Charged particle trap

Abstract

A charged particle trap is disclosed. The charged particle trap includes a substrate (31) and a layer structure (33, 37, 39) disposed on the substrate, the layer structure including an antenna layer (33) and an electrode layer (39). The antenna layer comprises a coplanar conductive bend line (12) comprising at least three elongated arms (13) parallel and coplanar and symmetrical about a central axis (15). The electrode layer comprises a set of electrodes (45, 46, 47) arranged to capture charged particles (16) along a well axis (17) parallel to the central axis and to generate a pseudo potential symmetric about the well axis.

Description

Technical Field

[0001] The present invention relates to a charged particle trap. Background Art

[0002] A promising approach to trapped-ion quantum computing is to perform quantum gates in the absence of laser fields. In this arrangement, quantum gates are driven by strong magnetic field gradients. These gradients can be generated by passing currents through traces on an ion trap chip.

[0003] The ideal setup for a multi-qubit quantum gate is to have a very high magnetic field gradient while having essentially zero magnetic field strength (referred to herein as "no field gradient"). This is because, while the gradient is responsible for generating the desired coupling, the field may generate undesired coupling, thereby increasing errors and / or reducing the effective interaction strength.

[0004] Two approaches have been used to generate field-free gradients.

[0005] C. Ospelkaus et al.: “Microwave quantum logic gates for trapped ions” https: / / arxiv.org / pdf / 1104.3573.pdf (2011) describes a first approach in which multiple current lines are formed on a trap chip and the corresponding phases and currents are adjusted to form the desired quadrupole. M. Wahnschaffe et al.: “Single-ion microwave near-field quantum sensor” https: / / arxiv.org / pdf / 1601.06460.pdf (2021) describes a second approach in which three bends are formed on the upper surface of the ion trap. The dimensions of the bends are simulated, and then bends with these dimensions are fabricated to create a quadrupole at the location of the ions.

[0006] However, these approaches have one or more disadvantages. The first approach requires multiple individually adjustable current sources and low differential noise between independent conductors, which can be difficult to achieve. In the second approach, aligning the magnetic field zero point with the ion location can be challenging, for example, due to manufacturing imperfections. In both cases, the AC current through the conductor generates an AC electric field that moves the ions away from the magnetic zero point. Finally, the design rules for the design of the current-carrying conductors often conflict with the design rules for the trap electrodes.

[0007] Some proposals have been made to resolve the conflicting requirements, where the bends are provided by a multilayer structure, with access to the top layer only in a few regions close to the ions, and reference is made to H.Hahn et al.:, “Multilayer ion trap with three-dimensional microwave circuitry for scalable quantum logic applications”, https: / / arxiv.org / pdf / 1812.02445.pdf (2021) (H. Hahn et al.: “Multilayer ion trap technology for scalable quantum computing and quantum simulation”, New Journal of Physics, volume 21, 043011 (2019)). However, this only partially alleviates the problem, as the top current-carrying electrode still imposes significant constraints on the design of the trapping electrode. In addition, the technology relies on high-current layer-to-layer interconnects, which are challenging to manufacture, as shown, for example, in A. Bautista-Salvador et al.: “Multilayer ion trap technology for scalable quantum computing and quantum simulation”, New Journal of Physics, volume 21, 043011 (2019) and may introduce significant resistance unless a large footprint is available.

[0008] GB 2 593 901 A describes a method for partially zeroing a magnetic field that is oriented in a direction that minimizes its influence on a quantum gate. The partially zeroed field may still have an influence on the qubit, for example in the form of rapid frequency modulation or dispersive qubit frequency shifts. Summary of the invention

[0009] According to a first aspect of the present invention, a charged particle trap is provided. The charged particle trap comprises a substrate and a layer structure arranged on the substrate. The layer structure comprises an antenna layer and an electrode layer. The antenna layer comprises a coplanar conductive meander line, the coplanar conductive meander line comprising at least three slender arms that are parallel and coplanar and symmetrical about a central axis. The electrode layer comprises a group of electrodes, the group of electrodes being arranged to capture charged particles along a trap axis parallel to the central axis and generate a pseudopotential that is symmetrical about the trap axis. For example, the pseudopotential may be symmetrical about the trap axis in an in-plane direction perpendicular to the trap axis (i.e., parallel to the electrode layer).

[0010] This arrangement can help generate magnetic field gradients and provide magnetic field cancellation where charged particles will be trapped.

[0011] The antenna layer may be interposed between the substrate and the electrode layer. The antenna layer may be located above or below the electrode layer (in other words, not coplanar with the electrode layer).

[0012] The electrode layer is preferably symmetrical about the trap axis at least in a cross section along the trap axis in which charged particles are to be trapped.

[0013] The bend line may include an odd number of elongated arms and include a middle arm such that the central axis extends along the middle arm. The bend line may include an even number of elongated arms and include a pair of middle arms such that the central axis extends between the pair of middle arms.

[0014] The conductive meander line may have a width between 5 and 500 μm. The conductive meander line may have a thickness t between 0.3 μm and 2 μm. The conductive meander line may comprise a superconducting material.

[0015] The layer structure may further include a conductive layer interposed between the antenna layer and the electrode layer. The conductive layer may provide a ground plane. The conductive layer may be sheet-shaped. The conductive layer may be formed of a metal such as aluminum.

[0016] The layer structure may also include a conductive connection layer (e.g., including a set of traces or wires) interposed between the antenna layer and the electrode layer. The conductive connection layer may be formed of a metal such as aluminum. The conductive connection layer may be used to route signals to the surface electrodes. The layer structure may also include at least one conductive via or at least two conductive vias connecting the conductive connection layer to at least one or at least two electrodes in the electrode layer.

[0017] The conductive meander wires may be arranged to extend in a bundle of at least two adjacent parallel strands, and three or more bundles may be symmetrical about the center line.

[0018] The set of electrodes may include a shielding effectiveness S=20 log 10A set of surface electrodes with [B0' / B1']≤20dB or <1dB, wherein B0' is the magnetic field gradient at the charged particle when captured by the charged particle trap in the absence of the set of surface electrodes, and B1' is the magnetic field gradient at the charged particle when captured by the charged particle trap in the presence of the set of surface electrodes.

[0019] The elongate arms are preferably straight, for example in the region through which the elongate arms and the central axis extend.

[0020] According to a second aspect of the present invention, a quantum information processing system is provided. The quantum information processing system includes a charged particle trap and a control system. The charged particle trap includes a substrate and a layer structure arranged on the substrate. The layer structure includes an antenna layer and an electrode layer. The antenna layer is inserted between the substrate and the electrode layer. The antenna layer includes at least three parallel and coplanar wires and symmetrical about a central axis, and wherein the electrode layer includes a group of electrodes, the group of electrodes being arranged to capture charged particles along a trap axis parallel to the central axis. The control system is used to control the charged particle trap, to apply a bias voltage to the group of electrodes to capture at least one ion, and to perform at least one quantum logic gate on at least one charged particle. The control system is arranged to drive a current through at least three wires so that each current has a corresponding phase and the current is symmetrical about the central axis.

[0021] This arrangement can help generate magnetic field gradients and provide magnetic field cancellation where charged particles would be trapped without the use of bends.

[0022] The control system may include at least two bias voltage sources.

[0023] The control system may comprise N bias sources. Each of the N bias sources is arranged to drive a respective current having a respective phase through a respective conductor or through at least two adjacent parallel conductors of a respective bundle.

[0024] The control system may include first and second bias sources. The first bias source is arranged to drive a first current having a first phase through the first group of at least one conductor or at least two adjacent parallel conductors of the first group of at least one bundle, and the second bias source is arranged to drive a second current having a second phase through the first group of at least one conductor or at least two adjacent parallel conductors of the first group of at least one bundle.

[0025] The at least three conductors may include an odd number of conductors, wherein the odd number of conductors includes a middle conductor and the central axis extends along the middle conductor. The at least three conductors may include an even number of conductors, wherein the even number of conductors includes a pair of middle conductors and the central axis extends between the pair of middle conductors.

[0026] The wire may have a width between 5 and 500 μm. The wire may have a thickness t between 0.3 μm and 2 μm. The wire may comprise a superconducting material.

[0027] The layer structure may further include a conductive layer interposed between the antenna layer and the electrode layer. The conductive layer may provide a ground plane. The conductive layer may be sheet-shaped. The conductive layer may be formed of a metal such as aluminum.

[0028] The layer structure may also include a conductive connection layer (e.g., including a set of traces or wires) interposed between the antenna layer and the electrode layer. The conductive connection layer may be formed of a metal such as aluminum. The conductive connection layer may be used to route signals to the surface electrodes. The layer structure may also include at least one conductive via or at least two conductive vias connecting the conductive connection layer to at least one or at least two electrodes in the electrode layer.

[0029] The wires may be arranged to extend in a bundle of at least two adjacent parallel wires, and three or more bundles may be symmetrical about a center line.

[0030] The set of electrodes may include a shielding effectiveness S=20 log 10 A set of surface electrodes with [B0' / B1']≤20dB or <1dB, wherein B0' is the magnetic field gradient at the charged particle when captured by the charged particle trap in the absence of the set of surface electrodes, and B1' is the magnetic field gradient at the charged particle when captured by the charged particle trap in the presence of the set of surface electrodes.

[0031] The wires are preferably straight, for example in the region through which the elongate arms and central axis extend.

[0032] According to a third aspect of the present invention, a quantum information processing system is provided, which includes the charged particle trap and a control system of the first aspect, wherein the control system is used to control the charged particle trap, to apply a bias voltage to the group of electrodes to capture at least one ion, and to perform at least one quantum logic gate on at least one charged particle.

[0033] The control system may be configured to pass an electric current having a frequency less than or equal to 1 GHz through the conductive meander wire or conductor.

[0034] According to a third aspect of the present invention, there is provided a method of operating the charged particle trap of the first aspect or the quantum information processing system of the second or third aspect, the method comprising: capturing at least one charged particle in the trap, each charged particle providing a corresponding quantum bit; preparing an initial quantum bit state; and applying a sequence of one or more gates to the quantum bit. Applying the sequence of one or more gates to the quantum bit comprises driving a current having a frequency less than or equal to 1 GHz through a meander or wire.

[0035] The method may also include reading out the qubit state.

[0036] The charged particles may be ions, such as calcium ions (such as 40 Ca + or 43 Ca + ). A charged particle can be an atom or molecule with a net charge, or a fundamental charged particle such as an electron or a positron. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Certain embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0038] Figure 1 is a schematic plan view of a first antenna structure including a wire for generating a magnetic field gradient;

[0039] Figure 2 is a schematic plan view of a second antenna structure including two bent arms for generating a magnetic field gradient;

[0040] Figure 3 is a schematic plan view of a third antenna structure including a three-arm folded structure for generating a magnetic field gradient;

[0041] Figure 4 is a schematic plan view of a fourth antenna structure including a four-arm folded structure for generating a magnetic field gradient;

[0042] Figure 5 Illustrated Figure 3 A diagram of simulated magnetic field and magnetic field gradient for the three-arm folded structure shown in FIG.

[0043] Figure 6 is a schematic diagram of a quantum information processing system including a surface electrode trap and a control system;

[0044] Figure 7 is a schematic orthogonal diagram of a charged particle trap including an antenna including four arm bends;

[0045] Figure 8 yes Figure 7 A schematic plan view of a charged particle trap shown in FIG.

[0046] Fig. 9 is a plan view of the antenna layer of the charged particle trap;

[0047] Fig.10 is a plan view of the electrode layer of the charged particle trap;

[0048] Fig.11 is a schematic plan view of a fifth antenna including a multi-bend three-arm bend for generating a magnetic field gradient;

[0049] Fig.12 is a schematic plan view of a sixth antenna including a multi-bend four-arm bend for generating a magnetic field gradient;

[0050] Fig.13 is a schematic diagram of a single source drive arrangement;

[0051] Fig.14 is a schematic diagram of a first multi-source drive arrangement;

[0052] Fig.15 is a schematic diagram of a second multi-source drive arrangement;

[0053] Fig.16 is a schematic plan view of a charged particle trap with surface antennas. DETAILED DESCRIPTION

[0054] Overview

[0055] Antenna structures are described herein. These structures can be driven by a single or multiple sources. These structures can be arranged to help align the magnetic field zero point with the trapped ions. These structures can be buried, thereby allowing shielding of the AC electric field and allowing greater freedom in top-level design. These structures are planar, thereby eliminating the need for low-resistance, low-footprint interconnects, thereby helping to simplify manufacturing. For example, signals can be supplied to these structures through large interconnects placed away from other structures or wire bonds attached directly to structures on a buried layer. Finally, these structures can be adapted to produce high gradients at low currents, thereby helping to reduce overall power consumption.

[0056] Structures for generating magnetic field gradients

[0057] refer to Figure 1 and 2 , a first and a second antenna structure 11 , 12 are shown.

[0058] The first antenna structure 11 takes the form of a single straight wire 2 extending along the central axis 5 (in this case, parallel to the x-axis) through which a current i can be driven. The first antenna structure 11 can be used to apply a magnetic field gradient (not shown) to one or more charged particles 6 positioned along an axis 7 that is parallel to the central axis 5 and offset vertically (along the z-axis) from the central axis.

[0059] The second antenna structure 12 takes the form of a meandering wire structure 2 (also referred to herein as a "dual-wire meandering structure," "dual-arm meandering structure," "single-bend meandering structure," or "single-segment meandering structure") having first and second elongated wire segments 3 (or "arms") that are straight, parallel (in this case, parallel to the x-axis) and coplanar (in this case, in the xy plane), connected by a transverse segment 4 (or "bridge"), and symmetrical about a central axis 5 (parallel to the x-axis). The second antenna structure 12 can be used to apply a magnetic field gradient (not shown) to one or more charged particles 6 positioned along an axis 7 that is parallel to the central axis 5 and offset perpendicularly (along the z-axis) from the central axis.

[0060] Although the first and second antenna structures 11 , 12 may be used to generate a magnetic field gradient (not shown), they are not able by themselves (eg without additional wires) to provide magnetic field cancellation, ie to generate a zero magnetic field region.

[0061] Structures for generating magnetic field gradients and magnetic field cancellation

[0062] refer to Figure 3 and 4 , a third and a fourth antenna structure 111 , 112 are shown.

[0063] The third antenna structure 111 takes the form of a meandering wire structure 12 (also referred to herein as a "three-wire meandering structure," "three-arm meandering structure," "double-bend meandering structure," or "1.5-segment meandering structure") having first, second, and third elongated wire segments 13 (or "arms") that are straight, parallel, connected by first and second transverse segments 14 (or "bridges"), and symmetrical about a central axis 15. Thus, the wire 12 is ox-plowed. The third antenna structure 111 can be used to apply a magnetic field gradient (not shown) to one or more charged particles 16 positioned along an axis 17 that is parallel to the central axis 15 and vertically offset from the central axis (in this case, along the z-axis).

[0064] A charged particle pseudopotential (not shown) is generated by the electrodes, which is symmetrical about the axis 17, in particular about the well axis 17 in an in-plane direction y perpendicular to the well axis, and about a plane P perpendicular to the z axis and in which the central axis and the well axes 15, 17 are located. The charged particles 16 can be trapped in chains, for example two or more charged particles, for example for use in a two-qubit gate.

[0065] The fourth antenna structure 112 takes the form of a meandering wire structure 12 (also referred to herein as a "quad-wire meandering structure," "four-arm meandering structure," "three-bend meandering structure," or "two-segment meandering structure") having first, second, third, and fourth elongated wire segments 13 that are straight, parallel, connected by first, second, and third transverse segments 14, and symmetrical about a central axis 15. The fourth antenna structure 112 may be used to apply a magnetic field gradient (not shown) to one or more charged particles 16 positioned along an axis 17 that is parallel to the central axis 15 and vertically offset from the central axis (in this case, along the z-axis).

[0066] A charged particle pseudopotential (not shown) is generated by the electrodes, which is symmetrical about the axis 17, in particular about the well axis 17 in an in-plane direction y perpendicular to the well axis, and about a plane P perpendicular to the z axis and in which the central axis and the well axes 15, 17 are located. The charged particles 16 can be trapped in chains, for example two or more charged particles, for example for use in a two-qubit gate.

[0067] refer to Figure 5 , shows the magnetic field along the y-axis (B) of a three-wire bend with z = 40 um (where z = 0 is the plane of the bend) y ), the magnetic field along the z-axis (B z ), y and z magnetic field gradients along the y and z axes respectively (dB y / dy, dB z / dz) and the z and y magnetic field gradients along the y and z axes (dB z / dy, dB y / dz), where a current of 1 A flows through the bend.

[0068] At y = 0, the magnetic field is zeroed (B y =B z =0). At the same time, the two gradient components (dB z / dy and dB y / dz) is not zero and is actually quite strong at 125 T / m.

[0069] Through symmetry, we can achieve B z = 0. On the other hand, B y = 0 is only the case when the gap is chosen appropriately. In the simulation, the trace is assumed to be infinitely thin. In this case, the optimal gap is equal to the ion height (40 μm. In a real device, due to the finite trace width (and the presence of nearby structures), the optimal gap may be different. Therefore, a finer-grained simulation can be used to find the optimal gap for a real device.

[0070] Quantum Information Processing Systems21

[0071] refer to Figure 6 , a quantum information processing system 21 including a surface electrode well 22 and a control system 23 is shown.

[0072] The surface electrode well 22 may be used to capture and control one or more charged particles 16 along the well axis 17 that provide a corresponding qubit.

[0073] The charged particles 16 take the form of ions, such as calcium ions ( 40 Ca + ), but they can also take the form of atoms or molecules with a net electric charge, or elementary charged particles such as electrons or positrons.

[0074] The surface electrode well 22 may be housed in a low temperature refrigerator (not shown) for cooling the surface electrode well 22 to a suitably low temperature T (e.g., below 77K or 4.2K). The surface electrode well 22 may be operated at room temperature. The surface electrode well 22 may be housed in a vacuum chamber (not shown) that provides an ultra-high vacuum environment that allows individual charged particles to be isolated.

[0075] Multilayer charged particle trap

[0076] refer to Figure 7 and 8 , an example of the surface electrode well 22 is shown.

[0077] The surface electrode well 22 comprises: a substrate 31, which comprises, for example, sapphire, having an upper surface 32 supporting an antenna layer 33; a first dielectric layer (not shown) comprising silicon dioxide and having an upper surface (not shown) supporting a conductive layer 37, which comprises a conductive material such as gold, aluminum or another suitable metal or degenerately doped silicon or other suitable semiconductor layer; a second dielectric layer (not shown) comprising silicon dioxide and having an upper surface (not shown) supporting a charged particle capture layer 39, which has an upper surface 40 on which one or more charged particles 16 can be captured. The conductive layer 37 can provide a ground plane. Additional layers (not shown) that provide conductive paths (not shown) and through holes (not shown) can be provided to provide signal lines to the surface electrodes and wires. The antenna layer 33 and the charged particle capture layer 39 are not coplanar, and in this case, the antenna layer 33 is located below the charged particle capture layer 39.

[0078] The antenna layer 33 includes an antenna structure 11 for generating a magnetic field gradient and magnetic field cancellation, such as, for example, the third or fourth antenna structure 111 described above ( Figure 3 )、112( Figure 4 ).

[0079] The antenna layer 33 comprises a coplanar conductive meander line 12 comprising at least three elongated arms 13 that are parallel and coplanar and symmetrical about a central axis 15 extending parallel to a well axis 17. The central axis 15 and the well axis 17 lie in a plane P that is perpendicular to the upper surface 40, and the well axis 17 lies above the central axis 15.

[0080] The meander line 12 may be formed of a metal such as gold, silver or aluminum; a superconductor such as rare earth barium copper oxide, ReBCO, niobium or an alloy containing niobium; or a semiconductor such as doped silicon. The line 12 may have a width w (transverse to the current flow) between 5 and 500 μm, and may have a thickness t between 0.3 μm and 20 μm.

[0081] The control system 23 comprises a signal source 42 attached to first and second ends 43 , 44 of the antenna structure 11 .

[0082] The charged particle trapping layer 39 includes an arrangement of electrodes 45, 46, 47 that can be used to trap and control one or more charged particles 16. In this case, the charged particles 16 are shown as being trapped in pairs for use in a two-qubit gate. However, the charged particles 16 can be trapped individually, or in longer chains of three or more particles 16.

[0083] The electrodes 45, 46, 47 include a central electrode 45 and first and second electrodes 46, the central electrode being in the form of a strip extending along a longitudinal axis 48 parallel to the trap axis 17, and the first and second electrodes being in the form of corresponding strips extending along either side of the central electrode 45, so that the central electrode 45 is interposed between the first and second electrodes 46. An AC signal of RF frequency is applied to the first and second electrodes 46 (also referred to herein as "first and second RF electrodes") to generate a ponderomotive force confinement potential. The electrodes 45, 46, 47 generate a pseudopotential (not shown) symmetric about the plane P. In particular, the pseudopotential (not shown) is symmetric about the trap axis 17 in the y direction. Along the z direction, the pseudopotential (not shown) is asymmetric.

[0084] The control system 10 applies appropriate DC and AC currents and bias voltages to the electrodes 45 , 46 , 47 of the surface electrode well 22 .

[0085] refer to Fig. 9 , the antenna layer 33 is shown.

[0086] refer to Fig.10 , a charged particle capturing layer 39 is shown.

[0087] The bend line 12 is completely symmetrical about y=0. Depending on the design, this helps to cancel the magnetic field along one axis (i.e., the y-axis or the z-axis). Fig.10In the 4-conductor configuration shown in Figure 1, symmetry ensures magnetic field cancellation along the y-axis. Cancellation along the other axis (the z-axis in the case of a 4-conductor design) can be arranged by judiciously setting the conductor gaps and widths. Cancellation along the x-direction can be achieved by making the structure long enough along the x-direction.

[0088] The ability to make the wells and bends symmetrical goes a long way toward canceling out the magnetic fields. The configuration could then become less sensitive to manufacturing and simulation uncertainties.

[0089] The antenna layer 33 takes the form of a single buried layer. This can bring one or more advantages. The geometry of the bend can be adjusted to obtain optimal performance without restricting the geometry of the top electrode. In contrast, the trace width w can be increased, thereby reducing the resistance and thus reducing power consumption. Similarly, the trace thickness t can be increased without compromising the manufacturing quality of the top electrode. The need for low-footprint, low-resistance vias can be avoided. This also makes the structure more suitable for the use of superconducting traces, because superconducting planar structures tend to be easier to manufacture than superconducting vias. The material of the bend trace can be freely selected to obtain optimal performance without considering its effects on ions, such as electric field noise.

[0090] The layers above the antenna layer 33 provide a shielding structure. This can help reduce the AC electric fields generated by the meander line 2, which can help improve the problem of aligning the magnetic zero point with the ion position. These electric fields can be further reduced by connecting the trace to the conductive plane 37 at a single point close to the charged particle 16 and driving it with a differential feed.

[0091] To help ensure that a sufficient magnetic field gradient is generated, the frequency of the current can be adjusted. Since low-frequency magnetic fields are less shielded, the structure is more suitable for quantum gates generated by low-frequency gradients.

[0092] Although thick, high conductivity layers shield electric and magnetic fields more effectively than thin, low conductivity layers, electric fields are generally attenuated more strongly than magnetic fields, at least at frequencies close to DC, e.g., less than 100 Hz. Therefore, adjusting the geometry and conductivity of the shielding layer allows the use of structures that shield the electric field to a sufficient degree while ensuring sufficient penetration of the magnetic field.

[0093] operate

[0094] The control system 23 passes a low frequency (<1 GHz) current through the meander line 12. This helps improve performance because passing higher frequencies through the line 12 can create fields that are sensitive to induced currents, ground bounce, and phase shift. Applying a low frequency current helps reduce currents in other layers and minimizes wave phase shift across the antenna.

[0095] Other structures

[0096] Reference again Figure 3 and 4 , the third and fourth antenna structures 111, 112 include a single conductive wire 12 that is bent back and forth in a single strand to form a bend (referred to herein as a "multi-bend single-wire bend").

[0097] refer to Fig.11 and 12 , fifth and sixth antenna structures 113, 114 are shown, which also include a single conductor 12, which is arranged into three or more parallel strands, and these parallel strands are turned back and forth in unison (e.g., in pairs, groups of three, or other multi-wire bundles) to form bends (referred to herein as "multi-bend multi-wire bends"). Within each bundle there are straight parallel strands.

[0098] In the fifth and sixth antenna structures 113, 114, the wires may be thinner than in the third and fourth antenna structures 111, 112. This helps reduce power consumption because one wire segment of width w carrying current I may be replaced by N parallel wire segments, each of which has a width of w / N and each carries current I / N, to produce a comparable field gradient while reducing power dissipation by a factor of N.

[0099] The fifth and sixth antenna structures 113, 114 are examples of multi-bend 3-wire bending and multi-bend 4-wire bending structures, respectively.

[0100] Drive layout

[0101] refer to Fig.13 , a single source 42 may be used to drive current I(t) through the series-connected elongated wire segments 13 or strands 18 ( Fig.11 ). By means of the meandering structure 12 comprising one or more bridges 14, the current in a given conductor segment 13 or a given strand 18 and the current in an adjacent conductor segment 13 or an adjacent strand 18 flow in antiparallel but with the same magnitude.

[0102] This arrangement, where one source 42 is used to drive more than one elongated wire segments 13 electrically connected in series, is referred to herein as a "passive arrangement", a "common source arrangement" or a "series wire drive arrangement".

[0103] However, this effect can be achieved in different ways.

[0104] refer to Fig.14 , multiple sources 421, 422, 423 may be used, whereby source 42 iThe respective elongated wires 131, 132, 133 (or respective strands) are driven, and the elongated wires 13 (or strands) are not electrically connected in series. Instead, the current in a given wire (e.g., the second wire 132) is driven with a given phase φ, and the currents in adjacent wires (in this case, the first and third wires 131, 133) are driven with the same magnitude and in anti-phase.

[0105] This arrangement, that is, using N sources 42 i (i=1, ..., N) to drive N elongated wires 13 that are not electrically connected in series. i An arrangement of N beams (i=1, . . . , N) is referred to herein as an "active arrangement", "independent source arrangement" or "parallel wire driven arrangement".

[0106] refer to Fig.15 , the same effect can be achieved using two sources 42, whereby a first source 421 drives one or more alternating wires 13 or alternating strands of a first group 201, wherein current flows in parallel; and a second source 422 drives one or more wires 13 or alternating strands of a second group 202, wherein current flows in anti-parallel with respect to the first group.

[0107] This arrangement, in which two sources 42 are used to drive N elongated wires 13, and the wires in one group are connected in parallel, while the wires in the other group are also connected in parallel, but the two groups are not electrically connected, is called a "semi-active arrangement", "shared source arrangement" or "split parallel wire driving arrangement".

[0108] Surface electrode shielding

[0109] The surface electrode trap described above may include one or more antennas (not shown) disposed below the surface electrode (in other words, interposed between the substrate and the surface electrode). The antenna may take the form of a current-carrying conductive path (or "wire") that generates a magnetic field that can act on the captured charged particles. A dielectric layer (such as silicon dioxide) having a thickness of, for example, between 1 μm and 10 μm may be deposited on the antenna to electrically isolate the antenna from the surface electrode, such that the dielectric layer is interposed between the antenna and the surface electrode.

[0110] Shielding effectiveness S (dB) is defined as:

[0111] S = 20 log 10 (B0' / B1') (1)

[0112] Where B0' is the magnetic field gradient at the charged particle in the absence of a shielding structure, and B1' is the magnetic field gradient at the charged particle in the presence of a shielding structure.

[0113] Shielding effectiveness can be divided into three states, namely:

[0114] - "Low shielding": S < 1dB (ie B1'> 0.9B0')

[0115] - "Medium shielding": 20dB ≥ S ≥ 1dB (i.e. 0.1Bo' ≤ B1' ≤ 0.9B0')

[0116] - "High shielding": S>20dB (ie B1'<0.1B0')

[0117] The surface electrodes are preferably arranged to provide no shielding of charged particles from the antenna, in other words, to provide low shielding. However, moderate shielding may be acceptable.

[0118] Low shielding can be achieved by (a) selecting suitable materials for the electrodes and selecting a thickness for the electrodes that is much smaller than the skin depth δ of the material (ie, t<<δ), and (b) configuring the electrode layout to have, for example, grooves and / or gaps.

[0119] The shielding effectiveness can be estimated by modeling the layer above the antenna as a solid ground plane with thickness t and conductivity σ. For example, a copper layer with a thickness of 500 nm at room temperature (t = 500 nm and σ = 5.96 × 10 7 S / m) is considered as a low shielding layer at a frequency of f = 10 MHz, because S < 1 dB. A copper layer with a residual resistivity ratio RRR = 100 at 4 Kelvin and a thickness of 5 μm (t = 5 μm, and σ = 5.96 × 10 7 S / m) is a high shielding layer at frequency f=300MHz because S>20dB.

[0120] The shielding effectiveness S is affected by the electrode geometry, especially the presence of slots and cutouts. However, the shielding effectiveness of a sheet without slots or cutouts can be used as an approximation.

[0121] Surface Antenna

[0122] The surface electrode wells described above employ buried antennas. However, the antennas may be provided at the surface. This may be used, for example, in situations where the surface electrodes provide too much shielding.

[0123] refer to Fig.16 , another example of the surface electrode well 22 ′ is shown.

[0124] The surface electrode well 22' is similar to the surface electrode well 22 described above ( Figure 8). However, an antenna structure 11, which in this case is a three-arm structure, is formed on the upper surface. The antenna structure 11 comprises a conductive bend 12, which in this case comprises three straight arms 13, which are parallel and symmetrical about a central axis 15 extending parallel to the well axis 17.

[0125] A second electrode 46 (or "RF electrode") is also provided on the upper surface between the arms 13. A third electrode 47 (or "DC electrode") is provided on either side of the bend 12, ie on either side of the well axis 17.

[0126] The electrodes 46, 47 are arranged to generate a pseudopotential (not shown) for trapping charged particles which is symmetric about the well axis 17 along a central section S of the well 22'. The pseudopotential (not shown) is symmetric about the well axis 17 along the y-direction parallel to the layers.

[0127] Revise

[0128] It will be appreciated that various modifications may be made to the embodiments described above. Such modifications may involve equivalent and other features known in the design, manufacture and use of charged particle traps and component parts thereof, as well as equivalent and other features that may be used instead of or in addition to features already described herein. Features of one embodiment may be replaced or supplemented by features of another embodiment.

[0129] The wells described herein have one layer of electrode or two layers of electrodes (where one of the multiple layers of electrodes is buried). Wells having three or more layers (including at least two buried electrode layers) may be used.

[0130] Although the claims in this application have described a specific combination of features, it should be understood that the disclosure scope of the present invention also includes any novel features or any novel combination of features disclosed explicitly or implicitly herein, or any generalization thereof, whether or not it relates to the same invention as currently claimed in any claim, and whether or not it alleviates any or all technical problems that are the same as the present invention. The applicant hereby notifies that new claims may be made for these features and / or combinations of these features during the examination of this application or any other application derived therefrom.

Claims

1. A charged particle trap, comprising: substrate; as well as A layer structure is provided on the substrate, the layer structure comprising: Antenna layer; as well as Electrode layer, The antenna layer comprises a coplanar conductive meander line comprising at least three elongated arms which are parallel, coplanar and symmetrical about a central axis, and the electrode layer comprises a set of electrodes arranged to capture charged particles along a trap axis parallel to the central axis and generate a pseudopotential which is symmetrical about the trap axis. 2 . The charged particle trap of claim 1 , wherein the antenna layer is interposed between the substrate and the electrode layer.

3. The charged particle trap of claim 1 or 2, wherein the meander line comprises an odd number of elongated arms, wherein the odd number of elongated arms comprises a middle arm, and the central axis extends along the middle arm.

4. The charged particle trap of claim 1 or 2, wherein the meander line comprises an even number of elongated arms, wherein the even number of elongated arms comprises a pair of middle arms, and the central axis extends between the pair of middle arms.

5. The charged particle trap of any one of claims 1 to 4, wherein the conductive meander line has a width between 5 and 500 μm. 6 . The charged particle trap according to claim 1 , wherein the conductive meander line has a thickness t between 0.3 μm and 2 μm.

7. The charged particle trap of any one of claims 1 to 6, wherein the electrically conductive meander line comprises a superconducting material.

8. The charged particle trap according to any one of claims 1 to 7, wherein the layer structure further comprises: A conductive layer is interposed between the antenna layer and the electrode layer.

9. The charged particle trap according to any one of claims 1 to 8, wherein the layer structure further comprises: A conductive connection layer is interposed between the antenna layer and the electrode layer.

10. The charged particle trap of any one of claims 1 to 9, wherein the electrically conductive meander wires are arranged to extend in a bundle of two or more parallel strands, and wherein three or more bundles are symmetrical about the center line.

11. A charged particle trap according to any one of claims 1 to 10, wherein the set of electrodes comprises a shielding effectiveness S = 20 log 10 [B0' / B1']≤20dB, wherein B0' is the magnetic field gradient at the charged particle when captured by the charged particle trap in the absence of the set of surface electrodes, and B1' is the magnetic field gradient at the charged particle when captured by the charged particle trap in the presence of the set of surface electrodes.

12. A quantum information processing system, comprising: A charged particle trap, the charged particle trap comprising: substrate; and A layer structure is provided on the substrate, the layer structure comprising: an antenna layer; and Electrode layer, wherein the antenna layer comprises at least three elongated arms that are parallel and coplanar and symmetrical about a central axis, and wherein the electrode layer comprises a set of electrodes arranged to capture charged particles along a trap axis parallel to the central axis and to generate a pseudopotential that is symmetrical about the trap axis; and a control system for controlling the charged particle trap, for applying a bias voltage to the set of electrodes to trap at least one ion, and for performing at least one quantum logic gate on the at least one charged particle, Wherein the control system is arranged to drive currents through the at least three elongated arms such that each current has a respective phase and the currents are symmetrical about the central axis.

13. The quantum information processing system of claim 12, wherein the control system comprises at least two bias voltage sources.

14. The quantum information processing system according to claim 12 or 13, wherein the control system comprises: N bias sources, Each of the N bias sources is arranged to drive a respective current having a respective phase through a respective elongated arm or through at least two adjacent parallel strands of a respective bundle.

15. The quantum information processing system according to claim 12 or 13, wherein the control system comprises: first and second bias voltage sources, Wherein the first bias source is arranged to drive a first current having a first phase through at least two adjacent parallel strands of at least one arm of the first group or at least one bundle of the first group, and the second bias source is arranged to drive a second current having a second phase through at least two adjacent parallel strands of at least one arm of the first group or at least one bundle of the first group.

16. A quantum information processing system, comprising: A charged particle trap according to any one of claims 1 to 11; as well as A control system for controlling the charged particle trap, for applying a bias to the set of electrodes to trap at least one ion, and for performing at least one quantum logic gate on the at least one charged particle.

17. The quantum control information processing system according to any one of claims 12 to 16, wherein the control system is configured to pass a current having a frequency less than or equal to 1 GHz through the conductive meander line.

18. A method of operating a charged particle trap according to any one of claims 1 to 11 or a quantum information processing system according to any one of claims 12 to 17, the method comprising: capturing at least one charged particle in the trap, each charged particle providing a corresponding quantum bit; Prepare initial qubit state; as well as applying a sequence of one or more gates to the qubit; Wherein applying the sequence of one or more gates to the quantum bit comprises driving a current having a frequency less than or equal to 1 GHz through the conductive meander or wire.

19. The method according to claim 18, further comprising: Read out the qubit state.

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