A method including providing a quantum computer, and a quantum computer

Abstract

Provides improvements in or relating to quantum computing. [Solution] A quantum computer is provided that includes modules arranged in a plane, the modules including a plurality of quantum processors, a radiation source configured to direct a radiation beam towards the module, and a first reflector in the path of the radiation beam, configured to redirect the radiation beam in a direction substantially parallel to the plane of the module.

Description

[Technical Field]

[0001] The present invention relates to providing a scalable laser system for ion trap quantum computers. [Background technology]

[0002] Unlike so-called "classical computing" in general, quantum computing relies on the quantum mechanical properties of particles or matter to produce or modify data. Data can be represented by quantum bits or "qubits," which are two-state quantum mechanical systems. Unlike classical computing, qubits can be in a superposition of quantum states. Another feature of quantum computing is entanglement between qubits, where the state of one particle or atom is influenced by the state of another particle or atom.

[0003] Quantum mechanical qubits can simultaneously encode information as combinations of zeros and ones. This property enables many complex numerical applications that are traditionally difficult for classical computers. Examples include artificial intelligence, image processing and recognition, cryptography, or secure communications.

[0004] Within ions, hyperfine electronic states (Zeeman split states) can be revealed by the use of magnetic fields, and different electronic levels used as different qubit states, and electrons moving between levels using microwave radiation or lasers.

[0005] In ion trap quantum computers (quantum charge-coupled devices), ion traps can be used to control ions used in quantum computing, with surface electrodes used to generate electric fields to manipulate and trap ions floating in free space. The surface electrode potential of the ion trap is in turn controlled by a DAC. State-of-the-art quantum computers use many DACs of the same type, for example, 16-bit DACs with update rates exceeding 1 MHz.

[0006] There are multiple quantum gates on a single chip. For example, there may be 4,096 gate zones on a chip measuring 300 x 300 mm. However, there is a limit to the size of individual chips that can be easily manufactured. Therefore, one solution is to create an array of chips (or modules) with a spacing of a few micrometers between each chip, as illustrated in Figure 1. Ions, or qubits, can be transferred between different chips as needed, thus enabling the development of significantly larger computers. For example, an array of 10 x 10 chips or modules may have 409,600 different gate zones.

[0007] Radiation beams are used for various purposes in quantum computers. They are used to detect the quantum state of qubits and also to cool the qubits. The beams are preferably highly coherent so that diffraction is limited. Lasers are typically used; for example, near-UV lasers are often used to detect quantum states. An exemplary wavelength is 350 nm.

[0008] Although highly coherent radiation beams are often used, there is still some divergence, and therefore the radiation beam must be generated relatively close to the location of the ions. Significant divergence can mean that the radiation beam will impinge on other regions and therefore have undesirable effects on the charged parts of the trap, e.g., dielectric oxides. Summary of the Invention

[0009] While quantum computers are relatively small in terms of the number of qubits, providing a substantially non-diverging beam of radiation over the distances involved has been relatively straightforward because the distances involved are relatively small, while providing a beam of radiation that remains sufficiently parallel becomes more difficult as the size of quantum computers increases.

[0010] A further problem is that laser devices can be relatively bulky and therefore can occupy a large volume close to where they are used, and the space / volume occupied can limit the design of quantum computers.

[0011] It is therefore an object to provide an improved arrangement for providing a beam of radiation.

[0012] According to the present invention there is provided a method comprising providing a quantum computer comprising: a module arranged in a plane, the module comprising a plurality of quantum processors, each having a corresponding ion position capable of performing an operation on ions; a radiation source configured to direct a radiation beam substantially perpendicular to the plane of the module; a first reflector in a path of the radiation beam, the first reflector configured to redirect the radiation beam along a radiation path substantially parallel to the plane of the module; and a controller configured to control the quantum processor and the radiation source, the method comprising irradiating with the radiation beam a plurality of ions at respective ion positions along the radiation path.

[0013] The method may further include providing a plurality of ions to a plurality of ion locations, which may be achieved by trapping ions at the ion locations using an ion trap, for example a surface ion trap.

[0014] The source has a focal point, but the plurality of ion locations are not at the focal point of the source.

[0015] The radiation source may be a cooling laser, and the controller may be configured to irradiate the plurality of ions for a duration and with an intensity sufficient to cool the ions at any one of the ion locations along the radiation path. The ions may be irradiated for a longer duration or, alternatively, with a higher intensity compared to the irradiation and cooling of ions located at a focus of the radiation beam. The irradiation may be sufficient to cool the ions at any one of the ion locations below a predetermined temperature.

[0016] Each quantum processor may further comprise a detector, and the controller is configured to set a detection threshold and / or detection period for each detector such that at least two of the detectors have different detection thresholds and / or detection periods, the detection thresholds and / or detection periods being based on position within the radiation beam, such that detectors further from the focal point have lower detection thresholds and / or longer detection periods than detectors closer to the focal point.

[0017] According to the present invention, there is provided a quantum computer comprising: modules arranged in a plane, the modules comprising a plurality of quantum processors, each having a corresponding ion position capable of performing an operation on an ion; a radiation source configured to direct a radiation beam substantially perpendicular to the plane of the module; and a first reflector in the path of the radiation beam, the first reflector configured to redirect the radiation beam along a radiation path substantially parallel (within 5°) to the plane of the module, the radiation path intersecting a plurality of ion positions. In this way, the radiation source can be removed from the plane of the module and placed further away from the module, allowing for more space. In particular, the radiation source may be at least 5 mm away from the module. The radiation source may be more than 1 cm away from the module. The radiation beam should be sufficiently collimated so as not to irradiate the surface material of the ion trap.

[0018] The quantum computer may further include a plurality of ions at a plurality of ion locations.

[0019] The radiation source has a focal point along a radiation path parallel to the plane of the module, and multiple ion positions are not at the focal point. In the present invention, a radiation beam is used to irradiate the ions that are not at the focal point, and the intensity or duration of the radiation beam or the detector can be adjusted so that all ions complete an operation (e.g., cooling, detection, or quantum gate operation). This allows multiple ions to be subjected to radiation simultaneously, resulting in a more scalable device.

[0020] The quantum computer may further comprise a controller configured to control the radiation source to irradiate the plurality of ions for a duration and intensity sufficient to cool the ions at any one of the ion positions along the radiation path.

[0021] The quantum computer may further comprise a controller, and each quantum processor may further comprise a detector, the controller configured to set a detection threshold and detection period for each detector, at least two of the detectors having different detection thresholds and / or detection periods, the detection threshold and / or detection period being based on position within the radiation beam. Thus, ion positions further from the focal position may have a longer detection period and / or lower detection threshold than ion positions closer to the focal position. The detection threshold and / or detection period are set to compensate for the intensity of the radiation beam and such that the overall detection level is substantially the same across all of the ion positions.

[0022] The radiation source is preferably configured to direct a beam of radiation towards the module in a direction substantially perpendicular (85°-95°) to the plane of the module.

[0023] There may be a second reflector positioned in the path of the radiation and configured to redirect the radiation beam away from the module, the distance between the first and second reflectors typically being in the range of 30-300 mm.

[0024] The apparatus may also comprise an absorber configured to absorb the radiation beam after reflection by the second reflector.

[0025] The module forms a qubit path along which the qubit may travel, and the radiation path is substantially parallel to the plane of the module and either intersects or overlaps with the qubit path. The plurality of electrodes and the signal generator may form a surface Paul trap. In operation, the plurality of electrodes form a qubit path along which the qubit may travel.

[0026] The one or more qubit paths and the radiation path preferably intersect substantially parallel to the plane of the module, with a diagonal angle between 25° and 65°, preferably 45°. The one or more qubit paths include a gate zone where a gate operation is applied to the qubit and the radiation path intersects the qubit path in the gate zone. The gate zone may have a magnetic field, in particular a magnetic field gradient.

[0027] There may also be a plurality of radiation sources, a plurality of first reflectors in the path of each radiation beam, and a plurality of second reflectors in the path of the radiation.

[0028] There may be a first plurality of radiation sources having radiation paths in a first direction parallel to the plane of the substrate, and a second plurality of radiation sources having radiation paths in a second direction parallel to the plane of the substrate and perpendicular to the first direction. The first plurality of radiation sources may have wavelengths in a first range, and the second plurality of radiation sources have wavelengths in a second range. The first and second ranges may not overlap. One or more of the qubit paths may comprise a gating zone where a gating operation may be applied to the qubits, and the radiation paths intersect with the qubit paths at the gating zone. As described above, the gating zone may have a magnetic field and / or a magnetic field gradient.

[0029] One or more of the reflectors may comprise a mirror. Molybdenum coated with a dielectric material has been found to be a particularly suitable mirror. The mirror surface may be aluminum with a protective dielectric coating to maximize reflectivity. An alternative reflector is a prism, and suitable prisms may include sapphire, fused silica, and / or quartz. Sapphire or glass may also be used as the mirror substrate, and may be metallized with aluminum. These materials are particularly suitable because they have good compressive strength.

[0030] The reflector forms a support for the module. In this way, one or more modules may be supported and the reflector may form a structural part of the device. The reflector is preferably thermally stable with a low coefficient of expansion.

[0031] There may be multiple modules, each with multiple processors.

[0032] The one or more radiation sources may generate radiation at a wavelength in the range of 250-1000 nm. For example, a wavelength range of 250-400 nm, particularly 369 nm, may be used for detection. The one or more radiation sources may have a wavelength in the range of 600-700 nm, particularly 635 nm, and may be used for cooling the qubit. The one or more radiation sources may have a wavelength in the range of 900-1000 nm, particularly 935 nm, and may be used for re-exciting the qubit. [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 1 illustrates a portion of the module. [Figure 2] FIG. 2 shows the DC electrodes in the gate zone. [Figure 3] FIG. 3 shows a prior art arrangement. [Figure 4] FIG. 4 shows a prior art arrangement. [Figure 5] FIG. 5 shows an arrangement according to the invention. [Figure 6] FIG. 6 shows an alternative arrangement according to the present invention. [Figure 7] FIG. 7 shows an arrangement according to the invention. [Figure 8] FIG. 8 shows an arrangement of modules and prisms according to the present invention. [Figure 9a] FIG. 9a shows a prism according to the invention. [Figure 9b] FIG. 9b shows a prism according to the invention. [Figure 10a] Figure 10a shows an arrangement according to the invention. [Figure 10b] Figure 10b shows an alternative arrangement according to the present invention. [Figure 11] FIG. 11 shows an arrangement according to the invention. [Figure 12] FIG. 12 shows an arrangement according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0034] The quantum processor includes multiple electrodes to which voltages can be applied by signal generators to trap qubits. One or more of the signal generators can generate radio frequency signals that, when applied to the multiple electrodes, can be used to confine ions in two perpendicular directions. The ions are thus suspended above the surface. This forms an energy trap known as a quadrupole ion trap or Paul trap. Another signal generator can then be used to generate signals that, when applied to the multiple electrodes, create a potential well in a third direction perpendicular to the other two directions in which the ions can be trapped. The signals applied to the different electrodes can be varied to move the position of the trapped ions. In this way, the ions (forming the qubits) can be moved above the module.

[0035] An example of a portion of a module depicting a surface linear Paul trap is illustrated in Figure 1. The module includes multiple electrodes 12 to which a voltage can be applied to form a potential well for trapping ions. Some of the electrodes 12 are RF electrodes controlled by one or more signal generators 17 (e.g., RF sources) that generate an RF field. There may be a separate signal generator 17 for each electrode, or alternatively, one signal generator 17 may control several electrodes 12. While coupled to the electrodes, the signal generators may be remote. The RF field generated by these electrodes creates an ion trap in which ions are positioned at minimum energy and confined by energy barriers in the y and z directions. Thus, the generated RF field confines ions in the y and z directions as shown in the figure. In a typical quantum processor, ions may be suspended above the electrodes or module at a height of 30 to 320 μm, typically 125 μm. Thus, the RF field generated by the multiple RF electrodes creates a minimum-energy path in the x direction along which ions can travel.

[0036] The RF electrode 12 and associated signal generator 17 generate a radio frequency field with a time-averaged energy depth. As an example, for an RF DAC generating an amplitude of 200 V at 20 MHz at a height of 125 μm, the time-averaged energy depth for Yb171 ions is 500 meV.

[0037] Additionally, there is a DC electrode 11 controlled by a DAC 16 configured to generate a DC electric field. The DAC 16 is coupled to the electrode 11, and as shown in FIG. 2, the DAC is often located remotely from the DC electrode simply due to space constraints. There may be a different DAC for each electrode, or a DAC may control multiple electrodes. Different DC voltages can be applied to different electrodes to create potential wells in which ions are located. As the DC voltages of the different electrodes change, ions move in the x-direction along the path of least energy. Thus, the combination of the RF electrode 12 and the DC electrode 11 controls the position of the ions. Thus, ions may be moved above the module as desired. While a DAC is used as an example, any type of signal generator could equally be used.

[0038] Typically, there are hundreds or even thousands of junctions and gate zones on a single module. However, to further increase capacity, there may be multiple modules arranged adjacent to each other. Figure 2 shows an exemplary two-dimensional arrangement of modules. Qubits formed by trapped ions may be held above a module or may pass to another module.

[0039] A typical quantum processor requires different laser beams for various uses. Laser beams with wavelengths in the 250-400 nm range, especially 369 nm, are used to detect the state of the qubits and are used for detection. It is also important to keep the qubits cool to reduce noise, and lasers with wavelengths in the 600-700 nm range, especially 650 nm, are used to cool the qubits, especially in the process of sympathetic cooling. Lasers are also sometimes used to re-excite the qubits; lasers with wavelengths in the 900-1000 nm range, especially 935 nm, are used for this purpose.

[0040] Quantum computers therefore typically comprise one or more lasers, and a prior art arrangement is shown in Figure 3, which illustrates a laser 20 used to generate a laser beam above the module. The laser beam may be used to detect the state of the qubits and may have a wavelength of 250-400 nm, particularly 369 nm. Alternatively, a laser may have a wavelength in the range 600-700 nm and be used to cool the qubits.

[0041] Although Figure 3 illustrates a single laser, there may be multiple lasers arranged around the module, some used for detection and some for cooling, which may be arranged in a grid fashion as illustrated in Figure 4, with different laser beams addressing different qubit positions.

[0042] Although lasers are highly coherent, they naturally have some divergence, and therefore the divergence of the laser may limit the distance that the laser can travel within a quantum computer before it becomes ineffective or causes problems for other elements of the device.

[0043] FIG. 5 illustrates an arrangement according to the present invention in which laser 20 directs a laser beam not parallel to the plane of module 10. The laser beam is preferably oriented substantially perpendicular to the plane of the module. A prism 25 is positioned in the path of the laser beam, reflecting the beam in a direction parallel to the plane of the module. In this manner, the laser beam travels along a path above the module and parallel to the plane of the module, allowing it to interact with any qubits suspended above the module in the path of the laser beam. The laser and prism are configured to direct the laser beam on a parallel path, the height of which above the module is the same as the minimum energy height of the ion trap. As an exemplary height, the laser beam may be directed 100-150 μm above the module, particularly 125 μm. A laser beam directed in this manner can be used to cool qubits suspended above module 10 in a quadrupole ion trap. Alternatively, a laser beam directed in this manner can be used to detect qubits suspended above the module.

[0044] The laser beam may have a width of 100 μm or more so that it can interact with the qubit. The width and divergence of a laser beam are inversely proportional, so a decrease in width results in an increase in divergence.

[0045] The prism should be grounded to prevent excessive charge buildup. Additionally, the prism may form part of the support for the module itself.

[0046] The prisms are preferably made of a thermally stable material with limited expansion, and for this purpose sapphire has been found to be particularly suitable as a reflecting prism.

[0047] As an alternative to a prism, a mirror can be used, again preferably a thermally stable material. An exemplary mirror is molybdenum coated with a dielectric, for example aluminum.

[0048] Figure 6 shows a further embodiment of the present invention, in which there are multiple prisms 25. The second side of the prisms can be used to reflect the laser beam towards the absorber 30, where the laser is absorbed. Thus, the path of the laser is restricted so that only limited divergence occurs within the path. Furthermore, the laser beam is directed away from the module after completing its parallel path, thereby reducing excess heat. The distance between adjacent prisms can be in the range of 30-300 mm.

[0049] Figure 6 illustrates different sides of a prism used to reflect a laser beam onto and off a parallel path. As will be appreciated by those skilled in the art, different prisms can be used equally well.

[0050] Figure 7 shows a plan view of an individual module 10 with its associated prisms, lasers, and absorbers. The prisms 25 are elongated, forming a truss along which the module is supported. Along the left side are multiple radiation sources 20, each of which projects a laser beam toward a prism, which is redirected along a parallel path toward a corresponding prism on the other side of the module. The corresponding prism redirects the laser beam upward toward a corresponding absorber 30. On the top side are more radiation sources 20, which direct laser beams toward prisms, which are redirected along parallel paths toward a prism on the other side. In this way, a grid of laser beams may be developed to address individual qubits. In one example, the lasers along the left side may be lasers used for detection, e.g., at a wavelength of 369 nm, and the lasers along the top side may be lasers used for cooling and re-exciting the qubits.

[0051] The radiation source may be a laser, or alternatively, the laser may be located elsewhere and transmit the radiation through a fiber optic cable closer to the module. Beam collimation and preparation optics then form the radiation into individual beams. Furthermore, a laser beam may be split into several different beams by a splitter and then used as several radiation sources.

[0052] 8 illustrates a larger grid arrangement including multiple modules 10 and prisms 25. For simplicity, the lasers and absorbers are not shown, although each module may have an associated laser and absorber as illustrated in FIG.

[0053] When multiple modules 10 are used in a single quantum computer, qubits may pass from one module to another. To allow this, the prism 10 (or reflector) may have passages or openings therethrough; Figures 9a and 9b illustrate such prisms. Figure 9a illustrates a prism 10 with multiple holes 26 therethrough, allowing ions to pass to adjacent modules. The height of the holes is the height at which the ions (qubits) are suspended above the modules. Figure 9b shows an alternative arrangement with multiple arches 27.

[0054] FIG. 10a illustrates the arrangement of the radiation path and the qubit path. As can be seen, the qubit path 30 and the radiation path cross each other diagonally and at a 45° angle. The qubit path has distinct regions, and the region where the gating occurs is known as the gate zone. The gate zone has a magnetic field, which may be a magnetic gradient. The radiation path and the qubit path preferably cross in the gate zone so that cooling and detection can occur in the gate zone. FIG. 10a illustrates an arrangement with radiation sources along a first side of the module, and FIG. 10b illustrates an arrangement with radiation sources along both the first and second sides of the module. The radiation source along the first side of the module may be used for qubit detection, i.e., a radiation source having a wavelength suitable for detection. The radiation source along the second side may be used for qubit cooling and / or re-excitation.

[0055] 10a and 10b depict the radiation path and the qubit path overlapping at 45, they can also intersect diagonally at other angles. Other suitable intersection angles can be 30° and 60°.

[0056] 11 shows an arrangement in which a plurality of ions are positioned within a radiation beam. The radiation beam has a focal point FP and there are a plurality of ion positions 111, 112, 113, 114. An ion position is a position at which an ion may be located and at which an operation may be performed on the ion. As an example, the radiation beam may perform a cooling operation, or a detection operation, or a quantum gating operation on ions positioned at the ion positions.

[0057] In the embodiment shown in Figure 11, none of the ion positions are at the focal point of the radiation beam, however, in some embodiments one of the ion positions may be located at the focal point.

[0058] Also shown in FIG. 11 is a controller 115 that controls laser 20. In this example, laser 20 is used to cool ions. The laser may have a wavelength of, for example, 369 nm, although the exact wavelength depends on the type of ions being cooled. Ions are positioned at ion locations, and the laser irradiates the ions. Ions positioned at locations 112 and 113 are closer to the focal point of the radiation beam, and therefore the laser is more focused at those ion locations, and therefore the ions are cooled faster. To cool ions further from the focal point below a threshold, the laser must be operated at a higher intensity and / or for a longer period of time. However, the controller controls the laser to operate for a period of time sufficient to cool ions below a predetermined temperature at least at the ion locations where ions are located. For example, if ions are positioned at ion locations 111 and 113, the controller controls the laser to operate for a duration and / or at an intensity sufficient to cool ions at both locations below a predetermined threshold. The laser may be operated longer or alternatively (and additionally) at a higher intensity to cool ions not positioned at the focal point. The laser can cool each ion to less than 100 mK, or even less than 10 mK. An alternative form of cooling, sideband cooling, can cool each ion to less than one quantum.

[0059] The controller may control the laser to operate for a duration / intensity sufficient to cool ions below a predetermined threshold at any one of the ion positions in the radiation path, or alternatively, the controller may know which ion positions are occupied and control the laser to operate for a duration / intensity sufficient to cool ions below a predetermined threshold only at the occupied ion positions.

[0060] FIG. 12 shows an arrangement in which laser 20 emits a radiation beam used for detection. The detection laser beam may also be 369 nm, depending on the type of ion. At each of the positions are detectors 121, 122, 123, and 124. Each detector detects photons emitted at the respective ion position. Because ion positions 112 and 113 are closer to the focal point FP, they emit more photons than ions at ion positions 111 and 114. Therefore, the detection thresholds of detectors 112 and 113 are set by the controller to be higher than the detection thresholds of detectors 111 and 114. Alternatively, or additionally, the detection period of detectors closer to the focal point may be shorter than the detection period of detectors further away from the focal point. The detection period and detection threshold are set by the controller. In this way, the overall sensitivity is substantially the same at all ion positions, despite different laser intensities at different positions. Therefore, a single radiation beam can be used for detection of multiple ions.

[0061] An alternative to diagonally intersecting qubit and radiation paths is for the radiation paths and qubits to substantially overlap, but for qubits near the reflector to have a dog leg path to direct the qubit through the passageway.

[0062] Throughout the description, the term "prism" is used, but it will be understood that any reflector could equally be used.

[0063] Various further aspects and embodiments of the present invention will be apparent to those skilled in the art in view of the present disclosure.

[0064] As used herein, "and / or" should be taken as a specific disclosure of each of the two specified features or components with or without the other. For example, "A and / or B" should be taken as a specific disclosure of (i) A, (ii) B, and (iii) each of A and B, as if each were individually set forth herein.

[0065] Unless the context dictates otherwise, the above feature descriptions and definitions are not limited to any particular aspect or embodiment of the invention, but apply equally to all aspects and embodiments described.

[0066] Those skilled in the art will further appreciate that although the present invention has been described by way of example with reference to certain embodiments, it is not limited to the disclosed embodiments, and alternative embodiments may be constructed without departing from the scope of the invention as defined in the appended claims.

Claims

1. a module arranged in a plane, the module comprising a plurality of quantum processors, each having a corresponding ion position capable of performing an operation on an ion; a radiation source configured to direct a radiation beam substantially perpendicularly towards the plane of the module; a first reflector in the path of the radiation beam, the first reflector being configured to redirect the radiation beam along a radiation path substantially parallel to the plane of the module; a controller configured to control the quantum processor and the radiation source; 1. A method comprising providing a quantum computer comprising: The method includes irradiating a plurality of ions at respective ion positions along the radiation path with the radiation beam.

2. The method of claim 1 , wherein the radiation source has a focal point and a plurality of the ion locations are not at the focal point of the radiation source.

3. 3. The method of claim 1, wherein the radiation source is a cooled laser, and the controller is configured to irradiate the plurality of ions for a duration and with an intensity sufficient to cool the ions at any one of the ion positions along the radiation path.

4. 4. The method of claim 3, wherein the irradiation is sufficient to cool ions at any one of the plurality of ion locations below a predetermined temperature.

5. 5. The method of any one of claims 1 to 4, wherein each quantum processor further comprises a detector, and wherein the controller is configured to set a detection threshold and / or detection period for each detector, at least two of the detectors having different detection thresholds and / or detection periods, and wherein the detection thresholds and / or detection periods are based on the position within the radiation beam.

6. A quantum computer, a module arranged in a plane, the module comprising a plurality of quantum processors, each having a corresponding ion position capable of performing an operation on an ion; a radiation source configured to direct a radiation beam substantially perpendicularly towards the plane of the module; a first reflector in a path of the radiation beam, the first reflector configured to redirect the radiation beam along a radiation path substantially parallel to the plane of the module, the radiation path intersecting a plurality of the ion locations.

7. The quantum computer of claim 6 , wherein the radiation source has a focal point and a plurality of the ion locations are not at the focal point.

8. 8. The quantum computer of claim 6, further comprising a controller configured to control the radiation source to irradiate the plurality of ions for a duration and with an intensity sufficient to cool the ions at any one of the ion positions along the radiation path.

9. 9. A quantum computer according to any one of claims 6 to 8, further comprising a controller, wherein each quantum processor further comprises a detector, the controller configured to set a detection threshold and / or detection period for each detector, at least two of the detectors having different detection thresholds and / or detection periods, the detection thresholds and / or detection periods being based on the position within the radiation beam.

10. 10. The quantum computer of claim 6, further comprising a second reflector disposed in the path of the radiation and configured to redirect the radiation beam away from the module.

11. 11. The quantum computer of claim 10, further comprising an absorber configured to absorb the radiation beam after reflection by the second reflector.

12. 12. A quantum computer as claimed in any one of claims 6 to 11, wherein the modules form qubit paths along which qubits may travel, the radiation paths either intersecting or overlapping with the qubit paths and being substantially parallel to the plane of the modules.

13. 13. The quantum computer of claim 12, wherein the one or more qubit paths and the radiation path intersect substantially parallel to the plane of the module at a diagonal angle between 25° and 65°.

14. 14. A quantum computer as claimed in claim 12 or claim 13, wherein the one or more qubit paths comprise a gate zone in which a gate operation can be applied to a qubit, and the radiation path intersects the qubit path at the gate zone.

15. 15. The quantum computer of claim 6, wherein the first reflector comprises a passageway through which a qubit can pass.

16. 16. The quantum computer of any one of claims 6 to 15, further comprising a plurality of radiation sources, a plurality of first reflectors in the path of a respective radiation beam, and a plurality of second reflectors in the path of the radiation.

17. 17. The quantum computer of claim 16, wherein a first plurality of radiation sources have radiation paths in a first direction parallel to the plane of the substrate, and a second plurality of radiation sources have radiation paths in a second direction parallel to the plane of the module and perpendicular to the first direction.

18. 18. The quantum computer of claim 17, wherein the first plurality of radiation sources has a first range of wavelengths and the second plurality of radiation sources has a second range of wavelengths.

19. 19. The quantum computer of claim 6, wherein at least one of the first reflector and the second reflector comprises a mirror.

20. 20. The quantum computer of claim 6, wherein at least one of the first reflector and the second reflector comprises a prism.

21. 21. A quantum computer according to any one of claims 6 to 20, wherein the reflector forms a support for the module.

22. 22. The quantum computer of claim 6, further comprising a plurality of modules, each module comprising a plurality of processors.

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