Quantum-enabled device misalignment

Abstract

A system for determining misalignment between quantum-matter confinement regions of adjacent quantum-enabled devices comprises: a measurement arrangement 140 comprising a first distance sensor 142a co

Description

FIELD OF THE INVENTION 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. BACKGROUND OF THE INVENTION 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 is represented by quantum bits (i.e. qubits). To be able to solve problems that have the potential to profoundly impact society, a practical universal quantum computer will need to operate millions to billions of physical qubits. However, current state-of-the-art quantum computers are typically limited to -100 physical qubits, and therefore have limited utility. A promising device to address this issue is a microfabricated quantum chargecouple device. Such a device relies on an array of segmented electrodes that provide independent quantum-matter confinement regions. Nevertheless, these microfabricated devices 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 is best constructed in a modular fashion. Accordingly, a quantum-enabled device that is capable of hosting an unrestricted number of qubits may be realized. One method to connect multiple modules together is the use of photonic quantum links, based on the conversion of the quantum information held in quantum matter (e.g. an ion) to that of a photon such that entanglement may occur between optically connected modules. However, this method is limited by the inefficient ionphoton interface and link loss rates, with the best entangling rates between modules of approximately 182s-1, and a reliability of 94%. This constitutes the slowest, most limiting process in a quantum-enabled device when compared to the rate of other quantum operations. In an alternative method, adjacent modules can be connected using shuttling operations. In this architecture, individual trapped-ion qubits are physically transported (i.e. shuttled) 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%. For the matter-links to perform optimally, adjacent quantum-matter confinement regions must be accurately aligned to within a few microns (< 10 pm). To solve computationally hard problems, a quantum-enabled device based on this interconnection technology will require many tessellated modules. At such a scale, relative positioning of each module with micron-accuracy is difficult. Furthermore, maintaining alignment during operation is also complex, as the quantum device will ideally be operated at cryogenic temperatures (40-70 K). The device will therefore be subject to thermomechanical effects which lead to module misalignment during thermal cycles. Together these effects of scale and operating conditions render it difficult to maintain crucial module-module alignment. Therefore, there is a need for concepts that enable measurement of misalignment between quantum-matter confinement regions of adjacent quantum-enabled devices. SUMMARY OF THE INVENTION The present invention is defined by the claims. According to a first 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 of the 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. Thus, proposed are concepts pertaining to determining misalignment between quantum-matter confinement regions of adjacent quantum-enabled devices. 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 invention. 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, the invention aims 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 invention provides a simple, robust, and accurate means for assessment of the distance and corresponding (mis)alignment. 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. 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. In another embodiment, the first direction, the second direction and the third direction may be orthogonal. 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. 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. In some embodiments, the first distance sensor may be positioned on a corner of the first quantum-enabled device and a corner of the second quantum-enabled device. 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. In some embodiments, the processor may be integrated into at least one of the first quantum-enabled device and the second quantum-enabled device. 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. 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. Additionally, in some embodiments, the system may further comprise 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 specific embodiments, the quantum-matter confinement region may be formed by a surface ion-trap. 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. 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 quantum-matter confinement regions of the adjacent quantum-enabled devices according to another embodiment of the invention. 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. BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which: Figure 1 illustrates a system for determining misalignment between quantum-matter confinement regions of adjacent quantum-enabled devices according to an embodiment; Figure 2 is a flow diagram providing steps in a method for determining misalignment between quantum-matter confinement regions of adjacent quantum-enabled devices according to an exemplary embodiment; Figure 3 illustrates a top view of tessellated ion-trap quantum computing modules; 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 according to an embodiment; Figure 5 is a side view of adjacent ion-trap quantum computing devices having a measurement arrangement according to an aspect of the invention; 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 according to an aspect of the invention; Figure 7 illustrates the principle of operation of the measurement arrangement of Figure 6; 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 according to an aspect of the invention; Figure 9 illustrates the principle of operation of the measurement arrangement of Figure 8; Figure 10 further illustrates the principle of operation of the measurement arrangement of Figure 8; 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 according to an aspect of the invention; 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; Figure 13 presents an alternative configuration of the measurement arrangement according to an aspect of a further exemplary embodiment; and Figure 14 illustrates angular misalignment between adjacent quantum-enabled devices. DETAILED DESCRIPTION OF THE EMBODIMENTS The invention will be described with reference to the Figures. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts. Further, 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. It should also be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems, and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. The invention proposes concepts for the measurement of (mis)alignment between adjacent quantum-enabled devices (e.g. modules for a quantum computer). This is achieved by measurement of a distance between the adjacent devices by a measurement arrangement integrated with at least one of the quantum-enabled devices. Thus, this obviates the need for external means for assessment / measurement of the alignment of devices, facilitating self-contained assessment and potential correction. Accordingly, scalability of the solution (compared to a measurement means provided externally, such as a camera system) is improved, so that many quantum-enabled devices may be linked together. Presently, 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 are 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 is not viable at scale (i.e. in a system with >100s of quantum-enabled devices). In other words, by integrating a measurement arrangement for determining a distance to an adjacent quantum-enabled device within a quantum-enabled device, a scalable solution is provided. The measurement arrangement integrated in the quantum-enabled device ensures that the quantum-enabled device may operate in a modular system. In an embodiment of the present invention, the misalignment between adjacent quantum-enabled devices may be achieved by conductive plates directly integrated within the quantum enabled devices. Several methods for operating / driving conductive plates and deducing distances between the conductive plates are disclosed herein, but other adaptations / alternatives would be understood by the skilled person. By way of example, embodiments of the invention are based 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 (sub-micron measurements along all 3 translation directions and sub-degree measurements in all 3 directions of angular rotations). 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. 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 make it ideal in conjunction with a quantum-enabled devices, such as ion-trap quantum computer modules, as it can be easily integrated without significant modifications to the manufacturing process already used to fabricate the quantum-enabled device. Furthermore, the use of conductive plates is suitable for the environmental conditions under which quantum-enabled devices typically operate (ultra-high vacuum, cryogenic temperatures, etc.). However, despite the advantages associated with the use of conductive plates, other solutions would also work within the scope of the present invention. A large number of 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. Essentially, embodiments of the invention are directed to a core concept of directly integrating a distance sensor into a quantum-enabled device / module. This differs from known concepts for aligning quantum-enabled devices, which require analysis of the relative positioning of adjacent modules using a dedicated external camera system. By way of explanation, embodiments of the invention include a means for determining distance between adjacent quantum-enabled devices in a direction. If this determ ined / detected / measured distance deviates from an expected / known distance, it is therefore known that the quantum-enabled devices are misaligned. Of course, measurement arrangement may be configured to measure said distance using any known method / means. The selection of the means should also be suitable for operation in environments that quantum-enabled devices usually operate in (e.g. a very cold vacuum), and be small and compact such that it does not interfere / minimizes interference with normal operation of the quantum-enabled device. The measurement arrangement may thus utilize optical, thermal, capacitive, or inductive means for distance determination (or any other means known in the art). 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 accordance with the invention. Specifically, 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. Optionally, the measurement arrangement may comprise a plurality of distance sensors 142, a feedback control module 150, and / or an actuator 160. Moreover, the measurement arrangement 140 may at least partially be provided on a second quantum enabled device 120. By way of explanation, a quantum-matter confinement region is a region formed by a means for trapping 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. Accordingly, a quantum-enabled device 110 may be any device that has a quantum-matter confinement region integrated thereon, and means for moving / shuttling the quantum-matter in the quantum-matter confinement region, and to other quantum-matter confinement regions. In particular, the quantum-enabled device 110 may be a module for a quantum computer, capable of performing quantum operations and shuttling the quantum-matter. In a specific example, the quantum-enabled device 110 may be an ion-trap quantum computing module. In any case, the system 100 is capable of determining (mis)alignment between said quantum-enabled device 110 and another (adjacent) quantum enabled device 120. Both devices have a quantum-matter confinement region between which quantum-matter may be transported (e.g. for manipulation on one device before being used on another device). To reiterate, alignment between said quantum-matter confinement regions is important to ensure that the quantum-matter can be efficiently and reliably transported between the regions. For ensuring / assessing this alignment, the invention provides a measurement arrangement 140 integrated into (i.e. mechanically connected to / forming part of) at least one of the adjacent quantum-enabled devices 110, 120 (or potentially both). The measurement arrangement 140 comprises (at least) 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. That is, 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 (e.g. a lateral or vertical direction). 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, both the light source and detector provided on the first quantum-enabled device 110. 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 first quantum-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. By way of example, 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. The skilled person would fully understand how distance may be measured using the above principles, and also additional and / or alternative principles that may enable the measurement of distance. Preferably, the first distance sensor 142a determines the distance based on a capacitance between conductive plates. Such a distance determination may be particularly suitable for operation in a vacuum and cryogenic conditions that quantum-enabled devices are typically operated in. In one embodiment, 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. Of course, in this case there must also be provided driving electronics configured to apply a voltage to one of the conductive plates (in order to induce a capacitance between the metallic plates). Thus, the distance sensor 142a is 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. That is, the capacitance value is inversely proportional to a distance between the plates. Alternatively, 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 this case, driving electronics must be provided and configured to apply a voltage to at least one of the conductive plates. Moreover, the first signal in this embodiment 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). Furthermore, the system 100 further comprises a processor 130 configured to process the first signal (i.e. signal comprising a capacitance value, a temperature value, a time-of-flight value, etc.) to determine a misalignment value. The misalignment value describes a degree / extent / presence of misalignment between a quantum-matter confinement region of the first quantum-enabled device 110 and a quantum-matter confinement region of the second quantum-enabled device 120. By way of explanation, measuring the distance between two adjacent quantum-enabled devices 110, 120 in a known direction (i.e. a first direction) in a known location (i.e. the location of the first distance sensor 142a) enables the determination of whether the quantum-matter confinement regions of the quantum-enabled devices 110, 120 are misaligned. The quantum-matter confinement regions may only be (perfectly) aligned when the distance between the adjacent devices is at an expected value. For example, assuming that the quantum-enabled devices 110, 120 are only able to move / have a degree of freedom in one direction (i.e. 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. Of course, should the quantum-enabled devices 110, 120 have higher degrees of freedom (i.e. may be misaligned in three dimensions) a determination of the distance between the devices in further directions will need to be required to determine whether the devices are (perfectly) 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 will be required for measuring the distance in two different directions in that plane. Nevertheless, one distance sensor 142a will still provide sufficient data to determine whether the devices are misaligned, as a deviation from an expected value will indicate this. In a specific embodiment, 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 (i.e. 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 this case, 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. To reiterate, to determine the degree of misalignment (or degree of alignment) to a higher degree of accuracy and certainty, additional distance sensors 142b, 142c are required to provide a signal indicative of a distance between the devices in different directions. Accordingly, the measurement arrangement 140 according to some embodiments of the invention 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. Of course, the measurement arrangement 140 may also comprise further distance sensors. 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 quantummatter confinement regions. 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. It is worth noting that each of the distance sensors 142 may be based on the same principle of operation (i.e. capacitive, inductive, thermal, or optical), or may be based on different principles of operation. 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. 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 are provided on extremities of the quantum-enabled devices 110, 120. This means that 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. 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. According to another aspect, the distance sensors 142 may be positioned on a bottom layer of the quantum-enabled device 110, 120. The bottom layer (i.e. 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. As depicted, the processor 130 may be provided separately from the quantum enabled device 110, 120 (thus receiving the signals from the measurement arrangement wirelessly). However, preferably 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 this case, 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. More specifically, 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 this case, the electronics layer means 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. Optionally, as depicted, the system 100 may further comprise a feedback control module 150 and an actuator 160. The feedback module 150 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. In other words, some embodiments provide a means for automatically readjusting / realigning the quantum-enabled devices based on the detected misalignment. Accordingly, misalignment during operation (e.g. due to thermal effects) may be effectively suppressed, ensuring effective and efficient operation of quantum -matter links between the devices. Moreover, the above system 100 may be utilized by a quantum computer. Thus, embodiments of the invention 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. Figure 2 presents a flow diagram providing steps in a method for determining misalignment between quantum-matter confinement regions of adjacent quantum-enabled devices according to an exemplary embodiment. Specifically, in step 210, a first signal comprising information is generated by a measurement arrangement. The first signal indicates 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. Of course, 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. In step 220, the first signal is 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. More specifically, step 220 may comprise sub-steps 222, 224 and 226. In step 222, a distance value based on the first signal is determined. To be clear, the distance value indicates the distance between the first quantum-enabled device and the second quantum-enabled device in the first direction. Then, in step 224, the determined distance value is compared to an expected distance value (indicating a distance between the quantum-matter confinement regions of the quantum-enabled devices when they are aligned). Finally, in step 226 the misalignment value is determined based on the comparison. Furthermore, the method may also comprise additional step 230. In step 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 step 220. 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. As stated above, according to preferable embodiments the measurement arrangement may comprise a distance sensors comprising conductive plates, driven such that they exhibit a capacitance. In this case, embodiments of the invention comprise three main considerations: means and methods to extract the distance information from the conductive plates; arrangements and positions of said plates on the quantum-enabled device; and the configuration and placement of the appropriate signal processing electronics. There are several methods for deduction of the distance information between adjacent quantum-enabled devices. In one aspect, the deduction of distance information exploits a capacitive coupling effect between capacitive (i.e. conductive) plates to assess the distance between the two plates (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). Specifically: (i) 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. Indeed, the voltage amplitude of the received signal is inversely proportional to the distance between the plates. (ii) 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. (iii) 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. In a second aspect, the number of conductive plates affixed / integrated with a quantum enabled device at specific and precisely 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. There are several methods which permit the deduction of relative positions between the plates, and therefore between the quantum-enabled device. Specifically: (i) The conductive plate(s) acting as emitters can be operated / driven at different frequencies. For example, using a sensitive demodulation 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. (ii) 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. (iii) 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. (iv) 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. (v) The measurement accuracy of the distance between the conductive plates may be improved by executing a plurality of distance measurements and taking the average. Of course, it will be understood that any combination of the above may be implemented in order to obtain a distance measurement via a capacitive reading. 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. Of course, 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). Firstly, 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. More particularly: (i) The conductive plates used for distance measurement can be located on a top layer. In this case, the plates may need to 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 should permit the simultaneous operation of both quantum operations together with the operation of the measurement arrangement. (ii) Alternatively, 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) 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.). (iii) 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). (iv) 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. Secondly, the conductive plates may be positioned within an intermediary layer of the quantum-enabled device. This may avoid the generation of any 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. Specifically: (i) The plates may be part of the same layer as a buried ground plane typically used in a surface-electrode ion-trap. These can be patterned specifically to meet the desired plate geometries and ease ion-trap manufacturing. In other words, this would lower the number required of fabrication, decreasing production time, and increasing device fabrication yield. (ii) 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 directly underneath the plate as well as directly above it (again, the latter being separated from the plate by a dielectric material). Both of the above implementations (i.e. ground plane layer patterning and enhanced sensitivity) may be utilized. The conductive plates could also / alternatively 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. More particularly: (i) The plates may be positioned directly on the underside of the substrate (wafer material) onto which the means for confining the quantum matter (e.g. an iontrap) 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. (ii) The conductive plates may be located directly on the underside of the undercut of an ion-trap module edge. This may be easy to implement from a fabrication standpoint. Of course, the measurement arrangement may include an arrangement of a single pair of plates (for simplicity) or an arrangement comprising a plurality of plates (to enhance the measurement sensitivity or range). For instance pairs of plates can 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. Finally, the positioning and configuration of signal processing electronics (i.e. the processor) for driving the conductive plates and deducing distance information needs to be considered. For example, said processor (i.e. processing electronics) 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. 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 ion-trap 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. Alternatively, the processor may 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. By way of illustrative example, specific implementations of embodiments of the invention will now be 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) will be described, which utilize capacitive coupling. However, these exemplary embodiments should not be considered restrictive, nor exhaustive. Specifically, 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 use of ion-traps should not be considered restrictive for the invention. Indeed, methods for confining electrons, atoms, molecules, and other quantum matter are well known in the art. As also described above, capacitive coupling may also be replaced by other known means for measuring distance, such as thermal or optical based systems. Adaptations to the following examples to realize the above modifications would be within the normal capabilities of the skilled person. By way of explanation, 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 concepts where a top view 300a of tessellated ion-trap quantum computing modules 310, 320 is shown. In other words, individual ion-trap quantum computing modules are 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. 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. 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 solely as an example. 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-trap quantum computer module may comprise a microfabricated ion-trap that is connected to separate silicon substrates. These substrates may be connected using TSV and wafer stacking technology. The required 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. According to an embodiment of the invention, 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. It is worth noting, however, that the positioning of these devices within the ion-trap layout is not to be taken in a limiting sense (as will be described in more detail below). 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 is not to be taken in a limiting sense. Figure 5 illustrates a side view 400 of adjacent ion-trap quantum computing devices 410, 420 having a measurement arrangement 440 according to an aspect of the invention. 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). 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 does 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, as would be understood by the skilled person. 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 will be a known capacitance value when the modules (and thus confinement regions) are aligned. In other words, the confinement regions are aligned when the separation between the conductive plates 442a, 442b is measured to match that of the design. In a specific embodiment, 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 in-between the upper substrate supporting the surfaceion 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 realised. With voltage signals applied to the conductive plate with ~10 V amplitude at ~1 MHz it is estimated that the gap separation can be resolved with an accuracy of 0.04 pm (using for instance an 8 bit ADC). 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. 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. 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. 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 iontrap (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. 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. 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. Again, when the quantum-matter confinement region (e.g. the ion-trap surface) of module A and B are perfectly 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 criteria is fulfilled, and therefore when the confinement regions of the two modules are precisely vertically aligned. More specifically, 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 bottom conductive 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). Moving on, 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). 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 / altemative configurations of these conductive plates 630, 640 on the quantum-enabled device 610, 620 may be used, and may be realized by the skilled person. In this case, 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. 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. The conductive plates 630, 640 in Figure 8 are 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. 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 the configuration 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. Furthermore, 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. It is well understood how to deduce the distance between the conductive plates based in the capacitance between these plates on module A and those on Module B (as capacitance varies with distance between plates). In this case, 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. 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 this case, 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. More specifically, 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. 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 between devices 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. Figures 13a and b illustrate an alternative way 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 (i.e. conductive plates), these can also be located at the corner 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 this case 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. 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 does not matter which of the two plates is the largest. The comb and teeth structures can be realized through standard microfabrication technique 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. 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, as would be well understood by the skilled person. By locating the conductive plates 930, 940 as illustrated in the above embodiments at each corner 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 corner, the angular misalignment between these modules can then be determined. Of course, the conductive plates may be placed in locations other than the corners to determine an angular misalignment, but locating the plates on the corners results in a more accurate measurement. Figure 14 illustrates this angular misalignment between adjacent quantum-enabled devices 910, 920. Note that by comparing axial misalignment reading at each corner 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, an angular misalignment can be measured with an accuracy of 1 x 10'3 deg. Accordingly, provided by the invention 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. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. If a computer program is discussed above, it may be stored / distributed on a suitable medium, such as an optical storage medium ora solidstate medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. If the term "adapted to" is used in the claims or description, it is noted the term "adapted to" is intended to be equivalent to the term "configured to". Any reference signs in the claims should not be construed as limiting the scope. “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. Unless context dictates otherwise, the descriptions and definitions of the features set out above are not limited to any particular aspect or embodiment of the invention and apply equally to all aspects and embodiments which are described.

Claims

1. A system (100) for determining misalignment between quantum-matter confinement regions of adjacent quantum-enabled devices, the system comprising:a measurement arrangement (140) 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; anda 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.

2. The system of claim 1, 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, andwherein the processor (130) configured to process the first signal and the second signal to determine the misalignment value.

3. The system of claim 2, 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.

4. The system of claim 3, wherein the first direction, the second direction and the third direction are orthogonal.

5. The system of any of claims 1-4, 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); anddriving electronics configured to apply a voltage to one of the conductive plates, andwherein the first signal comprises a capacitance value describing a capacitance between the conductive plates.

6. The system of any of claims 1-4, 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); anddriving electronics configured to apply a voltage to at least one of the conductive plates, andwherein 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.

7. The system of any of claims 1-6, wherein the first distance sensor (142a) is positioned on a corner of the first quantum-enabled device (110) and a corner of the second quantum-enabled device (120).

8. The system of any of claims 1-7, 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).

9. The system of any of claims 1-8, 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.

10. The system of any of claims 1-9, 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.

11. The system of any of claims 1-10, 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).

12. The system of any of claims 1-11, wherein the quantum-matter confinement region is formed by a surface ion-trap.

13. The system of claim 12, wherein at least one of first quantum-enabled device (110) and the second first quantum-enabled device (120) is a quantum computing module.

14. 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 claim 13 for determining misalignment between quantum-matter confinement regions of the adjacent quantum-enabled devices.

15. A method (200) for determining misalignment between quantum-matter confinement regions of adjacent quantum-enabled devices, the method comprising: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; andprocessing (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.