Charged particle trap operation

Abstract

A method of operating a charged particle trap (3) comprising a set of trap electrodes (121, 122, 12N) is provided. The method comprises: capturing a first charged particle (11) at a first location (41), the first charged particle providing a first qubit (21) having a first transition frequency (f1); and trapping a second charged particle (12) at a second location (42), the second charged particle providing a second qubit (21) having a second transition frequency. The method comprises applying a potential gradient (11) to the first charged particle and the second charged particle, where the first charged particle and the second charged particle experience potential gradients of first and second sizes (g1, g2), respectively, and where the potential gradients oscillate at a given frequency (fG) and are monochromatic. The method comprises: applying a first oscillating potential to the first electrode (121) at a first given frequency (fE1) while applying the potential gradient in order to apply a first oscillating electric field (141) to the first charged particle; and applying a second oscillating potential to the second electrode (122) at a second frequency (fE2) in order to apply a second oscillating electric field to the second charged particles.

Description

Technical Field

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

[0002] Quantum computing architectures require the ability to control individual qubits. Typically, this is achieved using spatially varying control fields, whereby each qubit experiences a different, locally tunable coupling.

[0003] In trapped ion architectures, two main approaches are used, focused laser beams and spatially varying magnetic fields. However, generating highly controlled localized laser or magnetic fields on a large scale is challenging. Therefore, a common approach for processing single-qubit operations is to employ fields that are not completely local and manipulate the ions, i.e., move them in and out of the region where the field is applied. In this so-called "shuttle-based" approach, single-qubit operations involve shuttling the ions and applying laser or magnetic pulses.

[0004] These approaches may have one or more disadvantages. For example, ion shuttling is slow due to the need for filtering control electrodes, and this results in a bottleneck for performing single qubit operations. Furthermore, simply shuttling ions within a field generated by a single source does not allow for individual phase control. Therefore, in order to efficiently operate N qubits in parallel, O(N) individually adjustable laser or magnetic field sources are typically required. Integrating these sources into an ion trap system is challenging and resource intensive.

[0005] “Individual addressing of trapped ion qubits with geometric phase gates” by RT Sutherland, R. Srinivas, and DTC Allcock (June 14, 2022), available from https: / / arxiv.org / pdf / 2206.06546.pdf, describes a scheme for individually addressing trapped ion qubits, selecting them by the frequency of their motion. In the scheme, one ion serves as a “target” qubit and the other as a “spectator” qubit. The two qubits are driven by a pair of two-color microwave fields and a radio frequency B-field gradient, which produces a three-color potential gradient. Summary of the invention

[0006] According to a first aspect of the present invention, there is provided a method for operating a charged particle trap, the charged particle trap comprising a set of trap electrodes. The method comprises: trapping a first charged particle at a first position, the first charged particle providing a first quantum bit having a first transition frequency; and trapping a second charged particle at a second position, the second charged particle having a second transition frequency.

[0007] The method includes applying a potential gradient to a first charged particle and a second charged particle, wherein the first charged particle and the second charged particle experience a potential gradient of a first magnitude and a second magnitude, respectively, and the potential gradient oscillates at a given frequency and is substantially monochromatic. The method includes: while applying the potential gradient, applying a first oscillating potential to a first electrode at a first frequency so as to apply a first oscillating electric field to the first charged particle; and applying a second oscillating potential to a second electrode at a second frequency so as to apply a second oscillating electric field to the second charged particle.

[0008] The first oscillating electric field is preferably applied locally to the first charged particles and the second oscillating electric field is preferably applied locally to the second charged particles.

[0009] The first transition frequency and the second transition frequency may be different. The first frequency and the second frequency (of the oscillating potential) may be different.

[0010] The potential gradient may be applied for a longer time than the first oscillating potential and the second oscillating potential, or vice versa.

[0011] The first oscillating electric field may have a first phase value, and the second oscillating electric field may have a second, different phase value.The phase of the quantum gate (ie, the axis of rotation on the Bloch sphere) may be adjusted by changing the phase of the oscillating electric field relative to the phase of the potential gradient.

[0012] Applying the potential gradient may include applying at least one magnetic field gradient and / or a laser field to the first charged particles and the second charged particles.

[0013] The method may further include applying a charge drive to the first charged particles and the second charged particles.

[0014] Applying the electric potential gradient to the first charged particles and the second charged particles may include driving an oscillating current through an elongated conductive element for generating at least one magnetic field.

[0015] The elongated conductive element may include a first segment and a second segment, wherein the first segment and the second segment of the elongated conductive element are not collinear. The elongated conductive element may include driving a first oscillating current through the first elongated conductive element, and driving a second oscillating current through a second elongated conductive element spaced apart from the first elongated conductive element.

[0016] The charged particle trap may include a substrate having a major surface.

[0017] At least a first group of well electrodes or all well electrodes in the group of well electrodes can be arranged on the main surface or other surface of the substrate. A second group of well electrodes in the group of well electrodes can be supported on a different surface and is not coplanar with the first group of well electrodes. The charged particle trap can include at least one elongated conductive element, which can be arranged on the main surface or other surface of the substrate for generating at least one magnetic field.

[0018] At least one elongated conductive element may be disposed on a major surface of a substrate. At least one elongated conductive element may be disposed on another surface of a substrate. At least one elongated conductive element may be disposed on a different substrate.

[0019] The set of well electrodes may include a first well electrode array and a second well electrode array, and the at least one elongated conductive element may be interposed between the first well electrode array and the second well electrode array.

[0020] The first well electrode array may include first well electrodes spaced apart along a first direction, the second well electrode array may include second well electrodes spaced apart along the first direction, and the first well electrode array and the second well electrode array are preferably spaced apart along a second direction perpendicular to the first direction.

[0021] An elongated conductive element may be supported on a different surface and may not be coplanar with the first set of well electrodes.

[0022] Applying the electric potential gradient to the first charged particles and the second charged particles may include irradiating the first charged particles and the second charged particles with at least one laser beam.

[0023] The first charged particle may have a given oscillation mode having a given oscillation direction, and the method may include: applying an electric potential gradient so that the electric potential gradient at the first charged particle has a component that is not perpendicular to the given oscillation direction, and the electric potential gradient at the second charged particle has a component that is not perpendicular to the given oscillation direction; applying a first oscillating electric field so that the first oscillating electric field is not perpendicular to the given oscillation direction; and applying a second oscillating electric field so that the second oscillating electric field is not perpendicular to the given oscillation direction.

[0024] The set of well electrodes may include a first electrode and a second electrode. In other words, the well electrodes may be used to provide a local oscillating electric field.

[0025] The method may include: trapping a third charged particle at a third location, the third charged particle providing a third qubit having a third transition frequency; and applying a potential gradient to the third charged particle, wherein the third charged particle experiences a potential gradient of a third magnitude. The method may include: applying a third oscillating potential to a third electrode at a third frequency while applying the potential gradient, so as to apply a third oscillating electric field to the third charged particle.

[0026] The method may include capturing N charged particles, each charged particle being captured at a respective location, each charged particle providing a respective qubit having a respective transition frequency. The method may include applying a potential gradient to the N charged particles, wherein the charged particles experience a potential gradient of corresponding magnitude. The method may include applying a respective oscillating potential to a respective electrode at a respective frequency while applying the potential gradient so as to apply a respective oscillating electric field to the respective charged particle.

[0027] There may be 10 to 1000 charged particles present.

[0028] The charged particles may be ions, such as calcium ions, atoms or molecules with a net charge, electrons or positrons. The charged particles may include different charged particles, such as different ions.

[0029] According to a second aspect of the present invention, there is provided a system comprising a charged particle trap and a control system, the charged particle trap comprising a set of trap electrodes, the control system being used to control the charged particle trap. The control system is configured to: capture a first charged particle at a first position, the first charged particle providing a first quantum bit having a first transition frequency; capture a second charged particle at a second position, the second charged particle having a second transition frequency; apply a potential gradient to the first charged particle and the second charged particle, wherein the first charged particle and the second charged particle experience a potential gradient of a first magnitude and a second magnitude, respectively, and wherein the potential gradient oscillates at a given frequency. The control system is configured to: apply a first oscillating potential to the first electrode at a first frequency while applying the potential gradient, so as to apply a first oscillating electric field to the first charged particle; and apply a second oscillating potential to the second electrode at a second frequency, so as to apply a second oscillating electric field to the second charged particle. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Certain embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0031] Figure 1 is a schematic diagram of ions trapped in an ion trap, with each ion providing its own qubit;

[0032] Figure 2 yes Figure 1A schematic block diagram of a system for independently controlling quantum bits is shown;

[0033] Figure 3 is a flow chart of a method of operating a multi-qubit trapped ion gate including a set of trap electrodes.

[0034] Figure 4 is a schematic perspective view of a first trapped ion gate;

[0035] Figure 5 yes Figure 4 A schematic plan view of a first trapped ion gate is shown;

[0036] Figure 6 is a schematic circuit arrangement for combining a DC signal and an AC signal;

[0037] Figure 7 is a schematic perspective view of a second trapped ion gate; and

[0038] Figure 8 yes Figure 7 A schematic plan view of the second trapped ion gate is shown. DETAILED DESCRIPTION

[0039] introduce

[0040] In the following, methods for performing parallel single-qubit control are described that do not require the use of individually adjustable laser or magnetic field sources. The method does not require local lasers or magnetic fields, nor does it require the ions to be moved in and out of local areas for processing (i.e., areas where local lasers or magnetic fields are applied), thereby improving the speed bottleneck problem associated with ion shuttling. Instead, a global potential gradient (e.g., generated using one or more currents flowing through one or more elongated conductors (e.g., wires or tracks)) can be used in combination with a local oscillating electric field (preferably low frequency (e.g., 0.1 MHz to 20 MHz)). Such an electric field may be easier to locate and apply than a laser or magnetic field. In addition, local control can employ existing trap structures (e.g., surface electrode ion trap electrodes) rather than providing additional dedicated laser or magnetic field sources. These methods are parallelizable, and local control can be achieved by adjusting the amplitude and phase of the local electric field. In other words, the single-qubit rotation phase can be controlled via a locally adjustable electric field phase.

[0041] refer to Figure 1 , showing a plurality of charged particles 11, 12...1 N .

[0042] In this case, the charged particles 11, 12, ... 1 Nare ions. However, a charged particle can be an atom or molecule with a net charge, an electron, or a positron. There may be three or more charged particles11,12...1 N For example, there may be 10 to 1000 charged particles11,12...1 N , that is, 10≤N≤1000. There may be more than 1000 charged particles.

[0043] Each ion 11, 12...1 N Provide their own quantum bits 21, 22, ... 2 N , and are spatially confined to respective positions 41, 42, ... 4 in the ion trap 3. N Each quantum bit 21, 22...2 N There are two states 5, 6 and a transition 7 between the two states 5, 6. Each quantum bit 21, 22...2 N have their own transition frequencies f1, f2, ... f N .

[0044] Also refer to Figure 2 , each qubit 21, 22, ... 2 can be controlled independently using system 8 N .

[0045] The system 8 comprises a potential gradient generator 9 for generating a potential gradient 11. The potential gradient generator 9 may take the form of one or more magnetic field gradient sources and / or laser field sources which generate a potential gradient having an oscillation frequency f G An oscillating magnetic field gradient or laser field 11 that can be globally applied to ions 11, 12, ... 1 N One or more generators 9 may be used to generate the potential gradient 11, although the number of generators 9 is less than the number of ions 11, 12, ... 1 N The number of

[0046] Each ion 11, 12...1 N The experience sizes are g1, g2, ... g N The potential gradient can be in any direction.

[0047] Ion 11, 12...1 N are subjected to a monochromatic (or "single tone") potential gradient 11. Thus, if a single potential gradient generator 9 is used, it is arranged to generate a monochromatic potential gradient 11, and thus the ions 11, 12, ... 1 N A monochromatic potential gradient 11 is seen. However, if more than one potential gradient generator 9 is used, the potential gradient generators 9 are arranged to generate a net potential gradient 11, such as ions 11, 12, ... 1 N As can be seen, the net potential gradient is monochromatic.

[0048] A monochromatic gradient may have one or more benefits, such as making implementation easier and helping to reduce the resulting operating errors. For example, transmitting a single frequency may allow for simple single-point impedance matching.

[0049] The system 8 further comprises a plurality of electrodes 121, 122, ... 12 N and signal sources 131, 132, ... 13 N , which generate oscillating electric fields 141, 142, ... 14 N , these electric fields are applied locally to the corresponding ions 11, 12...1 N Electrodes 121, 122...12 N Can be used to capture ions 11, 12 ... 1 N At least some of the electrodes are identical.

[0050] Also refer to Figure 3 In the single-qubit operation method, the trapped ion qubit 21, 22, ... 2 N Confined in the ion trap 3 (step S1).

[0051] The potential gradient generator 9 is switched on for a period of time t i (Step S2). Each ion 11, 12...1 N The sizes of the experiences are g1, g2, ... g N The magnitude of the potential gradient 11 is proportional to the frequency f G Oscillates. The potential gradient 11 is monochromatic.

[0052] At the same time, signal sources 131, 132, ... 13 N Toward electrodes 121, 122...12 N Apply an oscillation signal (step S3). Each ion 11, 12 ... 1 N Experiencing their respective electric fields 141, 142...14 N , which have their respective frequencies f Ei , amplitude e i and phase k i (where i = 1, 2, ... N). These parameters can be adjusted locally. Local adjustment of phase k i Enables parallel operations to be performed.

[0053] Potential gradient 11 and electric field 141, 142...14 N are simultaneously applied for a period of time t i At the end of this time period, qubits 21, 22, ... 2 N One or more of them may have undergone an addressing operation.

[0054] Examples of systems employing globally applied potential gradients and locally applied electric fields will now be described.

[0055] Systems using magnetic field gradients generated by electric currents

[0056] refer to Figure 4 , a first system 31 for quantum information processing using trapped charged particles 32 is shown.

[0057] The system 31 includes a charged particle trap 33, which may be housed in a vacuum chamber (not shown) that provides an ultra-high vacuum environment allowing the separation of individual charged particles, and a control system 34 for the trap 33.

[0058] In this case, the charged particles 32 take the form of ions, such as calcium ions ( 40 Ca + ). For simplicity, charged particles are also referred to herein as "ions". However, charged particles can take the form of atoms or molecules with a net charge, or elementary charged particles such as electrons or positrons.

[0059] As described above, each ion 32 provides a respective qubit 35 and may be spatially confined at a respective location 36 in the trap 33. Each qubit has two states 37, 38 and a transition 39 between the two states 37, 38. Each qubit 35 has a respective transition frequency f i , which transition frequency can be measured, for example, using Rabi or Ramsey spectroscopy.

[0060] The well 33 takes the form of a surface electrode well and comprises a substrate 40 having an upper surface 41 supporting a plurality of electrodes 42 , 43 , 44 .

[0061] The electrodes 42, 43, 44 include a central electrode 42 in the form of a strip extending along the longitudinal axis 45, and first and second electrodes 431, 432 in the form of corresponding strips extending along either side of the central electrode 42, such that the central electrode 42 is interposed between the first and second electrodes 431, 432. An AC signal of RF frequency is applied to the first and second electrodes 431, 432 (also referred to herein as "first RF electrodes and second RF electrodes") for generating a ponderomotive force confinement potential.

[0062] The electrodes 42, 43, 44 include a set of well electrodes 44 1,1 , 44 1,2 , 44 1,3 , 44 1,4 , 44 1,5 , 44 1,6 , 44 2,1 , 442,2 , 44 2,3 , 44 2,4 , 44 2,5 , 44 2,6 , the set of trap electrodes are arranged in two linear arrays (or “columns” or “rows”) outside the first RF electrode 431 and the second RF electrode 432 .

[0063] Examples of surface electrode traps can be found in WO 2021 / 205145 A1, which is incorporated herein by reference.

[0064] The control system 34 includes a current source 46 for driving an oscillating current I(t) through a center electrode 42 located between a first end 47 and a second end 48. The second end 48 of the center electrode 52 is grounded. As will be explained in more detail, the current source 46 and the center electrode 42 are used to generate an oscillating current I(t) at a frequency f G Oscillating magnetic field 50. Ions experience magnetic field gradients 51 of varying magnitudes ( Figure 5 ).

[0065] The control system 34 includes a first voltage source 521 and a second voltage source 522 for applying signals to the first RF electrode 431 and the second RF electrode 432, respectively, and a control system 34 for applying corresponding signals to the well electrode 44. 1,1 , 44 1,2 , 44 1,3 , 44 1,4 , 44 1,5 , 44 1,6 , 44 2,1 , 44 2,2 , 44 2,3 , 44 2,4 , 44 2,5 , 44 2,6 Voltage source 53 1,1 , 53 1,2 , 53 1,3 , 53 1,4 , 53 1,5 , 53 1,6 , 53 2,1 , 53 2,2 , 53 2,3 , 53 2,4 , 53 2,5 , 53 2,6 Source 50, 521, 522, 53 1,1 , 53 1,2 , 53 1,3 , 53 1,4 , 53 1,5 , 53 1,6 , 53 2,1 , 53 2,2 , 532,3 , 53 2,4 , 53 2,5 , 53 2,6 Controlled by computer system 54.

[0066] Also refer to Figure 5 , the operation of system 31 is described in more detail.

[0067] Two trapped ions 321 , 322 can be addressed in parallel in the surface electrode well 33 .

[0068] The two ions 321, 322 are coupled to a potential gradient source, i.e., the central electrode 42. The potential gradient 51 is generated by passing an oscillating current I(t) through the central electrode 45. By injecting an oscillating voltage into the first electrode 44, respectively 1,1 and the second electrode 44 1,6 The ions 321 and 322 are spaced far enough from each other so that the ... 1,1 to the second ions 322 and from the second electrode 44 1,6 The coupling to the first ion 321 is very small.

[0069] The capture electrode 44 can be used not only to apply a DC electric field used in the capture, but also to apply an oscillating electric field. 1,1 A first DC offset voltage V may be added A and the first oscillating voltage V(t)=V1.cos(2πf E1 +k1), and a first combined voltage is applied to the first electrode 44 1,1 , and the second source 53 1,6 A second DC offset voltage V can be added B and the second oscillating voltage V(t) = V2.cos(2πf E2 +k2) and applying the first combined voltage to the second electrode 44 1,6 .

[0070] refer to Figure 6 , a suitable signal generator arrangement 55 is shown.

[0071] The DC voltage source 56 may include a digital-to-analog converter 57 and an amplifier 58. The voltage source 56 is coupled to the electrode 44 via a low-pass RC filter 59 through a node 60 between the resistor R and the capacitor C. The AC voltage source 61 may include an AC source 62 and an amplifier 63, and an optional series filter 64 coupled to the output of the source 61. The output of the source 61 or the filter 64 (if used) is connected to the node 60, and thus to the electrode.

[0072] Systems using laser-generated electric field gradients

[0073] refer to Figure 7 , a second system 71 using trapped charged particles 72 for quantum information processing is shown.

[0074] The system 71 includes a charged particle trap 73, which may be housed in a vacuum chamber (not shown) that provides an ultra-high vacuum environment allowing the separation of individual charged particles, and a control system 74 for the trap 73.

[0075] In this case, the charged particles 72 take the form of ions, such as calcium ions ( 40 Ca + ). For simplicity, charged particles are also referred to herein as "ions". However, charged particles can take the form of atoms or molecules with a net charge, or elementary charged particles such as electrons or positrons.

[0076] As described above, each ion 72 provides a respective qubit 75 and may be spatially confined at a respective location 76 in the trap 73. Each qubit has two states 77, 78 and a transition 79 between the two states 77, 78. Each qubit 75 has a respective transition frequency f i .

[0077] The well 73 takes the form of a microfabricated surface electrode well and comprises a substrate 80 having an upper surface 81. The well 73 comprises an elongated slot 82 through the substrate 80. On either side of the slot 82, the upper surface of the substrate 80 supports an electrode layer stack 831,832.

[0078] Each electrode stack layer 831, 832 includes a set of lower electrodes 841, 842, 84 1,1 , 84 2,1 (Most of the lower electrodes are Figure 6 or Figure 7 ), dielectric layers 851, 852 and a set of upper electrodes 861, 862, 86 1,1 ,86 1,2 ,86 1,3 ,86 1,4 ,86 1,5 ,86 2,1 ,86 2,2 ,86 2,3 ,86 2,4 ,86 2,5 Each dielectric layer 851 , 852 is interposed between a lower electrode 841 , 842 and an upper electrode 861 , 862 .

[0079] The control system 74 includes a laser 87 for generating a light beam 88 that produces an electric field gradient 89 .

[0080] The control system 74 includes a circuit for applying respective signals to the lower electrodes 84, 84 1,1 , 84 1,2 , 84 1,3 , 84 1,4 , 84 1,5 , 84 2,1 , 84 2,2 , 84 2,3 , 84 2,4 , 84 2,5 The first group of voltage sources 90, 90, 90 1,1 , 90 1,2 , 90 1,3 , 90 1,4 , 90 1,5 , 90 2,1 , 90 2,2 , 90 2,3 , 90 2,4 , 90 2,5 , and for applying respective signals to the upper electrodes 86, 86 1,1 ,86 1,2 ,86 1,3 ,86 1,4 ,86 1,5 ,86 2,1 ,86 2,2 ,86 2,3 ,86 2,4 ,86 2,5 The second group of voltage sources 91, 91 1,1 ,91 1,2 ,91 1,3 ,91 1,4 ,91 1,5 ,91 2,1 ,91 2,2 ,91 2,3 ,91 2,4 ,91 2,5 .

[0081] Sources 87 , 90 , 91 are controlled by a computer system 92 .

[0082] Also refer to Figure 8 , the operation of system 31 is described in more detail.

[0083] A first ion 721 and a second ion 722 are trapped close to each other in a microfabricated ion trap 73. The ions 721, 722 are illuminated by a laser beam 88 used as a gradient source.

[0084] The oscillating electric field is injected into the opposing pair of well electrodes 84 1,2 , 84 1,4 , 84 2,2 , 84 2,4By controlling the phase and amplitude of the voltages injected into the different electrodes, the electric field at the first ion 721 can be zero while creating a desired electric field at the second ion 722. This allows a single qubit rotation to be applied to the ion on the right while leaving the ion on the left unaffected.

[0085] Control using frequency, phase and amplitude

[0086] The method described in this paper allows local but parallel control in two ways. First, the amplitude e i and / or time t i to locally adjust the range or area of ​​the quantum gate. Secondly, the phase k i to locally adjust the phase of the quantum gate.

[0087] The transition frequency f of the i-th quantum bit i is known (e.g. determined by simulation) or can be measured. The oscillation frequency f of the gradient field G and the oscillation frequency f of the local oscillation field Ei Adjusted for the desired operation with the desired speed.

[0088] Calculation and experimental data show that when other parameters are fixed, the single quantum bit coupling rate is proportional to 1 / (f Mi 2 –f Ei 2 ) is proportional to, where f Mi is the frequency of motion of ion i. Therefore, f Ei Set to close to f Mi The coupling efficiency is improved, thereby increasing the operating speed.

[0089] These methods allow the realization of "spin flip" and "phase flip" quantum operations. The choice of operation depends on the gradient field oscillation frequency f G and the electric field oscillation frequency f Ei For example, by setting f Ei =f i ±f G to perform a "spin flip" operation (example values ​​are f i =300MHz, f G =6MHz, f Ei =306MHz), and can be set by Ei =f G to perform a "phase flip" quantum operation.

[0090] resonance

[0091] The operation can be performed using a combination of a potential gradient and an oscillating electric field, or a combination of a potential gradient, carrier drive, and an oscillating electric field. The carrier drive can be generated by (a) an electric field generated by one or more laser beams or (b) a magnetic field. The potential gradient can be generated by (a) one or more laser beams or (b) a magnetic field gradient using one or more sources.

[0092] The first method and the second method of performing the operation may be performed using a combination of a potential gradient and an oscillating electric field. The third method and the fourth method of performing the operation use a combination of a potential gradient, carrier driving, and an oscillating electric field, and are described below.

[0093] The first method is spin flip

[0094] The quantum bit has a transition frequency f i For a frequency of f G The oscillating potential gradient and frequency are f Ei An oscillating electric field can be used to generate a "spin-flip" operation using resonance:

[0095] f G = f i ± f Ei (1)

[0096] Spin flip rate Ω 自旋翻转 Given by:

[0097]

[0098] Among them, Ω sb is the sideband Rabi frequency (which quantifies the effective potential gradient strength), ω r is the oscillation mode (angular) frequency, ω e is the electric field (angular) frequency, and Ω e Given by:

[0099]

[0100] where q is the charge of the ion, E is the electric field component along the oscillation mode, is the reduced Planck constant, and r0 is the ion wave packet size, which can be calculated as follows:

[0101]

[0102] where m is the mass of the ion. As an example, for Ca 40 + ions, where Ω sb =2π×1kHz,ω r =2π×6MHz, the angular frequency is ω e=2π×5MHz oscillating electric field, magnitude is E=10V / m, Ω 自旋翻转 The calculation is 2π×35kHz.

[0103] Second method - phase flip

[0104] The quantum bit has a transition frequency f i For a frequency of f G The oscillating potential gradient and frequency are f Ei The oscillating electric field can be manipulated using resonance to generate a "phase flip":

[0105] f G = f Ei (5)

[0106] The third and fourth methods - spin flip

[0107] Sometimes, spin flipping is desired, but the first method cannot be used because it relies on the use of high frequency potential gradients.

[0108] In the third and fourth methods, in addition to the frequency f G The oscillation gradient and frequency are f Ei In addition to the oscillating electric field of Bi An additional oscillating field in the form of an oscillating magnetic or electric field.

[0109] The additional carrier drive can be applied in a number of different ways including: (a) a magnetic field generated using the same current electrodes used to generate the potential gradient, (b) a magnetic field generated using different electrodes, (c) a magnetic field generated using a remote source such as a microwave horn, (d) a laser field applied from an external laser beam or I, or) a laser field applied through a waveguide of an integrated well.

[0110] Therefore, in the third method, the qubit has a transition frequency f i , then for frequency f G An oscillating gradient field with a frequency of f Ei The oscillating electric field and frequency are f Bi An oscillating magnetic or electric field can be used to generate a "spin flip" using resonance:

[0111] f Bi – f i = m (f E – f G ) (6)

[0112] Here, m is an integer. Therefore, there are many resonances, each of which can be used to generate a spin flip.

[0113] The fourth method is an extension of the second method. Each phase flip operation corresponds to a shift in the frequency of the quantum bit. Therefore, once f G =f Ei , the quantum bit frequency changes from f i Shift to f i +d f , where d f is the qubit frequency shift, which depends on the oscillating electric field frequency f Ei 、Ion motion mode frequency f Mi , oscillation voltage V i , oscillating current I g , the phase difference k between the oscillating voltage and the oscillating current i and the trapping geometry, and can be measured by qubit spectroscopy.

[0114] Once the displacement offset d is calculated and / or measured f , we can apply the Bi =f i ±d f The carrier drive generates the spin flip. In general, the resonance condition is:

[0115] f G = f Ei (7-1)

[0116] f Bi – f i = d f (7-2)

[0117] Among them, d f Is the application G =f Ei The resulting quantum bit frequency shift.

[0118] Change the amplitude i , time t i and phase k i

[0119] The following may help to understand the adjustment of the local applied electric field 141, 142, ... 14 in the first method and the second method described above: N ( Figure 2 ) of the amplitude e i Duration t i and phase k i effect.

[0120] Refer to H. C. Roos and R. Blatt, “Quantum computing with trapped ions” (H. Hafner, C. Roos and R. Blatt, “Quantum computing with trapped ions”) https: / / arxiv.org / pdf / 0809.4368.pdf (2008).

[0121] The operation can be thought of as a single-qubit gate corresponding to a rotation on the Bloch sphere. A rotation about the z-axis is a phase flip, and a rotation about the other axis (i.e., the x-axis or the y-axis) is a spin flip.

[0122] The spin-flip rotation can be represented by the rotation operator R(θ,φ) (see H. C. Roos and R. Blatt (Equation 10, as mentioned above). θ controls the rotation angle and can be considered as the gate area, while φ adjusts the rotation axis and can be considered as the gate phase. The phase-flip rotation can be written as the rotation operator R z (θ).

[0123] In the first method, the rotation achieved is R(θ,φ). The individual applied electric fields 141, 142, ... 14 N The amplitude e i and duration t i To adjust θ, the applied electric fields 141, 142, ... 14 can be changed at the same time. N The phase k i To adjust φ. In the second method, the rotation achieved is Rz(θ). Changing the amplitude e i Duration t i and phase k i To adjust θ.

[0124] Additional Notes

[0125] When the electric field oscillation frequency f Ei The frequency f of the ions moving with the applied electric field Mi The above method works best when close to resonance. Operation For any electric field oscillation frequency f Ei are possible, but the speed of operation depends on the method in question (resonance) and can be 1 / (f Mi –f Ei ) or 1 / (f Mi 2 –f Ei 2 ).

[0126] The method described above has another advantage over methods involving ion transport in that byEi Adjust to f Mi Nearby, the voltage V i Very low.

[0127] Revise

[0128] It will be appreciated that various modifications may be made to the embodiments described above. Such modifications may include equivalent and other features known in the design, manufacture and use of trapped ion gates and components thereof, and 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] Although the claims have been formulated as specific combinations of features in this application, it should be understood that the scope of the disclosure of the present invention also includes any novel features or any novel combination of features disclosed herein explicitly or implicitly, or any generalization thereof, regardless of whether it relates to the same invention as currently claimed in any claim, and regardless of whether it alleviates any or all technical problems that are the same as the technical problems solved by the present invention. The applicant hereby draws attention that new claims may be formulated for these features and / or combinations of these features during the examination of this application or any further application derived therefrom.

Claims

1. A method of operating a charged particle trap comprising a set of trap electrodes, the method comprising: trapping a first charged particle at a first location, the first charged particle providing a first qubit having a first transition frequency; trapping a second charged particle at a second location, the second charged particle having a second transition frequency; applying an electric potential gradient to the first charged particle and the second charged particle, wherein the first charged particle and the second charged particle experience an electric potential gradient of a first magnitude and a second magnitude, respectively, and wherein the electric potential gradient oscillates at a given frequency and is monochromatic; While applying the potential gradient: applying a first oscillating electric potential to the first electrode at a first frequency so as to apply a first oscillating electric field to the first charged particles; as well as A second oscillating electric potential is applied to the second electrode at a second frequency so as to apply a second oscillating electric field to the second charged particles.

2. The method according to claim 1, further comprising: The first oscillating electric field has a first phase value; and / or The second oscillating electric field has a second different phase value.

3. The method according to claim 1 or 2, wherein: The applying the potential gradient comprises: applying at least one magnetic field gradient to the first charged particles and the second charged particles at the given frequency; applying a laser field to the first charged particles and the second charged particles at the given frequency; and / or A first laser field and a second laser field are applied to the first charged particles and the second charged particles, wherein the first laser field and the second laser field have a first laser frequency and a second laser frequency, respectively, and a difference between the first laser frequency and the second laser frequency is equal to the given frequency.

4. The method according to any one of claims 1 to 3, further comprising: Carrier driving is applied to the first charged particles and the second charged particles.

5. The method according to claim 3 or 4, wherein: The applying the potential gradient comprises: An oscillating current is driven through the elongated conductive element for generating the at least one magnetic field.

6. The method according to claim 5, wherein: The elongated conductive element includes a first segment and a second segment, wherein the first segment and the second segment of the elongated conductive element are not co-linear.

7. The method according to claim 3 or 4, wherein: Applying the at least one electric potential gradient to the first charged particles and the second charged particles comprises: driving a first oscillating current through the first elongated conductive element; and A second oscillating current is driven through a second elongated conductive element spaced apart from the first elongated conductive element.

8. The method according to any one of claims 1 to 7, wherein: The charged particle trap comprises a substrate having a major surface, wherein at least a first set of trap electrodes of a set of trap electrodes is disposed on the major surface of the substrate.

9. The method according to claim 8, wherein: A second set of well electrodes in the set of well electrodes is supported on a different surface and is not coplanar with the first set of well electrodes.

10. The method according to claim 8 or 9, wherein: The charged particle trap comprises at least one elongated electrically conductive element for generating the at least one magnetic field.

11. The method according to claim 10, wherein: The set of well electrodes includes a first well electrode array and a second well electrode array, and the at least one elongated conductive element is interposed between the first well electrode array and the second well electrode array.

12. The method according to claim 10, wherein: The one elongated conductive element is supported on a different surface and is non-coplanar with the first set of well electrodes.

13. The method according to any one of claims 1 to 12, wherein: Applying the electric potential gradient to the first charged particles and the second charged particles comprises: The first charged particles and the second charged particles are irradiated with at least one laser beam.

14. The method according to any one of claims 1 to 13, wherein: The first charged particle has a given oscillation mode, the given oscillation mode has a given oscillation direction, and the method comprises: applying the potential gradient so that the potential gradient at the first charged particle has a component that is not perpendicular to the given oscillation direction, and the potential gradient at the second charged particle has a component that is not perpendicular to the given oscillation direction; applying the first oscillating electric field so that the first oscillating electric field is not perpendicular to the given oscillation direction; and The second oscillating electric field is applied such that the second oscillating electric field is not perpendicular to the given oscillation direction.

15. The method according to any one of claims 1 to 14, wherein: The set of well electrodes includes a first electrode and a second electrode.

16. A system, comprising: a charged particle trap, the charged particle trap comprising a set of trap electrodes; as well as a control system, the control system being used to control the charged particle trap; The control system is configured to: trapping a first charged particle at a first location, the first charged particle providing a first qubit having a first transition frequency; trapping a second charged particle at a second location, the second charged particle having a second transition frequency; applying an electric potential gradient to the first charged particle and the second charged particle, wherein the first charged particle and the second charged particle experience an electric potential gradient of a first magnitude and a second magnitude, respectively, and wherein the electric potential gradient oscillates at a given frequency and is monochromatic; While applying the potential gradient: applying a first oscillating electric potential to the first electrode at a first frequency so as to apply a first oscillating electric field to the first charged particles; as well as A second oscillating electric potential is applied to the second electrode at a second frequency so as to apply a second oscillating electric field to the second charged particles.

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