Ion trap and method for adjusting a magnetic field

Abstract

An ion trap (1) is specified, with - a set of electrodes (2) configured to confine and / or manipulate at least one ion at a processing region (5), - at least one magnet arrangement (3) configured to establish a magnetic field in the processing region (5), and - at least two magnetic field sensor devices (4) spaced apart from the processing region (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 configured to provide a distribution information characteristic for the magnetic field in the processing region ( 5 ). Further, a method for adjusting a magnetic field is specified.

Description

[0001] P2023,1264 WO N September 17, 2024 - 1 - ION TRAP AND METHOD FOR ADJUSTING A MAGNETIC FIELD The present disclosure relates to an ion trap and a method for adjusting a magnetic field established by at least one magnet arrangement of an ion trap. Exemplarily, in order to perform quantum computing processes using trapped ions, the trapped ions have to be controllable and addressable individually from one another, in particular by the use of a magnetic field gradient. Such gradients can be generated by magnets. For example, a magnitude of the gradient might fluctuate due to drifts of permanent magnets and / or due to fluctuations of currents in coils. An object to be solved is to provide an ion trap, which has an improved magnetic field distribution. Furthermore, a method for adjusting a magnetic field established by at least one magnet arrangement of such an ion trap is to be provided. The object 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. According to at least one embodiment, the ion trap comprises a set of electrodes configured to confine and / or manipulate at least one ion at a processing region. The ion trap can be a Paul trap, a linear ion trap, a surface ion trap or a multi-layer ion trap. For example, a radio frequency, RF, voltage is applied to at least some electrodes of the set of electrodes such that a time-varying electric field is provided in the processing region configured to P2023,1264 WO N September 17, 2024 - 2 - confine and / or to manipulate the ion. For example, the ion intersects with a trapping axis and / or oscillates around a trapping axis within the processing region. Exemplarily, an extent in lateral directions and in vertical direction of the processing region is defined dependent on an arrangement of the set of electrodes and / or parameters of the time-varying electric field provided to the processing region by the set of electrodes. According to at least one embodiment, the ion trap comprises at least one magnet arrangement configured to establish a magnetic field in the processing region. The at least one magnet arrangement is, for example, spaced apart from the processing region in lateral directions and / or in vertical direction. In particular, the at least one magnet arrangement is configured to establish a gradient of magnitudes of the magnetic field in the processing region, e.g. along the trapping axis. This is that the magnetic field of the magnet arrangement has magnitudes being different from one another for different positions in the processing region and in particular for different positions on the trapping axis. Particularly, the gradient of magnitudes of the magnetic field being established by the magnet arrangement is at least 0.5 T / m or and at most 500 T / m. In particular, the gradient of magnitudes of the magnetic field in the processing region is at least 50 T / m and at most 250 T / m, exemplarily 150 T / m. Advantageously, if there are a plurality of ions in the processing region, a resonance frequency of each of the ions, P2023,1264 WO N September 17, 2024 - 3 - on which the gradient of magnitudes of the magnetic field of the magnet arrangement acts, is unique for each ion in the processing region. The at least one magnet arrangement can comprise at least one permanent magnets, in particular at least two permanent magnets, and / or at least one solenoid. Exemplarily, the permanent magnets do not require an external magnetic field to maintain magnetic properties such as a magnetization. Further, the permanent magnets are in particular configured to provide the magnetic field without being provided with an electrical current. Exemplarily, the solenoid is in particular configured to provide the magnetic field due to an electrical current applied to the solenoid. According to at least one embodiment, the ion trap comprises at least two magnetic field sensor devices spaced apart from the processing region. Exemplarily, the two magnetic field sensor devices do not overlap with the processing region. In particular, the at least two magnetic field sensor devices are spaced apart from the processing region in lateral directions and / or in vertical direction. Exemplarily, the two magnetic field sensor devices are spaced apart from one another, in particular in lateral directions and / or in vertical direction. 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 is, for example, that the at least two magnetic field sensor devices are arranged on and / or within an entity of the ion trap. P2023,1264 WO N September 17, 2024 - 4 - According to at least one embodiment of the ion trap, the at least two magnetic field sensor devices are configured to provide a distribution information characteristic for the magnetic field in the processing region. The distribution information comprises, inter alia, at least one of 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 region. Exemplarily, the magnetic field sensor devices are configured to sense the magnetic field of the magnet arrangement and optionally an external magnetic field at at least two specific locations each corresponding to a place where the magnetic field sensor devices are arranged. By combining the sensing of the at least two magnetic field sensor devices at the at least two specific locations, the magnetic field in the processing region can be determined and the distribution information can be provided. The external magnetic field results, for example, from at least one other source than the magnet arrangement. The external magnetic field is established by at least one of a nearby magnet, an electronic device, a power line, and a geomagnetic field. Typically, the magnetic field established by the magnet arrangement comprising the permanent magnet or the permanent magnets is dependent on a temperature of the magnet arrangement. When the temperatures are comparatively high, magnetic domains of the permanent magnets can become disordered, leading to a reduction in the magnitude of the magnetic field. When the temperatures are comparatively low, the magnetic domains of the permanent magnet can align more P2023,1264 WO N September 17, 2024 - 5 - coherently, leading to an increase in the magnitude of the magnetic field. Typically, the magnetic field established by the magnet arrangement comprising the solenoid is dependent on a fluctuation of the electrical current applied to the solenoid. This is that the magnetic field of the magnet arrangement can vary leading to a varying magnetic field in the processing region. Further, the external magnetic fields can influence the magnetic field of the magnet arrangement in the processing region. It is an idea, inter alia, to provide the ion trap with the magnetic field sensor devices such that the magnetic field in the processing region can be determined. If the magnetic field does not meet predetermined requirements, parameters of the magnet arrangement can be adjusted. In particular, the magnetic field sensor devices are configured to obtain an average magnetic field, comprising the magnitude of the magnetic field and the direction of the magnetic field, in the processing region. With these information, advantageously, the gradient of magnitudes of the magnetic field at the processing region is obtained as well as noise properties of the magnetic field in the processing region. Advantageously, the magnetic field sensor devices can be used to deliver information even when an ion is not available, e.g. for field measurements. Signals of several magnetic field sensor devices can be advantageously combined to infer P2023,1264 WO N September 17, 2024 - 6 - simultaneous information about different magnetic field components along different directions as well as magnetic field information at a location not directly accessible – i.e. the processing region. Further, 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 several magnets. Advantageously, by monitoring the magnetic field during magnetization, a vanishing magnetic field at a given position in the processing region can be obtained. This is that with such magnetic field sensor devices a feed-back during magnetization can be implemented to yield the desired magnetic field in the processing region. According to at least one embodiment of the ion trap, the ion trap comprises a substrate and / or a carrier. Exemplarily, 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. Exemplarily, at least some or all electrodes of the set of electrodes are arranged on the substrate. For example, at least some of the entities of the ion trap are arranged on the carrier. Exemplarily, the carrier is a mount for at least some of the entities of the ion trap. Exemplarily, 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 one of the at least two magnetic field sensor devices is arranged on the substrate. P2023,1264 WO N September 17, 2024 - 7 - 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. Exemplarily, at least some or all electrodes of the set of electrodes are, for example, arranged on the main surface, i.e. the top surface of the substrate or the bottom surface of the substrate, of the substrate. Exemplarily, all 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 one of the at least two magnetic field sensor devices is arranged on the bottom surface of the substrate. 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” means here 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. Exemplarily, 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. According to at least one embodiment of the ion trap, the ion trap further comprises a set of further electrodes. According to at least one embodiment of the ion trap, the further electrodes are electrically conductively connected to P2023,1264 WO N September 17, 2024 - 8 - the magnetic field sensor devices. Exemplarily, the further electrodes are configured to provide a signal characteristic for the magnetic field sensed by the magnetic field sensor devices to an external processing device. According to at least one embodiment of the ion trap, the at least two magnetic field sensor devices comprise at least one of a Hall sensor device, a flux gate sensor device and a superconducting quantum interference device. The Hall sensor device is, for example, a semiconductor sensing device. Typically, the Hall sensor device is configured to sense the magnetic field dependent on the Hall effect, wherein a Hall voltage is generated across a conductor when subjected to the magnetic field perpendicular to a current flow through the conductor. The flux gate sensor device comprises, for example, a core formed of a magnetically permeable material and two coils wound around the core. The core is driven into saturation by an alternating current, and the coils are used to measure the magnetic flux changes caused by the magnetic field. The superconducting quantum interference device, SQUID, comprises a superconducting loop interrupted by two Josephson junctions. A change in a critical current flowing through the junctions results when subjected to the magnetic field results in a change in a voltage or a magnetic flux. Exemplarily, all magnetic field sensor devices are of the same type. Alternatively, at least one of the magnetic field sensor devices is of a different type. P2023,1264 WO N September 17, 2024 - 9 - According to at least one embodiment of the ion trap, the ion trap comprises more than two magnetic field sensor devices. According to at least one embodiment of the ion trap, the magnetic field sensor devices surround the processing region. Exemplarily, the magnetic field sensor devices are arranged on predetermined specific locations on the substrate and / or the carrier. For example, the magnetic field sensor devices are arranged on virtual grid points of a virtual grid, being a regular or irregular grid. The virtual grid is, e.g. a one dimensional, a two dimensional or a three dimensional grid. For example, the virtual grid is 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. This is that the magnetic field sensor devices are displaced in space, i.e. in lateral directions and / or vertical direction, to the processing region. Advantageously, with such magnetic field sensor devices, the magnetic field at the ion location can be inferred, but none of the magnetic field sensor devices is in the processing region, e.g. at the ion location. 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 region. Exemplarily, the 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 least one magnet arrangement is embedded in the substrate, as described in connection with the magnetic field sensor devices. P2023,1264 WO N September 17, 2024 - 10 - 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 herein above. According to at least one embodiment of the ion trap, at least two magnetic field sensor devices are associated to each of the registers. This is that each register is, in particular, provided with at least two magnetic field sensor devices. This is that, advantageously, the magnetic field can be determined for each of the registers individually. According to at least one embodiment of the ion trap, at least one magnet arrangement is associated to each of the registers. This is that each register is, in particular, provided with at least one magnet arrangement. This is that, advantageously, each processing region can be provided with a gradient of magnitudes of the magnetic field individually. According to at least one embodiment of the ion trap, each register is part of the ion trap. Exemplarily, all sets of electrodes are arranged on the substrate being a single substrate. Furthermore, a method for adjusting a magnetic field established by at least one magnet arrangement of an ion trap is specified, wherein the ion trap is or can be the ion trap described herein above. This is to say that the features concerning the ion trap are also applicable for the method and vice versa. P2023,1264 WO N September 17, 2024 - 11 - According to at least one embodiment of the method, at least two information are provided, wherein each information is characteristic for measurement values of one of the at least two magnetic field sensor devices. Each information comprises, inter alia, 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. In particular, the specific locations are the places where the magnetic field sensor devices are arranged. According to at least one embodiment of the method, a distribution information is determined characteristic for the magnetic field in a processing region of the ion trap dependent on the at least two information. In particular, by combining the sensing of the at least two magnetic field sensor devices at the at least two specific locations, the distribution information characteristic for the magnetic field in the processing region can be determined. According to at least one embodiment of the method, a result information is determined for adjusting a magnetisation and / or a position and / or a current of the at least one magnet arrangement dependent on the distribution information. In particular, the magnetic field established by the at least one magnet arrangement is adjusted dependent on the result information. According to at least one embodiment of the method, a further information is provided characteristic for a measurement value of at least one ion in the processing region. The further information is provided by a read out of the at least one ion providing, inter alia, at least one of a magnitude of the magnetic field and a direction of the magnetic field at P2023,1264 WO N September 17, 2024 - 12 - the location of the at least one ion. The further information can advantageously be used for verifying and / or refining the distribution information. According to at least one embodiment of the method, the distribution information is determined dependent on the at least two information and the further information. This is that such a distribution information is advantageously particularly precise. According to at least one embodiment of the method, the result information is determined such that magnitudes of the magnetic field have a predetermined magnitude for a predetermined point in the processing region. 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 solenoid, and the permanent magnet and / or the solenoid is adjusted, in particular independently from one another, dependent on the result information. According to at least one embodiment of the method, the permanent magnets are adjusted during the magnetisation. In particular, the magnetisation can be advantageously monitored during magnetization due to the magnetic field sensor devices. In the following, the ion trap and the method are explained in more detail with reference to exemplary embodiments and the associated Figures. P2023,1264 WO N September 17, 2024 - 13 - Figure 1 shows a schematic view of the ion trap according to an exemplary embodiment. Figure 2 shows a flow diagram of the method according to an exemplary embodiment. Elements that are identical, similar or have the same effect are given the same reference signs in the Figures. The Figures and the proportions of the elements shown in the figures are not to be regarded as true to scale. Rather, individual elements may be shown exaggeratedly large for better representability and / or for better comprehensibility. The ion trap 1 according to the exemplary embodiment of Figure 1 is an ion trap chip comprising a substrate 6. The substrate 6 has a main surface 7 extending in lateral directions x, y, as indicated in Figure 1. A vertical direction extends perpendicular to the lateral directions. A main extension plane of the ion trap 1 extends also in lateral directions. Exemplarily, the substrate can be arranged on a carrier 8. A set of electrodes 2 is arranged on the main surface 7, which can be a top surface or a bottom surface. In particular, some of the electrodes 2 are configured to be provided with a RF voltage such 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 to manipulate at least one ion within the processing region 5. The ion trap 1 further comprises a magnet arrangement 3 configured to establish a magnetic field in the processing region 5. The at least one magnet arrangement 3 comprises in P2023,1264 WO N September 17, 2024 - 14 - particular at least one element, i.e. at least one permanent magnet and / or at least one solenoid. 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. If the magnet arrangement 3 comprises the permanent magnets, the permanent magnets have a main extension plane in lateral directions, i.e. being parallel to the main extension plane of the substrate 6. The permanent magnets, in particular at least two of the permanent magnets have a magnetization direction being parallel to one another. The magnetization directions each extend in vertical direction facing away from the substrate 6, as indicated by the arrow. Alternatively it is possible that the magnet arrangement comprises one permanent magnet and one solenoid. Such a magnet arrangement 3 is configured to establish a gradient of magnitudes of the magnetic field of the magnet arrangement 3 in the processing region 5. The processing region 5 is spaced apart from the magnet arrangement 3, i.e. from the two magnets. In particular, the processing region 5 is located in lateral directions between the two magnets. Further, the processing region 5 is located in vertical direction above the main surface 7 up to a predetermined distance. The predetermined distance is for example larger, in particular at least one magnitude larger, than a height of each of the magnets in vertical direction. The ion trap 1 additionally comprises four magnetic field sensor devices 4. The four magnetic field sensor devices 4 P2023,1264 WO N September 17, 2024 - 15 - 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. being parallel to the main extension plane of the substrate 6. The magnetic field sensor devices 4 are configured to sense, i.e. to measure, a vertical component, and exemplarily and optionally a horizontal component in lateral directions, of a magnetic field as indicated by the arrows in Figure 1, each at a specific location. In particular, the magnetic field sensor devices 4 are arranged on virtual grid points of a virtual grid, here being a two dimensional rectangular grid. The virtual grid points correspond the specific locations. The magnetic field sensor devices 4 are spaced apart from the processing region 5 in lateral directions and in vertical direction. By combining the measured vertical components of the magnetic field at the specific locations, a distribution information can be determined characteristic for a magnetic field in the processing region 5. In the method stage S1 in Figure 2, at least two information are provided, wherein each of the information is characteristic for measurement values of one of the at least two magnetic field sensor device 4. Subsequently, in method stage S2, a distribution information is determined characteristic for the magnetic field at a processing region 5 of the ion trap 1 dependent on the at least two information. P2023,1264 WO N September 17, 2024 - 16 - Subsequently, in the method stage S3, a result information is determined for adjusting a magnetisation and / or a position and / or a current of the at least one magnet arrangement 3 dependent on the distribution information. In particular, the magnetisation or a current of the magnet arrangement 3 can be adjusted based on the distribution information. Exemplarily, the magnetisation is adjusted such that such that magnitudes of the magnetic field vanish at a predetermined point in the processing region 5, in particular dependent on the result information. Alternatively or additionally the magnetisation is adjusted such that such that a gradient of the magnitudes of the magnetic field is maximized in the processing region 5, in particular dependent on the result information.

[0002] P2023,1264 WO N September 17, 2024 - 17 - Reference signs 1 ion trap 2 electrode 3 magnet arrangement 4 magnetic field sensor device 5 processing region 6 substrate 7 main surface 8 carrier S1..S3 method stages

Claims

P2023,1264 WO N September 17, 2024 - 18 - Claims 1. Ion trap (1), with - a set of electrodes (2) configured to confine and / or manipulate at least one ion at a processing region (5), - at least one magnet arrangement (3) configured to establish a magnetic field in the processing region (5), and - at least two magnetic field sensor devices (4) spaced apart from the processing region (5), wherein - the at least one magnet arrangement (3) is configured to establish a gradient of magnitudes of the magnetic field in the processing region (5) along a trapping axis, - 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 configured to provide a distribution information characteristic for the magnetic field in the processing region (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) are 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).P2023,1264 WO N September 17, 2024 - 19 - 4. Ion trap (1) according to one of the claims 1 to 3, wherein - the ion trap (1) further comprises at set of further electrodes (2), and - the further electrodes (2) are electrically conductively connected to the magnetic field sensor devices (4).

5. Ion trap (1) according to one of the claims 1 to 4, wherein - the at least two magnetic field sensor devices (4) comprise at least one of a Hall sensor device, a flux gate sensor device and a superconducting quantum interference device.

6. Ion trap (1) according to one of the 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 region (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 the claims 6 or 7, wherein - the ion trap (1) comprises at least two registers, - at least two magnetic field sensor devices (4) are associated to each of the registers, and - at least one magnet arrangement (3) is associated to each of the registers.

9. Ion trap (1) according to claim 8, whereinP2023,1264 WO N September 17, 2024 - 20 - - each register is part of the ion trap (1).

10. Method for adjusting a magnetic field established by at least one magnet arrangement (3) of an ion trap (1), wherein the at least one magnet arrangement (3) is configured to establish a gradient of magnitudes of the magnetic field in a processing region (5) along a trapping axis, with - providing at least two information each one characteristic for measurement values of one of the at least two magnetic field sensor devices (4), - determining a distribution information characteristic for the magnetic field at the processing region (5) of the ion trap (1) dependent on the at least two information, and - determining a result information for adjusting a magnetisation and / or a position and / or a current of the at least one magnet arrangement (3) dependent on the distribution information.

11. Method according to claim 10, wherein - a further information is provided characteristic for a measurement value of at least one ion in the processing region (5), and - the distribution information is determined dependent on the at least two information and the further information.

12. Method according to one of the claims 10 or 11, wherein - the result information is determined such that magnitudes of the magnetic field has a predetermined magnitude for a predetermined point in the processing region (5).

13. Method according to one of the claims 10 to 12, wherein - the magnet arrangement (3) comprises at least one permanent magnet and / or at least one solenoid, andP2023,1264 WO N September 17, 2024 - 21 - - the permanent magnet and / or the solenoid is adjusted, in particularly independently from one another, dependent on the result information.

14. Method according to one of the claim 13, wherein - the permanent magnets are adjusted during the magnetisation.

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