Coupling control method and device of xmon type superconducting quantum bit, equipment and medium

Abstract

The embodiment of the specification discloses a coupling control method, device and equipment of an Xmon type superconducting quantum bit and a medium. The method comprises the following steps: coupling two ends of a half-wavelength superconducting cavity with Xmon type superconducting quantum bits based on capacitance, and embedding a superconducting quantum interference device at a middle position of the half-wavelength superconducting cavity, wherein the distance between the Xmon type superconducting quantum bits is greater than a preset threshold, so that the direct coupling between the Xmon type superconducting quantum bits is lower than a preset influence value; acquiring the frequency of each Xmon type superconducting quantum bit through a reading cavity connected with each Xmon type superconducting quantum bit; adjusting the frequency of an adjustable cavity mode of the half-wavelength superconducting cavity according to a preset magnetic flux applied to the superconducting quantum interference device; and controlling the indirect coupling of the Xmon type superconducting quantum bits by adjusting the frequency difference between the adjustable cavity mode of the half-wavelength superconducting cavity and each Xmon type superconducting quantum bit, so as to realize the indirect coupling or disconnection between the Xmon type superconducting quantum bits.

Description

Technical Field

[0001] This specification relates to the field of quantum computing technology, and in particular to a coupling control method, device, equipment and medium for Xmon-type superconducting qubits. Background Technology

[0002] As transistor chips shrink to near their limits, the computational performance of classical computers is also reaching its peak. Quantum computing, as a potential alternative to existing classical computers, has been extensively studied in its principles and related algorithms since the last century. In mathematical problems such as large prime number factorization and global search, quantum computing offers a fundamental speed advantage. Scientists have now established different quantum systems and implemented some simple quantum algorithms, among which superconducting quantum computing is the most promising.

[0003] In quantum computing systems, achieving high-fidelity single-qubit gates and two-qubit CZ gates is of paramount importance. In superconducting quantum computing systems, single-qubit gates in existing Xmon designs have already achieved fidelity exceeding 99.5%, meeting the requirements of many quantum algorithms. However, in existing multi-qubit systems, direct coupling between adjacent qubits easily leads to ZZ crosstalk and magnetic flux noise, thus affecting the fidelity of CZ gates in multi-qubit systems.

[0004] Therefore, there is a need for a coupling control method for Xmon-type superconducting qubits with improved fidelity. Summary of the Invention

[0005] This specification provides one or more embodiments of a coupling control method, apparatus, device, and medium for Xmon-type superconducting qubits, which addresses the following technical problem: how to provide a coupling control method for Xmon-type superconducting qubits that can improve fidelity.

[0006] One or more embodiments of this specification employ the following technical solutions:

[0007] This specification provides one or more embodiments of a coupling control method for Xmon-type superconducting qubits, the method comprising:

[0008] The two ends of a half-wavelength superconducting cavity are capacitively coupled to Xmon-type superconducting qubits, and a superconducting quantum interference device is embedded in the middle of the half-wavelength superconducting cavity; wherein the distance between the Xmon-type superconducting qubits is greater than a preset threshold, so that the direct coupling between the Xmon-type superconducting qubits is lower than a preset influence value;

[0009] The frequency of each Xmon-type superconducting quantum bit is obtained through a readout cavity connected to each of the Xmon-type superconducting quantum bits;

[0010] The frequency of the tunable cavity mode of the half-wavelength superconducting cavity is adjusted according to the preset magnetic flux applied to the superconducting quantum interference device.

[0011] By adjusting the frequency difference between the tunable cavity mode of the half-wavelength superconducting cavity and the frequency of each Xmon-type superconducting quantum bit, the indirect coupling of the Xmon-type superconducting quantum bits is controlled, thereby achieving indirect coupling or disconnection between the Xmon-type superconducting quantum bits.

[0012] Furthermore, in one or more embodiments of this specification, the superconducting quantum interference device has a DC bias line;

[0013] After embedding the superconducting quantum interference device into the middle position of the half-wavelength superconducting cavity, the method further includes:

[0014] The distance between the DC bias line and the Xmon superconducting quantum bit is adjusted to be greater than a preset distance to reduce the magnetic flux noise of the Xmon superconducting quantum bit.

[0015] Furthermore, in one or more embodiments of this specification, adjusting the frequency of the tunable cavity mode of the half-wavelength superconducting cavity according to the preset magnetic flux applied to the superconducting quantum interference device specifically includes:

[0016] By adjusting the current in the DC bias line inside the superconducting quantum interference device (SQU), the magnetic flux of the SQU can be changed to obtain the preset magnetic flux applied to the SQU.

[0017] The first cavity mode frequency is obtained by controlling one of the adjustable cavity mode frequencies of the half-wavelength superconducting cavity to change according to the preset magnetic flux, while the other cavity mode frequency of the half-wavelength superconducting cavity remains unchanged to obtain the second cavity mode frequency.

[0018] Furthermore, in one or more embodiments of this specification, the indirect coupling of the Xmon-type superconducting qubits is controlled by adjusting the frequency difference between the tunable cavity mode of the half-wavelength superconducting cavity and the frequency of each Xmon-type superconducting qubit, specifically including:

[0019] Based on the first cavity mode frequency and the second cavity mode frequency in the half-wavelength superconducting cavity, indirect coupling between adjacent Xmon type superconducting qubits is induced respectively. The cavity mode frequency with opposite signs of the coupling terms and a difference in coupling strength less than a preset difference threshold is obtained as a preset frequency value.

[0020] If the frequency of the Xmon-type superconducting quantum bit is between the first cavity mode frequency and the second cavity mode frequency, and the first cavity mode frequency is adjusted to the preset frequency value, then the indirect coupling of the Xmon-type superconducting quantum bit is turned off.

[0021] If the frequency of the Xmon-type superconducting quantum bit is between the first cavity mode frequency and the second cavity mode frequency, and the first cavity mode frequency is not at the preset frequency value, then the indirect coupling of the Xmon-type superconducting quantum bit is activated.

[0022] In one or more embodiments of this specification, before obtaining the frequency of each of the Xmon-type superconducting qubits, the method further includes:

[0023] Obtain the transmission coefficient of the feeder when the Xmon-type superconducting quantum bit is in high power and low power conditions;

[0024] Based on the transmission coefficient, it is determined whether the Xmon-type superconducting quantum bit causes the cavity mode frequency of the half-wavelength superconducting cavity to shift and the direction of shift is the same as the detuning direction. If so, the Xmon-type superconducting quantum bit is in a normal state.

[0025] If not, the Xmon-type superconducting quantum bit is in an abnormal state; wherein, the abnormal state includes: short circuit and open circuit.

[0026] In one or more embodiments of this specification, after controlling the indirect coupling of the Xmon-type superconducting qubits by adjusting the frequency difference between the tunable cavity mode of the half-wavelength superconducting cavity and the frequency of each Xmon-type superconducting qubit to achieve coupling or disconnection between the Xmon-type superconducting qubits, the method further includes:

[0027] The measurement data corresponding to the Xmon-type superconducting quantum bit in different quantum states are obtained, and the control parameters corresponding to the measurement data are obtained; wherein, the control parameters include at least: a first cavity mode frequency, a second cavity mode frequency, and a preset frequency value; the quantum states include: |0> state and |1> state;

[0028] The fidelity of the Xmon-type superconducting quantum bit is determined based on the corresponding measurement data, and a set of correlation relationships containing multiple sets of control parameters and the fidelity is obtained.

[0029] Based on each of the relationships in the aforementioned relationships, control parameters that meet the requirements are determined through a preset maximization function, and a parameter model containing the relationships between multiple sets of control parameters and the fidelity is established based on the control parameters that meet the requirements.

[0030] Based on the set of relationships and the parameter model, candidate optimal control parameters are obtained from the multiple sets of control parameters;

[0031] If the fidelity corresponding to the candidate optimal control parameter is greater than the fidelity of the Xmon-type superconducting quantum bit at the current time, then the control parameters of the Xmon-type superconducting quantum bit are adjusted according to the candidate optimal control parameter.

[0032] In one or more embodiments of this specification, the superconducting quantum interference device is a dc-SQUID superconducting quantum interference device.

[0033] This specification provides one or more embodiments of a coupling control device for Xmon-type superconducting qubits, the device comprising:

[0034] A module is established to capacitively couple both ends of a half-wavelength superconducting cavity to Xmon-type superconducting qubits, and to embed a superconducting quantum interference device (QFID) into the middle of the half-wavelength superconducting cavity; wherein the distance between the Xmon-type superconducting qubits is greater than a preset threshold, so that the direct coupling between the Xmon-type superconducting qubits is lower than a preset influence value;

[0035] The acquisition module is used to acquire the frequency of each Xmon-type superconducting quantum bit through a readout cavity connected to each Xmon-type superconducting quantum bit;

[0036] The adjustment module is used to adjust the frequency of the tunable cavity mode of the half-wavelength superconducting cavity according to the preset magnetic flux applied to the superconducting quantum interference device.

[0037] The control module is used to control the indirect coupling of the Xmon-type superconducting qubits by adjusting the frequency difference between the tunable cavity mode of the half-wavelength superconducting cavity and the frequency of each Xmon-type superconducting qubit, so as to realize the indirect coupling or disconnection between the Xmon-type superconducting qubits.

[0038] This specification provides one or more embodiments of a coupling control device for Xmon-type superconducting qubits, comprising:

[0039] At least one processor; and,

[0040] A memory communicatively connected to the at least one processor; wherein,

[0041] The memory stores instructions executable by the at least one processor, which, when executed by the at least one processor, enable the at least one processor to:

[0042] The two ends of a half-wavelength superconducting cavity are capacitively coupled to Xmon-type superconducting qubits, and a superconducting quantum interference device is embedded in the middle of the half-wavelength superconducting cavity; wherein the distance between the Xmon-type superconducting qubits is greater than a preset threshold, so that the direct coupling between the Xmon-type superconducting qubits is lower than a preset influence value;

[0043] The frequency of each Xmon-type superconducting quantum bit is obtained through a readout cavity connected to each of the Xmon-type superconducting quantum bits;

[0044] The frequency of the tunable cavity mode of the half-wavelength superconducting cavity is adjusted according to the preset magnetic flux applied to the superconducting quantum interference device.

[0045] By adjusting the frequency difference between the tunable cavity mode of the half-wavelength superconducting cavity and the frequency of each Xmon-type superconducting quantum bit, the indirect coupling of the Xmon-type superconducting quantum bits is controlled, thereby achieving indirect coupling or disconnection between the Xmon-type superconducting quantum bits.

[0046] This specification provides one or more embodiments of a non-volatile computer storage medium storing computer-executable instructions, wherein the computer-executable instructions are configured as follows:

[0047] The two ends of a half-wavelength superconducting cavity are capacitively coupled to Xmon-type superconducting qubits, and a superconducting quantum interference device is embedded in the middle of the half-wavelength superconducting cavity; wherein the distance between the Xmon-type superconducting qubits is greater than a preset threshold, so that the direct coupling between the Xmon-type superconducting qubits is lower than a preset influence value;

[0048] The frequency of each Xmon-type superconducting quantum bit is obtained through a readout cavity connected to each of the Xmon-type superconducting quantum bits;

[0049] The frequency of the tunable cavity mode of the half-wavelength superconducting cavity is adjusted according to the preset magnetic flux applied to the superconducting quantum interference device.

[0050] By adjusting the frequency difference between the tunable cavity mode of the half-wavelength superconducting cavity and the frequency of each Xmon-type superconducting quantum bit, the indirect coupling of the Xmon-type superconducting quantum bits is controlled, thereby achieving indirect coupling or disconnection between the Xmon-type superconducting quantum bits.

[0051] The above-described at least one technical solution used in the embodiments of this specification can achieve the following beneficial effects:

[0052] With the aid of a half-wavelength superconducting cavity coupler, the distance between two Xmon-type superconducting qubits can be relatively large, resulting in weaker direct coupling between them. This effectively suppresses ZZ crosstalk-type crosstalk between the qubits. Furthermore, by adjusting the frequency of the half-wavelength superconducting qubits using a superconducting quantum interference device (SQU), the superconducting cavity maintains a high quality factor during qubit gate operations. This allows for the control of interactions between Xmon-type superconducting qubits through indirect coupling via the half-wavelength superconducting cavity without needing to adjust the Xmon qubits themselves. Attached Figure Description

[0053] To more clearly illustrate the technical solutions in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0054] Figure 1 A schematic flowchart illustrating a coupling control method for an Xmon-type superconducting quantum bit provided in an embodiment of this specification;

[0055] Figure 2 A schematic diagram of a tunable coupler structure for an Xmon-type superconducting quantum bit provided in the embodiments of this specification;

[0056] Figure 3 This is a schematic diagram of the internal structure of a half-wave superconducting cavity provided in an embodiment of this specification;

[0057] Figure 4 A schematic diagram illustrating the variation of cavity mode frequency with applied magnetic flux in a superconducting quantum interference device in an application scenario provided by an embodiment of this specification;

[0058] Figure 5 This is a schematic diagram of the internal structure of a coupling control device for an Xmon-type superconducting quantum bit, provided as an embodiment of this specification.

[0059] Figure 6 This is a schematic diagram of the internal structure of a coupling control device for an Xmon-type superconducting quantum bit, provided as an embodiment of this specification.

[0060] Figure 7 This is a schematic diagram of the internal structure of a non-volatile storage medium provided in the embodiments of this specification. Detailed Implementation

[0061] This specification provides a coupling control method, apparatus, device, and medium for Xmon-type superconducting qubits.

[0062] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. Based on the embodiments of this specification, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this specification.

[0063] like Figure 1 As shown in the figure, this specification provides a flowchart illustrating a coupling control method for Xmon-type superconducting qubits. The method includes the following steps:

[0064] S101: The two ends of the half-wavelength superconducting cavity are capacitively coupled to Xmon-type superconducting qubits, and a superconducting quantum interference device is embedded in the middle of the half-wavelength superconducting cavity; wherein the distance between the Xmon-type superconducting qubits is greater than a preset threshold, so that the direct coupling between the Xmon-type superconducting qubits is lower than a preset influence value.

[0065] The fidelity of two-qubit gate operations is crucial for quantum error correction and large-scale unified quantum computing. Currently, the main factors affecting the fidelity of two-qubit gate operations are magnetic flux noise between Xmon-type superconducting qubits and ZZcrosstalk-type crosstalk. Since the main source term of ZZcrosstalk-type crosstalk is proportional to the square of the direct coupling between the two Xmon-type superconducting qubits, reducing the direct coupling strength between the qubits is essential for improving the fidelity of two-qubit gate operations. Therefore, to reduce the direct coupling between the two Xmon-type superconducting qubits, such as... Figure 2 As shown, capacitive coupling is achieved by connecting the two ends of the half-wave superconducting cavity to two Xmon-type superconducting qubits based on capacitors, and as... Figure 3The diagram shows a superconducting quantum interference device (SQUID) embedded in the middle of a half-wavelength superconducting cavity. This allows the cavity to achieve indirect coupling between two qubits directly through frequency detuning of the cavity mode and the qubits, regulated by the SQUID. Simultaneously, it's understood that because the distance between the two Xmon qubits is greater than a preset threshold, the direct coupling between Xmon-type superconducting qubits is below a preset influence value, and can be ignored. This reduces the ZZ crosstalk type crosstalk between qubits caused by direct coupling. It should be noted that the superconducting quantum interference device is a direct-current superconducting quantum interference device (dc-SQUID).

[0066] As mentioned above, the main factors affecting the fidelity of two-qubit gate operations are ZZ crosstalk type crosstalk and magnetic flux noise between Xmon qubits. Therefore, in order to reduce the magnetic flux noise between two-qubit gate operations, in one or more embodiments of this specification, the superconducting quantum interference device (SQUID) has a DC bias line. After embedding the SQUID into the middle position of the half-wavelength superconducting cavity, the method further includes the following step: reducing the magnetic flux noise of the Xmon superconducting qubit by adjusting the distance between the DC bias line and the Xmon superconducting qubit to be greater than a preset distance. For example, adjusting the distance between the DC bias line of the DC-SQUID inductor and the Xmon superconducting qubit to be greater than 2 mm reduces the impact of magnetic flux noise on the Xmon superconducting qubit.

[0067] S102: Obtain the frequency of each Xmon-type superconducting quantum bit through a readout cavity connected to each Xmon-type superconducting quantum bit.

[0068] To avoid the problem of indirect coupling and gate operation failure caused by abnormal connections when two Xmon-type superconducting qubits are indirectly coupled at both ends of a half-wavelength superconducting cavity, the method further includes the following steps before obtaining the frequency of each Xmon-type superconducting qubit in one or more embodiments of this specification:

[0069] First, the transmission coefficients of the feeder of the Xmon-type superconducting qubit are obtained when it is at high and low power. Then, based on the obtained transmission coefficients, it is determined whether the Xmon-type superconducting qubit causes a shift in the cavity mode frequency of the half-wavelength superconducting cavity, and if the shift direction is the same as the detuning direction. If it causes a shift in the cavity mode frequency of the half-wavelength superconducting cavity, and the shift direction is the same as the detuning direction, then the Xmon-type superconducting qubit is in a normal state. If it causes no shift in the cavity mode frequency of the half-wavelength superconducting cavity, or if the shift direction is inconsistent with the detuning direction, then the Xmon-type superconducting qubit is in an abnormal state. It can be understood that abnormal states of the Xmon-type superconducting qubit can include short circuits, open circuits, etc. After testing that two Xmon-type superconducting qubits are in a normal state, in one or more embodiments of this specification, the frequency of each Xmon-type superconducting qubit is obtained through a readout cavity connected to each Xmon-type superconducting qubit. The frequency acquisition process is not limited here.

[0070] S103: Adjust the frequency of the tunable cavity mode of the half-wavelength superconducting cavity according to the preset magnetic flux applied to the superconducting quantum interference device.

[0071] In one or more embodiments of this specification, adjusting the cavity mode frequency of the half-wavelength superconducting cavity according to the preset magnetic flux applied to the superconducting quantum interference device specifically includes the following steps:

[0072] First, by adjusting the current in the DC bias line within the superconducting quantum interference device (SQU), the magnetic flux of the SQU is varied to obtain a preset applied magnetic flux. Then, one of the cavity mode frequencies of the half-wavelength superconducting cavity is controlled to vary according to the preset magnetic flux to obtain the first cavity mode frequency, while the other cavity mode frequency remains constant to obtain the second cavity mode frequency. That is, as follows... Figure 4 As shown, one set of cavity mode frequencies, such as ω3, ω5, and ω7, are controlled to change with magnetic flux, while the other set of cavity mode frequencies, such as ω2, ω4, and ω6, remain fixed and do not change with magnetic flux. It should be noted that the coupler, composed of a superconducting quantum interference device (SQU) and a half-wavelength superconducting cavity, uses only two cavity membranes close to the frequencies of the Xmon-type superconducting qubits. One cavity membrane has an adjustable frequency corresponding to the first cavity mode frequency, while the other has a non-adjustable frequency corresponding to the second cavity mode frequency. One cavity membrane frequency is above the frequencies of the two superconducting qubits, and the other is below the frequencies of the two qubits. The frequency detuning of other cavity membranes with the Xmon qubits is significant, but its impact is negligible.

[0073] S104: By adjusting the frequency difference between the tunable cavity mode of the half-wavelength superconducting cavity and the frequency of each Xmon-type superconducting quantum bit, the indirect coupling of the Xmon-type superconducting quantum bits is controlled to achieve coupling or disconnection between the Xmon-type superconducting quantum bits.

[0074] To avoid the noise effects caused by the direct coupling of Xmon-type superconducting qubits, in the above steps of the embodiments of this specification, a half-wavelength superconducting cavity is added to increase the distance between the two qubits, thereby making the coupling between them very weak. The coupling between the two qubits is an indirect coupling induced by the two modes of the superconducting cavity. In one or more embodiments of this specification, the indirect coupling of Xmon-type superconducting qubits is controlled based on the cavity mode frequency of the half-wavelength superconducting cavity and the frequency of each Xmon-type superconducting qubit, specifically including the following steps:

[0075] First, based on the first and second cavity mode frequencies within the half-wavelength superconducting cavity, indirect coupling between adjacent Xmon-type superconducting qubits is induced. The cavity mode frequency at which the coupling terms have opposite signs and the difference in coupling strength is less than a preset threshold is taken as the preset frequency value. If the frequency of the Xmon-type superconducting qubit falls between the first and second cavity mode frequencies, and the second cavity mode frequency is adjusted to the preset frequency value, then the indirect coupling of the Xmon-type superconducting qubit is closed. It should be noted that when the frequencies of the two qubits are between the two cavity membranes, the signs of the indirect coupling induced by the two cavity membranes will be opposite. However, when the second cavity mode frequency reaches the preset frequency value, i.e., reaches a specific point, the indirect coupling terms induced by the two cavity modes of the two Xmon-type superconducting qubits are of the same magnitude but opposite in direction, thus closing the indirect coupling of the Xmon-type superconducting qubits. If the frequency of an Xmon-type superconducting qubit lies between the first and second cavity mode frequencies, and the second cavity mode frequency is not at the preset frequency value, then the inter-qubit coupling will be enabled, thus activating the indirect coupling of the Xmon-type superconducting qubit. This allows for simultaneous operation between two qubit gates. Compared to traditional single-cavity coupling control methods, the coupling of a dual-cavity half-wavelength superconducting cavity is easier to adjust, resulting in a higher quality factor during qubit gate operation. Furthermore, the half-wavelength superconducting cavity allows for a greater distance between two Xmon-type superconducting qubits, thus weakening the direct coupling and effectively reducing ZZ crosstalk-type crosstalk between them.

[0076] To further improve the coupling of the qubit gate, in one or more embodiments of this specification, the indirect coupling of the Xmon-type superconducting qubits is controlled according to the cavity mode frequency of the half-wavelength superconducting cavity and the frequency of each Xmon-type superconducting qubit. After achieving coupling or disconnection between the Xmon-type superconducting qubits, the method further includes the following steps:

[0077] First, measurement data corresponding to different quantum states of the Xmon-type superconducting quantum bit are obtained, along with the corresponding control parameters. It should be noted that the control parameters include at least the first cavity mode frequency, the second cavity mode frequency, and a preset frequency value. The quantum states include |0> states and |1> states. Then, the fidelity of the Xmon-type superconducting quantum bit is determined based on the corresponding measurement data. Further, based on the relationship between the fidelity and the control parameters, a set of correlation relationships containing multiple sets of relationships between the control parameters and the fidelity is obtained. Based on each correlation relationship, a preset maximization function is used to determine the required control parameters, and a parameter model containing the correlation relationships between multiple sets of control parameters and the fidelity is established based on these required control parameters. For example, using a preset algorithm, each correlation relationship in the correlation relationship set is used as input to the algorithm. By running the algorithm, multiple sets of required control parameters and their corresponding fidelities are obtained, and the correlation relationships between these multiple sets of required control parameters and their corresponding fidelities are stored in the parameter model.

[0078] Then, based on the correlation set and parameter model, candidate optimal control parameters are obtained from multiple sets of control parameters. For example, the control parameters in the correlation set and the qualified control parameters in the parameter model are used as inputs to a preset learning model to obtain candidate control parameters from multiple sets of control parameters. If the fidelity corresponding to the selected candidate optimal control parameter is greater than the fidelity of the Xmon-type superconducting quantum bit at the current moment, then the control parameters of the Xmon-type superconducting quantum bit are adjusted according to the candidate optimal control parameter, thereby further improving the fidelity of the quantum bit.

[0079] like Figure 5 The diagram shows a coupling control device for an Xmon-type superconducting quantum bit provided in an embodiment of this specification. The device includes:

[0080] A module 501 is established to capacitively couple the two ends of a half-wavelength superconducting cavity to Xmon-type superconducting qubits, and to embed a superconducting quantum interference device (QFID) into the middle position of the half-wavelength superconducting cavity; wherein the distance between the Xmon-type superconducting qubits is greater than a preset threshold so that the direct coupling between the Xmon-type superconducting qubits is lower than a preset influence value.

[0081] The acquisition module 502 is used to acquire the frequency of each Xmon-type superconducting quantum bit through a readout cavity connected to each Xmon-type superconducting quantum bit;

[0082] The adjustment module 503 is used to adjust the frequency of the tunable cavity mode of the half-wavelength superconducting cavity according to the preset magnetic flux applied to the superconducting quantum interference device.

[0083] The control module 504 is used to control the indirect coupling of the Xmon-type superconducting qubits by adjusting the frequency difference between the tunable cavity mode of the half-wavelength superconducting cavity and the frequency of each Xmon-type superconducting qubit, so as to realize the coupling or disconnection between the Xmon-type superconducting qubits.

[0084] like Figure 6 The diagram shows a coupling control device for an Xmon-type superconducting quantum bit provided in an embodiment of this specification. The device includes:

[0085] At least one processor 601; and,

[0086] A memory 602 is communicatively connected to the at least one processor 601; wherein,

[0087] The memory 602 stores instructions that can be executed by the at least one processor 601, the instructions being executed by the at least one processor 601 to enable the at least one processor 601 to:

[0088] The two ends of a half-wavelength superconducting cavity are capacitively coupled to Xmon-type superconducting qubits, and a superconducting quantum interference device is embedded in the middle of the half-wavelength superconducting cavity; wherein the distance between the Xmon-type superconducting qubits is greater than a preset threshold, so that the direct coupling between the Xmon-type superconducting qubits is lower than a preset influence value;

[0089] The frequency of each Xmon-type superconducting quantum bit is obtained through a readout cavity connected to each of the Xmon-type superconducting quantum bits;

[0090] The frequency of the tunable cavity mode of the half-wavelength superconducting cavity is adjusted according to the preset magnetic flux applied to the superconducting quantum interference device.

[0091] By adjusting the frequency difference between the tunable cavity mode of the half-wavelength superconducting cavity and the frequency of each Xmon-type superconducting quantum bit, the indirect coupling of the Xmon-type superconducting quantum bits is controlled, thereby achieving coupling or disconnection between the Xmon-type superconducting quantum bits.

[0092] like Figure 7The diagram shown is an internal structure schematic of a non-volatile storage medium provided in an embodiment of this specification. The non-volatile storage medium stores computer-executable instructions, which include:

[0093] The two ends of the half-wavelength superconducting cavity are capacitively coupled to Xmon-type superconducting qubits, and a superconducting quantum interference device is embedded in the middle of the half-wavelength superconducting cavity.

[0094] The frequency of each Xmon-type superconducting quantum bit is obtained through a readout cavity connected to each of the Xmon-type superconducting quantum bits;

[0095] The frequency of the tunable cavity mode of the half-wavelength superconducting cavity is adjusted according to the preset magnetic flux applied to the superconducting quantum interference device.

[0096] By adjusting the frequency difference between the tunable cavity mode of the half-wavelength superconducting cavity and the frequency of each Xmon-type superconducting quantum bit, the indirect coupling of the Xmon-type superconducting quantum bits is controlled, thereby achieving coupling or disconnection between the Xmon-type superconducting quantum bits.

[0097] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the embodiments of apparatus, devices, and non-volatile computer storage media are basically similar to the method embodiments, so the descriptions are relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0098] The foregoing has described specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims may be performed in a different order than that shown in the embodiments and may still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired result. In some embodiments, multitasking and parallel processing are possible or may be advantageous.

[0099] The above description is merely one or more embodiments of this specification and is not intended to limit this specification. Various modifications and variations can be made to the one or more embodiments of this specification by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of one or more embodiments of this specification should be included within the scope of the claims of this specification.

Claims

1. A method of coupling control of an Xmon type superconducting qubit, the method comprising: The method comprises: Two ends of the half-wavelength superconducting cavity are coupled to Xmon type superconducting qubits based on capacitance, and a superconducting quantum interferometer is embedded in the middle position of the half-wavelength superconducting cavity; wherein the distance between the Xmon type superconducting qubits is greater than a preset threshold, so that the direct coupling between the Xmon type superconducting qubits is lower than a preset influence value; The frequency of each Xmon type superconducting qubit is obtained through a reading cavity connected to each Xmon type superconducting qubit; The frequency of the adjustable cavity mode of the half-wavelength superconducting cavity is adjusted according to a preset magnetic flux applied to the superconducting quantum interferometer; The indirect coupling of the Xmon type superconducting qubits is controlled by adjusting the frequency difference between the adjustable cavity mode of the half-wavelength superconducting cavity and each Xmon type superconducting qubit, so as to realize the coupling or disconnection between the Xmon type superconducting qubits; Before obtaining the frequency of each Xmon type superconducting qubit, the method further comprises: The transmission coefficient of the Xmon type superconducting qubit under high power and low power is obtained; And based on the transmission coefficient, it is judged whether the Xmon type superconducting qubit causes the frequency of the adjustable cavity mode of the half-wavelength superconducting cavity to move and the direction of movement is the same as the detuning direction, if yes, the Xmon type superconducting qubit is in normal state; If not, the Xmon type superconducting qubit is in an abnormal state; wherein the abnormal state includes: short circuit, open circuit; After controlling the indirect coupling of the Xmon type superconducting qubits by adjusting the frequency difference between the adjustable cavity mode of the half-wavelength superconducting cavity and each Xmon type superconducting qubit to realize the coupling or disconnection between the Xmon type superconducting qubits, the method further comprises: The measurement data corresponding to the Xmon type superconducting qubit in different quantum states is obtained, and the control parameters corresponding to the measurement data are obtained; wherein the control parameters at least include: first cavity mode frequency, second cavity mode frequency and preset frequency value; the quantum state includes: |0> state, |1> state; The fidelity of the Xmon type superconducting qubit is determined according to the corresponding measurement data, and a correlation relationship set containing the correlation relationship between multiple sets of control parameters and the fidelity is obtained; According to each correlation relationship in the correlation relationship, the control parameters meeting the requirements are determined through a preset maximum function, and a parameter model containing the correlation relationship between multiple sets of control parameters and the fidelity is established based on the control parameters meeting the requirements; According to the correlation relationship set and the parameter model, the candidate optimal control parameters in the multiple sets of control parameters are obtained; If the fidelity corresponding to the candidate optimal control parameters is greater than the fidelity of the Xmon type superconducting qubit at the current time, the control parameters of the Xmon type superconducting qubit are adjusted according to the candidate optimal control parameters.

2. The method of claim 1, wherein, The superconducting quantum interferometer has a direct current bias line; After embedding the superconducting quantum interferometer in the middle position of the half-wavelength superconducting cavity, the method further comprises: Adjusting a distance between the direct current bias line and the Xmon superconducting quantum bit to be greater than a preset distance to reduce magnetic flux noise of the Xmon superconducting quantum bit.

3. The method of claim 1, wherein, The adjusting the frequency of the adjustable cavity mode of the half-wavelength superconducting cavity according to the preset magnetic flux applied to the superconducting quantum interference device specifically comprises: The preset magnetic flux applied to the superconducting quantum interference device is obtained by adjusting a magnetic flux change of the superconducting quantum interference device through a current of a direct current bias line in the superconducting quantum interference device; One of the frequencies of the adjustable cavity mode of the half-wavelength superconducting cavity is changed to obtain a first cavity mode frequency according to the preset magnetic flux, and the other of the frequencies of the cavity mode of the half-wavelength superconducting cavity is fixed to obtain a second cavity mode frequency.

4. The method of claim 3, wherein, The indirect coupling of the Xmon superconducting quantum bit is controlled by adjusting a frequency difference between the frequency of the adjustable cavity mode of the half-wavelength superconducting cavity and the frequency of each Xmon superconducting quantum bit. Based on the first cavity mode frequency and the second cavity mode frequency in the half-wavelength superconducting cavity, the indirect coupling between adjacent Xmon superconducting quantum bits is induced respectively, and a cavity mode frequency, at which a coupling term symbol of the indirect coupling is opposite and a difference of coupling strengths is less than a preset difference threshold, is obtained as a preset frequency value. If the frequency of the Xmon superconducting quantum bit is between the first cavity mode frequency and the second cavity mode frequency, and the first cavity mode frequency is adjusted to be the preset frequency value, the indirect coupling of the Xmon superconducting quantum bit is closed. If the frequency of the Xmon superconducting quantum bit is between the first cavity mode frequency and the second cavity mode frequency, and the first cavity mode frequency is not at the preset frequency value, the indirect coupling of the Xmon superconducting quantum bit is opened.

5. The method of claim 1, wherein, The superconducting quantum interference device is a dc-SQUID superconducting quantum interference device.

6. A coupled control device for an Xmon type superconducting qubit, comprising: The device comprises: The establishing module is configured to couple two ends of a half-wavelength superconducting cavity to Xmon superconducting quantum bits based on capacitance, and embed a superconducting quantum interference device in a middle position of the half-wavelength superconducting cavity, wherein a distance between the Xmon superconducting quantum bits is greater than a preset threshold, so that direct coupling between the Xmon superconducting quantum bits is lower than a preset influence value; The obtaining module is configured to obtain a frequency of each Xmon superconducting quantum bit through a readout cavity connected to each Xmon superconducting quantum bit; The adjusting module is configured to adjust a frequency of an adjustable cavity mode of the half-wavelength superconducting cavity according to a preset magnetic flux applied to the superconducting quantum interference device; The control module is configured to control indirect coupling of the Xmon superconducting quantum bit by adjusting a frequency difference between the frequency of the adjustable cavity mode of the half-wavelength superconducting cavity and the frequency of each Xmon superconducting quantum bit, so as to realize coupling or disconnection between the Xmon superconducting quantum bits. Before obtaining the frequency of each Xmon superconducting quantum bit, the method further comprises: Obtaining a transmission coefficient of a lower feed line when the Xmon superconducting quantum bit is in a high power state and a low power state. and based on the transmission coefficient, judging whether the Xmon type superconducting quantum bit causes the frequency of the adjustable cavity mode of the half-wavelength superconducting cavity to move in the same direction as the detuning direction, and if so, the Xmon type superconducting quantum bit is in a normal state; if not, the Xmon type superconducting quantum bit is in an abnormal state; wherein the abnormal state includes: short circuit, open circuit; By adjusting the frequency difference between the adjustable cavity mode of the half-wavelength superconducting cavity and each Xmon type superconducting quantum bit, the indirect coupling of the Xmon type superconducting quantum bit is controlled to realize the coupling or disconnection between the Xmon type superconducting quantum bits, and further comprising: obtaining measurement data corresponding to different quantum states of the Xmon type superconducting quantum bit, and obtaining control parameters corresponding to the measurement data; wherein the control parameters at least include: first cavity mode frequency, second cavity mode frequency and preset frequency value; the quantum state includes: |0> state, |1> state; According to the corresponding measurement data, the fidelity of the Xmon type superconducting quantum bit is determined, and a correlation set containing the correlation between multiple sets of control parameters and the fidelity is obtained; According to each correlation in the correlation, the required control parameters are determined by a preset maximum function, and a parameter model containing the correlation between multiple sets of control parameters and the fidelity is established based on the required control parameters; According to the correlation set and the parameter model, candidate optimal control parameters in the multiple sets of control parameters are obtained; If the fidelity corresponding to the candidate optimal control parameters is greater than the fidelity of the Xmon type superconducting quantum bit at the current time, the control parameters of the Xmon type superconducting quantum bit are adjusted according to the candidate optimal control parameters.

7. A coupled control device for an Xmon-type superconducting qubit, comprising: The device comprises: at least one processor; and a memory connected in communication with the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to: couple the two ends of the half-wavelength superconducting cavity to the Xmon type superconducting quantum bit based on capacitance, and embed the superconducting quantum interference device into the middle position of the half-wavelength superconducting cavity; wherein the distance between the Xmon type superconducting quantum bits is greater than a preset threshold, so that the direct coupling between the Xmon type superconducting quantum bits is lower than a preset impact value; obtain the frequency of each Xmon type superconducting quantum bit through the reading cavity connected with each Xmon type superconducting quantum bit; adjust the frequency of the adjustable cavity mode of the half-wavelength superconducting cavity according to the preset magnetic flux applied to the superconducting quantum interference device; By adjusting the frequency difference between the adjustable cavity mode of the half-wavelength superconducting cavity and each Xmon type superconducting quantum bit, the indirect coupling of the Xmon type superconducting quantum bit is controlled to realize the coupling or disconnection between the Xmon type superconducting quantum bits; Before obtaining the frequency of each Xmon type superconducting quantum bit, further comprising: acquire transmission coefficients of the underfeed line when the Xmon type superconducting quantum bits are in high power and low power; and based on the transmission coefficients, determine whether the Xmon type superconducting quantum bits cause the frequency of the adjustable cavity mode of the half-wave superconducting cavity to move in the same direction as the detuning direction, if so, the Xmon type superconducting quantum bits are in a normal state; if not, the Xmon type superconducting quantum bits are in an abnormal state; wherein the abnormal state includes: short circuit, open circuit; By adjusting the frequency difference between the adjustable cavity mode of the half-wave superconducting cavity and each Xmon type superconducting quantum bit, the indirect coupling of the Xmon type superconducting quantum bits is controlled to realize the coupling or disconnection between the Xmon type superconducting quantum bits, and further comprising: acquire the measurement data corresponding to the Xmon type superconducting quantum bits in different quantum states, and acquire the control parameters corresponding to the measurement data; wherein the control parameters at least include: first cavity mode frequency, second cavity mode frequency and preset frequency value; the quantum state includes: |0> state, |1> state; According to the corresponding measurement data, the fidelity of the Xmon type superconducting quantum bits is determined, and a correlation relationship set containing the correlation relationship between multiple sets of control parameters and the fidelity is obtained; According to each correlation relationship in the correlation relationship, the required control parameters are determined by a preset maximum function, and a parameter model containing the correlation relationship between multiple sets of control parameters and the fidelity is established based on the required control parameters; According to the correlation relationship set and the parameter model, the candidate optimal control parameters in the multiple sets of control parameters are acquired; If the fidelity corresponding to the candidate optimal control parameters is greater than the fidelity of the Xmon type superconducting quantum bits at the current time, the control parameters of the Xmon type superconducting quantum bits are adjusted according to the candidate optimal control parameters.

8. A non-transitory storage medium storing computer-executable instructions, the computer-executable instructions comprising: The computer executable instructions include: The two ends of the half-wave superconducting cavity are respectively coupled with the Xmon type superconducting quantum bits based on the capacitance, and the superconducting quantum interference device is embedded in the middle position of the half-wave superconducting cavity; wherein the distance between the Xmon type superconducting quantum bits is greater than a preset threshold, so that the direct coupling between the Xmon type superconducting quantum bits is lower than a preset influence value; The frequency of each Xmon type superconducting quantum bit is acquired through the reading cavity connected with each Xmon type superconducting quantum bit; According to the preset magnetic flux applied to the superconducting quantum interference device, the frequency of the adjustable cavity mode of the half-wave superconducting cavity is adjusted; By adjusting the frequency difference between the adjustable cavity mode of the half-wave superconducting cavity and each Xmon type superconducting quantum bit, the indirect coupling of the Xmon type superconducting quantum bits is controlled to realize the coupling or disconnection between the Xmon type superconducting quantum bits; Before acquiring the frequency of each Xmon type superconducting quantum bit, further comprising: acquire transmission coefficients of the underfeed line when the Xmon type superconducting quantum bits are in high power and low power; And based on the transmission coefficient, judge whether the Xmon type superconducting quantum causes the frequency of the adjustable cavity mode of the half-wave superconducting cavity to move and the direction of movement is the same as the detuning direction, if so, the Xmon type superconducting quantum bit is in normal state; If not, the Xmon type superconducting quantum bit is in abnormal state; wherein, the abnormal state includes: short circuit, open circuit; By adjusting the frequency difference between the adjustable cavity mode of the half-wave superconducting cavity and each Xmon type superconducting quantum bit, the indirect coupling of the Xmon type superconducting quantum bit is controlled, so that after the coupling or disconnection between the Xmon type superconducting quantum bits, the following is included: Obtain the measurement data corresponding to the Xmon type superconducting quantum bit in different quantum states, and obtain the control parameters corresponding to the measurement data; wherein, the control parameters at least include: first cavity mode frequency, second cavity mode frequency and preset frequency value; the quantum state includes: |0> state, |1> state; According to the corresponding measurement data, determine the fidelity of the Xmon type superconducting quantum bit, obtain the association relationship set containing the association relationship between multiple groups of control parameters and the fidelity; According to each association relationship in the association relationship, determine the control parameter meeting the requirements through the preset maximum function, and establish the parameter model containing the association relationship between multiple groups of control parameters and the fidelity based on the control parameter meeting the requirements; According to the association relationship set and the parameter model, obtain the candidate optimal control parameter in the multiple groups of control parameters; If the fidelity corresponding to the candidate optimal control parameter is greater than the fidelity of the Xmon type superconducting quantum bit at the current time, adjust the control parameter of the Xmon type superconducting quantum bit according to the candidate optimal control parameter.

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