Microwave antenna and quantum computing system

Abstract

A microwave antenna (1) for emitting electromagnetic radiation provided to at least one ion (3) for quantum computation is specified, comprising - a plurality of antenna elements (2) arranged spaced apart from one another, wherein - at least some of the antenna elements (2) are connected to a respective signal line (14), and - each of the respective signal lines (14) is configured to be connected to a respective signal generator. Furthermore, a quantum computing system is specified.

Description

[0001] Description

[0002] MICROWAVE ANTENNA AND QUANTUM COMPUTING SYSTEM

[0003] The present disclosure relates to a microwave antenna for emitting electromagnetic radiation provided to at least one ion for quantum computation and a quantum computing system.

[0004] Typically, for microwave-controlled trapped ion qubits, each of the trapped ions is driven by a microwave pulse, e.g. a microwave field with a predetermined frequency, amplitude, and phase. Exemplarily, a ratio of achievable microwave field strength to irradiated power limits a gate speed or qubit number due to the dissipative heating of the ion trap, which is in particular critical for operating the ion trap in a cryogenic environment.

[0005] An object to be solved is to provide a microwave antenna which has an improved magnetic field distribution.

[0006] Furthermore, a quantum computing system is to be provided.

[0007] 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.

[0008] According to at least one embodiment, the microwave antenna is configured to emit electromagnetic radiation provided to at least one ion for quantum computation. Exemplarily, the microwave antenna is configured to provide electromagnetic radiation to an ion trap with a processing region. The processing region is in particular configured to host at least one ion, exemplarily a plurality of ions. Exemplarily, at most 100 ions or at most 60 ions are provided in the processing region. Exemplarily, the microwave antenna is configured to provide the electromagnetic radiation to the ions in the processing region.

[0009] The ion trap can be a Paul trap, a linear ion trap, a surface ion trap or a multi-layer ion trap. The ion trap comprises, for example, a set of electrodes configured to conf ine and / or manipulate at least one ion at a processing region. 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 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.

[0010] Exemplarily, the electromagnetic radiation, in particular a microwave radiation, is applied to at least some trapped ions, in particular, by the microwave antenna. The electromagnetic radiation is, for example, configured to induce a transition between the energy levels of at least some of the trapped ions. Exemplarily, by applying the electromagnetic radiation, an operation on the quantum states of the trapped ions, such as qubit rotations or state preparations, is performed. Microwave radiation is in particular characteristic of electromagnetic radiation with a frequency of at least 0.1 GHz and at most 500 GHz, in particular at least 0.3 GHz and at most 300 GHz.

[0011] The ion trap comprises, for example, at least one magnet arrangement configured to establish a magnetic field in the processing region. The at least one magnet arrangement can comprise at least one permanent magnet arrangement and / or at least one coil. 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 because the magnetic field of the magnet arrangement has different magnitudes for different positions in the processing region and in particular for different positions on the trapping axis.

[0012] Advantageously, if there is a plurality of ions in the processing region, the resonance frequency of each of the ions on which the gradient of magnitudes of the magnetic field of the magnet arrangement acts is unique for each ion in the processing region.

[0013] According to at least one embodiment, the microwave antenna comprises a plurality of antenna elements which are arranged spaced apart from one another. The antenna elements are, for example, planar, having a main extension plane extending in lateral directions. Exemplarily, the antenna elements are each formed by a flat metal plate. Each flat metal plate has, for example, a round shape, an elliptical shape or a polygonal shape, e.g. being triangular or quadrangular. In particular, directly neighboring antenna elements are not in direct and immediate contact with one another. For example, a minimal distance of directly neighboring antenna elements in lateral directions is at most 5 mm, at most 3 mm or at most 2 mm, approximately 1 mm. Exemplarily, the minimal distance of directly neighboring antenna elements is at least 0.1 mm or at least 0.5 mm. Exemplarily, the antenna elements comprise an electrically conductive material. In particular, the antenna elements comprise or consist of a metal. Exemplarily, the minimal distance is characteristic for an angular resolution of the microwave antenna. The angular resolution is, in particular, characteristic of a width of a main lobe of the emitted electromagnetic radiation of the microwave antenna.

[0014] According to at least one embodiment of the microwave antenna, at least some of the antenna elements are connected to a respective signal line. Exemplarily, each of the antenna elements is connected to a respective signal line. For example, a respective electrical signal is provided to each of the signal lines. Each electrical signal is, exemplarily, characteristic of a microwave frequency signal. This means that a respective electrical signal can be provided to each of the antenna elements via the respective signal line. In particular, each electrical signal is characteristic of an amplitude, a frequency and / or a phase of a respective beam to be emitted by the respective antenna element. Exemplarily, the amplitude, a frequency and / or a phase of at least some or all electrical signals are different to one another. The signal line is, for example, formed of an electrically conductive line and / or a coaxial cable.

[0015] According to at least one embodiment of the microwave antenna, each of the respective signal lines is configured to be connected to a respective signal generator. Exemplarily, each signal generator is configured to provide the respective electrical signal to the respective signal line. In particular, each signal generator is configured to predetermine the amplitude, the frequency and / or the phase of the respective electrical signal. Exemplarily, each signal generator is drivable independently from the other signal generators.

[0016] For example, each electrical signal comprises a continuous wave, a pulse, or a modulated wave signal, depending on specific requirements of the operation to be performed on the quantum states of the at least one ion.

[0017] It is an idea, inter alia, to use a microwave antenna with a plurality of individual adjustable and / or controllable antenna elements to provide electromagnetic radiation to the trapped ion to perform quantum computational processes. With such a microwave antenna, each amplitude, frequency and / or phase of the beams emitted by the respective antenna element is adjustable independently from one another, exemplarily via the respective signal generator. With such beams, the electromagnetic radiation, particularly a distribution thereof, of the microwave antenna can be advantageously precisely predetermined by the use of the signal generators. Having independent signal generators for at least some of the antenna elements advantageously allows precise control over individual antenna elements, which facilitates targeted addressing of trapped ions, e.g. qubits, and / or which ensures scalability.

[0018] Such a microwave antenna enables tailored manipulation of trapped ions, e.g. qubits, by emitting electromagnetic radiation at frequencies uniquely matched to each ion's resonance frequency. This precise targeting is particularly relevant for coherent control and for minimizing crosstalk between trapped ions, e.g. qubits. Thus, the fidelity of quantum operations can be advantageously maintained. By independently programming each antenna element, complex quantum gate operations can be advantageously implemented with unprecedented flexibility and scalability. Moreover, the dynamic nature of such antenna elements allows for rapid reconfiguration, facilitating adaptive quantum algorithms and error correction strategies.

[0019] According to at least one embodiment of the microwave antenna, at least some of the antenna elements are drivable independently from one another. In particular, by driving the respective signal generators independently from one another, each amplitude, frequency and / or phase of the beams emitted by the respective antenna element is adjustable independently from one another.

[0020] According to at least one embodiment of the microwave antenna, the antenna elements are configured to emit electromagnetic radiation. Exemplarily, each of the antenna elements is configured to emit a respective beam, wherein each beam is characteristic for electromagnetic radiation, in particular microwave radiation. All beams emitted by the antenna elements form the electromagnetic radiation of the microwave antenna provided to the processing region.

[0021] Exemplarily, each beam propagates in vertical direction, being perpendicular to the lateral directions, away from the respective antenna element.

[0022] According to at least one embodiment of the microwave antenna, the emitted electromagnetic radiation comprises a near field region, where the ion is configured to be located. Exemplarily, the beams emitted from neighboring antenna elements interact with one another, forming the emitted electromagnetic radiation of the microwave antenna having the near field region and a far field region. Exemplarily, the near field region extends within a distance of approximately one wavelength from the microwave antenna, wherein the far field region extends at distances several times larger than the wavelength of the emitted electromagnetic radiation. The near field region is, for example, characteristic of a distance of at most 1.5 times or at most 1 times of the wavelength of the emitted electromagnetic radiation of the microwave antenna. This means that the distance between the antenna element and the processing region is, for example, at most 1.5 times or at most 1 times of the wavelength of the emitted electromagnetic radiation of the microwave antenna.

[0023] Advantageously, the emitted electromagnetic radiation in the near field region can transfer power with comparatively highly efficiency in contrast to the far field region. In particular, in the near field region, the emitted electromagnetic radiation, i. e. the beams interfering constructively with one another, are more localized, allowing for a focused energy transfer. Further, such a microwave antenna is advantageously particularly compact in size, such that it can be combined with an ion trap without dramatically increasing the size of the system.

[0024] Exemplarily, the phases of the emitted electromagnetic radiation of different antenna elements are predetermined such that an intensity of the emitted electromagnetic radiation is maximized in the near field region, where the ion is configured to be located.

[0025] Exemplarily, the phases of the emitted electromagnetic radiation of different antenna elements are predetermined such that the intensity of the emitted electromagnetic radiation is minimized in a predetermined region, different to the processing region. Exemplarily, the phases of the emitted electromagnetic radiation of different antenna elements are predetermined such that an intensity of the emitted electromagnetic radiation is minimized at the predetermined region in the far field region.

[0026] Advantageously, such a microwave antenna can also be applied to a surface ion trap, e.g. a chip ion trap. For example, the antenna elements are integrated in the chip ion trap.

[0027] Exemplarily, the antenna elements are integrated in a substrate of the ion trap.

[0028] According to at least one embodiment of the microwave antenna, the emitted electromagnetic radiation is provided to an ion trap comprising at least two registers, and each register is configured to host at least one ion.

[0029] The ion trap comprises, for example, a zone or multiple zones. A zone can be a processing zone, a detection zone, a loading zone, or a register re-ordering zone. A register reordering zone is, for example, characteristic of reshuffle and / or reorder a register including split a register and / or merge registers. A processing zone is, for example, characteristic of at least one or more registers.

[0030] A non-processing zone is, for example, characteristic to comprise or not comprise a register.

[0031] Exemplarily, the emitted electromagnetic radiation is provided to at least one zone and further to at least one register thereof. For example, at least some of the antenna elements are drivable such that the near field region is controllable to be located in at least one of the zones, and particularly in at least one of the registers thereof.

[0032] In particular, the ion trap can be a multi zone ion trap, particularly a surface multi zone ion trap.

[0033] According to at least one embodiment of the microwave antenna, at least some of the antenna elements are drivable such that the near field region is controllable to be located in at least one of the registers.

[0034] According to at least one embodiment of the microwave antenna, the emitted electromagnetic radiation interferes constructively in the near field region. Particularly, at least some of the antenna elements are drivable such that the beams interfere constructively in at least one of the registers. It is further possible that the at least some of the antenna elements are drivable such that the beams interfere constructively in at least one of the registers and in at least one location of the ion in the at least one register. Exemplarily, the beams interfere constructively in at least one of the registers and the beams interfere destructively in at least another one of the registers, particularly simultaneously. It is possible that the near field region is controllable to be located in at least some or all of the registers, e.g. that the beams interf ere in at least some or all of the registers. Advantageously, specific trapped ions can be addressed individually in a specific register with such a microwave antenna.

[0035] Exemplarily, the power of the emitted electromagnetic radiation is advantageously boosted at in at least one of the registers, particularly for using less power in general. For example, at least some of the antenna elements are drivable such that the beams interfere constructively in at least one of the registers, wherein the emitted electromagnetic radiation is configured to decay before at least one adj acent register. The at least one adj acent register is located particularly next to the at least one of the registers, where the beams interfere constructively.

[0036] According to at least one embodiment of the microwave antenna, the antenna elements are arranged at grid points of a grid. The grid points are characteristic of a center of each of the antenna elements, in particular a center of mass. The grid is, for example, a circular grid, a linear grid or a polygonal grid, such as a triangular grid or a quadrangular grid. Exemplarily, the antenna elements are arranged at at least some of the grid points. For example, the grid points are spaced apart from one another by at least 5 mm and / or at most 2 cm, exemplarily 1 cm. The antenna elements are exemplarily arranged in a n × m arrangement, where n and m are each a natural number larger than two.

[0037] According to at least one embodiment of the microwave antenna, the signal generators are configured to be connected to a master clock. The master clock is characteristic of a timing reference for synchronizing the signal generators. Advantageously, by using the master clock, all of the signal generators operate in a coordinated manner, avoiding timing mismatches or phase inconsistencies of individual signal generators.

[0038] According to at least one embodiment of the microwave antenna, the signal generators are configured to be connected to a controller. Exemplarily, the controller is a field programmable gate array, FPGA, controller, being connected to all signal generators. In particular, the signal generators can be individually controlled by the controller.

[0039] Furthermore, a quantum computing system is specified, wherein the quantum computing system comprises the microwave antenna described herein above. This is to say that the features concerning the microwave antenna are also applicable for the quantum computing system and vice versa.

[0040] According to at least one embodiment, the quantum computing system comprises an ion trap configured to provide the at least one ion, as described in connection with the microwave antenna. The ion trap with the microwave antenna can be operated at room temperature and / or operated at a cryogenic temperature.

[0041] According to at least one embodiment, the quantum computing system comprises a cryostat configured to provide a cryogenic environment. The cryostat is configured to provide the cryogenic environment which has a temperature of at most 50 K or at most 20 K and / or at least 0.1 mK or at least 0.3 mK.

[0042] According to at least one embodiment of the quantum computing system, the microwave antenna and the ion trap are arranged within the cryogenic environment. The cryostat, in particular the cryogenic environment, is configured to cool the microwave antenna and the ion trap. Exemplarily, at least one of the microwave antenna and the ion trap are configured to be thermally conductively connected to a cooling stage of the cryostat. In the following, the microwave antenna and the quantum computing are explained in more detail with reference to exemplary embodiments and the associated figures.

[0043] Figure 1 shows a schematic view of the microwave antenna according to an exemplary embodiment.

[0044] Figure 2 shows a schematic view of the quantum computing system according to an exemplary embodiment.

[0045] 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.

[0046] The microwave antenna 1 according to the exemplary embodiment of Figure 1 comprises a plurality of antenna elements 2 arranged spaced apart from one another. The antenna elements 2 according to this embodiment are arranged along a linear grid, particularly an array. Each antenna element 2 is connected to a respective signal generator via a respective signal line 14. Each signal generator can provide a respective electrical signal to the respective antenna element 2 via the respective signal line 14. Additionally, each signal generator is connected to a controller 8 and a master clock 7. Further signal lines of the controller 8 and the master clock 7 for connection to the signal generators are indicated with dashed lines.

[0047] Each of the antenna elements 2 is configured to emit a beam of electromagnetic radiation dependent on the electrical signal. In particular, each beam is characteristic of microwave radiation with an amplitude, a frequency and / or a phase, particularly being predetermined. Each amplitude, frequency and / or phase is particularly predetermined and adjusted in such a way that constructive interference is created at a trapped ion's 3 position in an ion trap 4 of a respective register. The register is indicated with a dashed dotted line. Further, the near field region 5 and the far field region 6 of the electromagnetic radiation of the microwave antenna 1 are indicated schematically.

[0048] The quantum computing system 10 according to the exemplary embodiment of Figure 2 comprises a quantum processor comprising the ion trap 4 and the microwave antenna 1 which are arranged in a chamber 9, providing a vacuum environment and / or a cryogenic environment. The quantum processor and a possible laser system are connected by means of connections 11 to a control electronics system 12, which is connected to a device 13 being a classical computer device.

[0049] The invention is not limited to the exemplary embodiments by their description. Rather, the invention encompasses any new feature as well as any combination of features, which in particular includes any combination of features in the claims, even if this feature or combination itself is not explicitly indicated in the claims or exemplary embodiments. Reference signs list

[0050] 1 microwave antenna

[0051] 2 antenna elements

[0052] 3 ion

[0053] 4 ion trap

[0054] 5 near field region

[0055] 6 signal generator

[0056] 7 master clock

[0057] 8 controller

[0058] 9 chamber

[0059] 10 quantum computing system 11 connections

[0060] 12 control electronics system 13 device

[0061] 14 signal lines

Claims

Claims1. Microwave antenna (1) for emitting electromagnetic radiation provided to at least one ion (3 ) for quantum computation, comprising- a plurality of antenna elements (2) arranged spaced apart from one another, wherein- at least some of the antenna elements (2) are connected to a respective signal line (14), and- each of the respective signal lines (14) is configured to be connected to a respective signal generator.

2. Microwave antenna (1) according to claim 1, wherein- at least some of the antenna elements (2) are drivable independently from one another.

3. Microwave antenna (1) according to any one of claims 1 or 2, wherein- the antenna elements (2) are configured to emit electromagnetic radiation, and- the emitted electromagnetic radiation comprises a near field region (5), where the ion (3 ) is configured to be located.

4. Microwave antenna (1) according to claim 3, wherein- the emitted electromagnetic radiation is provided to an ion (3 ) trap comprising at least two registers,- each register is configured to host at least one ion (3 ), and- at least some of the antenna elements (2) are drivable such that the near field region is controllable to be located in at least one of the registers.

5. Microwave antenna (1) according to any one of claims 3 or 4, wherein- the emitted electromagnetic radiation interferes constructively in the near field region.

6. Microwave antenna (1) according to any one of claims 1 to 5, wherein- the antenna elements (2) are arranged at grid points of a grid.

7. Microwave antenna (1) according to any one of claims 1 to 5, wherein- the signal generators are configured to be connected to a master clock (7).

8. Microwave antenna (1) according to any one of claims 1 to 7, wherein- the signal generators are configured to be connected to a controller (8).

9. Quantum computing system (10), comprising- the microwave antenna (1) according to any one of claims 1 to 8, and- an ion trap (4) configured to provide the at least one ion (3 ).

10. Quantum computing system (10) according to claim 9, further comprising- a cryostat configured to provide a cryogenic environment, wherein- the microwave antenna (1) and the ion trap (4) are arranged within the cryogenic environment.

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