Ion trap and method for setting a magnetic field

Abstract

An ion trap (1) is specified, with - a set of electrodes (2) designed to enclose and / or manipulate at least one ion in a processing area (5), - at least one magnetic arrangement (3) configured to generate a magnetic field in the processing area (5), and - at least two magnetic field sensor devices (4) spaced apart from the processing area (5), wherein - the at least two magnetic field sensor devices (4) are arranged inside the ion trap (1), and - the at least two magnetic field sensor devices (4) are designed to provide characteristic distribution information for the magnetic field in the processing area (5). Furthermore, a method for adjusting a magnetic field is described.

Description

[0001] The present disclosure relates to an ion trap and a method for adjusting a magnetic field generated by at least one magnet arrangement of an ion trap.

[0002] To perform quantum computing processes with trapped ions, the trapped ions must be individually controllable and addressable, particularly through the use of a magnetic field gradient. Such gradients can be generated by magnets. For example, the magnitude of the gradient can fluctuate due to drift of permanent magnets caused by current fluctuations in coils.

[0003] The object to be achieved is to provide an ion trap with an improved magnetic field distribution. Furthermore, a method for adjusting a magnetic field generated by at least one magnet arrangement of such an ion trap is to be provided.

[0004] The problem is solved by the subject matter of the independent claims. Advantageous embodiments, implementations, and further developments are the subject matter of the respective dependent claims.

[0005] According to at least one embodiment, the ion trap comprises a set of electrodes configured to confine and / or manipulate at least one ion in a processing region.

[0006] The ion trap can be a Paul trap, a linear ion trap, a surface ion trap, or a multilayer ion trap. For example, a radiofrequency voltage is applied to at least some of the electrodes of the set of electrodes, thereby providing a time-varying electric field within the processing region that is designed to confine and / or manipulate the ion. For example, the ion intersects a trapping axis and / or oscillates about a trapping axis within the processing region.

[0007] The extent of the processing area in lateral directions and in vertical direction is defined, for example, depending on the arrangement of the set of electrodes and / or the parameters of the time-varying electric field provided to the processing area by the set of electrodes.

[0008] According to at least one embodiment, the ion trap comprises at least one magnet arrangement configured to generate a magnetic field in the processing area. The at least one magnet arrangement is spaced from the processing area, for example, in lateral directions and / or in the vertical direction.

[0009] In particular, the at least one magnet arrangement is designed to generate a gradient of magnetic field magnitudes in the processing area, e.g., along the capture axis. This means that the magnetic field of the magnet arrangement has different magnitudes for different positions in the processing area and, in particular, for different positions on the capture axis.

[0010] Advantageously, when there are a plurality of ions in the processing area, the resonance frequency of each of the ions affected by the size gradient of the magnetic field of the magnet array is unique for each ion in the processing area.

[0011] The at least one magnet arrangement can comprise at least one permanent magnet, in particular at least two permanent magnets, and / or at least one coil. The permanent magnets, for example, do not require an external magnetic field to maintain magnetic properties such as magnetization. Furthermore, the permanent magnets are particularly designed to generate the magnetic field without being supplied with an electric current. For example, the coil is particularly designed to generate the magnetic field due to an electric current applied to the coil.

[0012] According to at least one embodiment, the ion trap comprises at least two magnetic field sensor devices that are spaced apart from the processing area. For example, the two magnetic field sensor devices do not overlap with the processing area. In particular, the at least two magnetic field sensor devices are spaced apart from the processing area in lateral directions and / or in the vertical direction. For example, the two magnetic field sensor devices are spaced apart from each other, in particular in lateral directions and / or in the vertical direction.

[0013] According to at least one embodiment of the ion trap, the at least two magnetic field sensor devices are arranged within the ion trap. In particular, the at least two magnetic field sensor devices are part of the ion trap. This means, for example, that the at least two magnetic field sensor devices are arranged on and / or within an entity of the ion trap.

[0014] According to at least one embodiment of the ion trap, the at least two magnetic field sensor devices are configured to provide distribution information characteristic of the magnetic field in the processing area. The distribution information includes, among other things, at least a magnitude of the magnetic field and a direction of the magnetic field for at least one point or a plurality of points in space in the processing area.

[0015] For example, the magnetic field sensor devices are configured to detect the magnetic field of the magnet arrangement and, optionally, an external magnetic field at at least two specific locations, each corresponding to a location where the magnetic field sensor devices are arranged. By combining the detection of the at least two magnetic field sensor devices at the at least two specific locations, the magnetic field in the processing area can be determined and the distribution information can be provided.

[0016] For example, the external magnetic field originates from at least one source other than the magnet array. The external magnetic field is generated by at least one nearby magnet, an electronic device, a power line, or a geomagnetic field.

[0017] Typically, the magnetic field generated by the magnet assembly with the permanent magnet(s) depends on the temperature of the magnet assembly. At comparatively high temperatures, the magnetic domains of the permanent magnets can become disordered, leading to a reduction in the magnitude of the magnetic field. At comparatively low temperatures, the magnetic domains of the permanent magnet can align more coherently, leading to an increase in the magnitude of the magnetic field.

[0018] Typically, the magnetic field generated by the magnet assembly with the coil depends on a fluctuation in the electric current applied to the coil.

[0019] This means that the magnetic field of the magnet assembly can vary, resulting in a varying magnetic field in the processing area. Furthermore, external magnetic fields can influence the magnetic field of the magnet assembly in the processing area.

[0020] One idea is to equip the ion trap with magnetic field sensors so that the magnetic field in the processing area can be determined. If the magnetic field does not meet the specified requirements, the parameters of the magnet arrangement can be adjusted.

[0021] In particular, the magnetic field sensor devices are configured to determine an average magnetic field in the processing area, which includes the magnitude and direction of the magnetic field. This information advantageously provides the gradient of the magnetic field magnitudes in the processing area, as well as the noise characteristics of the magnetic field in the processing area.

[0022] Advantageously, the magnetic field sensor devices can provide information even when an ion is unavailable, e.g., for field measurements. The signals from multiple magnetic field sensor devices can be advantageously combined to simultaneously derive information about different magnetic field components along different directions, as well as magnetic field information at a location not directly accessible—the processing area.

[0023] Furthermore, the magnetic field sensor devices can be used during a magnetization process of the permanent magnets to monitor the magnetization of individual magnets and the balance of multiple magnets. Advantageously, by monitoring the magnetic field during magnetization, a vanishing magnetic field can be obtained at a predetermined position in the processing area. This means that with such magnetic field sensor devices, feedback can be implemented during magnetization to maintain the desired magnetic field in the processing area.

[0024] According to at least one embodiment of the ion trap, the ion trap comprises a substrate and / or a support. For example, the substrate has a main extension plane in lateral directions. A main surface is represented by a top surface or a bottom surface extending in lateral directions. For example, at least some or all of the electrodes of the set of electrodes are arranged on the substrate.

[0025] For example, at least some of the entities of the ion trap are arranged on the carrier. For example, the carrier serves as a holder for at least some of the entities of the ion trap. For example, all magnetic field sensor devices are arranged on the carrier. Alternatively, one of the at least two magnetic field sensor devices is arranged on the carrier and the other of the at least two magnetic field sensor devices is arranged on the substrate.

[0026] According to at least one embodiment of the ion trap, at least one of the at least two magnetic field sensor devices is arranged on a main surface of the substrate and / or a main surface of the carrier. For example, at least some or all of the electrodes of the set of electrodes are arranged, for example, on the main surface of the substrate, i.e., the top surface of the substrate or the bottom surface of the substrate. For example, all of the magnetic field sensor devices are arranged on the top surface of the substrate or the bottom surface of the substrate. Alternatively, one of the at least two magnetic field sensor devices is arranged on the top surface of the substrate and the other of the at least two magnetic field sensor devices is arranged on the bottom surface of the substrate.

[0027] According to at least one embodiment of the ion trap, at least one of the at least two magnetic field sensor devices is embedded in the substrate and / or the carrier. "Embedded" here means that at least one outer surface of the at least one of the at least two magnetic field sensor devices is covered by the substrate and / or the carrier. For example, all outer surfaces of the at least one of the at least two magnetic field sensor devices are covered by the substrate and / or the carrier. Alternatively, all outer surfaces except a top surface and / or a bottom surface of the at least one of the at least two magnetic field sensor devices are covered by the substrate and / or the carrier.

[0028] According to at least one embodiment of the ion trap, the ion trap further comprises a set of further electrodes.

[0029] According to at least one embodiment of the ion trap, the additional electrodes are electrically connected to the magnetic field sensor devices. For example, the additional electrodes are configured to provide a characteristic signal for the magnetic field detected by the magnetic field sensor devices to an external processing device.

[0030] According to at least one embodiment of the ion trap, the at least two magnetic field sensor devices comprise at least one of the following devices: a Hall sensor device, a flux gate sensor device, and a superconducting quantum interference device.

[0031] The Hall sensor device is, for example, a semiconductor sensor device. Typically, the Hall sensor device is designed to detect the magnetic field dependent on the Hall effect, generating a Hall voltage across a conductor when it is exposed to the magnetic field perpendicular to a current flow through the conductor.

[0032] The flux-gate sensor, for example, comprises a core molded with a magnetically permeable material and two coils wound around the core. The core is driven to saturation by an alternating current, and the coils are used to measure changes in magnetic flux caused by the magnetic field.

[0033] The superconducting quantum interference device (SQUID) consists of a superconducting loop interrupted by two Josephson junctions. A change in the critical current flowing through the junctions results in a change in the voltage or magnetic flux when exposed to a magnetic field.

[0034] For example, all magnetic field sensor devices are of the same type. Alternatively, at least one of the magnetic field sensor devices may be of a different type.

[0035] According to at least one embodiment of the ion trap, the ion trap comprises more than two magnetic field sensor devices.

[0036] According to at least one embodiment of the ion trap, the magnetic field sensor devices surround the processing area. For example, the magnetic field sensor devices are arranged at predetermined specific locations on the substrate and / or the carrier. For example, the magnetic field sensor devices are arranged at virtual grid points of a virtual grid, which is a regular or irregular grid. The virtual grid is, for example, a one-dimensional, a two-dimensional, or a three-dimensional grid. The virtual grid is, for example, an array for a one-dimensional grid or, for the two- or three-dimensional grid, a polygonal grid, e.g., a triangular grid, a rectangular grid, or a hexagonal grid.

[0037] This means that the magnetic field sensor devices are spatially offset, i.e., laterally and / or vertically, from the processing area. Advantageously, such magnetic field sensor devices allow conclusions to be drawn about the magnetic field at the ion location, but none of the magnetic field sensor devices are located in the processing area, e.g., at the ion location.

[0038] According to at least one embodiment of the ion trap, the at least one magnet arrangement is arranged in or around the ion trap. In particular, the at least one magnet arrangement is part of the ion trap and surrounds the processing area. By way of example, the at least one magnet arrangement is arranged on the main surface of the substrate, e.g., on the top surface or the bottom surface. Alternatively, the at least one magnet arrangement is embedded in the substrate, as described in connection with the magnetic field sensor devices.

[0039] According to at least one embodiment of the ion trap, the ion trap comprises at least two registers. Each register comprises a set of electrodes and a processing region, as described above.

[0040] According to at least one embodiment of the ion trap, at least two magnetic field sensor devices are assigned to each of the registers. This means that, in particular, at least two magnetic field sensor devices are provided for each register. This has the advantage that the magnetic field can be determined individually for each of the registers.

[0041] According to at least one embodiment of the ion trap, at least one magnet arrangement is assigned to each of the registers. This means that, in particular, at least one magnet arrangement is provided for each register. This has the advantage that each processing area can be individually provided with a gradient of magnetic field magnitudes.

[0042] According to at least one embodiment of the ion trap, each register is part of the ion trap. For example, all sets of electrodes are arranged on a single substrate.

[0043] Furthermore, a method for adjusting a magnetic field generated by at least one magnet arrangement of an ion trap is specified, wherein the ion trap is or can be the ion trap described here. This means that the features relating to the ion trap also apply to the method, and vice versa.

[0044] According to at least one embodiment of the method, at least two pieces of information are provided, each piece of information being characteristic of measured values ​​from one of the at least two magnetic field sensor devices. Each piece of information comprises, among other things, at least one of a magnitude of the magnetic field and a direction of the magnetic field at one of the at least two specific locations. The specific locations are, in particular, the locations where the magnetic field sensor devices are arranged.

[0045] According to at least one embodiment of the method, distribution information characteristic of the magnetic field in a processing region of the ion trap is determined as a function of the at least two pieces of information.< In particular, by combining the detection of the at least two magnetic field sensor devices at the at least two specific locations, the distribution information characteristic of the magnetic field in the processing region can be determined.

[0046] According to at least one embodiment of the method, result information for adjusting a magnetization and / or a position and / or a current of the at least one magnet arrangement is determined depending on the distribution information. In particular, the magnetic field generated by the at least one magnet arrangement is adjusted depending on the result information.

[0047] According to at least one embodiment of the method, further information is provided that is characteristic of a measured value of at least one ion in the processing area. The further information is provided by reading the at least one ion, which, among other things, provides at least one magnitude of the magnetic field and a direction of the magnetic field at the location of the at least one ion. The further information can advantageously be used to verify and / or refine the distribution information.

[0048] According to at least one embodiment of the method, the distribution information is determined as a function of the at least two pieces of information and the further information.

[0049] This has the advantage that such distribution information is particularly accurate.

[0050] According to at least one embodiment of the method, the result information is determined such that the magnitudes of the magnetic field have a predetermined magnitude for a predetermined point in the processing area.

[0051] According to at least one embodiment of the method, the magnet arrangement comprises at least one permanent magnet, in particular at least two permanent magnets, and / or at least one coil, and the permanent magnet and / or the coil are adjusted depending on the result information, in particular independently of one another.

[0052] According to at least one embodiment of the method, the permanent magnets are adjusted during magnetization. In particular, the magnetization can advantageously be monitored during magnetization by the magnetic field sensor device.

[0053] In the following, the ion trap and the method are explained in more detail with reference to embodiments and the associated figures. Fig. 1 shows a schematic view of the ion trap according to an embodiment. Fig. 2 shows a flowchart of the method according to an embodiment.

[0054] Elements that are identical or similar, or that have the same effect, are provided with the same reference numerals in the figures. The figures and the proportions of the elements depicted in the figures are not to be considered true to scale. Rather, individual elements may be exaggerated for clarity and / or clarity.

[0055] The ion trap 1 according to the embodiment in Fig. 1 is an ion trap chip with a substrate 6. The substrate 6 has a main surface 7 extending in the lateral directions x, y, as in Fig. 1. A vertical direction extends perpendicular to the lateral directions. A main extension plane of the ion trap 1 also extends in lateral directions. For example, the substrate can be arranged on a carrier 8.

[0056] A set of electrodes 2 is arranged on the main surface 7, which may be a top surface or a bottom surface. In particular, some of the electrodes 2 are configured to be supplied with an RF voltage, so that a time-varying electric field is provided in a processing region 5. In particular, the ion trap 1 is configured to confine and / or manipulate at least one ion within the processing region 5.

[0057] The ion trap 1 further comprises a magnet arrangement 3 designed to generate a magnetic field in the processing area 5. The at least one magnet arrangement 3 comprises, in particular, at least one element, i.e., at least one permanent magnet and / or at least one coil. If the at least one magnet arrangement 3 comprises, in particular, at least two elements, the elements are spaced apart from one another in lateral directions. The magnet arrangement 3 is arranged on or within the substrate 6.

[0058] If the magnet arrangement 3 comprises the permanent magnets, the permanent magnets have a main extension plane in lateral directions, i.e., parallel to the main extension plane of the substrate 6. The permanent magnets, in particular at least two of the permanent magnets, have a mutually parallel magnetization direction. The magnetization directions each extend in a vertical direction, facing away from the substrate 6, as indicated by the arrow. Alternatively, it is possible for the magnet arrangement to comprise a permanent magnet and a coil.

[0059] Such a magnet arrangement 3 is designed to generate a gradient of sizes of the magnetic field of the magnet arrangement 3 in the processing area 5.

[0060] The processing area 5 is spaced apart from the magnet arrangement 3, i.e., from the two magnets. In particular, the processing area 5 is arranged between the two magnets in lateral directions. Furthermore, the processing area 5 is arranged vertically up to a predetermined distance above the main surface 7. The predetermined distance is, for example, greater, in particular at least one order of magnitude greater, than a height of each of the magnets in the vertical direction.

[0061] The ion trap 1 additionally comprises four magnetic field sensor devices 4. The four magnetic field sensor devices 4 are each arranged on or within the substrate 6. The magnetic field sensor devices 4 have, for example, a main extension plane in lateral directions, i.e., parallel to the main extension plane of the substrate 6.

[0062] The magnetic field sensor devices 4 are designed to detect a vertical component and, for example and optionally, a horizontal component in lateral directions of a magnetic field, as indicated by the arrows in Fig. 1, each of which is intended to detect, i.e., measure, a specific location. In particular, the magnetic field sensor devices 4 are arranged on virtual grid points of a virtual grid, which in this case is a two-dimensional rectangular grid. The virtual grid points correspond to the specific locations.

[0063] The magnetic field sensor devices 4 are spaced apart from the processing area 5 in lateral directions and in vertical directions.

[0064] By combining the measured vertical component of the magnetic field at the specific locations, distribution information characteristic of a magnetic field in the processing area 5 can be determined.

[0065] In process stage S1 in Fig.2 at least two pieces of information are provided, each of the pieces of information being characteristic of measured values ​​of one of the at least two magnetic field sensor devices 4.

[0066] Subsequently, in process step S2, distribution information characteristic of the magnetic field is determined in a processing area 5 of the ion trap 1 as a function of the at least two pieces of information.

[0067] Subsequently, in process step S3, result information for setting a magnetization and / or a position and / or a current of the at least one magnet arrangement 3 is determined as a function of the distribution information.

[0068] In particular, the magnetization or a current of the magnet arrangement 3 can be adjusted based on the distribution information.

[0069] For example, the magnetization is adjusted such that at a predetermined point in the processing area 5, in particular depending on the result information, certain magnetic field magnitudes disappear. Alternatively or additionally, the magnetization is adjusted such that a gradient of the magnetic field magnitudes in the processing area 5 is maximized, in particular depending on the result information. Reference character list 1 ion trap 2 electrodes 3 Magnet arrangement 4 Magnetic field sensor device 5 Processing area 6 Substrat 7 Main area 8 carriers S1..S3 process steps

Claims

[1] Ion trap (1), with - a set of electrodes (2) designed to confine and / or manipulate at least one ion in a processing region (5), - at least one magnet arrangement (3) designed to generate a magnetic field in the processing area (5), and - at least two magnetic field sensor devices (4) which are spaced from the processing area (5), wherein - the at least two magnetic field sensor devices (4) are arranged within the ion trap (1), and - the at least two magnetic field sensor devices (4) are designed to provide characteristic distribution information for the magnetic field in the processing area (5). [2] Ion trap (1) according to claim 1, wherein - the ion trap (1) comprises a substrate (6) and / or a carrier (8). [3] Ion trap (1) according to claim 2, wherein - at least one of the at least two magnetic field sensor devices (4) is arranged on a main surface (7) of the substrate (6) and / or on a main surface (7) of the carrier (8), and / or - at least one of the at least two magnetic field sensor devices (4) is embedded in the substrate (6) and / or the carrier (8). [4] Ion trap (1) according to one of claims 1 to 3, wherein - the ion trap (1) further comprises a set of further electrodes (2), and - the further electrodes (2) are electrically connected to the magnetic field sensor devices (4). [5] Ion trap (1) according to one of claims 1 to 4, wherein - the at least two magnetic field sensor devices (4) comprise at least one of the following devices: a Hall sensor device, a flux gate sensor device and a superconducting quantum interference device. [6] Ion trap (1) according to one of claims 1 to 5, wherein - the ion trap (1) comprises more than two magnetic field sensor devices (4), and - the magnetic field sensor devices (4) surround the processing area (5). [7] Ion trap (1) according to claim 6, wherein - the at least one magnet arrangement (3) is arranged in or around the ion trap (1). [8] Ion trap (1) according to one of claims 6 or 7, wherein - the ion trap (1) comprises at least two registers, - at least two magnetic field sensor devices (4) are assigned to each of the registers, and - each of the registers is assigned at least one permanent magnet arrangement (3). [9] Ion trap (1) according to claim 8, wherein - each register is part of the ion trap (1). [10] Method for adjusting a magnetic field generated by at least one magnet arrangement (3) of an ion trap (1), comprising - providing at least two pieces of information which are each characteristic of measured values from one of the at least two magnetic field sensor devices (4), - determining distribution information which is characteristic of the magnetic field in a processing region (5) of the ion trap (1) as a function of the at least two pieces of information, and - Determining result information for adjusting a magnetization and / or a position and / or a current of the at least one magnet arrangement (3) as a function of the distribution information. [11] The method of claim 10, wherein - further information is provided which is characteristic of a measured value of at least one ion in the processing area (5), and - the distribution information is determined depending on the at least two pieces of information and the further information. [12] Method according to one of claims 10 or 11, wherein - the result information is determined such that the magnitudes of the magnetic field have a predetermined magnitude for a predetermined point in the processing area (5). [13] Method according to one of claims 10 to 12, wherein - the magnet arrangement (3) comprises at least one permanent magnet and / or at least one coil, and - the permanent magnet and / or the coil are adjusted, in particular independently of each other, depending on the result information. [14] Method according to one of claims 13, wherein - the permanent magnets are adjusted during magnetization.

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