MICROWAVE ANTENNA AND QUANTUM COMPUTER SYSTEM

Abstract

A microwave antenna (1) for the emission of electromagnetic radiation, which is provided to at least one ion (3) for quantum computing, is specified, comprising - a plurality of spaced-apart antenna elements (2), wherein - at least some of the antenna elements (2) are designed to emit electromagnetic radiation with a different phase. Furthermore, a quantum computer system (10) is specified.

Description

[0001] The present disclosure relates to a microwave antenna for the emission of electromagnetic radiation, which is provided to at least one ion for quantum computing, and a quantum computer system.

[0002] Typically, in microwave-controlled trapped ion qubits, the microwave intensity at a location of the trapped ion defines the rate at which a qubit state can change. For example, the ratio of achievable microwave field strength to radiated power limits the gate velocity or qubit number due to dissipative heating of the ion trap, which is particularly critical for operating the ion trap in a cryogenic environment.

[0003] One task to be solved is to provide a microwave antenna with an improved magnetic field distribution. Furthermore, a quantum computer system is to be provided.

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

[0005] According to at least one embodiment, the microwave antenna is configured to emit electromagnetic radiation that is provided to at least one ion for quantum computing. For example, the microwave antenna is configured to provide electromagnetic radiation to an ion trap with a processing area. The processing area is specifically configured to provide at least one ion, for example, several ions. For example, a maximum of 100 ions or a maximum of 60 ions are provided in the processing area. The microwave antenna is, for example, configured to provide the electromagnetic radiation to the ions in the processing area.

[0006] The ion trap can be a Paul trap, a linear ion trap, a surface ion trap, or a multilayer ion trap. The ion trap comprises, for example, a set of electrodes configured to confine and / or manipulate at least one ion within a processing area. For example, a high-frequency (HF) voltage is applied to at least some of the electrodes in the electrode set, providing a time-varying electric field within the processing area designed to confine and / or manipulate the ion. For example, the ion intersects a capture axis and / or oscillates within the processing area around a capture axis.

[0007] For example, electromagnetic radiation, particularly microwave radiation, is applied to at least some of the captured ions, especially by the microwave antenna. The electromagnetic radiation is designed, for example, to induce a transition between the energy levels of at least some of the captured ions. For example, by applying the electromagnetic radiation, an operation is performed on the quantum states of the captured ions, such as qubit rotations or state preparations.

[0008] Microwave radiation is particularly characteristic of electromagnetic radiation with a frequency of at least 0.1 GHz and at most 500 GHz, especially at least 0.3 GHz and at most 300 GHz.

[0009] The ion trap comprises, for example, at least one magnetic arrangement configured to generate a magnetic field in the processing area. This magnetic arrangement may include at least one permanent magnet arrangement and / or at least one coil. The magnetic arrangement is, for example, spaced laterally and / or vertically from the processing area. In particular, the magnetic arrangement is configured to generate a gradient of magnetic field strength in the processing area, e.g., along the capture axis. This is because the magnetic field of the magnetic arrangement has different strengths for different positions in the processing area and, in particular, for different positions on the capture axis.

[0010] When a large number of ions are present in the processing area, the resonance frequency of each of the ions, on which the gradient of the magnitudes of the magnetic field of the magnetic arrangement acts, is advantageously unique for each ion in the processing area.

[0011] According to at least one embodiment, the microwave antenna comprises a plurality of antenna elements arranged at intervals from one another. For example, the antenna elements have a surface and a base opposite the surface, the surface and the base being connected by at least one side surface. For example, side surfaces of directly adjacent antenna elements face each other. In particular, the side surfaces of directly adjacent antenna elements are not in direct and immediate contact with each other. For example, a minimum distance between the side surfaces of directly adjacent antenna elements is at most 5 mm, at most 3 mm, or at most 2 mm, approximately 1 mm. For example, the minimum distance between the side surfaces of directly adjacent antenna elements is at least 0.1 mm or at least 0.5 mm.

[0012] For example, the antenna elements comprise an electrically conductive material. In particular, the antenna elements comprise or consist of a metal.

[0013] For example, the minimum distance is characteristic of the angular resolution of the microwave antenna. The angular resolution is particularly characteristic of the width of the main cone of the emitted electromagnetic radiation from the microwave antenna.

[0014] According to at least one embodiment of the microwave antenna, at least some of the antenna elements are configured to emit electromagnetic radiation with different phases. In particular, each of the antenna elements is configured to emit a beam, especially microwave radiation, wherein each beam is characteristic of electromagnetic radiation with a specific phase. In particular, at least some or all phases are different from one another. In particular, at least some or all beams are configured to be provided to the ion as emitted electromagnetic radiation.

[0015] For example, a predetermined phase and / or amplitude of the emitted electromagnetic radiation at the ion's location is specified, depending on the phases and, in particular, the amplitudes of the electromagnetic radiation of the beams. Advantageously, beam guidance and / or phase alignment can be implemented at the ion's location.

[0016] In particular, the phases of individual beams are determined such that individual beams generate a converging wavefront characteristic for a given maximum intensity of the emitted electromagnetic radiation at the location of the ion.

[0017] For example, each antenna element is connected to a signal line. All signal lines are, for example, part of a supply network designed to distribute electrical signals to the individual antenna elements via the signal lines. The electrical signals are, for example, characteristic of microwave frequency signals. In particular, each electrical signal is characteristic of a phase of the respective radiated beam. Each phase can be adjusted independently, for example, via the electrical signals.

[0018] One idea is to use a microwave antenna with multiple individually adjustable and / or controllable antenna elements to provide electromagnetic radiation to the trapped ion for quantum information processing. With such a microwave antenna, dissipative heating is advantageously reduced compared to typical microwave antennas for ion traps, while maintaining or improving the intensity of the electromagnetic radiation at the location of the trapped ions.

[0019] 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 point for 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 or a quadrilateral grid. For example, the antenna elements are arranged at at least some of the grid points.

[0020] For example, the grid points are spaced apart by at least 5 mm and / or at most 2 cm, for example 1 cm.

[0021] According to at least one embodiment of the microwave antenna, the antenna elements are arranged in an n × m configuration, where n and m are each a natural number greater than two. For example, n and m are different from each other, or n and m are the same. Preferably, n and m are each at least 3 or at least 6.

[0022] According to at least one embodiment of the microwave antenna, each of the antenna elements has a principal extension plane. For example, the principal extension plane of each of the antenna elements is parallel to the respective surface and / or the respective base surface of the respective antenna element.

[0023] According to at least one embodiment of the microwave antenna, the principal extension planes lie in a common plane. In particular, lateral directions are parallel to the common plane and a vertical direction is oriented perpendicular to the common plane. Specifically, the surface of each microwave antenna and / or the base surface of each microwave antenna are parallel to the common plane. For example, the top surfaces do not overlap each other in the vertical direction facing the ion trap.

[0024] According to at least one embodiment of the microwave antenna, the antenna elements are arranged on a support. For example, the antenna elements are arranged directly on the support. The support comprises a substrate and / or a carrier.

[0025] For example, at least some of the signal lines are located at least partially on and / or within the holder. In particular, at least some of the signal lines are located on and / or within the substrate.

[0026] The mounting includes, for example, a cover element on which the antenna elements are arranged. The cover element can comprise or consist of a dielectric substrate.

[0027] For example, the mounting bracket has a rear element facing away from the antenna elements. The rear element may comprise or consist of a support, in particular comprising aluminum, steel, or composite materials, especially to provide mechanical stability. The rear element may have a coating such as copper, gold, or silver, especially to increase electrical performance.

[0028] For example, the holder can include a flexible substrate, such as a polymer composite or a metal alloy.

[0029] For example, the signal lines can be partially embedded in the bracket.

[0030] According to at least one embodiment of the microwave antenna, the emitted electromagnetic radiation has a near-field region in which the ion is located. The beams emitted by neighboring antenna elements interact with each other and form the emitted electromagnetic radiation with a near-field region and a far-field region.

[0031] For example, the near field area is located at a distance of about one wavelength from the microwave antenna, while the far field area extends at distances that are several times greater than one wavelength of the emitted electromagnetic radiation.

[0032] The near-field region is characterized, for example, by a distance of at most 1.5 times or at most 1 time the wavelength of the emitted electromagnetic radiation. This means that the distance between the antenna element and the ion is, for example, at most 1.5 times or at most 1 time the wavelength of the emitted electromagnetic radiation.

[0033] Advantageously, the emitted electromagnetic radiation in the near field can transfer power with a comparatively high efficiency, unlike in the far field. In the near field, in particular, the emitted electromagnetic radiation, i.e., the beams, are more localized, enabling focused energy transfer. Furthermore, such a microwave antenna is advantageously very compact, allowing it to be combined with an ion trap without drastically increasing the overall system size.

[0034] According to at least one embodiment of the microwave antenna, at least some of the antenna elements are connected to an active phase shifter.

[0035] For example, the active phase shifter comprises at least one electronic component. This electronic component includes, for example, a transistor, such as a field-effect transistor and / or a bipolar junction transistor, diodes, and / or integrated circuits. The active phase shifter is configured to dynamically control the phase of at least some or all of the antenna elements. In particular, the active phase shifter is connected to at least some or all of the signal lines.

[0036] The active phase shifter is, for example, mounted on the bracket or on an external control device. For example, the external control device is positioned at a distance from the microwave antenna. The external control device is connected to the microwave antenna, in particular via the signal lines.

[0037] Advantageously, the phases can be continuously controlled using the active phase shifter, achieving precise adjustment of the phase angles for the different beams. This allows for advantageous beam guidance and / or phase alignment.

[0038] Furthermore, the use of an active phase shifter advantageously leads to a minimization of insertion losses.

[0039] According to at least one embodiment of the microwave antenna, at least some of the antenna elements are connected to a passive phase-delayed feed line. The passive phase-delayed feed line comprises, for example, a coaxial cable, a microstrip line, and / or a waveguide. For example, the phase of the beams depends on the length of the passive phase-delayed feed line. The phases can be predefined by specifying the lengths of the passive phase-delay feed line.

[0040] Advantageously, a simple, reliable and cost-effective phase difference of the antenna elements can be achieved by using the passive phase delay feed line.

[0041] For example, the antenna elements are designed to be connected to the active phase shifter and / or the passive phase delay feed line.

[0042] Furthermore, a quantum computer system is specified, which includes the microwave antenna described above. That is, the characteristics relating to the microwave antenna are also applicable to the quantum computer system and vice versa.

[0043] According to at least one embodiment, the quantum computer system comprises an ion trap configured to provide at least one ion, as described in connection with the microwave antenna.

[0044] The ion trap with the microwave antenna can be operated at room temperature and / or at cryogenic temperatures.

[0045] According to at least one embodiment, the quantum computer 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.

[0046] According to at least one embodiment of the quantum computer system, the microwave antenna and the ion trap are arranged within the cryogenic environment. The cryostat, and in particular the cryogenic environment, is configured to cool the microwave antenna and the ion trap. Preferably, the microwave antenna and / or the ion trap are thermally connected to a cooling stage of the cryostat.

[0047] The microwave antenna and the quantum computer system are explained in more detail below using exemplary embodiments and the associated figures. Fig. Figure 1 shows a schematic view of the microwave antenna according to an exemplary embodiment. Fig. Figure 2 shows a schematic view of the quantum computer system according to one embodiment.

[0048] Elements with the same, similar, or identical effect are marked with the same reference symbols in the figures. The figures and the proportions of the elements depicted within them are not to scale. Rather, individual elements may be exaggerated for clarity and / or better understanding.

[0049] The microwave antenna 1 according to the embodiment of the Fig. 1 comprises a plurality of spaced-apart antenna elements 2. The antenna elements 2 are arranged at grid points of a grid, in particular a regular grid. The antenna elements 2 according to this embodiment are arranged along a linear grid, in particular an array. Preferably, the antenna elements 2 are arranged at grid points of a rectangular grid.

[0050] Each of the antenna elements 2 is connected to a signal line 14. The signal lines 14 are connected to an external control device. The external control device is configured to provide an electrical signal to each of the antenna elements 2.

[0051] Furthermore, the external control device is in particular a generator 8 configured to generate an electrical signal with a microwave frequency. For example, the generated electrical signal is made available to all antenna elements 2.

[0052] Each of the antenna elements 2 is configured to emit a beam of electromagnetic radiation depending on the electrical signal. In particular, each beam is characteristic of microwave radiation with a phase. Furthermore, each beam is characteristic of microwave radiation with a specific amplitude. Each phase and / or each amplitude can be predefined. Each phase corresponding to a respective beam is predefined and adjusted such that constructive interference occurs in a desired direction, especially at the position of the captured ions. Additionally, each beam's amplitude is predefined and adjusted such that a predetermined signal strength and quality are achieved.

[0053] Each of the antenna elements 2 is connected to an active phase shifter 6, in particular by a further signal line 16 that is distinct from the signal line 14. The active phase shifter 6 is configured to provide each of the antenna elements 2 with a further electrical signal for changing the phase. In particular, the phase of a respective beam depends on the further electrical signal. Alternatively or additionally, a passive phase-delaying feed line 7 is included from at least one of the signal lines 14 for changing the phase.

[0054] At least some of the antenna elements 2 are configured to emit electromagnetic radiation with different phases. In particular, at least some of the beams emitted by at least some of the antenna elements 2 have different phases.

[0055] All beams interact with each other and form the electromagnetic radiation emitted by the microwave antenna 1. In particular, the electromagnetic radiation exhibits a converging wavefront formed by the beams. The emitted electromagnetic radiation, i.e., the wavefront, is represented by the dashed lines facing the ion trap 4 containing the ion 3. Advantageously, the phases of individual beams are determined such that individual beams generate the converging wavefront characteristic for a given maximum intensity of the electromagnetic radiation at the location of the ion 3.

[0056] The emitted electromagnetic radiation is provided to an ion 3 trapped in an ion trap 4. The microwave antenna 1 and the ion 3 are spaced apart, the distance being characteristic of a near-field region 5 of the emitted electromagnetic radiation. This means that the distance between the microwave antenna 1 and the ion 3 is at most 1.5 times or at most 1 time to the wavelength of the emitted electromagnetic radiation.

[0057] The ion trap 4 comprises in particular a set of electrodes 15, wherein a high-frequency, RF voltage can be applied to at least some of the electrodes 15, so that a time-varying electric field is provided in a processing area designed to capture the ion 3.

[0058] The quantum computer system 1 according to the embodiment of the Fig.Assembly 2 comprises a quantum processor including the ion trap 4 and the microwave antenna 1, which are arranged in a chamber 9 that provides a vacuum and / or cryogenic environment. The quantum processor and a possible laser system are connected via links 11 to a control electronics system 12, which is connected to a classical computer device 13.

[0059] The invention is not limited to the embodiments described in its description. Rather, the invention encompasses every new feature and every combination of features, in particular every combination of features in the claims, even if that feature or combination itself is not explicitly stated in the claims or embodiments. Reference list 1 microwave antenna 2 antenna elements 3 Ion 4 ion trap 5 Near field 6 active phase shifters 7 passive phase-delaying feed line 8 Generator 9th Chamber 10 quantum computer systems 11 connections 12 Control electronics system 13 Device 14 signal lines 15 electrodes 16 additional signal lines

Claims

[1] Microwave antenna (1) for emitting electromagnetic radiation which is provided to at least one ion (3) for quantum computing, comprising - a plurality of spaced-apart antenna elements (2), wherein - at least some of the antenna elements (2) are designed to emit electromagnetic radiation with a different phase. [2] Microwave antenna (1) according to claim (1), wherein - the antenna elements (2) are arranged at grid points of a grid. [3] Microwave antenna (1) according to one of claims 1 or 2, wherein - the antenna elements (2) are arranged in an n × m arrangement, where n and m are each a natural number greater than two. [4] Microwave antenna (1) according to one of claims 1 to 3, wherein - each of the antenna elements (2) has a principal extension plane, and - the main extension planes are located in a common plane. [5] Microwave antenna (1) according to any one of claims 1 to 4, wherein - the antenna elements (2) are arranged on a bracket. [6] Microwave antenna (1) according to any one of claims 1 to 5, wherein - the emitted electromagnetic radiation has a near-field region (5) in which the ion (3) is located. [7] Microwave antenna (1) according to any one of claims 1 to 6, wherein - at least some of the antenna elements (2) are connected to an active phase shifter (6). [8] Microwave antenna (1) according to any one of claims 1 to 7, wherein - at least some of the antenna elements (2) are connected to a passive phase-delaying feed line (7). [9] Quantum computer system (10), comprising - the microwave antenna (1) according to any one of claims 1 to 8, and - an ion trap (4) designed to provide the at least one ion (3). [10] Quantum computer system (10) according to claim 9, further comprising - a cryostat designed to provide a cryogenic environment, whereby - the microwave antenna (1) and the ion trap (4) are arranged within the cryogenic environment.

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