disposed along a first end of a reconfigurable quantum processing unit, a second boundary MZI column disposed along a second end of a reconfigurable quantum processing unit, and one or more inner MZI columns positioned between the first boundary MZI column and the second boundary MZI column, wherein the first boundary MZI column is optically coupled to an adjacent inner MZI column with an offset orientation, and the second boundary MZI column is optically coupled to an adjacent inner MZI column with an offset orientation.

[0040] The 34th aspect includes the quantum computing system of the aforementioned 32nd or 33rd aspect, wherein each MZI includes an uplink path, a downlink path, a first beam splitter and a second beam splitter of the optically coupled uplink path and downlink path, a first phase shifter arranged along the uplink path or downlink path, and a second phase shifter arranged along the uplink path or downlink path.

[0041] The thirty-fifth aspect includes the quantum computing system of the thirty-fourth aspect, wherein a controller is configured to generate control signals to change the phase settings of a first phase shifter, a second phase shifter, or both the first and second phase shifters.

[0042] The thirty-sixth aspect includes the quantum computing system of the thirty-fourth or thirty-fifth aspects, wherein a controller is configured to generate control signals to change the coupling ratio of a first beam splitter, a second beam splitter, or both the first beam splitter and the second beam splitter.

[0043] The thirty-seventh aspect includes any of the thirty-two to thirty-six aspects of a quantum computing system, wherein the photon source is a single-photon source and the photon detector is a single-photon detector.

[0044] The thirty-eighth aspect includes a quantum computing system comprising any one of the thirty-second to thirty-seventh aspects, wherein each of the first and second quantum memory arrays is configured to emit photons by reverse emission, such that the photons emitted by both the first and second quantum memory arrays are directed toward a reconfigurable quantum processing unit.

[0045] The following detailed description will describe additional features and advantages, which will be apparent to those skilled in the art from this description, or will become apparent by practicing the embodiments described herein, including the following detailed description, claims, and drawings.

[0046] It should be understood that both the foregoing general description and the following detailed description describe various embodiments, and they are intended to provide an overview or framework for understanding the nature and characteristics of the claimed subject matter.

[0047] The accompanying drawings are included to provide a further understanding of the various embodiments, and are incorporated into and form part of this specification. The drawings illustrate the various embodiments described herein and, together with the specification, serve to explain the principles and operation of the claimed subject matter. Attached Figure Description

[0048] The following detailed description of specific embodiments of this disclosure can be best understood when read in conjunction with the following accompanying drawings, in which the same structures are indicated by the same reference numerals, and in the drawings:

[0049] Figure 1 A quantum computing system according to one or more embodiments shown and described herein is schematically depicted, the quantum computing system including a reconfigurable quantum processing unit, an optical node array, and two quantum memory arrays;

[0050] Figure 2 A reconfigurable quantum processing unit including an MZI lattice is schematically depicted according to one or more embodiments shown and described herein;

[0051] Figure 3A An example MZI is schematically depicted according to one or more embodiments shown and described herein;

[0052] Figure 3B A portion of a reconfigurable quantum processing unit according to one or more embodiments shown and described herein is schematically depicted, the portion of which is optically coupled to a portion of a first quantum memory array, a second quantum memory array, and an optical node array;

[0053] Figure 4 An example optical node of an optical node array according to one or more embodiments shown and described herein is schematically depicted;

[0054] Figure 5A An example quantum computing system according to one or more embodiments shown and described herein is schematically depicted, the example quantum computing system including reconfigurable quantum processing units, an array of optical nodes, and a single quantum memory array;

[0055] Figure 5BAnother example quantum computing system according to one or more embodiments shown and described herein is schematically depicted, the example quantum computing system including reconfigurable quantum processing units, an optical node array, and two quantum memory arrays; and

[0056] Figure 6 The efficiency of a quantum memory, which varies with the optical depth of the quantum memory, is illustrated graphically according to one or more embodiments shown and described herein when the stored quantum information is released using forward propagation and when the stored quantum information is released using backward propagation. Detailed Implementation

[0057] Reference will now be made in detail to an embodiment of a quantum computing system comprising a reconfigurable quantum processing unit and one or more arrays of quantum memories for use in the quantum computing process, an example of which is illustrated in the accompanying drawings. Where possible, the same reference numerals will be used throughout the drawings to indicate the same or similar components. The reconfigurable quantum processing unit can accelerate the prototyping and scaling of quantum algorithms by enabling dynamic implementation of any single linear optical transformation using a lattice of a dynamically tunable Mach-Zehnder interferometer (MZI). Each MZI is reconfigurable in response to instructions received from a controller, allowing the reconfigurable quantum processing unit to execute a wide variety of quantum algorithms. In fact, the reconfigurable quantum processing unit is capable of implementing large, arbitrary single optical transformations to facilitate the development, optimization, and verification of linear optical quantum algorithms. Furthermore, the reconfigurable quantum processing unit is optically coupled to one or more arrays of quantum memories. These quantum memory arrays include quantum memories configured to store quantum information of received photons and release photons carrying the quantum information of the received photons. This allows each MZI to be modified while quantum information is stored in the quantum memory, enabling larger quantum algorithms to be executed by reconfiguring a smaller total number of MZIs during computational tasks. This approach allows reconfigurable quantum processing units to compute increasingly large and complex algorithms without increasing the number of optical components or the length of the chip on which these optical components are mounted.

[0058] Now for reference Figure 1The diagram schematically depicts a quantum computing system 100. The quantum computing system 100 includes a reconfigurable quantum processing unit 110, an optical node array 180, and one or more quantum memory arrays 160. The optical node array 180 is positioned between the reconfigurable quantum processing unit 110 and one of the quantum memory arrays 160, and is optically coupled to the reconfigurable quantum processing unit 110 and one of the quantum memory arrays 160. The optical node array 180 includes a plurality of optical nodes 182, each optical node 182 including a photon source 184 and a photon detector 186. Figure 4 This serves as the start and end point for each computational task. As used herein, "optical coupling" refers to two or more components arranged such that photon pulses and / or quantum information can be transmitted between them. For example, connection path 150 may optically couple a reconfigurable quantum processing unit 110, one or more quantum memory arrays 160, and an optical node array 180. Connection path 150 may include free space, free space combined with collecting optics (such as lenses), and / or optical waveguides (such as optical fibers comprising a core and a cladding surrounding the core), planar waveguides, etc.

[0059] The quantum computing system 100 further includes a controller 105, which is communicatively coupled to, for example, a reconfigurable quantum processing unit 110, one or more quantum memory arrays 160, and an optical node array 180 via one or more communication paths 102. In operation, the controller 105 provides control signals to each of them. In some embodiments, the quantum computing system 100 may be implemented as an integrated photonic device, such as a “on-chip” device. Some or all components of the quantum communication system 100 may be embedded in a planar waveguide, or may be part of a planar waveguide (e.g., a laser-written waveguide). In other embodiments, the quantum computing system 100 may include bulk optics.

[0060] Also refer to Figure 2 The reconfigurable quantum processing unit 110 is described in more detail. The reconfigurable quantum processing unit 110 includes a first end 112, a second end 114, and a plurality of MZI 122 arranged in an MZI lattice 120 between the first end 112 and the second end 114. Each MZI 122 includes a pair of beam splitters 140a and 140b and a pair of phase shifters 142a and 142b. Figure 3AThe MZI 122 can perform unitary functions on photons passing through it during operation. Multiple MZI 122s are each communicatively coupled to a controller 105, which provides control signals to the multiple MZI 122s to configure beam splitters 140a, 140b and phase shifters 142a, 142b to achieve specific unitary functions. The configuration of beam splitters 140a, 140b and phase shifters 142a, 142b of the multiple MZI 122s can be changed based on the control signals provided by the controller 105, thereby allowing each MZI 122 to implement selective, reconfigurable unitary functions. The reconfigurability throughout the MZI lattice 120 allows the MZI lattice 120 to perform computational tasks including selective, reconfigurable functions (i.e., algorithms) of arbitrarily large sizes.

[0061] Still referencing Figure 1 and Figure 2 One or more quantum memory arrays 160 may include a first quantum memory array 160a and a second quantum memory array 160b, the first quantum memory array 160a and the second quantum memory array 160b being arranged such that a reconfigurable quantum processing unit 110 is positioned between the first quantum memory array 160a and the second quantum memory array 160b. Although Figure 1 Two quantum memory arrays 160 are depicted, but it should be understood that embodiments are contemplated to have a single quantum memory array 160, such as Figure 5A The embodiment depicted herein. Each quantum memory array 160 includes a plurality of quantum memories 165, each quantum memory 165 including a first end 166 opposite to a second end 168. The first end 166 of each quantum memory 165 is optically coupled to a reconfigurable quantum processing unit 110 such that photons output by the reconfigurable quantum processing unit 110 are received by the first end 166. For example, the first end 166 of each quantum memory 165 can be optically coupled to the reconfigurable quantum processing unit 110 using a connection path 150. Figure 1 In the schematic arrangement shown, the first end 166 of each quantum memory 165 in the first quantum memory array 160a faces the first end 112 of the reconfigurable quantum processing unit 110, and the first end 166 of each quantum memory 165 in the second quantum memory array 160b faces the second end 114 of the reconfigurable quantum processing unit 110. However, it should be understood that various spatial arrangements can be conceived while maintaining the optical coupling between the reconfigurable quantum processing unit 110 and the first ends 166 of the quantum memories 165 in the first quantum memory array 160a and the second quantum memory array 160b.

[0062] Each quantum memory 165 is structurally configured to store quantum information of a received photon and release the received quantum information on another photon. More specifically, while not intended to be theoretically limited, each quantum memory 165 is structurally configured to absorb a photon pulse upon receipt via a nonlinear optical process, thereby exciting the atomic ensemble state of the quantum memory 165 from a first energy state (such as a ground state) to a second energy state (such as a non-ground state, e.g., an excited state). As used herein, an “atomic ensemble state” refers to the arrangement of energy states comprising the atoms of the quantum memory 165. As a non-limiting example, in the first energy state, the electrons of the quantum memory 165 may be in the ground state, and in the second energy state, some of those electrons may enter an excited state. In some embodiments, the first energy state may have a lower total energy than the second energy state.

[0063] While not intended to be theoretically limited, the atomic ensemble state of each quantum memory 165 can return to a first energy state after a period of time without external stimulation, or upon receiving an external stimulus (such as a control signal from controller 105). While not intended to be theoretically limited, photons emitted by quantum memory 165 can include quantum information (e.g., quantum properties), such as coherence properties, of photons received and absorbed by quantum memory 165. As used herein, “quantum” refers to information relating to the state of a photon, such as one or more measurable quantum properties of the photon, for example, polarization (such as linear, circular, elliptical, or any other polarization), translational displacement, orbital angular momentum, phase, etc. In other words, photons emitted by quantum memory 165 can be in the same quantum state as photon pulses received by quantum memory 165.

[0064] This allows controller 105 to reconfigure some or all of the MZI 122 in the MZI lattice 120 while the quantum information of the photons already stored in the quantum memory array 160 via the reconfigurable quantum processing unit 110. Therefore, after performing the first computational step, the MZI 122 can be reconfigured to perform a second computational step. Then, when the quantum memory 165 releases photons carrying the quantum information of the received photons, these released photons can return through the MZI lattice 120 as if the MZI lattice 120 included additional MZI 122. This process can be repeated to perform additional computational steps. In effect, one or more quantum memory arrays 160 allow the quantum computing system 100 to perform increasingly larger and more complex functions without requiring a larger number of MZI 122. For example, in Figure 1In the embodiments depicted, the first quantum memory array 160a and the second quantum memory array 160b can be optically coupled to opposite sides (i.e., the first end 112 and the second end 114) of the reconfigurable quantum processing unit 110, allowing photons to propagate between the first quantum memory array 160a and the second quantum memory array 160b through the reconfigurable quantum processing unit 110 during each pass. Furthermore, including one or more quantum memory arrays 160 allows for error detection during computational tasks, enabling the task to be aborted and restarted during the process.

[0065] In operation, photons are directed in the memory input direction to each quantum memory 165 in one or more quantum memory arrays 160, and photons are released in the memory output direction from each of the quantum memory arrays 160. Without being theoretically limited, each quantum memory 165 can be configured to release particles via forward or backward emission. During backward emission, the memory input direction of the quantum memory 165 is opposite to the memory output direction. For example, during backward emission, the quantum memory 165 receives and releases photons at a first end 166. During forward emission, the memory input direction of the quantum memory 165 is the same as the memory output direction. For example, during forward emission, the quantum memory 165 receives photons at a first end 166 and releases photons at a second end 168, which may be opposite the first end 166.

[0066] exist Figure 1 In the embodiment depicted, photons are directed in the memory input direction 10a to each quantum memory 165 in the first quantum memory array 160a, and in the memory input path 10b to each quantum memory 165 in the second quantum memory array 160b. Photons are released from each quantum memory 165 in the first quantum memory array 160a in the memory output direction 12a, and from each quantum memory 165 in the second quantum memory array 160b in the memory output direction 12b. Figure 1 In the quantum computing system 100, quantum memory 165 in the first quantum memory array 160a and the second quantum memory array 160b is configured to release photons by reverse emission, thereby directing the photons back to the reconfigurable quantum processing unit 110 in the opposite direction to where they were received. In alternative embodiments (such as...) Figure 5A and Figure 5B In the embodiment depicted herein, a quantum memory 165' configured to release photons via forward emission is envisioned. Figure 5A and Figure 5BIn the quantum memory 165', photons are received at the first end 166 and released from the second end 168.

[0067] Each quantum memory 165 in one or more quantum memory arrays 160 may include any known or undeveloped quantum memory, such as a quantum memory based on an atomic frequency comb (AFC) atomic ensemble or a quantum memory based on a controlled reversible non-uniform broadening (CRIB) atomic ensemble. Using each of these atomic ensembles, individual photon pulses can be absorbed in such a manner that the quantum information of the received photon pulse is preserved by the atomic ensemble, and can be released as a released photon that shares quantum information with the corresponding received photon, such as some or all of the measurable quantum properties of the corresponding received photon. For example, the released photon may be released upon request (e.g., upon receiving a control signal from controller 105) or after a set delay.

[0068] Some examples of quantum memories are described in Sangouard et al., “Quantum Repeaters Based on Atomic Ensembles and Linear Optics” (Review of Modern Physics, January–March 2011, Vol. 83, pp. 33–80), where quantum memories are used in quantum repeaters to achieve entanglement swapping. Other examples of quantum memories include the quantum memory system described in U.S. Patent Publication No. 2018 / 0322921, entitled “Quantum Memory Systems and Quantum Repeater Systems Comprising Doped Polycrystalline Ceramic Optical Devices and Methods of Manufacturing the Same,” assigned to Corning Incorporated, Corning, NY. Other examples of quantum memories can be implemented in microwave or radio frequency (RF) environments, where the electromagnetic field of photons is used as the fundamental carrier of information along a waveguide (e.g., a metallic, superconducting waveguide). An example of this approach is described in Moiseev et al., “Broadband Multiresonator Quantum Memory-Interface” (Scientific Reports 8:3982 (2018)). Other example quantum memories can be implemented using microresonators for photons in the optical and / or telecommunications wavelength range. Furthermore, these example quantum memories can convert optical photons to microwave photons and vice versa. An example of this approach is described in Williamson et al., “Magneto-Optic Modulator with Unit Quantum Efficiency”, Physical Review Letters 113, 203601 (November 14, 2014).

[0069] Still referencing Figure 1 and Figure 2The MZI lattice 120 of the reconfigurable quantum processing unit 110 includes a first boundary MZI 123 column disposed along a first end 112 of the reconfigurable quantum processor 110, a second boundary MZI 125 column disposed along a second end 114 of the reconfigurable quantum processor 110, and one or more internal MZI 124 columns positioned between the first boundary MZI 123 and the second boundary MZI 125. For example, using connection path 150, a plurality of first boundary MZI 123 are optically coupled to a first quantum memory array 160a, and a plurality of second boundary MZI 125 are optically coupled to a second quantum memory array 160b. Figure 2 As depicted, the first boundary MZI 123 column and the second boundary MZI 125 column each comprise a single column MZI 122. Furthermore, although the inner MZI 124 column... Figure 2 It is depicted as a single-row MZI 122, but it should be understood that the MZI lattice 120 may include multiple rows of internal MZI 124.

[0070] Now for reference Figure 3A A single MZI 122 is schematically depicted. The MZI 122 includes a first beam splitter 140a, a second beam splitter 140b, a first phase shifter 142a, and a second phase shifter 142b. Furthermore, the MZI 122 includes a pair of first end links 134a and 134b, a pair of second end links 136a and 136b, and a pair of intermediate links 132a and 132b. Specifically, the MZI 122 includes: an upper first end link 134a and a lower first end link 134b, each optically coupled to the first beam splitter 140a; an upper intermediate link 132a and a lower intermediate link 132b, each optically coupled to the first beam splitter 140a and the second beam splitter 140b and extending between the first beam splitter 140a and the second beam splitter 140b; and an upper second end link 136a and a lower second end link 136b, each optically coupled to the second beam splitter 140b. The first-end links 134a and 134b, the second-end links 136a and 136b, and the intermediate links 132a and 132b may include waveguides, such as optical fibers or planar waveguides.

[0071] Furthermore, it should be understood that the terms "upper" and "lower" are used to distinguish the individual links in each pair of links in MZI 122, and are not limited to the specific geometric relationship between the links. The upper first-end link 134a, upper intermediate link 132a, or upper second-end link 136a can be collectively referred to as the upper link and together form the upper link path 130a. The lower first-end link 134b, lower intermediate link 132b, or lower second-end link 136b can be collectively referred to as the lower link and together form the lower link path 130b. Moreover, this document uses link path 130 as a general description of the upper link path 130a or the lower link path 130b. For example, each individual optical node 182 is optically coupled to its respective link path 130.

[0072] exist Figure 3A In the embodiment depicted, a first phase shifter 142a is disposed on an upper intermediate link 132a, and a second phase shifter 142b is disposed on an upper second end link 136a. Each phase shifter 142a, 142b is configured to adjust the phase (between 0 and 2π) of photons passing through the phase shifters 142a, 142b. This also changes the relative phase between photons passing through a link with a phase shifter (e.g., upper link path 130a) and photons passing through a link without a phase shifter (e.g., lower link path 130b). A controller 105 is communicatively coupled to each MZI 122, for example along communication path 102, and is configured to change the phase setting of the phase shifters 142a, 142b of each MZI 122 in the MZI lattice 120. For example, the controller 105 may be configured to change the phase setting of photons from the physical phase shifter (e.g., ...) of each MZI 122. Figure 3A The propagation (travel) time is the time taken from the start to the end of the journey of phase shifters 142a and 142b. Changing the propagation (travel) time can be achieved, for example, by changing the refractive index n of the material of phase shifters 142a and 142b, and thus changing the optical path length L. The net phase change applied by controller 105 can be any value between 0 and 2π. Tuning the phase difference allows each MZI 122 to achieve any 2×2 unitary function.

[0073] Phase shifter 142 may include tunable phase shifters, such as thermo-optic phase shifters, electro-optic phase shifters, and all-optical phase shifters. An example thermo-optic phase shifter is described in Harris et al., “Efficient, compact and low loss thermo-optic phase shifter in silicon,” Optics Express 22(9), 10487–10493 (2014). An example electro-optic phase shifter is described in Macik et al., “Optimization of electro-optic phase shifters for integrated optical phased arrays,” SPIE Proceedings 10181, Advanced Optics for Defense Applications: UV to LWIR II, 1018105 (May 11, 2017). Furthermore, an example all-optical phase shifter is described in Wu et al.'s "An alloptical phase shifter and switch near 1550nm using tungsten disulfide (WS2) deposited tapered fiber" (arXiv: 1612.04525).

[0074] Although not depicted, it should be understood that the first phase shifter 142a may alternatively be disposed on the lower intermediate link 132b, and the second phase shifter 142b may alternatively be disposed on the lower second terminal link 136b. Furthermore, some embodiments may include additional phase shifters. As an example, a third phase shifter may be disposed on either the lower intermediate link 132b or the lower second terminal link 136b. As another example, a third phase shifter may be disposed on the lower intermediate link 132b, and a fourth phase shifter may be disposed on the lower second terminal link 136b. Including additional phase shifters in the MZI 122 can add additional tunability to the MZI 122.

[0075] The first beamsplitter 140a and the second beamsplitter 140b may include 50:50 beamsplitters. The 50:50 beamsplitters have a 50:50 coupling ratio, such that beamsplitters 140a and 140b direct 50% of the photons entering beamsplitters 140a and 140b to the uplink and 50% of the photons entering beamsplitters 140a and 140b to the downlink. However, it should be understood that the first beamsplitter 140a and the second beamsplitter 140b may include other coupling ratios, for example, a coupling ratio range from 10:90 to 90:10, such as 20:80, 25:75, 40:60, 45:55, 50:50, 55:45, 60:40, 75:25, 80:20, etc. In practice, in some embodiments, for example, the coupling ratio of the first beam splitter 140a and the second beam splitter 140b can be changed based on control signals received from the controller 105 along one or more communication paths 102. The first beam splitter 140a and the second beam splitter 140b may include, for example, directional couplers, multimode interferometers, stimulated Raman adiabatic channel (STIRAP) couplers, or other beam splitting devices known in the art.

[0076] Now for reference Figures 2-3B The first boundary MZI 123 column is optically coupled to the adjacent inner MZI 124 column with an offset orientation, and the second boundary MZI column is optically coupled to the adjacent inner MZI 124 column with an offset orientation. Furthermore, in embodiments including multiple inner MZI 124 columns, adjacent inner MZI columns are optically coupled to each other with an offset orientation. In fact, in some embodiments, each adjacent MZI 122 column is offset. As used herein, when an uplink path 130a of one MZI 122 connects to a downlink path 130b of an adjacent MZI, the optically coupled MZI 122 are offset from each other. In some embodiments, the MZI lattice 120 may further include one or more bypass edge links 129 that extend along the top or bottom of the MZI lattice 120 through at least one column of inner MZI 124. Figure 2 In the illustrated embodiment, the bypass edge link 129 extends between the uplink path 130a of the topmost first boundary MZI 123 and the second boundary MZI 125, and between the downlink path 130b of the bottommost first boundary MZI 123 and the second boundary MZI 125. In practice, because the reconfigurable quantum processing unit 110 has some finite size, the bypass edge link 129 is located at the edges (i.e., the topmost and bottommost edges of the reconfigurable quantum processing unit 110) to provide finite edge paths.

[0077] Figure 3BThe offset orientation is shown in more detail by depicting a portion of each of the first boundary MZI column 123, the second boundary MZI column 125, and the inner MZI column 124. Specifically, Figure 3B The diagram depicts two first boundary MZIs 123a and 123b in column 123 of the first boundary MZI, two second boundary MZIs 125a and 125b in column 125 of the second boundary MZI, and a single internal MZI 124a in column 124 of the inner boundary MZI. An uplink path 130a of the internal MZI 124a connects to a downlink path 130b of the first boundary MZI 123a and the second boundary MZI 125a at the opposite end of the internal MZI 124a. Furthermore, a downlink path 130b of the internal MZI 124a connects to an uplink path 130a of the first boundary MZI 123b and the second boundary MZI 125b. Offsetting each adjacent MZI 122 column without intending to be theoretically constrained increases the possible paths for photons to propagate from the first end 112 to the second end 114 of the reconfigurable quantum processing unit 110, thereby increasing the complexity of the algorithm that can be implemented by the reconfigurable quantum processing unit 110.

[0078] Now for reference Figures 1-4 An optical node array 180 is positioned between a reconfigurable quantum processing unit 110 and one of one or more quantum memory arrays 160, and is optically coupled to the reconfigurable quantum processing unit 110 and one of the one or more quantum memory arrays 160. Figure 1 In the embodiment depicted, the optical node array 180 is positioned between the first end 112 of the reconfigurable quantum processing unit 110 and the first quantum memory array 160a. However, it should be understood that the optical node array 180 may be positioned adjacent to and optically coupled to the first end 112 or the second end 114 of the reconfigurable quantum processing unit 110. Figure 4 As shown, each optical node 182 in the optical node array 180 includes a photon source 184, a photon detector 186, and an optical switch 188 positioned between and optically coupled to the photon source 184 and the photon detector 186. The photon source 184 may include a single-photon source, such as a quantum dot, color center, etc. Furthermore, the photon detector 186 includes a single-photon detector, such as a superconducting nanowire single-photon detector, a carbon nanowire detector, an avalanche photodiode detector, a low-dark-count photodiode detector, etc.

[0079] Optical node 182 includes a detection path 190 and a processing path 192. Detection path 190 extends between photon source 184 and photon detector 186 and passes through optical switch 188. Processing path 192 also passes through optical switch 188 non-parallel to detection path 190, for example, orthogonal to detection path 192. Connecting path 190 and processing path 192 may include free space, free space combined with collecting optics (such as lenses) and / or optical waveguides (such as optical fibers including a core and a cladding surrounding the core), planar waveguides, etc. Processing path 192 is optically coupled to reconfigurable quantum processing unit 110 and first quantum memory array 160a. In some embodiments, processing path 192 may extend from link path 130 of first boundary MZI 123 to respective quantum memories 165 and pass through optical switch 188. In other embodiments, processing path 192 passes through optical switch 188 and is optically coupled via link path 130 to the first boundary MZI 123 and the respective quantum memory 165 via connection path 150. Furthermore, each optical node 182 is communicatively coupled to controller 105, such that photon source 184, photon detector 186, and optical switch 188 can receive control signals from controller 105 and provide feedback to controller 105, for example, along communication path 102.

[0080] In operation, photon source 184 generates photons and guides them along detection path 190 from photon source 184 to optical switch 188. At optical switch 188, photons can be guided toward reconfigurable quantum processing unit 110, quantum memory array 160 (i.e., first quantum memory array 160a), or photon detector 186. In operation, optical switch 188 can selectively guide photons from photon source 184 to respective quantum memories 165 of quantum memory array 160 or respective MZIs 122 of reconfigurable quantum processing unit 110. Optical switch 188 can also selectively allow photons to pass, for example, along processing path 192 between respective quantum memories 165 of quantum memory array 160 and respective MZIs 122 of reconfigurable quantum processing unit 110. Furthermore, the optical switch 188 can selectively direct photons received from the respective quantum memories 165 of the quantum memory array 160 or the respective MZI 122 of the reconfigurable quantum processing unit 110 to the photon detector 186 for detection and measurement. The detection results at the photon detector 186 can then be sent to the controller 105.

[0081] refer to Figures 1-4The method of performing computational tasks using the quantum computing system 100 will now be described. At the start of a computational task, the controller 105 sends control signals to the photon source 184 and optical switch 188 of each optical node 182. The control signals instruct the photon source 184 to emit one or more photons respectively, and instruct the optical switch 188 to guide the emitted photons from the optical node array 180 to a first quantum memory array 160a or a first end 112 of a reconfigurable quantum processing unit 110. Guiding photons to the first quantum memory array 160a before their first passage through the reconfigurable quantum processing unit 110 allows the photons to be released from the first quantum memory array 160a, ensuring that the photons arrive at the reconfigurable quantum processing unit 110 synchronously. However, during some operations, the optical switch 188 may initially guide some or all of the emitted photons directly toward the reconfigurable quantum processing unit 110.

[0082] Before photons arrive at the reconfigurable quantum processing unit 110, the controller 105 sends control signals to the reconfigurable quantum processing unit 110 to configure each MZI 122 of the reconfigurable quantum processing unit 110 for the first step of the computational task. For example, the control signals may set (i.e., change or maintain) the phase setting of each phase shifter 142 among the multiple MZIs 122, and in some embodiments, the coupling ratio of each beam splitter 140 may be set. In the operation in which photons are first sent to the first quantum memory array 160a, the controller 105 may send control signals to the first quantum memory array 160a to time the release of photons, such that the reconfigurable quantum processing unit 110 is configured to perform the first computational step on it when photons arrive at the reconfigurable quantum processing unit 110.

[0083] Next, the photons propagate through a reconfigurable quantum processing unit 110, where they undergo a first computational step before reaching a second quantum memory array 160b. At the second quantum memory array 160b, the photons are absorbed by a quantum memory 165 to store the output state (i.e., quantum information) of each photon. For example, absorbing photons received by the quantum memory 165 excites the atomic ensemble states of the quantum memory 165 from a first energy state to a second energy state. The method then includes generating control signals using a controller 105 to set (i.e., change or maintain) the phase setting of the phase shifter 142, and in some embodiments, setting (i.e., changing or maintaining) the coupling ratio of the beam splitters 140 of a plurality of MZIs 122. These phase settings and / or coupling ratios correspond to a second computational step of the computational task. Next, the method includes releasing photons carrying the absorbed quantum information from the second quantum memory array 160b into the reconfigurable quantum processing unit 110, such that the released photons pass through the reconfigurable quantum processing unit 110 when the MZI 122 is set up for the second computational step of the computational task.

[0084] For example, in response to a control signal from controller 105, photons are released when the atomic ensemble state of the quantum memory returns to the first energy state. Each released photon carries quantum information corresponding to the absorbed photon, and the released photon passes through the reconfigurable quantum processing unit 110 to undergo the second computational step of the computational task. Furthermore, the release of photons from the second quantum memory array 160b can be controlled to facilitate the synchronous arrival of photons at the reconfigurable quantum processing unit for the second computational step. In practice, each computational step can be synchronized by the controller 105 sending a control signal to release photons from the first quantum memory array 160a and the second quantum memory array 160b.

[0085] After passing through the reconfigurable quantum processing unit 110, photons that have undergone the second computational step can be absorbed by the first quantum memory array 160a. Next, control signals are sent by the controller 105 to set (i.e., change or maintain) the phase setting of the phase shifter 142, and in some embodiments, to set (i.e., change or maintain) the coupling ratio of the beam splitter 140 of the plurality of MZIs 122. These phase settings and / or coupling ratios correspond to the third computational step of the computational task. Next, photons carrying the absorbed quantum information are released from the first quantum memory array 160a and pass through the reconfigurable quantum processing unit 110 to undergo the third computational step. Additional passages through the reconfigurable quantum processing unit 110 can be repeated to perform additional computational steps. These additional passages include: absorbing quantum information in the quantum memory array 160, setting the phase setting and / or coupling ratio of the MZIs 122 of the reconfigurable quantum processing unit 110, and guiding photons through the reconfigurable quantum processing unit 110.

[0086] Next, the method includes measuring the quantum properties of one or more emitted photons using a photon detector, wherein the quantum properties correspond to at least a portion of the computational task. Specifically, controller 105 may send control signals to one or more optical switches 188, causing these optical switches 188 to direct photons to photon detector 186. In some embodiments, controller 105 may also send control signals to photon sources 184 of optical nodes 182 where a detection event has occurred, instructing these photon sources 184 to emit one or more additional photons as needed to perform the computational task. In practice, in some embodiments, a portion of the reconfigurable quantum processing unit 110 may be programmed by controller 105 to run intermediate measurements (i.e., tasks in computation) to determine if an error has occurred. These intermediate tasks allow controller 105 to determine whether an error has occurred during, rather than after, the computational task. If an error is detected, controller 105 may instruct the reconfigurable quantum processing unit 110 to stop operating and restart the computational task. This allows for faster error correction than embodiments that determine errors upon completion of the computational task.

[0087] Without being theoretically constrained, in order to perform intermediate measurements, controller 105 configures some of the optical nodes 182 and their corresponding (i.e., optically coupled) MZIs 122 as auxiliary channels. For example, a subset of the optically coupled MZIs 122 extending from the first end 112 to the second end 114 of the reconfigurable quantum processing unit 110 can be programmed to perform intermediate computation tasks on photons, such that intermediate measurements can be performed at the associated optical nodes 182. Furthermore, this subset of MZIs 122 can be programmed to sequester photons emitted by one or more optical nodes 182 configured to run intermediate measurements from photons (i.e., used as qubits) passing through the reconfigurable quantum processing unit 110 performing computation tasks, so that these intermediate photons do not interrupt the computation task. Without being bound by theory, when performing a computational task using the reconfigurable quantum processing unit 110, photons passing through the reconfigurable quantum processing unit 110 (i.e., photons used as qubits) form a collective superposition, making it possible that only photons passing through the reconfigurable quantum processing unit 110 can correctly perform the computational task. Therefore, by performing intermediate measurements during the computational task to determine whether the collective superposition has caused an error, the computational task can be stopped and restarted midway through the computation, thereby reducing the total computation time and improving the speed and efficiency of the quantum computing system 100.

[0088] In some embodiments, such as Figure 1 As shown, photons are guided back and forth between the first quantum memory array 160a and the second quantum memory array 160 during each pass. In fact, in Figure 1 In the embodiment depicted, each of the quantum memories 165 emits photons via reverse emission, wherein the memory output direction 12a of the first quantum memory array 160a is opposite to the memory input direction 10a of the first quantum memory array 160a, and the memory output direction 12b of the second quantum memory array 160b is opposite to the memory input direction 10b of the second quantum memory array 160b. Because the first quantum memory array 160a and the second quantum memory array 160b operate via reverse emission in the embodiment of the quantum computing system 100, photons can pass back and forth through the MZI lattice 120 multiple times. Therefore, each pass through the MZI lattice 120 executes a single computational step of the quantum algorithm.

[0089] In other embodiments, a quantum memory 165 operating via forward emission can be used to perform computational tasks. Now refer to... Figure 5A and Figure 5B Embodiments of quantum computing systems 100' and 100" are depicted, wherein a quantum memory 165 operates via forward emission. For example, Figure 5AThe quantum computing system 100' includes a single quantum memory array 160', which includes a quantum memory 165' configured to release photons via forward emission. Specifically, in Figure 5A In the embodiment depicted, the memory input direction 10a and memory output direction 12a of the quantum memory 165' are identical. Therefore, photons are released into a bypass optical path 152 optically coupled to the reconfigurable quantum processing unit 110; instead of being guided back along the same path that received the photons (e.g., along the connection path 150). Figure 5A In the embodiment depicted, a quantum memory array 160' is optically coupled to a first end 112 of a reconfigurable quantum processing unit 110 via an optical node array 180, and optically coupled to a second end 114 of the reconfigurable quantum processor 110 via a bypass optical path 152. In fact, the bypass optical path 152 extends from the quantum memory 165' to the second end 114 of the reconfigurable quantum processing unit 110. Therefore, in operation, photons emitted from the quantum memory array 160' travel from the second end 114 through the reconfigurable quantum processing unit 110 to the first end 112. Each computational step allows the reconfigurable quantum processing unit 110 to perform a computational task.

[0090] Now for reference Figure 5B The quantum computing system 100" includes a quantum memory 165 that operates via forward emission and is arranged in a first quantum memory array 160a' and a second quantum memory array 160'. The first quantum memory array 160a' of the quantum computing system 100" is arranged in a manner similar to... Figure 5A The operation is carried out in the manner of a single quantum memory array 160': wherein quantum memory 165' in the first quantum memory array 160a' receives photons at a first end 166 in the memory input direction 10a, and releases the received photons from a second end 168 into a bypass optical path 152 in the memory output direction 12a, the same as the memory input direction 10a. However, with Figure 5A Unlike the first quantum computing system 100a', the second quantum memory array 160b' includes a second quantum memory array 160b' located near the second end 114 of the reconfigurable quantum processing unit 110. Similar to the first quantum memory array 160a', the second quantum memory array 160b' includes a plurality of quantum memories 165' configured to operate via forward emission. The second quantum memory array 160b' can be used to facilitate the synchronous arrival of photons at the reconfigurable quantum processing unit 110. For example, the second quantum memory array 160b' can correct any timing misalignments that occur when photons pass through the bypass optical path 152.

[0091] Now for reference Figure 6 Figure 50 depicts the quantum memory efficiency (e.g., absorption efficiency) dependent on the optical depth αL for example quantum memories that release photons via forward emission (such as quantum memory 165') (line 52) and example quantum memories that release photons via reverse emission (such as quantum memory 165) (line 54). Without intending to be theoretically limited, during forward emission, the released photons can be partially reabsorbed by the quantum memory material, which may lead to measurement errors in quantum computing systems 100, 100', 100" . However, this partial reabsorption can be reduced and / or eliminated by reverse emission, as reverse emission suppresses the reabsorption of released photons. In fact, as... Figure 6 As shown, reverse emission can occur with up to 100% efficiency (line 54), while forward emission can occur with no more than 54% efficiency (line 52). Therefore, the quantum computing system 100 including the quantum memory 165 can operate with increased efficiency and reduced error. However, in some embodiments, using forward emission can be advantageous, for example, when a single quantum memory array is desired, to reduce the cost and size of the quantum computing system, such as... Figure 5A As shown in the image.

[0092] Based on the above description, it should be understood that a quantum computing system may include reconfigurable quantum processing units and one or more arrays of quantum memories for quantum computing processes. The reconfigurable quantum processing units comprise lattices of dynamically tunable quantum quantum inks (MZIs), each of which can be reconfigured in response to instructions received by a controller, thereby allowing the reconfigurable quantum processing units to execute a wide variety of quantum algorithms. Furthermore, the quantum memory arrays include quantum memories that allow modification of each MZI while quantum information is stored in the quantum memory and facilitate synchronization of photon propagation through the reconfigurable quantum processing units. Therefore, by reconfiguring during computational tasks, a smaller number of MZIs can be used to process larger quantum algorithms. Thus, the quantum computing system described herein provides a scalable system for computing increasingly large and complex algorithms.

[0093] In order to describe and define the technology of this invention, it should be noted that the use of the term "function" as a parameter or other variable herein is not intended to imply that the variable is merely a function of the listed parameters or variables. Rather, the use of the term "function" as a listed parameter herein is intended to be open-ended, such that the variable may be a function of a single parameter or multiple parameters.

[0094] It should also be noted that the description of "at least one" component, element, etc. in this article should not be used to infer that the alternative use of the article "a" or "one" should be limited to a single component, element, etc.

[0095] Note that descriptions herein of components being “configured” in a particular manner to embody particular characteristics or function in a particular way are structural descriptions, contrary to descriptions of their intended use. More specifically, references herein to a component being “configured” refer to the existing physical conditions of the component and are therefore considered explicit descriptions of the component’s structural characteristics.

[0096] For purposes of describing and defining the techniques of the invention, note that the terms “substantially” and “about” are used herein to indicate the inherent uncertainty attributable to any quantitative comparison, numerical value, measurement, or other representation. The terms “substantially” and “about” are also used herein to indicate the extent to which a quantitative representation may differ from the stated reference without altering the essential function of the subject matter.

[0097] Having described the subject matter of this disclosure in detail and with reference to specific embodiments thereof, it should also be noted that the various details disclosed herein should not be construed as implying that such details relate to elements that are fundamental components of the various embodiments described herein, even where specific elements are shown in each of the accompanying drawings. Furthermore, it will be apparent that modifications and variations are possible without departing from the scope of this disclosure, including but not limited to the embodiments defined in the appended claims. More specifically, while some aspects of this disclosure are identified herein as preferred or particularly advantageous, it is conceivable that this disclosure is not necessarily limited to these aspects.

[0098] Note that one or more of the appended claims use the term "characterized in / wherein" as a transitional phrase. For the purpose of defining the technology of the invention, it should be noted that this term is introduced into the appended claims as an open-ended transitional phrase used to introduce a description of a series of characteristics of the structure, and should be interpreted in a similar manner to the more commonly used open-ended prepositional term "comprising".

Claims

1. A quantum computing system, comprising: A reconfigurable quantum processing unit, optically coupled to a photon source and a photon detector, the reconfigurable quantum processing unit comprising multiple Mach-Zehnder interferometers (MZIs); A controller, communicatively coupled to the plurality of MZIs, wherein the controller is configured to generate control signals to change the phase setting of at least one of the plurality of MZIs, and the plurality of MZIs are configured to change the phase of one or more photons passing through the plurality of MZIs; as well as A quantum memory array comprising multiple quantum memories optically coupled to the plurality of MZIs, wherein each quantum memory is configured to absorb photons including quantum information received by the quantum memory from the reconfigurable quantum processing unit, and to release photons including the quantum information of the received photons into the reconfigurable quantum processing unit. The plurality of MZI atoms are arranged in an MZI lattice, the MZI lattice comprising: A first boundary MZI column is set along the first end of the reconfigurable quantum processing unit; A second boundary MZI column is arranged along the second end of the reconfigurable quantum processing unit; and One or more inner MZI columns are positioned between the first boundary MZI column and the second boundary MZI column, wherein the first boundary MZI column is optically coupled to the adjacent inner MZI column with an offset orientation, and the second boundary MZI column is optically coupled to the adjacent inner MZI column with an offset orientation.

2. The quantum computing system of claim 1, wherein the one or more internal MZI columns comprise multiple columns of internal MZI, and the internal MZI of adjacent columns are optically coupled to each other with an offset orientation.

3. A quantum computing system, comprising: A reconfigurable quantum processing unit, optically coupled to a photon source and a photon detector, the reconfigurable quantum processing unit comprising multiple Mach-Zehnder interferometers (MZIs); A controller, communicatively coupled to the plurality of MZIs, wherein the controller is configured to generate control signals to change the phase setting of at least one of the plurality of MZIs, and the plurality of MZIs are configured to change the phase of one or more photons passing through the plurality of MZIs; as well as A quantum memory array comprising multiple quantum memories optically coupled to the plurality of MZIs, wherein each quantum memory is configured to absorb photons including quantum information received by the quantum memory from the reconfigurable quantum processing unit, and to release photons including the quantum information of the received photons into the reconfigurable quantum processing unit. The plurality of MZI atoms are arranged in an MZI lattice, the MZI lattice comprising: A first boundary MZI column is set along the first end of the reconfigurable quantum processing unit; A second boundary MZI column is arranged along the second end of the reconfigurable quantum processing unit; and One or more inner MZI columns are located between the first boundary MZI column and the second boundary MZI column. Each first boundary MZI is optically coupled to at least one quantum memory in the quantum memory array, such that photons guided from each first boundary MZI are received by at least one quantum memory.

4. A quantum computing system, comprising: A reconfigurable quantum processing unit, optically coupled to a photon source and a photon detector, the reconfigurable quantum processing unit comprising multiple Mach-Zehnder interferometers (MZIs); A controller, communicatively coupled to the plurality of MZIs, wherein the controller is configured to generate control signals to change the phase setting of at least one of the plurality of MZIs, and the plurality of MZIs are configured to change the phase of one or more photons passing through the plurality of MZIs; as well as A quantum memory array comprising multiple quantum memories optically coupled to the plurality of MZIs, wherein each quantum memory is configured to absorb photons including quantum information received by the quantum memory from the reconfigurable quantum processing unit, and to release photons including the quantum information of the received photons into the reconfigurable quantum processing unit. Each MZI includes an uplink path, a downlink path, a first beam splitter and a second beam splitter optically coupling the uplink path and the downlink path, a first phase shifter arranged along the uplink path or the downlink path, and a second phase shifter arranged along the uplink path or the downlink path. in i) The controller is configured to generate control signals to change the phase settings of the first phase shifter, the second phase shifter, or both the first phase shifter and the second phase shifter; or ii) The controller is configured to generate control signals to change the coupling ratio of the first beam splitter, the second beam splitter, or both the first beam splitter and the second beam splitter; or iii) The first beam splitter and the second beam splitter each have a coupling ratio of 50:

50.

5. A quantum computing system, comprising: A reconfigurable quantum processing unit, optically coupled to a photon source and a photon detector, the reconfigurable quantum processing unit comprising multiple Mach-Zehnder interferometers (MZIs); A controller, communicatively coupled to the plurality of MZIs, wherein the controller is configured to generate control signals to change the phase setting of at least one of the plurality of MZIs, and the plurality of MZIs are configured to change the phase of one or more photons passing through the plurality of MZIs; as well as A quantum memory array comprising multiple quantum memories optically coupled to the plurality of MZIs, wherein each quantum memory is configured to absorb photons including quantum information received by the quantum memory from the reconfigurable quantum processing unit, and to release photons including the quantum information of the received photons into the reconfigurable quantum processing unit. The photon source and the photon detector are each part of an optical node, the optical node further comprising an optical switch positioned between the photon source and the photon detector and optically coupled to the photon source and the photon detector, and The optical node is disposed between the first end of the reconfigurable quantum processing unit and the quantum memory array, and the optical node further includes: The detection path extends between the photon source and the photon detector and passes through the optical switch; as well as A processing path extends through the optical switch, not parallel to the detection path, wherein the processing path is optically coupled to at least one MZI and at least one quantum memory in the quantum memory array.

6. A quantum computing system, comprising: A reconfigurable quantum processing unit, optically coupled to a photon source and a photon detector, the reconfigurable quantum processing unit comprising multiple Mach-Zehnder interferometers (MZIs); A controller, communicatively coupled to the plurality of MZIs, wherein the controller is configured to generate control signals to change the phase setting of at least one of the plurality of MZIs, and the plurality of MZIs are configured to change the phase of one or more photons passing through the plurality of MZIs; as well as A quantum memory array comprising multiple quantum memories optically coupled to the plurality of MZIs, wherein each quantum memory is configured to absorb photons including quantum information received by the quantum memory from the reconfigurable quantum processing unit, and to release photons including the quantum information of the received photons into the reconfigurable quantum processing unit. The photon source and the photon detector are each part of an optical node, and the optical node further includes an optical switch positioned between the photon source and the photon detector and optically coupled to the photon source and the photon detector. The optical nodes are arranged in an optical node array, which includes a plurality of optical nodes disposed between a first end of the reconfigurable quantum processing unit and the quantum memory array and optically coupled to the first end of the reconfigurable quantum processing unit and the quantum memory array.

7. A quantum computing system, comprising: A reconfigurable quantum processing unit, optically coupled to a photon source and a photon detector, the reconfigurable quantum processing unit comprising multiple Mach-Zehnder interferometers (MZIs); A controller, communicatively coupled to the plurality of MZIs, wherein the controller is configured to generate control signals to change the phase setting of at least one of the plurality of MZIs, and the plurality of MZIs are configured to change the phase of one or more photons passing through the plurality of MZIs; as well as A quantum memory array comprising multiple quantum memories optically coupled to the plurality of MZIs, wherein each quantum memory is configured to absorb photons including quantum information received by the quantum memory from the reconfigurable quantum processing unit, and to release photons including the quantum information of the received photons into the reconfigurable quantum processing unit. Each MZI includes an uplink path, a downlink path, a first beam splitter and a second beam splitter optically coupling the uplink path and the downlink path, a first phase shifter arranged along the uplink path or the downlink path, and a second phase shifter arranged along the uplink path or the downlink path. in: The uplink path includes a first uplink, an upper intermediate link, and a second uplink; The downlink path includes a first downlink, a lower intermediate link, and a second downlink; The first upper link and the first lower link are optically coupled to the first beam splitter; The upper intermediate link and the lower intermediate link extend between the first beam splitter and the second beam splitter and are optically coupled to the first beam splitter and the second beam splitter; The second upper link and the second lower link are optically coupled to the second beam splitter; The first phase shifter is disposed on one of the upper intermediate link and the lower intermediate link; and The second phase shifter is disposed on one of the second upper link and the second lower link.

8. The quantum computing system of claim 7, wherein the first upper link and the first lower link, the second upper link and the second lower link, and the upper intermediate link and the lower intermediate link each include an optical waveguide.

9. The quantum computing system of any one of claims 1 and 3-7, wherein the photon source comprises a single-photon source and the photon detector comprises a single-photon detector.

10. A quantum computing system, comprising: A reconfigurable quantum processing unit, optically coupled to a photon source and a photon detector, the reconfigurable quantum processing unit comprising multiple Mach-Zehnder interferometers (MZIs); A controller, communicatively coupled to the plurality of MZIs, wherein the controller is configured to generate control signals to change the phase setting of at least one of the plurality of MZIs, and the plurality of MZIs are configured to change the phase of one or more photons passing through the plurality of MZIs; as well as A quantum memory array comprising multiple quantum memories optically coupled to the plurality of MZIs, wherein each quantum memory is configured to absorb photons including quantum information received by the quantum memory from the reconfigurable quantum processing unit, and to release photons including the quantum information of the received photons into the reconfigurable quantum processing unit. in: The quantum memory array includes a first quantum memory array; The quantum computing system further includes a second quantum memory array; and The reconfigurable quantum processing unit is positioned between the first quantum memory array and the second quantum memory array and is optically coupled to the first quantum memory array and the second quantum memory array.

11. The quantum computing system of claim 10, wherein each quantum memory in the first quantum memory array and the second quantum memory array is configured to emit photons by reverse emission, such that the photons emitted by both the first quantum memory array and the second quantum memory array are directed toward the reconfigurable quantum processing unit.

12. The quantum computing system of claim 10, wherein: The photon source and the photon detector are each part of an optical node, and the optical node further includes an optical switch positioned between the photon source and the photon detector and optically coupled to the photon source and the photon detector; The optical nodes are the individual optical nodes in an optical node array; and The optical node array is disposed between the reconfigurable quantum processing unit and the first quantum memory array, such that photons propagating from the reconfigurable quantum processing unit to the first quantum memory array pass through the optical switches of the respective optical nodes in the optical node array.

13. The quantum computing system of claim 12, wherein the optical switches of the respective optical nodes in the optical node array are configured to selectively direct photons toward the first quantum memory array, the reconfigurable quantum processing unit, and the respective photon detectors of the respective optical nodes.

14. A quantum computing system, comprising: A reconfigurable quantum processing unit, optically coupled to a photon source and a photon detector, the reconfigurable quantum processing unit comprising multiple Mach-Zehnder interferometers (MZIs); A controller, communicatively coupled to the plurality of MZIs, wherein the controller is configured to generate control signals to change the phase setting of at least one of the plurality of MZIs, and the plurality of MZIs are configured to change the phase of one or more photons passing through the plurality of MZIs; as well as A quantum memory array comprising multiple quantum memories optically coupled to the plurality of MZIs, wherein each quantum memory is configured to absorb photons including quantum information received by the quantum memory from the reconfigurable quantum processing unit, and to release photons including the quantum information of the received photons into the reconfigurable quantum processing unit. Each quantum memory in the quantum memory array is configured to release photons by forward emission, such that photons guided from a first end of the reconfigurable quantum processing unit to a first end of the quantum memory are released from a second end of the quantum memory into a bypass optical path optically coupled to the second end of the reconfigurable quantum processing unit.

15. A method for performing a computational task, the method comprising: One or more photons are directed into a reconfigurable quantum processing unit comprising multiple Mach-Zehnder interferometers (MZIs) such that at least one of the one or more photons passes through the reconfigurable quantum processing unit. Using a quantum memory in a quantum memory array, photons received by the quantum memory from the reconfigurable quantum processing unit are absorbed, the received photons including quantum information, wherein the quantum memory array includes multiple quantum memories optically coupled to the multiple MZIs of the reconfigurable quantum processing unit; A controller is used to communicate with the plurality of MZIs of the reconfigurable quantum processing unit to generate a control signal that changes the phase setting of at least one of the plurality of MZIs. Photons are released from the quantum memory into the reconfigurable quantum processing unit such that the released photons pass through the reconfigurable quantum processing unit, wherein the released photons include the quantum information of the absorbed photons; as well as A photon detector is used to measure the quantum properties of one or more emitted photons, wherein the quantum properties correspond to at least a portion of the computational task. Directing the one or more photons into the reconfigurable quantum processing unit includes: The one or more photons are emitted from one or more photon sources; Directing the one or more photons into the quantum memory array, such that one or more quantum memories in the quantum memory array absorb the one or more photons; and One or more photons are released from the one or more quantum memories in the quantum memory array into the reconfigurable quantum processing unit, such that the released photons include the quantum information of the corresponding absorbed photons.

16. The method of claim 15, wherein the quantum property includes at least one of linear polarization, circular polarization, elliptic polarization, translational displacement, orbital angular momentum, and phase.

17. The method of claim 15, wherein directing the one or more photons into the reconfigurable quantum processing unit comprises emitting the one or more photons from one or more photon sources and directing the one or more photons into the reconfigurable quantum processing unit.

18. The method of claim 15, wherein the released photons arrive synchronously at the reconfigurable quantum processing unit.

19. The method of claim 15, wherein the computational steps of the computational task are performed on the one or more photons by passing them through the reconfigurable quantum processing unit.

20. A method for performing a computational task, the method comprising: One or more photons are directed into a reconfigurable quantum processing unit comprising multiple Mach-Zehnder interferometers (MZIs) such that at least one of the one or more photons passes through the reconfigurable quantum processing unit. Using a quantum memory in a quantum memory array, photons received by the quantum memory from the reconfigurable quantum processing unit are absorbed, the received photons including quantum information, wherein the quantum memory array includes multiple quantum memories optically coupled to the multiple MZIs of the reconfigurable quantum processing unit; A controller is used to communicate with the plurality of MZIs of the reconfigurable quantum processing unit to generate a control signal that changes the phase setting of at least one of the plurality of MZIs. Photons are released from the quantum memory into the reconfigurable quantum processing unit such that the released photons pass through the reconfigurable quantum processing unit, wherein the released photons include the quantum information of the absorbed photons; as well as A photon detector is used to measure the quantum properties of one or more emitted photons, wherein the quantum properties correspond to at least a portion of the computational task. in: Absorbing the photon received by the quantum memory excites the atomic ensemble state of the quantum memory from a first energy state to a second energy state; and When the atomic ensemble state of the quantum memory returns to the first energy state, a photon is released, the photon containing the quantum information of the absorbed photon.

21. The method of claim 20, wherein the atomic ensemble state of the quantum memory returns to the first energy state in response to a control signal received from the controller.

22. A method for performing a computational task, the method comprising: One or more photons are directed into a reconfigurable quantum processing unit comprising multiple Mach-Zehnder interferometers (MZIs) such that at least one of the one or more photons passes through the reconfigurable quantum processing unit. Using a quantum memory in a quantum memory array, photons received by the quantum memory from the reconfigurable quantum processing unit are absorbed, the received photons including quantum information, wherein the quantum memory array includes multiple quantum memories optically coupled to the multiple MZIs of the reconfigurable quantum processing unit; A controller is used to communicate with the plurality of MZIs of the reconfigurable quantum processing unit to generate a control signal that changes the phase setting of at least one of the plurality of MZIs. Photons are released from the quantum memory into the reconfigurable quantum processing unit such that the released photons pass through the reconfigurable quantum processing unit, wherein the released photons include the quantum information of the absorbed photons; as well as A photon detector is used to measure the quantum properties of one or more emitted photons, wherein the quantum properties correspond to at least a portion of the computational task. in: The quantum memory array includes a first quantum memory array; The reconfigurable quantum processing unit is positioned between the first quantum memory array and the second quantum memory array and is optically coupled to the first quantum memory array and the second quantum memory array; The photon detector is part of an optical node, which further includes an optical switch positioned between the photon source and the photon detector and optically coupled to the photon source and the photon detector; The optical nodes are the individual optical nodes in an optical node array; and The optical node array is disposed between the reconfigurable quantum processing unit and the first quantum memory array, such that photons propagating from the reconfigurable quantum processing unit to the first quantum memory array pass through the optical switches of the respective optical nodes in the optical node array.

23. The method of claim 22, wherein each quantum memory in the first quantum memory array and the second quantum memory array is configured to emit photons by reverse emission, such that the photons emitted by both the first quantum memory array and the second quantum memory array are directed toward the reconfigurable quantum processing unit.

24. The method of claim 22, wherein measuring the quantum properties of one or more emitted photons comprises using the optical switch to direct the photons toward the photon detector, wherein the optical switch of each respective optical node is configured to selectively direct the photons toward the first quantum memory array, the reconfigurable quantum processing unit, and the photon detector of the respective optical node.

25. A quantum computing system, comprising: A reconfigurable quantum processing unit having a first end, a second end, and a plurality of Mach-Zehnder interferometers (MZIs) disposed between the first end and the second end, wherein the reconfigurable quantum processing unit is disposed between a first quantum memory array and a second quantum memory array. An optical node array comprising multiple optical nodes, wherein: Each optical node includes a photon source, a photon detector, and an optical switch positioned between the photon source and the photon detector and optically coupled to the photon source and the photon detector; The optical node array is disposed between the first end of the reconfigurable quantum processing unit and the first quantum memory array, such that photons propagating from the first end of the reconfigurable quantum processing unit to the respective quantum memories in the first quantum memory array pass through the optical switch; and A controller, communicatively coupled to the plurality of MZIs, wherein the controller is configured to generate control signals to change the phase setting of at least one of the plurality of MZIs, and the plurality of MZIs are configured to change the phase of one or more photons output from the photon source; and Each quantum memory in the first quantum memory array and the second quantum memory array is configured to absorb photons including quantum information received from the reconfigurable quantum processing unit and release photons including the quantum information of the received photons into the reconfigurable quantum processing unit, wherein the plurality of MZIs are arranged in an MZI lattice, the MZI lattice comprising: A first boundary MZI column is set along the first end of the reconfigurable quantum processing unit; A second boundary MZI column is arranged along the second end of the reconfigurable quantum processing unit; and One or more inner MZI columns are positioned between the first boundary MZI column and the second boundary MZI column, wherein the first boundary MZI column is optically coupled to the adjacent inner MZI column with an offset orientation, and the second boundary MZI column is optically coupled to the adjacent inner MZI column with an offset orientation.

26. A quantum computing system, comprising: A reconfigurable quantum processing unit having a first end, a second end, and a plurality of Mach-Zehnder interferometers (MZIs) disposed between the first end and the second end, wherein the reconfigurable quantum processing unit is disposed between a first quantum memory array and a second quantum memory array. An optical node array comprising multiple optical nodes, wherein: Each optical node includes a photon source, a photon detector, and an optical switch positioned between the photon source and the photon detector and optically coupled to the photon source and the photon detector; The optical node array is disposed between the first end of the reconfigurable quantum processing unit and the first quantum memory array, such that photons propagating from the first end of the reconfigurable quantum processing unit to the respective quantum memories in the first quantum memory array pass through the optical switch; and A controller, communicatively coupled to the plurality of MZIs, wherein the controller is configured to generate control signals to change the phase setting of at least one of the plurality of MZIs, and the plurality of MZIs are configured to change the phase of one or more photons output from the photon source; and Each quantum memory in the first and second quantum memory arrays is configured to absorb photons containing quantum information received from the reconfigurable quantum processing unit, and to release photons containing the quantum information of the received photons into the reconfigurable quantum processing unit. Each MZI includes an uplink path, a downlink path, a first beam splitter and a second beam splitter optically coupling the uplink path and the downlink path, a first phase shifter arranged along the uplink path or the downlink path, and a second phase shifter arranged along the uplink path or the downlink path.

27. The quantum computing system of claim 26, wherein the controller is configured to generate control signals to change the phase settings of the first phase shifter, the second phase shifter, or both the first and second phase shifters.

28. The quantum computing system of claim 26, wherein the controller is configured to generate control signals to change the coupling ratio of the first beam splitter, the second beam splitter, or both the first beam splitter and the second beam splitter.

29. A quantum computing system, comprising: A reconfigurable quantum processing unit having a first end, a second end, and a plurality of Mach-Zehnder interferometers (MZIs) disposed between the first end and the second end, wherein the reconfigurable quantum processing unit is disposed between a first quantum memory array and a second quantum memory array. An optical node array comprising multiple optical nodes, wherein: Each optical node includes a photon source, a photon detector, and an optical switch positioned between the photon source and the photon detector and optically coupled to the photon source and the photon detector; The optical node array is disposed between the first end of the reconfigurable quantum processing unit and the first quantum memory array, such that photons propagating from the first end of the reconfigurable quantum processing unit to the respective quantum memories in the first quantum memory array pass through the optical switch; and A controller, communicatively coupled to the plurality of MZIs, wherein the controller is configured to generate control signals to change the phase setting of at least one of the plurality of MZIs, and the plurality of MZIs are configured to change the phase of one or more photons output from the photon source; and Each quantum memory in the first and second quantum memory arrays is configured to absorb photons containing quantum information received from the reconfigurable quantum processing unit, and to release photons containing the quantum information of the received photons into the reconfigurable quantum processing unit. The photon source includes a single-photon source, and the photon detector includes a single-photon detector.

30. A quantum computing system, comprising: A reconfigurable quantum processing unit having a first end, a second end, and a plurality of Mach-Zehnder interferometers (MZIs) disposed between the first end and the second end, wherein the reconfigurable quantum processing unit is disposed between a first quantum memory array and a second quantum memory array. An optical node array comprising multiple optical nodes, wherein: Each optical node includes a photon source, a photon detector, and an optical switch positioned between the photon source and the photon detector and optically coupled to the photon source and the photon detector; The optical node array is disposed between the first end of the reconfigurable quantum processing unit and the first quantum memory array, such that photons propagating from the first end of the reconfigurable quantum processing unit to the respective quantum memories in the first quantum memory array pass through the optical switch; and A controller, communicatively coupled to the plurality of MZIs, wherein the controller is configured to generate control signals to change the phase setting of at least one of the plurality of MZIs, and the plurality of MZIs are configured to change the phase of one or more photons output from the photon source; and Each quantum memory in the first and second quantum memory arrays is configured to absorb photons containing quantum information received from the reconfigurable quantum processing unit, and to release photons containing the quantum information of the received photons into the reconfigurable quantum processing unit. Each quantum memory in the first and second quantum memory arrays is configured to emit photons by reverse emission, such that the photons emitted by both the first and second quantum memory arrays are directed toward the reconfigurable quantum processing unit.

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