Quantum-enabled device misalignment

Abstract

Proposed are schemes, solutions, concepts, designs, methods, and systems pertaining to determining misalignment between quantum-matter confinement regions of adjacent quantum- enabled devices. Alignme

Description

QUANTUM-ENABLED DEVICE MISALIGNMENTCROSS-REFERENCE

[0001] This application claims the benefit of United Kingdom Patent Application No. GB2306908.1, filed May 10, 2023, which application is incorporated herein by reference.BACKGROUND

[0002] Quantum computing is based on the exploitation of quantum mechanical properties (e.g., superpositions and entanglement) of particles of light or matter in order to produce or alter data. Data in a quantum computer may be represented by quantum bits (e.g., qubits). Quantum computers may have fewer physical qubits than may be ideal. For example, a quantum computer may be limited to -100 physical qubits. It may be useful to provide quantum devices which are scalable to large numbers of qubits. In an example, microfabricated quantum charge-coupled devices (QCCDs) may provide improved scalability. Microfabricated quantum charge-coupled devices may comprise, for example, ion-trap quantum computers.SUMMARY

[0003] Microfabricated QCCDs may comprise an array of segmented electrodes that provide independent quantum-matter confinement regions. Nevertheless, these microfabricated devices may remain subject to the size constraints of the wafer over which they are fabricated, thereby limiting the number of controllable qubits on a single device. To overcome this obstacle, a quantum-enabled device may be constructed in a modular fashion. With sufficient modules and high fidelity module-to-module coupling a quantum-enabled device that is capable of hosting an unrestricted number of qubits may be realized.

[0004] An example method of connecting multiple modules together may comprise the use of photonic quantum links. A photonic quantum link may be based at least in part on the conversion of the quantum information held in quantum matter (e.g., an ion, an atom, a quantum dot, etc.) to that of a photon such that entanglement may occur between optically connected modules. However, this method may be limited by inefficiencies in the ion-photon interface and high link loss rates. In some cases, entangling rates between modules may be less than approximately 182s' and a reliability of 94%. In some cases, inefficiencies in the ion-photon interface and high link loss rates may constitute the slowest, most limiting process in a quantum-enabled device when compared to the rate of other quantum operations.

[0005] In another example method, adjacent modules can be connected using shuttling operations. In this architecture, individual trapped-ion qubits may be physically transported orshuttled between neighboring modules, connecting the modules through matter-based quantum links. This method may provide high connectivity rates of approximately 2421s'1, with a reliability of 99.999995%.

[0006] In some cases, it may be advantageous for adjacent quantum -matter confinement regions to be accurately aligned to within a few microns (e.g., < 10 pm). In some cases, to solve computationally hard problems, a quantum-enabled device based on this interconnection technology may comprise many tessellated modules. As the scale of device increases with additional modules, relative positioning of each module with micron-accuracy may become more difficult. Furthermore, maintaining alignment during operation may also be complex. For example, the quantum device may be operated at cryogenic temperatures (e.g., 40-70 K). The device may be subject to thermomechanical effects which lead to module misalignment during thermal cycles. Together these effects of scale and operating conditions may render it difficult to maintain module-module alignment.

[0007] Therefore, there is a need for concepts that enable measurement of misalignment between quantum -matter confinement regions of adjacent quantum- enabled devices. The present application relates to concepts related to quantum-enabled device misalignment, and more particularly to concepts for determining misalignment between adjacent quantum-enabled devices.

[0008] In an aspect, a system for determining misalignment between quantum-matter confinement regions of adjacent quantum-enabled devices. The system may comprise a first distance sensor configured to generate a first signal comprising information indicating a distance between a first quantum-enabled device and a second quantum-enabled device adjacent to the first quantum-enabled device in a first direction, wherein the distance sensor is integrated into at least one of the first quantum-enabled device and the second quantum-enabled device.

[0009] In some embodiments, the system further comprises: a processor configured to process the first signal to determine a misalignment value describing a degree of misalignment between a quantum-matter confinement region of the first quantum-enabled device and a quantum-matter confinement region of the second quantum-enabled device. In some embodiments, the processor is configured to determine the degree of misalignment by comparing the distance to an expected distance value. In some embodiments, the processor is configured to determine the degree of misalignment in 3D translation space, 3D rotation space, or both.

[0010] In some embodiments, the processor is configured to determine the degree of misalignment at a plurality of instances of time and to provide an instruction to update an alignment at each of the plurality of instances of time. In some embodiments, the system furthercomprises a feedback control module and an actuator, wherein the feedback control module is configured to receive the misalignment value from the processor and determine an alignment error signal for controlling the actuator for realignment of at least one of the first quantum- enabled device and the second quantum-enabled device. In some embodiments, wherein the feedback control module and the actuator are configured to update an alignment during operation of the first quantum-enabled device, the second quantum-enabled device, or both. In some embodiments, the feedback control module 150 and the actuator 160 are configured to maintain an alignment of the first quantum-enabled device, the second quantum-enabled device, or both to within 10 microns, optionally, to within 1 micron.

[0011] In some embodiments, the first distance sensor comprises a portion of a measurement arrangement. In some embodiments, the measurement arrangement is configured to determine a misalignment along a direction, wherein the direction is a lateral direction, a vertical direction, one of three axes of translation, one of three axes of rotation, or any combination thereof. In some embodiments, the measurement arrangement is configured to determine the misalignment in three spatial dimensions, three rotational dimensions, or both. In some embodiments, the measurement arrangement comprises one or more sensor types selected from the group consisting of: capacitive sensors, inductive sensors, thermal sensors, optical sensors, time of flight sensors, or any combination thereof.

[0012] In some embodiments, the first sensor is configured to determine a distance based on a capacitance between a pair of conductive plates. In some embodiments, the first sensor comprises a first conductive plate positioned on a first quantum-enabled device and a second conductive plate positioned on a second quantum-enabled device. In some embodiments, the system further comprises a driving electronics configured to apply voltage to either of the pair of conductive plates. In some embodiments, the first sensor is configured to operate at cryogenic temperature, in a vacuum, or both. In some embodiments, the first sensor is positioned at an extremity of the first quantum-enabled device. In some embodiments, the first distance sensor comprises a portion of a measurement arrangement , wherein the measurement arrangement further comprises a second distance sensor configured to generate a second signal comprising information indicating a distance between the first quantum-enabled device and the second quantum-enabled device in a second direction, the second direction different to the first direction, and wherein the processor configured to process the first signal and the second signal to determine the misalignment value. In some embodiments, the measurement arrangement further comprises a third distance sensor configured to generate a third signal comprising information indicating a distance between the first quantum-enabled device and the second quantum-enabled device in a third direction, thethird direction different to the first direction and the second direction, and wherein the processor is configured to process the first signal, the second signal and the third signal to determine the misalignment value. In some embodiments, the first direction, the second direction and the third direction are orthogonal.

[0013] In some embodiments, the first distance sensor comprises: a conductive plate positioned on the first quantum-enabled device; a conductive plate positioned on the second quantum- enabled device; and driving electronics configured to apply a voltage to one of the conductive plates, wherein the first signal comprises a capacitance value describing a capacitance between the conductive plates.

[0014] In some embodiments, the first distance sensor comprises: a first conductive plate and a second conductive plate positioned on the first quantum-enabled device; a conductive plate positioned on the second quantum-enabled device; and driving electronics configured to apply a voltage to at least one of the conductive plates, and wherein the first signal comprises a capacitance value describing a capacitance between the first conductive plate of the first quantum computing module and the conductive plate of the second quantum-enabled device, and a capacitance between the second conductive plate of the first quantum-enabled device and the conductive plate of the second quantum-enabled device.

[0015] In some embodiments, the first distance sensor is positioned on a corner of the first quantum-enabled device and a corner of the second quantum-enabled device. In some embodiments, the first distance sensor is positioned on a bottom layer of the first quantum- enabled device and a bottom layer of the second quantum-enabled device. In some embodiments, the system further comprises a processor, wherein the processor is integrated into at least one of the first quantum-enabled device and the second quantum- enabled device. In some embodiments, the processor is positioned in an electronics layer of at least one of the first quantum-enabled device and the second quantum-enabled device, the electronics layer comprising control electronics for the quantum-enabled device.

[0016] In some embodiments, the processor is configured to: determine a distance value based on the first signal, the distance value indicating the distance between the first quantum-enabled device and the second quantum-enabled device in the first direction; compare the determined distance value to an expected distance value, wherein the expected distance value indicates a distance between the first quantum-enabled device and the second quantum-enabled device in the direction when the quantum-matter confinement regions of the quantum-enabled devices are aligned; and determine the misalignment value based on the comparison.

[0017] In some embodiments, the quantum-matter confinement region is formed by a surface ion-trap. In some embodiments, at least one of first quantum-enabled device and the second first quantum-enabled device is a quantum computing module. In some embodiments, the first quantum-enabled device and the second quantum-enabled device are maintained with an alignment accuracy of better than 10 microns, optionally, better than 1 micron.

[0018] In another aspect, the present disclosure provides a system for determining misalignment between quantum -matter confinement regions of adjacent quantum-enabled devices. The system may comprise: a measurement arrangement comprising a first distance sensor configured to generate a first signal comprising information indicating a distance between a first quantum- enabled device and a second quantum-enabled device adjacent to the first quantum-enabled device in a first direction, wherein the measurement arrangement is integrated into at least one of the first quantum-enabled device and the second quantum-enabled device; and a processor (130) configured to process the first signal to determine a misalignment value describing a degree of misalignment between a quantum-matter confinement region of the first quantum-enabled device and a quantum-matter confinement region of the second quantum-enabled device.

[0019] In some embodiments, the measurement arrangement further comprises a second distance sensor configured to generate a second signal comprising information indicating a distance between the first quantum-enabled device and the second quantum-enabled device in a second direction, the second direction different to the first direction, and wherein the processor is configured to process the first signal and the second signal to determine the misalignment value. In some embodiments, the measurement arrangement (140) further comprises a third distance sensor (142c) configured to generate a third signal comprising information indicating a distance between the first quantum-enabled device (110) and the second quantum-enabled device (120) in a third direction, the third direction different to the first direction and the second direction, and wherein the processor (130) configured to process the first signal, the second signal and the third signal to determine the misalignment value. In some embodiments, the first direction, the second direction and the third direction are orthogonal.

[0020] In some embodiments, the first distance sensor comprises: a conductive plate positioned on the first quantum-enabled device; a conductive plate positioned on the second quantum- enabled device; and driving electronics configured to apply a voltage to one of the conductive plates, wherein the first signal comprises a capacitance value describing a capacitance between the conductive plates.

[0021] In some embodiments, the first distance sensor comprises: a first conductive plate and a second conductive plate positioned on the first quantum-enabled device; a conductive platepositioned on the second quantum-enabled device; and driving electronics configured to apply a voltage to at least one of the conductive plates, and wherein the first signal comprises a capacitance value describing a capacitance between the first conductive plate of the first quantum computing module and the conductive plate of the second quantum-enabled device, and a capacitance between the second conductive plate of the first quantum-enabled device and the conductive plate of the second quantum-enabled device.

[0022] In some embodiments, the first distance sensor is positioned on a corner of the first quantum-enabled device and a corner of the second quantum-enabled device. In some embodiments, the first distance sensor is positioned on a bottom layer of the first quantum- enabled device and a bottom layer of the second quantum-enabled device. In some embodiments, the processor is integrated into at least one of the first quantum-enabled device and the second quantum-enabled device, and optionally wherein the processor is positioned in an electronics layer of at least one of the first quantum-enabled device and the second quantum-enabled device, the electronics layer comprising control electronics for the quantum-enabled device. In some embodiments, the processor is configured to: determine a distance value based on the first signal, the distance value indicating the distance between the first quantum-enabled device and the second quantum-enabled device in the first direction; compare the determined distance value to an expected distance value, wherein the expected distance value indicates a distance between the first quantum-enabled device and the second quantum-enabled device in the direction when the quantum-matter confinement regions of the quantum-enabled devices are aligned; and determine the misalignment value based on the comparison.

[0023] In some embodiments, wherein the system further comprises a feedback control module configured to: receive the misalignment value from the processor; determine an alignment error signal for controlling an actuator for realignment of at least one of the first quantum-enabled device and the second quantum-enabled device. In some embodiments, the quantum-matter confinement region is formed by a surface ion-trap. In some embodiments, at least one of first quantum-enabled device (110) and the second first quantum-enabled device is a quantum computing module.

[0024] In another aspect, a quantum computer is provided. The quantum computer may comprise: a first quantum-enabled device; a second quantum-enabled device adjacent to the first quantum-enabled device; and the system any aspect or embodiment for determining misalignment between quantum- matter confinement regions of the adjacent quantum-enabled devices.

[0025] In some embodiments, the quantum computer is a trapped ion quantum computer. In some embodiments, the first quantum-enabled device and the second quantum-enabled device are individual ion-trap modules of the trapped ion quantum computer. In some embodiments, an iontrap module of the trapped ion quantum computer comprises a size within a range from about 5x5mm to about 200x200mm. In some embodiments, each of the individual ion-trap modules comprise a microfabricated ion-trap on a substrate and electronics for controlling and driving the microfabricated ion-trap on a separate substrate layer of the substrate. In some embodiments, the electronics comprise one or more members selected from the group consisting of digital-to- analogue converters (DACs), application specific integrated circuits (ASICs), electronic filtering circuits, detection electronics, and ion loading electronics. In some embodiments, the first quantum-enabled device and the second quantum-enabled device are maintained with an alignment accuracy of better than 10 microns, optionally, better than 1 micron.

[0026] In another aspect, the present disclosure provides a method for determining misalignment between quantum -matter confinement regions of adjacent quantum-enabled devices. The method may comprise: (a) generating, by a measurement arrangement, a first signal comprising information indicating a distance between a first quantum-enabled device and a second quantum- enabled device adjacent to the first quantum-enabled device in a first direction, wherein the measurement arrangement is integrated into at least one of the first quantum-enabled device and the second quantum-enabled device; and (b) processing the first signal to determine a misalignment value describing a degree of misalignment between a quantum-matter confinement region of the first quantum-enabled device and a quantum-matter confinement region of the second quantum-enabled device.

[0027] In some embodiments, (b) comprises determining the degree of misalignment by comparing the distance to an expected distance value. In some embodiments, (b) comprises determining the degree of misalignment in 3D translation space, 3D rotation space, or both. In some embodiments, (b) comprises determining the degree of misalignment at a plurality of instances of time and to provide an instruction to update an alignment at each of the plurality of instances of time.

[0028] In some embodiments, the method further comprises: receiving at a feedback control module the misalignment value from the processor; and determining an alignment error signal for controlling an actuator for realignment of at least one of the first quantum-enabled device and the second quantum-enabled device. In some embodiments, the method further comprises updating an alignment during operation of the first quantum-enabled device, the second quantum-enabled device, or both. In some embodiments, the method further comprises maintaining an alignment ofthe first quantum-enabled device, the second quantum-enabled device, or both to within 10 microns, optionally, to within 1 micron. In some embodiments, the first distance sensor comprises a portion of a measurement arrangement. In some embodiments, the method further comprises, at the measurement arrangement, determining a misalignment along a direction, wherein the direction is a lateral direction, a vertical direction, one of three axes of translation, one of three axes of rotation, or any combination thereof. In some embodiments, the method further comprises, at the measurement arrangement, determining the misalignment in three spatial dimensions, three rotational dimensions, or both. In some embodiments, the measurement arrangement comprises one or more sensor types selected from the group consisting of capacitive sensors, inductive sensors, thermal sensors, optical sensors, time of flight sensors, or any combination thereof.

[0029] In some embodiments, (a) comprises, at the first sensor, determining the first signal based on a capacitance between a pair of conductive plates. In some embodiments, the first sensor comprises a first conductive plate positioned on a first quantum-enabled device and a second conductive plate positioned on a second quantum-enabled device. In some embodiments, the method further comprises applying a voltage, at a driving electronics, to either of the pair of conductive plates.

[0030] In some embodiments, the first sensor is configured to operate at cryogenic temperature, in a vacuum, or both. In some embodiments, the first sensor is positioned at an extremity of the first quantum-enabled device. In some embodiments, the method further comprises, subsequent to (a) generating, at a second distance sensor, a second signal comprising information indicating a distance between the first quantum-enabled device and the second quantum-enabled device in a second direction, the second direction different to the first direction, and wherein (b) further comprises processing the first signal and the second signal to determine the misalignment value. In some embodiments, subsequent to (a) generating, at a third distance sensor, a third signal comprising information indicating a distance between the first quantum-enabled device and the second quantum-enabled device in a third direction, the third direction different to the first direction and the second direction, and wherein (b) further comprises processing the first signal, the second signal and the third signal to determine the misalignment value. In some embodiments, the first direction, the second direction and the third direction are orthogonal. In some embodiments, the first distance sensor comprises: a conductive plate positioned on the first quantum-enabled device; a conductive plate positioned on the second quantum-enabled device; and driving electronics configured to apply a voltage to one of the conductive plates, wherein thefirst signal comprises a capacitance value describing a capacitance between the conductive plates.

[0031] In some embodiments, the first distance sensor comprises: a first conductive plate and a second conductive plate positioned on the first quantum-enabled device; a conductive plate positioned on the second quantum-enabled device; and driving electronics configured to apply a voltage to at least one of the conductive plates, and wherein the first signal comprises a capacitance value describing a capacitance between the first conductive plate of the first quantum computing module and the conductive plate of the second quantum-enabled device, and a capacitance between the second conductive plate of the first quantum-enabled device and the conductive plate of the second quantum-enabled device.

[0032] In some embodiments, the first distance sensor is positioned on a corner of the first quantum-enabled device and a corner of the second quantum-enabled device. In some embodiments, the first distance sensor is positioned on a bottom layer of the first quantum- enabled device and a bottom layer of the second quantum-enabled device. In some embodiments, the processor is integrated into at least one of the first quantum-enabled and the second quantum- enabled device, and optionally wherein the processor is positioned in an electronics layer of at least one of the first quantum-enabled device and the second quantum-enabled device, the electronics layer comprising control electronics for the quantum-enabled device.

[0033] In some embodiments, (b) further comprises: determining a distance value based on the first signal, the distance value indicating the distance between the first quantum-enabled device and the second quantum-enabled device in the first direction; comparing the determined distance value to an expected distance value, wherein the expected distance value indicates a distance between the first quantum-enabled device and the second quantum-enabled device in the direction when the quantum-matter confinement regions of the quantum-enabled devices are aligned; and determining the misalignment value based on the comparison. In some embodiments, the quantum-matter confinement region is formed by a surface ion-trap. In some embodiments, at least one of first quantum-enabled device and the second first quantum-enabled device is a quantum computing module.

[0034] According to another aspect, there is provided a system for determining misalignment between quantum -matter confinement regions of adjacent quantum- enabled devices, the system comprising: a measurement arrangement comprising a first distance sensor configured to generate a first signal comprising information indicating a distance between a first quantum- enabled device and a second quantum-enabled device adjacent to the first quantum-enabled device in a first direction, wherein the measurement arrangement is integrated into at least one ofthe first quantum-enabled device and the second quantum-enabled device; and a processor configured to process the first signal to determine a misalignment value describing a degree of misalignment between a quantum-matter confinement region of the first quantum-enabled device and a quantum-matter confinement region of the second quantum-enabled device.

[0035] Thus, proposed are concepts pertaining to determining misalignment between quantummatter confinement regions of adjacent quantum-enabled devices.

[0036] Alignment between quantum-matter confinement regions is key for ensuring that quantum matter-links connecting the quantum-enabled devices are reliable and efficient. Specifically, a signal indicative of a distance between adjacent quantum- enabled devices is generated by a measurement arrangement. The signal is processed in order to determine a degree of misalignment between quantum-matter confinement regions. The measurement arrangement is integrated into at least one of the quantum-enabled devices. Thus, an accurate and robust means for determining misalignment is provided by the disclosure.

[0037] Advantageously, a measurement arrangement directly integrated in / mechanically connected to quantum-enabled devices provides a simple means for determining misalignment with adjacent quantum enabled devices. When the distance between the adjacent devices varies from an expected value, then the devices may be considered misaligned, and can be corrected in order to ensure reliability and efficiency of quantum-matter links between quantum-matter confinement regions of the quantum devices. Accordingly, at least one aim of the present disclosure is to provide a solution to the problem of alignment of the devices which is suitable when a large number of quantum-enabled devices are provided. Thus, the disclosure provides a simple, robust, and accurate systems and methods for assessment of the distance and corresponding (mis)alignment.

[0038] In some embodiments, the measurement arrangement may further comprise a second distance sensor configured to generate a second signal comprising information indicating a distance between the first quantum-enabled device and the second quantum-enabled device in a second direction, the second direction different to the first direction. The processor may be configured to process the first signal and the second signal to determine the misalignment value.

[0039] Additionally, the measurement arrangement may further comprise a third distance sensor configured to generate a third signal comprising information indicating a distance between the first quantum-enabled device and the second quantum- enabled device in a third direction, the third direction different to the first direction and the second direction. The processor may be configured to process the first signal, the second signal and the third signal to determine the misalignment value.

[0040] In another embodiment, the first direction, the second direction and the third direction may be orthogonal.

[0041] In a further embodiment, the first distance sensor may comprise: a conductive plate positioned on the first quantum-enabled device; a conductive plate positioned on the second quantum-enabled device; and driving electronics configured to apply a voltage to one of the conductive plates. The first signal may comprise a capacitance value describing a capacitance between the conductive plates.

[0042] In yet another embodiment, the first distance sensor may comprise: a first conductive plate and a second conductive plate positioned on the first quantum- enabled device; a conductive plate positioned on the second quantum-enabled device; and driving electronics configured to apply a voltage to at least one of the conductive plates. The first signal may comprise a capacitance value describing a capacitance between the first conductive plate of the first quantum computing module and the conductive plate of the second quantum-enabled device, and a capacitance between the second conductive plate of the first quantum-enabled device and the conductive plate of the second quantum-enabled device.

[0043] In some embodiments, the first distance sensor may be positioned on a comer of the first quantum-enabled device and a corner of the second quantum-enabled device.

[0044] In additional embodiments, the first distance sensor may be positioned on a bottom layer of the first quantum-enabled device and a bottom layer of the second quantum-enabled device.

[0045] In some embodiments, the processor may be integrated into at least one of the first quantum-enabled device and the second quantum-enabled device.

[0046] In specific embodiments, the processor may be positioned in an electronics layer of at least one of the first quantum-enabled device and the second quantum-enabled device, the electronics layer comprising control electronics for the quantum- enabled device.

[0047] In other embodiments, the processor may be configured to: determine a distance value based on the first signal, the distance value indicating the distance between the first quantum- enabled device and the second quantum-enabled device in the first direction; compare the determined distance value to an expected distance value, wherein the expected distance value indicates a distance between the first quantum-enabled device and the second quantum-enabled device in the direction when the quantum-matter confinement regions of the quantum-enabled devices are aligned; and determine the misalignment value based on the comparison.

[0048] Additionally, in some embodiments, the system may further comprise a feedback control module configured to: receive the misalignment value from the processor; determine analignment error signal for controlling an actuator for realignment of at least one of the first quantum-enabled device and the second quantum-enabled device.

[0049] In specific embodiments, the quantum-matter confinement region may be formed by a surface ion-trap.

[0050] Furthermore, in some embodiments, at least one of first quantum-enabled device and the second first quantum-enabled device may be a quantum computing module.

[0051] According to a second aspect of the invention there is provided a quantum computer, comprising: a first quantum-enabled device; a second quantum-enabled device adjacent to the first quantum-enabled device; and the system for determining misalignment between quantummatter confinement regions of the adjacent quantum-enabled devices according to another embodiment of the invention.

[0052] According to another aspect of the invention there is provided a method for determining misalignment between quantum-matter confinement regions of adjacent quantum-enabled devices, the method comprising: generating, by a measurement arrangement, a first signal comprising information indicating a distance between a first quantum-enabled device and a second quantum-enabled device adjacent to the first quantum-enabled device in a first direction, wherein the measurement arrangement is integrated into at least one of the first quantum-enabled device and the second quantum-enabled device; and processing the first signal to determine a misalignment value describing a degree of misalignment between a quantum-matter confinement region of the first quantum-enabled device and a quantum-matter confinement region of the second quantum-enabled device.

[0053] Another aspect of the present disclosure provides a system comprising one or more computer processors and computer memory coupled thereto. The computer memory comprises machine executable code that, upon execution by the one or more computer processors, implements any of the methods above or elsewhere herein.

[0054] Additional aspects and advantages of the present disclosure will become readily apparent to those skilled in this art from the following detailed description, wherein only illustrative embodiments of the present disclosure are shown and described. As will be realized, the present disclosure is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the disclosure. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.INCORPORATION BY REFERENCE

[0055] All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference. To the extent publications and patents or patent applications incorporated by reference contradict the disclosure contained in the specification, the specification is intended to supersede and / or take precedence over any such contradictory material.BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings (also “Figure” and “FIG.” herein), of which:

[0057] Figure 1 illustrates a system for determining misalignment between quantum- matter confinement regions of adjacent quantum-enabled devices, in accordance with some embodiments;

[0058] Figure 2 is a flow diagram providing operations in a method for determining misalignment between quantum-matter confinement regions of adjacent quantum-enabled devices, in accordance with some embodiments;

[0059] Figure 3 illustrates a top view of tessellated ion-trap quantum computing modules;

[0060] Figure 4 is a top view and an isometric view of an example ion-trap quantum computing module having an integrated system for determining misalignment, in accordance with some embodiments;

[0061] Figure 5 is a side view of adjacent ion-trap quantum computing devices having a measurement arrangement, in accordance with some embodiments;

[0062] Figure 6 is a side view of adjacent ion-trap quantum computing devices having an alternative measurement arrangement for measuring misalignment in a vertical direction, in accordance with some embodiments;

[0063] Figure 7 illustrates the principle of operation of the measurement arrangement of Figure 6;

[0064] Figure 8 is a top view of adjacent ion-trap quantum computing devices having an alternative measurement arrangement for measuring misalignment in a lateral direction, in accordance with some embodiments;

[0065] Figure 9 illustrates the principle of operation of the measurement arrangement of Figure 8;

[0066] Figure 10 further illustrates the principle of operation of the measurement arrangement of Figure 8;

[0067] Figure 11 is a side view of adjacent ion-trap quantum computing devices having an alternative measurement arrangement for measuring misalignment in a lateral and vertical direction, in accordance with some embodiments;

[0068] Figure 12 illustrates an alternative side view of the devices of Figure 11, and further indicates the principle of operation of the measurement arrangement of Figure 11;

[0069] Figure 13 presents an alternative configuration of the measurement arrangement, in accordance with some embodiments; and

[0070] Figure 14 illustrates angular misalignment between adjacent quantum-enabled devices.DETAILED DESCRIPTION

[0071] While various embodiments of the invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions may occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed.

[0072] Whenever the term “at least,” “greater than,” or “greater than or equal to” precedes the first numerical value in a series of two or more numerical values, the term “at least,” “greater than” or “greater than or equal to” applies to each of the numerical values in that series of numerical values. For example, greater than or equal to 1, 2, or 3 is equivalent to greater than or equal to 1, greater than or equal to 2, or greater than or equal to 3.

[0073] Whenever the term “no more than,” “less than,” or “less than or equal to” precedes the first numerical value in a series of two or more numerical values, the term “no more than,” “less than,” or “less than or equal to” applies to each of the numerical values in that series of numerical values. For example, less than or equal to 3, 2, or 1 is equivalent to less than or equal to 3, less than or equal to 2, or less than or equal to 1.

[0074] Certain inventive embodiments herein contemplate numerical ranges. When ranges are present, the ranges include the range endpoints. Additionally, every sub range and value within the range is present as if explicitly written out.

[0075] The term “about” or “approximately” may mean within an acceptable error range for the particular value, which will depend in part on how the value is measured or determined, e.g., the limitations of the measurement system. For example, “about” may mean within 1 or more than 1 standard deviation, per the practice in the art. Alternatively, “about” may mean a range of up to 20%, up to 10%, up to 5%, or up to 1% of a given value. Where particular values are described in the application and claims, unless otherwise stated the term “about” meaning within an acceptable error range for the particular value may be assumed.

[0076] “ and / or” where used herein is to be taken as specific disclosure of each of the two specified features or components with or without the other. For example “A and / or B” is to be taken as specific disclosure of each of (i) A, (ii) B and (iii) A and B, just as if each is set out individually herein.

[0077] The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and / or flowchart illustration, and combinations of blocks in the block diagrams and / or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions.

[0078] Systems and method disclosed herein provide concepts for the measurement of (mis)alignment between adjacent quantum-enabled devices. In some cases, a quantum-enabled device may comprise a module for a quantum computer. In some cases, a module of a quantum computer comprises a module of a trapped ion computer. Systems and methods of the present disclosure provide a measurement arrangement integrated with at least one of the quantum- enabled devices. A measurement arrangement may provide a measurement of a distance between the adjacent devices. Integrated measurement units may reduce a need for external devices for assessment / measurement of the alignment of devices, facilitating self-contained assessment and potential correction. Accordingly, scalability of the solution (such as for example, compared to a measurement means provided externally, such as a camera system) is improved, so that many quantum-enabled devices may be linked together.

[0079] In some cases, assessment of the alignment of the quantum-enabled devices may be performed by a camera system, which images the quantum-enabled devices an enables measurement of small misalignments. Any detected misalignments may be corrected, ensuring that quantum matter links between confinement regions of quantum-enabled devices perform effectively and efficiently. However, this process of determining alignment is complex, error- prone, and may not viable at scale (e.g., in a system with >100s of quantum-enabled devices).

[0080] By integrating a measurement arrangement for determining a distance to an adjacent quantum-enabled device within a quantum-enabled device, a scalable solution may be provided. The measurement arrangement integrated in the quantum-enabled device may ensures that the quantum-enabled device may operate in a modular system.

[0081] Systems and methods of the present disclosure provide conductive plates directly integrated within the quantum enabled devices. The conductive plates may allow a measurement of the (mis)alignment between adjacent quantum-enabled devices. Several methods for operating / driving conductive plates and deducing distances between the conductive plates are disclosed herein.

[0082] By way of example, systems and methods disclosed herein may be based at least in part on the physical principle that the capacitance between two conductive plates varies as the inverse of the distance separating both these plates. A capacitance constitutes a physical quantity that can be measured by some signal processing electronics after which information on the distance separating both plates can be determined. A measurement arrangement can be constructed from conductive plates to provide high-accuracy measurements of the alignment between adjacent quantum-enabled devices / modules over all 6 relative degrees of freedom therebetween (submicron measurements along all 3 translation directions and sub-degree measurements in all 3 directions of angular rotations).

[0083] Such a measurement of a misalignment may be used as part of an electronic feedback control system, such that, the misalignment can be dynamically or intermittently corrected. For example, misalignment may be corrected using (for instance) precision actuators automatically. This may be particularly beneficial, for example, when the alignment between quantum-enabled devices is altered due to thermal effects during operation.

[0084] Advantageously, the measurement arrangement implemented as a number of conductive plates may be relatively simple to implement, may be robust and compact such that only a small space on a quantum-enabled device is occupied. Its all-electronic feature makes it ideal in conjunction with a quantum-enabled devices, such as ion-trap quantum computer modules, as it can be easily integrated with smaller modifications to the manufacturing process already used to fabricate the quantum-enabled device. Furthermore, the use of conductive plates may be suitable for the environmental conditions under which quantum-enabled devices typically operate (ultra- high vacuum, cryogenic temperatures, etc.).

[0085] Despite the advantages associated with the use of conductive plates, other physical principles could also be exploited to detect / measure a distance between adjacent quantum- enabled devices. Such methods can be based, amongst others, on additional electronic principles(capacitive, inductive, etc.), optical principles (interferometry, reflection, refraction, etc.), and heat transfer principles (thermal coupling, etc.). Each of these principles may be used in isolation, or together with other physical principles to detect the distance between adjacent devices in a simple manner.

[0086] Systems and methods of the present disclosure may directly integrate a distance sensor into a quantum-enabled device / module. Systems and methods of the present disclosure may be configured to determine distance between adjacent quantum-enabled devices in a direction. If this determined / detected / measured distance deviates from an expected / known distance, it may be determined that the quantum-enabled devices are misaligned.

[0087] In some cases, the measurement arrangement may be configured to measure a distance. A method of measuring a distance may be suitable for operation in environments that quantum- enabled devices usually operate. For example, the measurement arrangement may be compatible with ultracold temperatures. For example, the measurement arrangement may be compatible with operation in a vacuum. A method of measurement a distance may be small and compact such that it does not interfere / minimizes interference with normal operation of the quantum-enabled device. The measurement arrangement may utilize optical, thermal, capacitive, or inductive measuring devices for distance determination.

[0088] Figure 1 presents a simplified block diagram of a system 100 for determining misalignment between quantum-matter confinement regions of adjacent quantum-enabled devices 110,120. In the illustrated example, there is provided a measurement arrangement 140 comprising at least a first distance sensor 142a integrated in / on a first quantum-enabled device 110, and a processor 130. In some cases, the measurement arrangement may comprise a plurality of distance sensors 142, a feedback control module 150, and / or an actuator 160. In some cases, the measurement arrangement 140 may at least partially be provided on a second quantum enabled device 120.

[0089] A quantum-matter confinement region may comprise a region formed by a trap for quantum-matter in a state in which information is held. For example, the quantum-matter confinement region may be formed by an ion trap, for example a surface ion trap or a 3D ion trap. The trapped quantum-matter may include an ion, an electron, an atom, a molecule, or any other type of quantum particle by which information may be held.

[0090] In some cases, a quantum-enabled device 110 may be any device that has a quantummatter confinement region integrated thereon and which moves / shuttles the quantum-matter in the quantum-matter confinement region and to other quantum-matter confinement regions. In some cases, the quantum-enabled device 110 may be a module for a quantum computer. Themodule may be capable of performing quantum operations and shuttling the quantum-matter. In some examples, the quantum-enabled device 110 may be an ion-trap quantum computing module.

[0091] In some cases, the system 100 may be capable of determining (mis)alignment between the quantum-enabled device 110 and another (e.g., adjacent, near, etc.) quantum enabled device 120. Both devices may comprise a quantum-matter confinement region between which quantummatter may be transported. In some cases, quantum-matter may be transported for manipulation on one device before being used on another device. In some cases, quantum-matter may be transported from one module to another module of a device. In some cases, quantum-matter may be transported to perform a refilling operation. In some cases, quantum-matter may be transported to perform a quantum gate. Alignment between said quantum-matter confinement regions may be important to ensure that the quantum-matter can be efficiently and reliably transported between the regions.

[0092] For ensuring / assessing this alignment, systems and methods of the present disclosure provide a measurement arrangement 140 integrated into at least one of the adjacent quantum- enabled devices 110, 120 (or potentially both). Integrated into may comprise, for example, mechanically connected to / forming part of. The measurement arrangement 140 may comprise a first distance sensor 142a configured to generate a first signal comprising information indicating a distance, in a first direction, between a first quantum-enabled device 110 and a second quantum-enabled device 120 adjacent to the first quantum-enabled device 110. In some cases, the measurement arrangement 140 has at least one distance sensor 142 for measuring / detecting / determining a distance between the adjacent quantum-enabled devices 110, 120 in a direction. A direction may be a lateral direction, a vertical direction, one of three axes of translation, one of three axes of rotation, etc.

[0093] The distance sensor 142 may be provided on / in / with only one of the quantum- enabled devices 110, 120. For example, when the distance sensor 142 determines a distance based on a time-of-flight of incident light, the distance sensor 142 may comprise a light source for irradiating light toward a second quantum-enabled device 120, and a light detector to detect light reflected off the second quantum-enabled device 120. In some cases, both the light source and detector provided on the first quantum-enabled device 110.

[0094] In other cases, the distance sensor 142 may be provided on / in / with both of the adjacent quantum enabled devices 110, 120. For example, when the distance sensor 142 determines a distance based on a capacitance of metallic plates, one metallic plate may be placed on a firstquantum-enabled device 110, and another metallic plate may be placed on a second-quantum enabled device 120. One of the metallic plates may act as a transmitter and another as a receiver.

[0095] In some examples, the distance sensor(s) 142 may be based on capacitive, inductive, thermal, or optical principles in order to measure the distance between the adjacent quantum- enabled devices 110, 120. In some cases, the first distance sensor 142a determines the distance based on a capacitance between conductive plates. A distance determination may be particularly suitable for operation in a vacuum and cryogenic conditions that quantum-enabled devices may be operated in.

[0096] In some cases, the distance sensor 142a may comprise a conductive plate positioned on the first quantum-enabled device 110, and a conductive plate positioned on the second quantum- enabled device 120. In some cases, there may also be provided driving electronics configured to apply a voltage to one of the conductive plates. For example, voltage may be applied to one of the conductive plates or both in order to induce a capacitance between the metallic plates. The distance sensor 142a may be able to produce a signal comprising a capacitance value describing a capacitance between the conductive plates. Such a capacitance value may be indicative of a distance between the plates, and therefore between the devices to which they’re integrated. In some case, the capacitance value is inversely proportional to a distance between the plates.

[0097] In some cases, the first distance sensor 142a may comprise a first conductive plate and a second conductive plate positioned on the first (or second) quantum- enabled device 110, and a conductive plate positioned on the second (or first) quantum-enabled device 120. In some cases, driving electronics may be provided and configured to apply a voltage to at least one of the conductive plates. In some cases, the first signal comprises a capacitance value describing a capacitance between the first conductive plate of the first quantum computing module 110 and the conductive plate of the second quantum-enabled device 120, and a capacitance between the second conductive plate of the first quantum-enabled device 110 and the conductive plate of the second quantum-enabled device 120. In this way, a more accurate and precise distance measurement may be obtained via triangulation.

[0098] In some cases, the system 100 further comprises a processor 130 configured to process the first signal to determine a misalignment value. In some cases, the first signal comprises a capacitance value, a temperature value, a time-of-flight value, etc. to determine a (mis)alignment value. The (mis)alignment value may describe a degree / extent / presence of misalignment between a quantum-matter confinement region of the first quantum-enabled device 110 and a quantummatter confinement region of the second quantum-enabled device 120.

[0099] In some cases, measuring the distance between two adjacent quantum-enabled devices 110, 120 in a known direction (e.g., a first direction) in a known location (e.g., the location of the first distance sensor 142a) may enable the determination of whether the quantum-matter confinement regions of the quantum-enabled devices 110, 120 are misaligned. The quantummatter confinement regions may be considered aligned when the distance between the adjacent devices is at or about at an expected value.

[0100] For example, assuming that the quantum-enabled devices 110, 120 are able to move / have a degree of freedom in one direction (e.g., the first direction), if the distance is very large (compared to an expected value) it follows that the devices are misaligned. Equally, if the distance value is very small (compared to an expected value), it follows that the devices are also misaligned. However, if the distance is approximately the same as an expected distance value, this will indicate that the devices are likely to be aligned.

[0101] In some cases, should the quantum-enabled devices 110, 120 have higher degrees of freedom (e.g., may be misaligned in three dimensions or may be misaligned in the three translation directions and / or the three rotational directions) a determination of the distance between the devices in further directions may be used to determine whether the devices are aligned. For example, if the quantum-enabled device 110, 120 is able to move laterally / in one plane, then at least two distance sensors 142a, 142b may be used for measuring the distance in two different directions in that plane. In some cases, one distance sensor 142a may still provide sufficient data to determine whether the devices are misaligned, as a deviation from an expected value may indicate misalignment on some axis.

[0102] In some cases, the processor 130 may be configured to determine a distance value based on the first signal, the distance value indicating the distance between the first quantum-enabled device and the second quantum-enabled device in the first direction. In some cases, the distance value may be determined by converting a capacitance / temperature value indicated by the signal into a distance value using an algorithm. The processor 130 may then compare the determined distance value to an expected distance value. In some cases, the expected distance value indicates a distance between the first quantum-enabled device 110 and the second quantum-enabled device 120 in the direction when the quantum -matter confinement regions of the quantum-enabled devices 110, 120 are aligned. This expected value may be ascertained experimentally and provided to the processor 130, or the processor 130 may determine this automatically by monitoring a quantum-matter link and comparing the performance of the quantum-matter link to a distance value. Finally, the processor 130 may determine the misalignment value based on the comparison.

[0103] In some cases, to determine the degree of misalignment (or degree of alignment) to a higher degree of accuracy and certainty, additional distance sensors 142b, 142c may be used to provide a signal indicative of a distance between the devices in different directions.

[0104] In some cases, the measurement arrangement 140 further comprises a second distance sensor 142b configured to generate a second signal comprising information indicating a distance between the first quantum-enabled device 110 and the second quantum-enabled device 120 in a second direction. The second direction may be different to the first direction. Similarly, a third distance sensor 142c may be provided for producing a third signal indicative of a distance between the devices in a third direction. In some cases, the measurement arrangement 140 may also comprise further distance sensors.

[0105] In the case that the measurement arrangement 140 comprises the second (and potentially third) distance sensor 142b, the processor 130 is configured to process the signals produced by the distance sensors 142 to determine the misalignment value. That is, the processer 130 receives the signals, determines distances from the signals, and from the distances determines a degree of misalignment between the quantum-matter confinement regions.

[0106] The first direction, the second direction (and the third direction, if a third distance sensor is provided) may be orthogonal. For example, the first direction may be a first lateral direction, the second direction may be a second lateral direction (at a right angle to the first direction), and the third direction may be a vertical direction. In the case that distance sensors are provided for all three orthogonal directions, an absolute determination (in three dimensions) as to whether the quantum-matter confinement regions are aligned may be performed. In another example, the first direction may be a first rotational direction, the second direction may be a second rotational direction (e.g., around an axis at a right angle to the first direction), and the third direction may be a third rotational direction. In some cases, the axes of rotation or translation are orthogonal. In some cases, three non-orthogonal non-colinear axis may define a basis for determining position even if the axes are non-orthogonal. In some cases, alignment is defined in both three rotational and three translational dimensions.

[0107] In some cases, each of the distance sensors 142 may be based on the same principle of operation. For example, each of the distance sensors may be capacitive, inductive, thermal, or optical, etc. In some cases, each of the distance sensors 142 may be based on different principles of operation. For example, some sensors may be optical, others capacitive, etc. In some cases, for simplicity and consistency, one principle of operation may be desirable. However, different principles of operation may ensure provide redundancy useful in case of faulty sensors, or variable conditions where certain principles of operation provide better results.

[0108] Moreover, (one or more of) the distance sensors 142 may be positioned in corners of the first and / or second quantum-enabled devices 110, 120. In other words, the distance sensors 142 may be provided on extremities of the quantum-enabled devices 110, 120. In some cases, even a small angular misalignment between adjacent devices may result in a significant change in a distance indicated by the signal produced by such distance sensors 142 when the sensors are on the extremities. Moreover, the corner of the quantum-enabled devices 110, 120 may be distant from other functional electronics of the devices, ensuring that interference is minimized.

[0109] In some cases, the distance sensors 142 may be positioned on a bottom layer of the quantum-enabled device 110, 120. The bottom layer (e.g., a bottom region / part) of the quantum- enabled device 110,120 may be distant from other functional electronics of the device, ensuring that interference is minimized.

[0110] In the illustrated example, the processor 130 may be provided separately from the quantum enabled device 110, 120 (thus receiving the signals from the measurement arrangement wirelessly). However, in some cases, the processor 130 may be integrated into at least one of the first quantum-enabled device 110 and the second quantum-enabled device 120. In some cases, the signal(s) from the measurement arrangement 140 may be communicated to the processor 130 by an arrangement of vias and electrical connectors. By providing the processor 130 on one (or both) of the quantum-enabled devices 110, 120, there may not be a need for external communication to the processor 130, reducing the chance of interference and / or signal loss.[OHl] In some cases, the processor 130 may be positioned in an electronics layer of at least one of the first quantum-enabled device 110 and the second quantum- enabled device 120. In some cases, the electronics layer may be the layer / region containing control electronics for the quantum-enabled device 110, 120. The control electronics may be the electronics responsible for, for example, shuttling operations and / or quantum manipulations.

[0112] In some cases, as depicted, the system 100 may further comprise a feedback control module 150 and an actuator 160. The feedback module 150 may be configured to receive the misalignment value from the processor 130 and determine an alignment error signal for controlling the actuator 160 for realignment of at least one of the first quantum-enabled device 110 and the second quantum-enabled device 120.

[0113] In some cases, the methods and systems disclosed herein may be capable of automatically readjusting / realigning the quantum-enabled devices based on the detected misalignment. Accordingly, misalignment during operation (e.g., due to thermal effects, shifting or settling of the components, a tool dropped on the table, etc.) may be effectively suppressed, ensuring effective and efficient operation of quantum-matter links between the devices.

[0114] In some cases, the system 100 may be utilized by a quantum computer. Thus, systems and methods of the present disclosure provide a quantum computer comprising a first quantum- enabled device 110 (e.g., a quantum computing module), a second quantum- enabled device 120 (e.g., another quantum computing module) adjacent to the first quantum-enabled device, and the system 100 described above for determining misalignment between quantum-matter confinement regions of the adjacent quantum- enabled devices 110, 120.

[0115] Figure 2 presents a flow diagram providing operations in an example method for determining misalignment between quantum-matter confinement regions of adjacent quantum- enabled devices.

[0116] At an operation 210, a first signal comprising information may be generated by a measurement arrangement. The first signal may indicate a distance between a first quantum- enabled device and a second quantum-enabled device adjacent to the first quantum-enabled device in a first direction. In some cases, the method may also include generation of a second signal, a third signal and so in for distances in different directions, as described above. However, further discussion of this will not be repeated for the sake of brevity.

[0117] At an operation 220, the first signal may be processed to determine a misalignment value describing a degree of misalignment between a quantum-matter confinement region of the first quantum-enabled device and a quantum-matter confinement region of the second quantum- enabled device.

[0118] In some cases, operation 220 may comprise sub-operations 222, 224, and 226. In operation 222, a distance value based on the first signal is determined. For example, the distance value may indicate the distance between the first quantum-enabled device and the second quantum-enabled device in the first direction. Then, in operation 224, the determined distance value is compared to an expected distance value (indicating a distance between the quantummatter confinement regions of the quantum-enabled devices when they are aligned). Finally, in operation 226 the misalignment value is determined based on the comparison.

[0119] Furthermore, the method may also comprise additional operation 230. In operation 230, an alignment error signal for controlling an actuator for realignment of at least one of the first quantum-enabled device and the second quantum-enabled device is determined based on the misalignment value determine in operation 220.

[0120] In this way, a method is provided for determining misalignment between adjacent quantum-enabled device. Such a method may be used to decide whether to readjust the quantum- enabled devices so that a quantum-matter link between the devices may perform in a more effective and / or efficient manner.

[0121] As stated above, in some cases, the measurement arrangement may comprise a distance sensors comprising conductive plates, driven such that they exhibit a capacitance. Disclosed herein are systems and methods to extract the distance information from the conductive plates; arrangements and positions of those plates on the quantum-enabled device; and the configuration and placement of the appropriate signal processing electronics.

[0122] There are several methods for deduction of the distance information between adjacent quantum-enabled devices. In some cases, the deduction of distance information exploits a capacitive coupling effect between capacitive (e.g., conductive) plates to assess the distance between the two plates (e.g., that are part of, or mechanically linked to, the quantum-enabled devices). A first plate mounted on a quantum-enabled device can be considered as an emitter (Tx) and a second plate, mounted to another adjacent quantum-enabled device, can be considered as the receiver (Rx).

[0123] Various emitter-receiver interactions are provided herein. In an example, by applying an oscillating signal to the emitter plate and measuring the amplitude of the signal received on the second plate (the signal on the second plate arising from the capacitive coupling effect), it is possible to deduce the distance between the two plates. The voltage amplitude of the received signal may be inversely proportional to the distance between the plates.

[0124] In another example, by measuring the received signal on the second plate using an inverting amplifier with capacitive feedback (with feedback capacitor used as reference) at the same frequency sent to the emitter plate, the capacitance between the two plates (and thus their distance to one another) can be deduced.

[0125] In another example, by grounding the receiving capacitance and supplying the first plate with an oscillating current, the voltage amplitude of the plate is proportional to the distance between the two plates.

[0126] In some cases, the number of conductive plates affixed / integrated with a quantum enabled device at known positions can be used such that a unique set of measured capacitances values between conductive plates is provided. To this unique set of measured capacitance values a unique misalignment distance between modules is associated via triangulation. This may be enabled by use of one or more plates on one quantum-enabled device acting as transmitters, and one or more plates positioned on an adjacent quantum-enabled device acting as receivers. The plates acting as receivers are capacitively coupled to the transmitters.

[0127] There are several methods which permit the deduction of relative positions between the plates, and therefore between the quantum-enabled device. In an example, the conductive plate(s) acting as emitters can be operated / driven at different frequencies. For example, using a sensitivedemodulation technique (e.g., synchronous demodulation), the value of each signal amplitude can be measured and the position of the conductive plate acting as a receiver with respect to the conductive plate(s) acting as emitter(s) can be deduced.

[0128] In another example, the conductive plates acting as emitters on a quantum-enabled device can be operated / driven at the same frequency, but operated alternatively (e.g., switched between the same supply or connected to different supplies operating alternately). The value of each signal amplitude can be measured alternatively and the position of the conductive plate(s) acting as receiver(s) with respect to the conductive plate(s) acting as emitter(s) can be deduced.

[0129] In another example, voltage signals at the same frequencies can be used to drive the conductive plate(s) acting as emitters, but with different phase such that the signal detected on the conductive plate acting as a receiver exhibits a specific signal characteristic (for instance a zero amplitude) when a specific relative positioning of the quantum-enabled devices is satisfied. This could (for instance) be used to assess how well a module is locked to a predetermined position.

[0130] In another example, a single conductive plate acting as an emitter on a quantum-enabled device can be operated / driven at a single frequency and received on a plurality of conductive plates acting as detectors on an adjacent quantum-enabled device. The relative value of the amplitude received on the conductive plate(s) can be measured using a differential or instrumentation amplifier set-up. This could for instance be used to assess how well a quantum- enabled device is locked to a predetermined position where a relative value of one received signal compared to the other is satisfied.

[0131] In another example, the measurement accuracy of the distance between the conductive plates may be improved by executing a plurality of distance measurements and taking the average.

[0132] In some cases, any combination of the above may be implemented in order to obtain a distance measurement via a capacitive reading.

[0133] As well as methods for deduction of the distance information, there are also many different aspects to the arrangement and positioning of the conductive plates that may be considered. In some cases, a combination of the following may be utilized (e.g., plates on the top layer for measurement of distance in an x direction, and plates on the bottom layer for measurement in a y direction).

[0134] In some cases, the conductive plates may be positioned on the top layer of the quantum- enabled device. For example, the conductive plates may be positioned near a surface- electrode ion-trap.

[0135] In an example, the conductive plates used for distance measurement can be located on a top layer. In some cases, the plates may be positioned sufficiently away from the means for quantum -matter confinement (e.g., trapping electrodes) to prevent any interference with the means for quantum-matter confinement, such as an ion trap. This may permit the simultaneous operation of both quantum operations together with the operation of the measurement arrangement.

[0136] In another example, the plates may be positioned on the top layer of the ion trap but in relative proximity to the means for quantum-matter confinement (e.g., trapping electrodes). However, to prevent any undesired effect on the confinement and / or shuttling potential, these can be only operated when quantum-matter (e.g., ions, electrons, atoms, etc.) are not located in proximity to the plate. For instance (but not restricted to that), distance measurement may occur during the quantum computer cycle time interval when quantum-matter / information is not being shuttled between adjacent quantum-enabled devices, or the time interval during which any detrimental interaction between a quantum operation and the operation of the measurement arrangement is avoided (noise pick up during quantum gate operation, etc.).

[0137] In another example, the plates (still positioned on the ion-trap top layer) may be surrounded in their co-plane by grounded electrodes to enhance the electric field sensitivity. This could also be further enhanced by adding, and also grounding, the layer directly underneath the plate (the latter being separated from the plate by a dielectric material).

[0138] In another example, all of the above factors could be combined. That is, the plates may be positioned remotely from quantum-matter confinement means, not operated when matter is being moved between devices and / or when a quantum operation is being performed and surrounded by grounded electrodes.

[0139] In some cases, the conductive plates may be positioned within an intermediary layer of the quantum-enabled device. This may avoid the generation of significant direct detrimental interaction between the electric field generated by operation / driving of the conductive plates, and the quantum-matter in the quantum-matter confinement region owing to the additional distance and shielding.

[0140] For example, the plates may be part of the same layer as a buried ground plane used in a surface-electrode ion-trap. These can be patterned specifically to meet the specified plate geometries and ease ion-trap manufacturing. This may lower the number required of fabrication, decreasing production time, and increasing device fabrication yield. In another example, the plates may be surrounded in their co-plane by guard electrodes to enhance the electric field sensitivity. This could also be further enhanced by adding as a guard the layer directlyundemeath the plate as well as directly above it (again, the latter being separated from the plate by a dielectric material). In some cases, both of the above implementations (e.g., ground plane layer patterning and enhanced sensitivity) may be utilized.

[0141] The conductive plates may also / altematively be positioned on the bottom layer of a quantum-enabled device (e.g., the bottom layer of a surface-electrode ion-trap module). This may prevent any detrimental interaction between the electric field used to operate the conductive plate and the trapping potential utilized by means for confining quantum-matter.

[0142] In an example, the plates may be positioned directly on the underside of the substrate (e.g., a wafer material) onto which the means for confining the quantum matter (e.g., an ion-trap, an atom trap, etc.) is built. This further avoids any electromagnetic interference with signals being delivered to the trap by a conductive path / via through the trap substrate owing to the large distances (several 100 pm) separating the electronic elements.

[0143] In another example, the conductive plates may be located directly on the underside of the undercut of an ion-trap module edge. This may be easier to implement from a fabrication standpoint.

[0144] In some cases, the measurement arrangement may include an arrangement of a single pair of plates (such as for simplicity) or an arrangement comprising a plurality of plates (such as to enhance the measurement sensitivity or range). For instance, pairs of plates may be configured to form a Vernier scale. The Vernier scale principle is one possible arrangement, amongst others, which enhances the accuracy of the distance measurement while also providing an opportunity to increase the range of misalignment measurement available.

[0145] In some cases, the positioning and configuration of signal processing electronics (e.g., the processor) for driving the conductive plates and deducing distance information may to be considered.

[0146] For example, the processor (e.g., processing electronics, computer, digital computer, etc.) may be positioned within electronic layers (hosting DACs, ASICs, etc.) that are used to drive and operate the quantum-enabled device. Hosting the electronics for determining distance directly within the quantum-enabled device significantly reduces the number of vacuum-to- airside feedthrough connections, thereby minimizing vacuum leak risks, electric noise pick-up and electric interference with surrounding components.

[0147] More particularly, the processor can be positioned in close proximity to the plates it connects to minimize electric interference with surrounding electronics used to operate the iontrap quantum computer module. Additionally, the processor may be positioned in a location where the power generated by the processing electronics dissipates is judiciously removed(thermal management) in order to not affect the operation of the quantum-enabled device through adverse thermal effects.

[0148] In some cases, the processor may be positioned within an additional, distinct layer mechanically linked to the electronic layers (hosting DACs, ASICs, etc.) that is used to drive and operate the quantum-enabled device.

[0149] By way of illustrative example, specific examples of the systems and method disclosed herein are described by reference to Figures 3-14. In these Figures, concepts for determining (mis)alignment between adjacent surface ion-trap based quantum computing modules (as the quantum enabled devices) are described, which utilize capacitive coupling. However, these examples should not be considered restrictive, nor exhaustive.

[0150] In some cases, the surface ion-traps of the following examples may instead be replaced by a 3D ion trap. Further, the ion-traps may be replaced with other types of confinement regions, such as those that may confine other quantum matter, such as electrons, individual atoms, molecules. Thus, the systems and methods disclosed herein are not restricted to the use of ion traps. As also described above, capacitive coupling may also be replaced by methods for measuring distance, such as thermal or optical based systems.

[0151] In some examples, quantum-enabled devices / modules can be tessellated to form a large quantum computing / device architecture where quantum information is shared between the quantum-enabled device through matter-based quantum links. Figure 3 illustrates this concept where a top view 300a of tessellated ion-trap quantum computing modules 310, 320 is shown. For example, individual ion-trap quantum computing modules may be tessellated to one another. For illustrative purposes, only two modules (module A 310, and module B 320) are rendered in their entirety, additional modules are partially rendered.

[0152] An individual ion-trap module is illustrated separately, and in more detail, in Figure 4 on a top view 300b, and an isometric view 300c. By way of example only, such an ion-trap module may have a surface area of approximately 90 x 90 mm2 or within a range from about 5x5mm to about 200x200mm. Within a single module, quantum information held within individual ions may be distributed / moved by routing the ions on an array of X-junctions 330. In Figures 3 and 4, each module has a total of 9 X-junctions 330, but this number is chosen as an example.

[0153] As shown, the ion-trap surface of the module may be formed of a plurality of conductive and insulating materials 350. For a microfabricated surface ion-trap, the top layer may comprise a metal conductor (gold, aluminium, etc.) forming planes, and electrodes which can be grounded, or connected to DC or RF potentials. Additional conducting planes of the ion-trap (which are not shown in the example illustrated in Figure 4), can be used for signal routing. Each ion-trapquantum computer module may comprise a microfabricated ion-trap that is connected to separate silicon substrates. These substrates may be connected using through-silicon via (TSV) and wafer stacking technology. The electronics for controlling and driving the ion-trap may be housed on said separate substrate layers. Such electronics may include, but are not limited to, digital-to- analogue converters (DACs), application specific integrated circuits (ASICs), electronic filtering circuits, detection electronics and ion loading electronics. As an example, approximately 9 stacked electronic substrate layers can be used to drive 36 X-junction ion-trap structures (although only 9 are shown here) on a single module.

[0154] In some cases, and as shown in Figure 4, the ion-trap quantum computer modules 300 may include a measurement arrangement 340 for determining a distance in a first direction (z) to an adjacent ion-trap quantum computer module (not shown). In the illustrated case, the measurement arrangement may include capacitive devices 340 which are used to measure the misalignment with respect to other modules when the modules are tessellated together. In this example, the capacitive devices 340 are positioned close to the corners of the ion-trap quantum computer module 300. The positions and arrangement of the capacitive device / metallic plates 340 on the module 300 may be designed to form a repeating, interlocking pattern with capacitive devices 340 on adjacent modules. The positioning of these devices within the ion-trap layout may be flexible.

[0155] Dedicated electronic circuitry may be used to drive the capacitive devices / plates 340. This circuitry may be directly integrated within one of the electronic substrate layers which may also be used to host the electronics for controlling the ion- trap to perform ion trapping and / or coherent quantum operations. For example, these electronics may be integrated on the uppermost electronic substrate layer below the ion-trap layer to minimize the connection pathlength to the capacitive sensors, thereby minimizing noise pick-up and optimizing the accuracy with which the misalignment between modules is measured. In order to provide a similar benefit, the electronics may be positioned at corners of the ion-trap quantum computing module 300. Again, the positioning of the electronic circuitry may be changed and is shown in a particular position by way of example.

[0156] Figure 5 illustrates a side view 400 of an example of adjacent ion-trap quantum computing devices 410, 420 having a measurement arrangement 440. In this example, the presented devices / modules have conductive plates 442a, 442b integrated within them. Thus, the measuring arrangement 440 comprises metal plates that permit the measurement of the relative distance between both modules along the vertical direction (z direction).

[0157] As illustrated, a conductive plate 442a is positioned on the underside of an overhanging portion of module A 410. Opposing this, on module B 420, is a conductive plate 442b, positioned on the upper side of an ion-trap substrate layer. As shown, one of the conductive plates 442a may include a smaller surface area than the other. This ensures that small displacements (for instance in the order of 10 — 100 pm) along lateral directions (x-y plane) do not lead to a substantially change in capacitance between these plates and therefore do not impact the measurement of the distance separating them in the z direction. It is worth noting that it may not matter which of the two plates is the largest (on either module, or either a transmitting or receiving plate). Both conductive plates 442a, 442b can be fabricated using a plurality of conductive materials (e.g., gold, copper, aluminium, etc.) with a thickness of 100 — 500 nm or larger. Electrical connections to these plates may be realized using vias to another conductive layer (not shown) and conductive trace routed to the plates (also not shown). Using methods described herein, it is possible to deduce the capacitance between the conductive plates 442a 442b and calculate (based the geometry of the plates) the separation between those plates. During system design, the placement of the conductive plates 442a, 442b on each respective module can be chosen so as to leave a gap of known separation between both plates when confinement regions of each module are aligned in the vertical direction. For instance, this gap may be between 10 — 50 pm. Thus, there may be a known capacitance value when the modules (and thus confinement regions) are aligned. For example, the confinement regions may be aligned when the separation between the conductive plates 442a, 442b is measured to match that of the design.

[0158] In some cases, the overhang structure of the module may be created by precisely etching a large single substrate, or by fusing an intermediary substrate (dotted) of precise thickness inbetween the upper substrate supporting the surface- ion trap and the lower substrate connected to electronics layers. For example, using conductive plates 442a, 442b with a surface area in a y-x plane being around 50 x 50 pm2 to 100 x 100 pm2 a capacitance in the order of 0.5 — 10 femtofarads can be realized. With voltage signals applied to the conductive plate with ~10 V amplitude at ~1 MHz it is estimated that the gap separation may be resolved with an accuracy of 0.04 pm (using for instance an 8-bit ADC).

[0159] Furthermore, the measurements of the misalignment between quantum- enabled devices 410, 420 along the vertical (z) direction may be refined further using additional conductive plates integrated in the quantum-enabled devices.

[0160] This concept is illustrated in Figure 6, which presents a side view 500 of such a quantum- enabled device having a measurement arrangement comprising one conductive plate 530 positioned on module A 510 and two conductive plates 540a, 540b positioned on module B 520.

[0161] On module A 510 the conductive plate 530 may be positioned between two grounded conductive layers 550. Note that, in this illustration, the upper most ground plane may also be used as the buried ground plane of an ion-trap if module A 510 is a trapped-ion quantum computing module. It is useful to note that this layer may act as an electromagnetic shield, reducing interference.

[0162] On the module B 520, a first conductive plate 540a is illustrated as being in a region that may be part of the same layer as the ground plane of the module B ion- trap (not shown). It should be noted that the first conductive plate 540a may also be located on a separate layer, which could be useful to enhance electromagnetic shielding of the ion-trap top-layer conductor. A second conductive plate 540b may be separated from the first conductive plate 540a by approximately 5 — 10 pm. The layer within which this plate 540b is a part may be patterned (not shown) such that the second conductive plate 540b is surrounded by conductive material forming a guard. This also permits the focusing of electric fields to the side of the module which allows measurement of the (mis)alignment with greater sensitivity.

[0163] The conductive plate 530 may be positioned on module A 510 such that the vertical alignment of a quantum matter confinement region corresponds to the positioning of this plate 530 in the middle of the two other conductive plates 540a, 540b positioned in module B 520 along the z direction.

[0164] Figure 7 illustrates the principle of operation of the measurement arrangement of Figure 6. Specifically, Figure 7 demonstrates the principle of a misalignment in the vertical direction when the quantum-matter confinement region of module A (500a) is below that of module B, when the quantum-matter confinement region of module A (500b) is aligned with that of module B, and when the quantum-matter confinement region of module A (500c) is above that of module B.

[0165] In some cases, when the quantum -matter confinement region (e.g., the ion -trap surface) of module A and B are aligned the conductive plate in module A is positioned precisely in-between (equidistant) between the two conductive plates of the second module in the vertical (z) direction. Thus, by using methods described herein, it can be possible to deduce when this criterium is fulfilled, and therefore when the confinement regions of the two modules are precisely vertically aligned.

[0166] In some cases, by using conductive plates with both width (along x) and length (along y) in the order of 100 pm and provided a separation between modules in the range of 1 — 20 pm, a capacitance in the order of 2 — 4 femtofarads can be realized. With voltage signals of ~10 V amplitudes at ~1 MHz applied to the conductive plate of module A, the top and bottomconductive plates of module B receive a signal of similar amplitude and frequency which can be compared using, for instance, a known differential amplifier set-up. Accordingly, the alignment of the two modules along the vertical (z) direction can be verified with submicron accuracy (limited by the accuracy of the fabricated structures and precision of the electronics employed).

[0167] Figure 8 illustrates a top view 600 of conductive plates that may be integrated in quantum-enabled devices 610, 620 (such as ion-trap quantum computing modules) so as to enable the measurement of a distance between the devices / modules into which they are integrated along their lateral directions (x — y directions).

[0168] This measurement arrangement provides a plurality of conductive plates 630, 640 that may be positioned at the edge of adjacent modules (module A 610 and module B 620) in the way illustrated. The conductive plates 630, 640 are surrounded by a dielectric (shown in grey). On module B 620, the conductive plates 640 may be surrounded by a conductive guard that is grounded. Note that other / al ternative configurations of these conductive plates 630, 640 on the quantum-enabled device 610, 620 may be used. In some cases, the conductive plates 630, 640 are surrounded by a conductive material 650 which acts as a guard and permits an increase the sensitivity of the conductive plates to a signal produced by a voltage applied to at least one of the conductive plates.

[0169] All conductive plates 630, 640 can be fabricated using a plurality of conductive materials (e.g., gold, copper, aluminium, etc.) with a thickness of 100 — 500 nm (or larger, if these layers are also used for trap operation for instance). Electrical connection to these elements can be realized using vias to other conductive layers (not shown) and conductive traces routed to these elements (also not shown). Insulation between these elements can be formed using a plurality if dielectric materials (e.g., silicon dioxide, silicon nitride, etc.). Using plates with typical width (along x) and length (along y) in the order of 200 pm and 50 pm, respectively, and provided a separation between modules in the range of 1 — 20 pm, a capacitance in the order of 1 — 2 femtofarads can be realized.

[0170] The conductive plates 630, 640 in Figure 8 may be used to determine the misalignment along the y direction. These plates can also be arranged according to the Vernier scale principle, enabling greater accuracy of the measured misalignment over a larger range.

[0171] Figure 9 illustrates the principle of operation of the measurement arrangement of Figure 8. In particular, the conductive plates used for specific misalignments are shown in black. The capacitance between the conductive plates on module A and those on module B can be determined using known methods. From these capacitance values a single measurement value for the misalignment between modules along y may be determine. It is worth noting that theconfiguration of the conductive plates presented in Figure 8 is only provided as an example and adding more conductive plates, using plates with different dimensions, positioning plates at different locations, or different arrangements can be used. These can also be used to create the device with arbitrary measurement accuracy and range along the y direction.

[0172] In some cases, some of the conductive plates illustrated in Figure 8 may be used to determine the misalignment along the x direction. This is shown in Figure 10, with the plates used for this purpose presented in black. Figure 10 illustrates top view of misalignment along the x direction between portions of quantum-enabled devices aligned in the z and y direction. The top image shows when the modules are substantially misaligned the bottom image shows when the modules are well aligned. As capacitance varies with distance between plates, it is possible deduce the distance between the conductive plates based in the capacitance between these plates on module A and those on Module B. In some cases, the capacitance may be between 1 — 2 femtofarads when the confinement regions are aligned in the x direction. From these capacitance values is then associated a unique measurement value for the misalignment between modules along x.

[0173] Figure 11 illustrates a side view 700 of a quantum-enabled device (projection on the x — z plane) including a measurement arrangement comprising conductive plates 730, 740. In some cases, the measurement arrangement integrated within the adjacent quantum-enabled devices enables misalignment determination in all directions (x, y, and z). Plates 730a, 740a and 740b enable distance detection in an x and y direction, while plates 730b and 740c enable distance detection in a z direction. In some cases, the arrangement presented in Figure 11 presents a system which utilizes a measurement arrangement analogous to those presented in Figures 5, 6 and 8 for the measurement of the misalignment between ion-trap quantum computer modules along x, y and z respectively.

[0174] Figure 12 presents side views (projection on the y — z plane) of the system illustrated in Figure 11. Specifically, the top three images 710a-c represent a first module, and the bottom three images 720a-c represent a second, adjacent, module. The top three images 710a-c illustrate the position of conductive plates for a first module 710 as already illustrated in Figures 5, 6 and 8 (as shown from left to right in Figure 12). The lower three side views 720a-c of Figure 12 illustrate the position of conductive plates for module B 720 as already illustrated in Figures 5, 6 and 8 (as shown from left to right on Figure 12). As shown, the conductive plates may be distributed along the y direction of the module such that each measurement device can be operated without influencing the operations of others through electromagnetic coupling. If electromagnetic coupling between conductive plates is problematic, the distances betweendevices can be increased, additional electromagnetic shielding layers can be constructed, and the operation of each conductive plate pairing can be cycled (rather than being operated / driven by a voltage simultaneously). Using such a measurement arrangement, misalignment along all 3 translation directions (x, y and z) between adjacent quantum-enabled devices may be measured with an accuracy « 1 pm.

[0175] Figures 13a and b illustrate another example of configuring the measurement arrangement / capacitive devices of the measurement arrangement. Quantum enabled devices 810, 820 are depicted at right angles to each other: the combs of each device would interlink. As with the location of the previous implementation of these capacitive devices (e.g., conductive plates), these can also be located at the comer of the modules. Here the conductive plates are arranged to enable (primarily) the measurement of the distance between adjacent quantum enabled devices 810, 820 along the lateral direction (x or y directions). The measurement arrangement in some cases comprises a structure 830, 840 of capacitive / metal plates forming two complementary combs that can interlink when the adjacent devices / modules are precisely aligned, and which allows to amplify the capacitive signal which carries the distance information between modules. Each “tooth” of the comb consists of either a conductive plate itself or an assembly formed of a conductive plate affixed to an insulating layer or an insulating layer sandwiched between two metal plates. During system design, the placement / relative positioning of the teeth of the comb containing the plates on each respective device / module 810, 820 can be chosen to leave a gap of known separation between plates belonging to either device / module. For instance, this gap may be approximately 10 — 100 pm wide, or larger. Alignment between both modules in the lateral direction may then be asserted if the measured capacitance reflects a specific positioning (for instance equally distances between teeth either side of each tooth) of one of the combs containing the plates on one module with respect to the other one.

[0176] As with the other implementations, conductive plates can be fabricated using a plurality of conductive materials (e.g., gold, copper, aluminium, etc.) with a thickness of 100 — 500 nm or larger. To ensure that small displacements (for instance in the order of 1 — 100 pm) along the vertical direction do not lead to a substantially change in capacitance between these plates, and therefore do not impact the measurement of the distance separating them in the lateral (x-y plane) direction, the plates on one side of tooth forming the comb, or plates belong to one of the two modules, can be substantially larger than the other. It may not matter which of the two plates is the largest. The comb and teeth structures can be realized through microfabrication techniques such as by precisely etching a large single substrate (implementation not shown in Figure 13a and b) or by fusing a substrate of precise thicknesses together.

[0177] As with previous implementations described in other illustrations, electrical connections to these plates can be realized using vias to another conductive layer (not shown) and conductive trace routed to the plates (also not shown). Thus, it is possible to measure the capacitance between both plates and calculate from the geometry of the plates the separation between the plates.

[0178] By locating the conductive plates 930, 940 as illustrated in the above examples at each comer of the quantum enabled devices 910, 920 as illustrated in Figure 14 (Note that these can also be located at locations other than the corners) and comparing the values of misalignments at each comer, the angular misalignment between these modules can then be determined. In some cases, the conductive plates may be placed in locations other than the comers to determine an angular misalignment but locating the plates on the corners results in a more accurate measurement.

[0179] Figure 14 illustrates this angular misalignment between adjacent quantum- enabled devices 910, 920. Note that by comparing axial misalignment reading at each comer of a module with that of all the modules surrounding a central module, it becomes possible to deduce all angular misalignments (all 3 rotational degrees of freedom). For instance, for a module with typical dimensions 90 x 90 mm2, or within a range from about 5x5mm to about 200x200mm, an angular misalignment can be measured with an accuracy of 1 x 10-3 deg.

[0180] Accordingly, provided by the disclosure is a simple means for generating information regarding (mis)alignment between adjacent quantum-enabled devices. The proposed solution is particularly suitable for systems with large numbers of quantum-enabled devices, which requires a simple, robust, and accurate method for determining alignment.

[0181] While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. It is not intended that the invention be limited by the specific examples provided within the specification. While the invention has been described with reference to the aforementioned specification, the descriptions and illustrations of the embodiments herein are not meant to be construed in a limiting sense. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. Furthermore, it shall be understood that all aspects of the invention are not limited to the specific depictions, configurations or relative proportions set forth herein which depend upon a variety of conditions and variables. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is therefore contemplated that the invention shall also cover any such alternatives, modifications, variations,or equivalents. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.

Claims

CLAIMSWHAT IS CLAIMED IS:

1. A system (100) for determining misalignment between quantum-matter confinement regions of adjacent quantum-enabled devices, the system comprising: a first distance sensor (142a) configured to generate a first signal comprising information indicating a distance between a first quantum-enabled device (110) and a second quantum-enabled device (120) adjacent to the first quantum-enabled device in a first direction, wherein the distance sensor is integrated into at least one of the first quantum-enabled device and the second quantum-enabled device.

2. The system of claim 1, wherein the system further comprises: a processor (130) configured to process the first signal to determine a misalignment value describing a degree of misalignment between a quantum-matter confinement region of the first quantum-enabled device and a quantum-matter confinement region of the second quantum-enabled device.

3. The system of claim 2, wherein the processor is configured to determine the degree of misalignment by comparing the distance to an expected distance value.

4. The system of claim 3, wherein the processor is configured to determine the degree of misalignment in 3D translation space, 3D rotation space, or both.

5. The system of any one of claims 2-4, wherein the processor is configured to determine the degree of misalignment at a plurality of instances of time and to provide an instruction to update an alignment at each of the plurality of instances of time.

6. The system of any one of claims 2-5, further comprising a feedback control module (150) and an actuator (160), wherein the feedback control module is configured to receive the misalignment value from the processor (130) and determine an alignment error signal for controlling the actuator (160) for realignment of at least one of the first quantum-enabled device (110) and the second quantum-enabled device (120).

7. The system of claim 6, wherein the feedback control module (150) and the actuator 160 are configured to update an alignment during operation of the first quantum-enabled device, the second quantum-enabled device, or both.

8. The system of claim 6 or 7, wherein the feedback control module (150) and the actuator 160 are configured to maintain an alignment of the first quantum-enabled device, the second quantum-enabled device, or both to within 10 microns, optionally, to within 1 micron.

9. The system of any one of claims 1-8, wherein the first distance sensor comprises a portion of a measurement arrangement.

10. The system of claim 9, wherein the measurement arrangement is configured to determine a misalignment along a direction, wherein the direction is a lateral direction, a vertical direction, one of three axes of translation, one of three axes of rotation, or any combination thereof.

11. The system of claim 10, wherein the measurement arrangement is configured to determine the misalignment in three spatial dimensions, three rotational dimensions, or both.

12. The system of any one of claims 9-11, wherein the measurement arrangement comprises one or more sensor types selected from the group consisting of: capacitive sensors, inductive sensors, thermal sensors, optical sensors, time of flight sensors, or any combination thereof.

13. The system of any one of claims 1-12, wherein the first sensor is configured to determine a distance based on a capacitance between a pair of conductive plates.

14. The system of claim 13, wherein the first sensor comprises a first conductive plate positioned on a first quantum-enabled device and a second conductive plate positioned on a second quantum-enabled device.

15. The system of claim 13 or 14, wherein the system further comprises a driving electronics configured to apply voltage to either of the pair of conductive plates.

16. The system of any one of claims 1-15, wherein the first sensor is configured to operate at cryogenic temperature, in a vacuum, or both.

17. The system of any one of claims 1-16, wherein the first sensor is positioned at an extremity of the first quantum-enabled device.

18. The system of any one of claims 1-17, wherein the first distance sensor comprises a portion of a measurement arrangement , wherein the measurement arrangement (140) further comprises a second distance sensor (142b) configured to generate a second signal comprising information indicating a distance between the first quantum-enabled device (110) and the second quantum-enabled device (120) in a second direction, the second direction different to the first direction, and wherein the processor (130) configured to process the first signal and the second signal to determine the misalignment value.

19. The system of claim 18, wherein the measurement arrangement (140) further comprises a third distance sensor (142c) configured to generate a third signal comprising information indicating a distance between the first quantum-enabled device (110) and the second quantum-enabled device (120) in a third direction, the third direction different to the first direction and the second direction, andwherein the processor (130) configured to process the first signal, the second signal and the third signal to determine the misalignment value.

20. The system of claim 19, wherein the first direction, the second direction and the third direction are orthogonal.

21. The system of any of claims 1-20, wherein the first distance sensor (142a) comprises: a conductive plate positioned on the first quantum-enabled device (110); a conductive plate positioned on the second quantum-enabled device (120); and driving electronics configured to apply a voltage to one of the conductive plates, wherein the first signal comprises a capacitance value describing a capacitance between the conductive plates.

22. The system of any of claims 1-21, wherein the first distance sensor (142a) comprises: a first conductive plate and a second conductive plate positioned on the first quantum-enabled device (110); a conductive plate positioned on the second quantum-enabled device (120); and driving electronics configured to apply a voltage to at least one of the conductive plates, and wherein the first signal comprises a capacitance value describing a capacitance between the first conductive plate of the first quantum computing module and the conductive plate of the second quantum-enabled device, and a capacitance between the second conductive plate of the first quantum-enabled device and the conductive plate of the second quantum- enabled device.

23. The system of any of claims 1-22, wherein the first distance sensor (142a) is positioned on a comer of the first quantum-enabled device (110) and a comer of the second quantum-enabled device (120).

24. The system of any of claims 1-23, wherein the first distance sensor (142a) is positioned on a bottom layer of the first quantum-enabled device (110) and a bottom layer of the second quantum-enabled device (120).

25. The system of any of claims 1-24, further comprising a processor, wherein the processor (130) is integrated into at least one of the first quantum-enabled device (110) and the second quantum- enabled device (120).

26. The system of claim 25, wherein the processor is positioned in an electronics layer of at least one of the first quantum-enabled device and the second quantum-enabled device, the electronics layer comprising control electronics for the quantum-enabled device.

27. The system of any of claims 1-26, wherein the processor (130) is configured to: determine a distance value based on the first signal, the distance value indicating the distance between the first quantum-enabled device (110) and the second quantum-enabled device (120) in the first direction; compare the determined distance value to an expected distance value, wherein the expected distance value indicates a distance between the first quantum-enabled device and the second quantum-enabled device in the direction when the quantum-matter confinement regions of the quantum-enabled devices are aligned; and determine the misalignment value based on the comparison.

28. The system of any of claims 1-27, wherein the quantum -matter confinement region is formed by a surface ion-trap.

29. The system of claim 28, wherein at least one of first quantum-enabled device (110) and the second first quantum-enabled device (120) is a quantum computing module.

30. The system of any one of claims 1-29, wherein the first quantum-enabled device and the second quantum-enabled device are maintained with an alignment accuracy of better than 10 microns, optionally, better than 1 micron.

31. A system (100) for determining misalignment between quantum-matter confinement regions of adjacent quantum-enabled devices, the system comprising: a measurement arrangement (1 0) comprising a first distance sensor (142a) configured to generate a first signal comprising information indicating a distance between a first quantum-enabled device (110) and a second quantum-enabled device (120) adjacent to the first quantum-enabled device in a first direction, wherein the measurement arrangement is integrated into at least one of the first quantum-enabled device and the second quantum-enabled device; and a processor (130) configured to process the first signal to determine a misalignment value describing a degree of misalignment between a quantum-matter confinement region of the first quantum-enabled device and a quantum-matter confinement region of the second quantum-enabled device.

32. The system of claim 31, wherein the measurement arrangement (140) further comprises a second distance sensor (142b) configured to generate a second signal comprising information indicating a distance between the first quantum-enabled device (110) and the secondquantum-enabled device (120) in a second direction, the second direction different to the first direction, and wherein the processor (130) configured to process the first signal and the second signal to determine the misalignment value.

33. The system of claim 32, wherein the measurement arrangement (140) further comprises a third distance sensor (142c) configured to generate a third signal comprising information indicating a distance between the first quantum-enabled device (110) and the second quantum-enabled device (120) in a third direction, the third direction different to the first direction and the second direction, and wherein the processor (130) configured to process the first signal, the second signal and the third signal to determine the misalignment value.

34. The system of claim 33, wherein the first direction, the second direction and the third direction are orthogonal.

35. The system of any of claims 31-34, wherein the first distance sensor (142a) comprises: a conductive plate positioned on the first quantum-enabled device (110); a conductive plate positioned on the second quantum-enabled device (120); and driving electronics configured to apply a voltage to one of the conductive plates, wherein the first signal comprises a capacitance value describing a capacitance between the conductive plates.

36. The system of any of claims 31-35, wherein the first distance sensor (142a) comprises: a first conductive plate and a second conductive plate positioned on the first quantum-enabled device (110); a conductive plate positioned on the second quantum-enabled device (120); and driving electronics configured to apply a voltage to at least one of the conductive plates, and wherein the first signal comprises a capacitance value describing a capacitance between the first conductive plate of the first quantum computing module and the conductive plate of the second quantum-enabled device, and a capacitance between the second conductive plate of the first quantum-enabled device and the conductive plate of the second quantum- enabled device.

37. The system of any of claims 31-36, wherein the first distance sensor (142a) is positioned on a comer of the first quantum-enabled device (110) and a comer of the second quantum-enabled device (120).

38. The system of any of claims 31-37, wherein the first distance sensor (142a) is positioned on a bottom layer of the first quantum-enabled device (110) and a bottom layer of the second quantum-enabled device (120).

39. The system of any of claims 31-38, wherein the processor (130) is integrated into at least one of the first quantum-enabled device (110) and the second quantum- enabled device (120), and optionally wherein the processor is positioned in an electronics layer of at least one of the first quantum-enabled device and the second quantum-enabled device, the electronics layer comprising control electronics for the quantum-enabled device.

40. The system of any of claims 31-39, wherein the processor (130) is configured to: determine a distance value based on the first signal, the distance value indicating the distance between the first quantum-enabled device (110) and the second quantum-enabled device (120) in the first direction; compare the determined distance value to an expected distance value, wherein the expected distance value indicates a distance between the first quantum-enabled device and the second quantum-enabled device in the direction when the quantum-matter confinement regions of the quantum-enabled devices are aligned; and determine the misalignment value based on the comparison.

41. The system of any of claims 31-40, further comprising a feedback control module (150) configured to: receive the misalignment value from the processor (130); determine an alignment error signal for controlling an actuator (160) for realignment of at least one of the first quantum-enabled device (110) and the second quantum- enabled device (120).

42. The system of any of claims 31-41, wherein the quantum-matter confinement region is formed by a surface ion-trap.

43. The system of claim 42, wherein at least one of first quantum-enabled device (110) and the second first quantum-enabled device (120) is a quantum computing module.

44. A quantum computer, comprising: a first quantum-enabled device (110); a second quantum-enabled device (120) adjacent to the first quantum-enabled device; andthe system (100) of any of claims 1-43 for determining misalignment between quantum- matter confinement regions of the adjacent quantum-enabled devices.

45. The quantum computer of claim 44, wherein the quantum computer is a trapped ion quantum computer.

46. The quantum computer of claim 45, wherein the first quantum-enabled device and the second quantum-enabled device are individual ion-trap modules of the trapped ion quantum computer.

47. The quantum computer of claim 46, wherein an ion-trap module comprises a size within a range from about 5x5mm to about 200x200mm.

48. The quantum computer of claim 46 or 47, wherein each of the individual ion-trap modules comprise a microfabricated ion-trap on a substrate and electronics for controlling and driving the microfabricated ion-trap on a separate substrate layer of the substrate.

49. The quantum computer of claim 48, wherein the electronics comprise one or more members selected from the group consisting of: digital-to-analogue converters (DACs), application specific integrated circuits (ASICs), electronic filtering circuits, detection electronics, and ion loading electronics.

50. The quantum computer of any of claims 44-48, wherein the first quantum-enabled device and the second quantum-enabled device are maintained with an alignment accuracy of better than 10 microns, optionally, better than 1 micron.

51. A method (200) for determining misalignment between quantum-matter confinement regions of adjacent quantum-enabled devices, the method comprising:(a) generating (210), by a measurement arrangement, a first signal comprising information indicating a distance between a first quantum-enabled device and a second quantum- enabled device adjacent to the first quantum-enabled device in a first direction, wherein the measurement arrangement is integrated into at least one of the first quantum-enabled device and the second quantum-enabled device; and(b) processing (220) the first signal to determine a misalignment value describing a degree of misalignment between a quantum-matter confinement region of the first quantum-enabled device and a quantum-matter confinement region of the second quantum- enabled device.

52. The method of claim 51, wherein (b) comprises determining the degree of misalignment by comparing the distance to an expected distance value.

53. The method of claim 52, wherein (b) comprises determining the degree of misalignment in 3D translation space, 3D rotation space, or both.

54. The method of any of claims 51-53, wherein (b) comprises determining the degree of misalignment at a plurality of instances of time and to provide an instruction to update an alignment at each of the plurality of instances of time.

55. The method of any of claims 51-54, further comprising: receiving at a feedback control module the misalignment value from the processor; and determining an alignment error signal for controlling an actuator for realignment of at least one of the first quantum-enabled device and the second quantum-enabled device.

56. The method of claim 55, further comprising updating an alignment during operation of the first quantum-enabled device, the second quantum-enabled device, or both.

57. The method of claim 55 or 56, further comprising maintaining an alignment of the first quantum-enabled device, the second quantum-enabled device, or both to within 10 microns, optionally, to within 1 micron.

58. The method of any of claims 51-57, wherein the first distance sensor comprises a portion of a measurement arrangement.

59. The method of claim 58, further comprising, at the measurement arrangement, determining a misalignment along a direction, wherein the direction is a lateral direction, a vertical direction, one of three axes of translation, one of three axes of rotation, or any combination thereof.

60. The method of claim 59, further comprising, at the measurement arrangement, determining the misalignment in three spatial dimensions, three rotational dimensions, or both.

61. The method of any of claims 58-60, wherein the measurement arrangement comprises one or more sensor types selected from the group consisting of: capacitive sensors, inductive sensors, thermal sensors, optical sensors, time of flight sensors, or any combination thereof.

62. The method of any of claims 51-61, wherein (a) comprises, at the first sensor, determining the first signal based on a capacitance between a pair of conductive plates.

63. The method of claim 62, wherein the first sensor comprises a first conductive plate positioned on a first quantum-enabled device and a second conductive plate positioned on a second quantum-enabled device.

64. The method of claim 62 or 63, further comprising applying a voltage, at a driving electronics, to either of the pair of conductive plates.

65. The method of any of claims 51-64, wherein the first sensor is configured to operate at cryogenic temperature, in a vacuum, or both.

66. The method of any of claims 51-65, wherein the first sensor is positioned at an extremity of the first quantum-enabled device.

67. The method of any of claims 51-66, further comprising, subsequent to (a) generating, at a second distance sensor, a second signal comprising information indicating a distance between the first quantum-enabled device and the second quantum-enabled device in a second direction, the second direction different to the first direction, and wherein (b) further comprises processing the first signal and the second signal to determine the misalignment value.

68. The method of claim 67, further comprising, subsequent to (a) generating, at a third distance sensor, a third signal comprising information indicating a distance between the first quantum-enabled device and the second quantum-enabled device in a third direction, the third direction different to the first direction and the second direction, and wherein (b) further comprises processing the first signal, the second signal and the third signal to determine the misalignment value.

69. The method of claim 68, wherein the first direction, the second direction and the third direction are orthogonal.

70. The method of any of claims 51-69, wherein the first distance sensor (142a) comprises: a conductive plate positioned on the first quantum-enabled device (110); a conductive plate positioned on the second quantum-enabled device (120); and driving electronics configured to apply a voltage to one of the conductive plates, wherein the first signal comprises a capacitance value describing a capacitance between the conductive plates.

71. The method of any of claims 51-70, wherein the first distance sensor (142a) comprises: a first conductive plate and a second conductive plate positioned on the first quantum-enabled device (110); a conductive plate positioned on the second quantum-enabled device (120); and driving electronics configured to apply a voltage to at least one of the conductive plates, and wherein the first signal comprises a capacitance value describing a capacitance between the first conductive plate of the first quantum computing module and the conductive plate of the second quantum-enabled device, and a capacitance between the second conductiveplate of the first quantum-enabled device and the conductive plate of the second quantum- enabled device.

72. The method of any of claims 51-71, wherein the first distance sensor (142a) is positioned on a comer of the first quantum-enabled device (110) and a comer of the second quantum-enabled device (120).

73. The method of any of claims 51-72, wherein the first distance sensor (142a) is positioned on a bottom layer of the first quantum-enabled device (110) and a bottom layer of the second quantum-enabled device (120).

74. The method of any of claims 51-73, wherein the processor (130) is integrated into at least one of the first quantum-enabled device (110) and the second quantum- enabled device (120), and optionally wherein the processor is positioned in an electronics layer of at least one of the first quantum-enabled device and the second quantum-enabled device, the electronics layer comprising control electronics for the quantum-enabled device.

75. The method of any of claims 51-74, wherein (b) further comprises: determining a distance value based on the first signal, the distance value indicating the distance between the first quantum-enabled device (110) and the second quantum- enabled device (120) in the first direction; comparing the determined distance value to an expected distance value, wherein the expected distance value indicates a distance between the first quantum-enabled device and the second quantum-enabled device in the direction when the quantum-matter confinement regions of the quantum-enabled devices are aligned; and determining the misalignment value based on the comparison.

76. The method of any of claims 51-75, wherein the quantum-matter confinement region is formed by a surface ion-trap.

77. The method of claim 76, wherein at least one of first quantum-enabled device (110) and the second first quantum-enabled device (120) is a quantum computing module.

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