Method and device for controlling coupling relationship between quantum bits, and quantum computer

Abstract

The application discloses a kind of control method, device and quantum computer of coupling relationship between qubits, utilize the scheme of the present application can effectively reduce the coupling strength between the first qubit and the second qubit for executing two-qubit logic gate, and reduce the coupling strength of the adjacent qubit in quantum chip, i.e. third qubit, effectively improve the accuracy of two-qubit logic gate execution, improve the execution accuracy of quantum computer to a certain extent.

Description

Technical Field

[0001] This invention relates to the field of quantum computing technology, and in particular to a method, apparatus, and quantum computer for controlling the coupling relationship between qubits. Background Technology

[0002] Quantum computing and quantum information is an interdisciplinary field that uses the principles of quantum mechanics to perform computational and information processing tasks. It is closely related to quantum physics, computer science, and informatics. It has experienced rapid development in the last two decades. Quantum algorithms based on quantum computers, such as factorization and unstructured search, have demonstrated performance far exceeding that of existing algorithms based on classical computers, leading to expectations that this field will surpass current computing capabilities. Because quantum computing has the potential to far exceed the performance of classical computers in solving specific problems, realizing a quantum computer requires a quantum chip containing a sufficient number and quality of qubits, capable of performing high-fidelity quantum logic gate operations and readouts on these qubits. The quantum chip is to a quantum computer what a CPU is to a traditional computer; it is the core component of a quantum computer, the processor that performs quantum computations. Before each quantum chip is officially put into use, the parameters of the qubits within the chip must be tested and characterized.

[0003] Similar to classical bits, performing quantum computing using qubits inevitably requires applying qubit logic gates. For qubits, these logic gates are essentially a series of control signals, and the accuracy of the parameters of these signals is crucial. Qubit logic gates mainly consist of two types: single-qubit logic gates and two-qubit logic gates. Two-qubit logic gates include, but are not limited to, CNOT gates, SWAP gates, and CZ gates. To ensure the execution of two-qubit logic gates, the coupling strength between the two qubits in the initial state must be minimized.

[0004] Therefore, a scheme is needed to improve the execution accuracy of two-qubit logic gates.

[0005] It should be noted that the information disclosed in the background section of this application is intended only to enhance the understanding of the general background of this application, and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a method, apparatus, and quantum computer for controlling the coupling relationship between qubits, in order to solve the problem that there is no solution in the prior art that can effectively shut off the coupling relationship between two qubits.

[0007] To address the above technical problems, this invention proposes a method for controlling the coupling relationship between qubits, comprising:

[0008] The energy level of the third qubit is adjusted to be far away from the energy levels of the first and second qubits. When the coupling strength between the first and second qubits is 0, the magnetic flux of the first tunable coupler is the first magnetic flux. The first qubit and the second qubit are coupled and connected through the first tunable coupler.

[0009] The magnetic flux of the first tunable coupler is set to the first magnetic flux, and the energy level of the third quantum bit is set to the initial state. When the coupling strength between the second quantum bit and the third quantum bit is 0, the magnetic flux of the second tunable coupler is the second magnetic flux, and the second quantum bit and the third quantum bit are coupled and connected through the second tunable coupler.

[0010] The magnetic flux magnitude of the first adjustable coupler is set to the first magnetic flux, and the magnetic flux magnitude of the second adjustable coupler is set to the second magnetic flux, so as to shut off the coupling between the first qubit, the second qubit, and the third qubit.

[0011] Optionally, the energy level of the third qubit is adjusted by the bit frequency of the third qubit.

[0012] Optionally, obtaining the magnetic flux magnitude of the first tunable coupler as the first magnetic flux when the coupling strength between the first qubit and the second qubit is 0 includes:

[0013] Set one of the two qubits to the |0> state and the |1> state respectively, and use the Ramsey experiment to obtain the frequency of the other qubit. The two qubits are the first qubit and the second qubit.

[0014] Based on the two frequencies obtained, the coupling strength between the first qubit and the second qubit is obtained as a first value;

[0015] Determine whether the first value is 0. If it is, obtain the magnetic flux of the first adjustable coupler at this time as the first magnetic flux.

[0016] If not, adjust the magnetic flux of the first tunable coupler and return to the step of setting one of the two qubits to the |0> state and the |1> state respectively, and using the Ramsey experiment to obtain the frequency of the other qubit.

[0017] Optionally, obtaining the coupling strength between the first qubit and the second qubit as a first value based on the two obtained frequencies includes:

[0018] The difference between the two frequencies is obtained, and the difference is divided by two to obtain the coupling strength between the first qubit and the second qubit.

[0019] Optionally, when the coupling strength between the second qubit and the third qubit is 0, the magnetic flux magnitude of the second tunable coupler is the second magnetic flux, including:

[0020] One of the two qubits is set to the |0> state and the |1> state respectively. The frequency of the other qubit is obtained by the Ramsey experiment. The two qubits are the second qubit and the third qubit.

[0021] Based on the two frequencies obtained, the coupling strength between the second quantum bit and the third quantum bit is obtained as a second value;

[0022] Determine if the second value is 0. If it is, obtain the magnetic flux magnitude of the second adjustable coupler at this time as the second magnetic flux.

[0023] If not, adjust the magnetic flux of the second tunable coupler and return to the step of setting one of the two qubits to the |0> state and the |1> state respectively, and using the Ramsey experiment to obtain the frequency of the other qubit.

[0024] Optionally, after setting the magnetic flux magnitude of the first adjustable coupler to a first magnetic flux and the magnetic flux magnitude of the second adjustable coupler to a second magnetic flux, the method further includes:

[0025] Obtain the coupling strength between the first qubit and the second qubit. If the coupling strength between the first qubit and the second qubit is not 0 at this time, update the value of the first magnetic flux and return to execute the step of setting the magnetic flux size of the first adjustable coupler to the first magnetic flux and the magnetic flux size of the second adjustable coupler to the second magnetic flux.

[0026] Based on the same inventive concept, this invention also proposes a control device for the coupling relationship between qubits, comprising:

[0027] The first magnetic flux acquisition unit is configured to adjust the energy level of the third qubit to be away from the energy levels of the first qubit and the second qubit, and to acquire the magnetic flux magnitude of the first tunable coupler when the coupling strength between the first qubit and the second qubit is 0. The first qubit and the second qubit are coupled and connected through the first tunable coupler.

[0028] The second magnetic flux acquisition unit is configured to set the magnetic flux of the first tunable coupler to the first magnetic flux, and set the energy level of the third quantum bit to the initial state. When the coupling strength between the second quantum bit and the third quantum bit is 0, the magnetic flux magnitude of the second tunable coupler is the second magnetic flux, and the second quantum bit and the third quantum bit are coupled and connected through the second tunable coupler.

[0029] A coupling shutdown unit is configured to set the magnetic flux magnitude of the first adjustable coupler to a first magnetic flux and the magnetic flux magnitude of the second adjustable coupler to a second magnetic flux to shut off the coupling between the first qubit, the second qubit, and the third qubit.

[0030] Based on the same inventive concept, the present invention also proposes a quantum control system, which utilizes a control method for the coupling relationship between qubits described in any of the above-described features, or a control device that includes the coupling relationship between qubits described in the above-described features.

[0031] Based on the same inventive concept, the present invention also proposes a quantum computer, including the quantum control system described in the above feature description.

[0032] Based on the same inventive concept, the present invention also proposes a readable storage medium storing a computer program thereon, which, when executed by a processor, can implement the method for controlling the coupling relationship between qubits as described in any of the above-described features.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The method for controlling the coupling relationship between qubits proposed in this invention first adjusts the energy level of the third qubit to distance it from the energy levels of the first and second qubits. When the coupling strength between the first and second qubits is 0, the magnetic flux of the first tunable coupler is set to the first magnetic flux. Then, the magnetic flux of the first tunable coupler is set to the first magnetic flux, and the energy level of the third qubit is set to its initial state. When the coupling strength between the second and third qubits is 0, the magnetic flux of the second tunable coupler is set to the second magnetic flux. Finally, the magnetic flux of the first tunable coupler is set to the first magnetic flux, and the magnetic flux of the second tunable coupler is set to the second magnetic flux, thereby shutting off the coupling between the first, second, and third qubits. Using this solution, the coupling strength between the first and second qubits used to execute two-qubit logic gates can be effectively reduced, and the coupling strength with the neighboring qubit (the third qubit) in the quantum chip can also be reduced, effectively improving the execution accuracy of the two-qubit logic gates and, to a certain extent, improving the execution precision of the quantum computer.

[0035] The control device, quantum control system, quantum computer, and readable storage medium for the coupling relationship between qubits proposed in this invention belong to the same inventive concept as the control method for the coupling relationship between qubits, and therefore have the same beneficial effects, which will not be elaborated here. Attached Figure Description

[0036] Figure 1 This is a flowchart illustrating the method for controlling the coupling relationship between qubits proposed in an embodiment of the present invention.

[0037] Figure 2 This is a simplified structural diagram of a quantum chip proposed in an embodiment of the present invention;

[0038] Figure 3 This is a simplified structural diagram of the control device for the coupling relationship between qubits proposed in this invention. Detailed Implementation

[0039] The specific embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. The advantages and features of the present invention will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0040] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0041] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0042] To better understand the technical solution of this application, the Ramsey experiment involved in this application will be briefly described below:

[0043] The Ramsey experiment involves applying two π / 2 quantum logic gate operations to a qubit, with a time interval τ between the two operations. A readout pulse is then applied to the qubit after the second π / 2 quantum logic gate operation to obtain the excited state distribution P1(τ). The process of changing the time interval τ to obtain P1(τ) is repeated. A typical Ramsey experiment shows that P1(τ) decays exponentially with time interval τ, as shown in the following mathematical model:

[0044]

[0045] In Equation 1, A and B are fitting coefficients, T0 is the decoherence time of the qubit, and f d Let f0 be the carrier frequency of the microwave pulse signal corresponding to the π / 2 quantum logic gate operation, and f0 be the oscillation frequency of the qubit. Furthermore, f0 is related to the actual frequency f0 of the qubit. q The carrier frequency of π / 2 quantum logic gate operations satisfies:

[0046] f0(f d )=f q -f d (2)

[0047] In summary and in conjunction with Formula 2, we can obtain the results of the Ramsey experiment, namely, that the oscillation frequency of the curve is equal to the difference between the carrier frequency of the quantum logic gate operation and the true frequency of the qubit. Therefore, in addition to obtaining the decoherence time of the qubit, the Ramsey experiment can also accurately obtain the true frequency of the qubit at the same time.

[0048] Those skilled in the art will understand that, to ensure the execution of a two-qubit logic gate, the two qubits need to be set to an initial state. If there is still a significant coupling between the two qubits at this point, crosstalk will inevitably lead to inaccurate initial state settings, ultimately affecting the execution result of the two-qubit logic gate. Therefore, we need to minimize the coupling strength between the two qubits in the initial state as much as possible.

[0049] Please refer to Figure 1 This invention proposes a method for controlling the coupling relationship between qubits, comprising:

[0050] S100: Adjust the energy level of the third quantum bit to be far away from the energy levels of the first quantum bit and the second quantum bit, and obtain the magnetic flux magnitude of the first adjustable coupler when the coupling strength between the first quantum bit and the second quantum bit is 0. The first quantum bit and the second quantum bit are coupled and connected through the first adjustable coupler.

[0051] S200: Set the magnetic flux of the first tunable coupler to the first magnetic flux, and set the energy level of the third quantum bit to the initial state. When the coupling strength between the second quantum bit and the third quantum bit is 0, the magnetic flux of the second tunable coupler is the second magnetic flux, and the second quantum bit and the third quantum bit are coupled and connected through the second tunable coupler.

[0052] S300: Set the magnetic flux of the first adjustable coupler to a first magnetic flux and the magnetic flux of the second adjustable coupler to a second magnetic flux to shut off the coupling between the first quantum bit, the second quantum bit and the third quantum bit.

[0053] Unlike existing technologies, the method for controlling the coupling relationship between qubits proposed in this embodiment first adjusts the energy level of the third qubit to distance it from the energy levels of the first and second qubits. When the coupling strength between the first and second qubits is 0, the magnetic flux of the first tunable coupler is set to the first magnetic flux. Then, the magnetic flux of the first tunable coupler is set to the first magnetic flux, and the energy level of the third qubit is set to its initial state. When the coupling strength between the second and third qubits is 0, the magnetic flux of the second tunable coupler is set to the second magnetic flux. Finally, the magnetic flux of the first tunable coupler is set to the first magnetic flux, and the magnetic flux of the second tunable coupler is set to the second magnetic flux, thereby shutting off the coupling between the first, second, and third qubits. Using the scheme of this application, the coupling strength between the first and second qubits used to execute two-qubit logic gates can be effectively reduced, and the coupling strength with the neighboring qubit in the quantum chip, i.e., the third qubit, can also be reduced, effectively improving the execution accuracy of the two-qubit logic gates and, to a certain extent, improving the execution precision of the quantum computer.

[0054] Please refer to Figure 2 , Figure 2 This is a simplified schematic diagram of a quantum chip structure proposed in this embodiment. Q1, Q2, and Q3 are the first, second, and third qubits, respectively; C1 and C2 are the first and second tunable couplers, respectively; Q1 and Q2 are the two qubits in the quantum chip used to execute a two-qubit logic gate; and Q3 is a qubit coupled to Q2. In addition to considering the first and second qubits involved in executing the two-qubit logic gate, the scheme in this application also considers the coupling relationship of the neighboring qubit, i.e., the third qubit. Other qubits in the quantum chip similar to the third qubit can have their coupling turned off using this scheme, eliminating the coupling effect of neighboring qubits.

[0055] Specifically, in this embodiment, the energy level of the third qubit is adjusted by the bit frequency of the third qubit. Those skilled in the art will understand that the bit frequency refers to the signal frequency required for the qubit to transition from the |0> state to the |1> state.

[0056] Specifically, in this embodiment, obtaining the magnetic flux magnitude of the first tunable coupler as the first magnetic flux when the coupling strength between the first qubit and the second qubit is 0 includes:

[0057] Set one of the two qubits to the |0> state and the |1> state respectively, and use the Ramsey experiment to obtain the frequency of the other qubit. The two qubits are the first qubit and the second qubit.

[0058] Based on the two frequencies obtained, the coupling strength between the first qubit and the second qubit is obtained as a first value;

[0059] Determine whether the first value is 0. If it is, obtain the magnetic flux of the first adjustable coupler at this time as the first magnetic flux.

[0060] If not, adjust the magnetic flux of the first tunable coupler and return to the step of setting one of the two qubits to the |0> state and the |1> state respectively, and using the Ramsey experiment to obtain the frequency of the other qubit.

[0061] Specifically, in this embodiment, obtaining the coupling strength between the first qubit and the second qubit as a first value based on the two obtained frequencies includes:

[0062] The difference between the two frequencies is obtained, and the difference is divided by two to obtain the coupling strength between the first qubit and the second qubit.

[0063] Specifically, in this embodiment, when the coupling strength between the second quantum bit and the third quantum bit is 0, the magnetic flux magnitude of the second tunable coupler is the second magnetic flux, which includes:

[0064] One of the two qubits is set to the |0> state and the |1> state respectively. The frequency of the other qubit is obtained by the Ramsey experiment. The two qubits are the second qubit and the third qubit.

[0065] Based on the two frequencies obtained, the coupling strength between the second quantum bit and the third quantum bit is obtained as a second value;

[0066] Determine if the second value is 0. If it is, obtain the magnetic flux magnitude of the second adjustable coupler at this time as the second magnetic flux.

[0067] If not, adjust the magnetic flux of the second tunable coupler and return to the step of setting one of the two qubits to the |0> state and the |1> state respectively, and using the Ramsey experiment to obtain the frequency of the other qubit.

[0068] Specifically, in this embodiment, after setting the magnetic flux magnitude of the first adjustable coupler to a first magnetic flux and the magnetic flux magnitude of the second adjustable coupler to a second magnetic flux, the method further includes:

[0069] Obtain the coupling strength between the first qubit and the second qubit. If the coupling strength between the first qubit and the second qubit is not 0 at this time, update the value of the first magnetic flux and return to execute the step of setting the magnetic flux size of the first adjustable coupler to the first magnetic flux and the magnetic flux size of the second adjustable coupler to the second magnetic flux.

[0070] Based on the same inventive concept, please refer to Figure 3 The present invention also proposes a control device for the coupling relationship between qubits, comprising:

[0071] The first magnetic flux acquisition unit 100 is configured to adjust the energy level of the third quantum bit to be away from the energy levels of the first quantum bit and the second quantum bit, and to acquire the magnetic flux magnitude of the first tunable coupler when the coupling strength between the first quantum bit and the second quantum bit is 0, and the first quantum bit and the second quantum bit are coupled and connected through the first tunable coupler.

[0072] The second magnetic flux acquisition unit 200 is configured to set the magnetic flux of the first tunable coupler to the first magnetic flux, and set the energy level of the third quantum bit to the initial state. When the coupling strength between the second quantum bit and the third quantum bit is 0, the magnetic flux magnitude of the second tunable coupler is the second magnetic flux, and the second quantum bit and the third quantum bit are coupled and connected through the second tunable coupler.

[0073] The coupling shutdown unit 300 is configured to set the magnetic flux magnitude of the first adjustable coupler to a first magnetic flux and the magnetic flux magnitude of the second adjustable coupler to a second magnetic flux to shut off the coupling between the first qubit, the second qubit, and the third qubit.

[0074] It is understood that the first flux acquisition unit 100, the second flux acquisition unit 200, and the coupling shutdown unit 300 can be implemented in a single device, or any one of these modules can be divided into multiple sub-modules. Alternatively, at least some of the functions of one or more modules of the first flux acquisition unit 100, the second flux acquisition unit 200, and the coupling shutdown unit 300 can be combined with at least some of the functions of other modules and implemented in a single functional module. According to embodiments of the present invention, at least one of the first flux acquisition unit 100, the second flux acquisition unit 200, and the coupling shutdown unit 300 can be at least partially implemented as hardware circuitry, such as a field-programmable gate array (FPGA), a programmable logic array (PLA), a system-on-a-chip, a system-on-a-substrate, a system-on-package, an application-specific integrated circuit (ASIC), or any other reasonable method of integrating or packaging the circuitry, or implemented in hardware or firmware, or in a suitable combination of software, hardware, and firmware implementations. Alternatively, at least one of the first magnetic flux acquisition unit 100, the second magnetic flux acquisition unit 200, and the coupling shutdown unit 300 can be at least partially implemented as a computer program module, which can perform the functions of the corresponding module when the program is run by a computer.

[0075] Based on the same inventive concept, embodiments of the present invention also propose a quantum control system, which utilizes a control method for the coupling relationship between qubits described in any of the above-described features, or a control device that includes the coupling relationship between qubits described in the above-described features.

[0076] Based on the same inventive concept, embodiments of the present invention also propose a quantum computer, including the quantum control system described in the above feature description.

[0077] Based on the same inventive concept, embodiments of the present invention also propose a readable storage medium storing a computer program thereon, wherein the computer program, when executed by a processor, can implement the method for controlling the coupling relationship between qubits as described in any of the above-described features.

[0078] The readable storage medium can be a tangible device capable of holding and storing instructions for use by an instruction execution device, such as, but not limited to, electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination thereof. More specific examples of readable storage media (a non-exhaustive list) include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination thereof. The computer programs described herein can be downloaded from the readable storage medium to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network can include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. Each computing / processing device's network adapter card or network interface receives the computer program from the network and forwards it for storage in a readable storage medium within the respective computing / processing device. The computer program used to perform the operations of this invention can be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as "C" or similar languages. The computer program can be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving remote computers, the remote computer can be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuits, such as programmable logic circuits, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), are personalized by utilizing state information from a computer program. These electronic circuits can execute computer-readable program instructions, thereby realizing various aspects of the present invention.

[0079] Various aspects of the present invention are described herein with reference to flowchart illustrations and / or block diagrams of methods, systems, and computer program products according to embodiments of the invention. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by a computer program. These computer programs can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to produce a machine such that, when executed by the processor of the computer or other programmable data processing apparatus, they create means for implementing the functions / actions specified in one or more blocks of the flowchart illustrations and / or block diagrams. These computer programs can also be stored in a readable storage medium that causes a computer, programmable data processing apparatus, and / or other device to operate in a particular manner; thus, the readable storage medium storing the computer program comprises an article of manufacture including instructions for implementing aspects of the functions / actions specified in one or more blocks of the flowchart illustrations and / or block diagrams.

[0080] A computer program may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable data processing apparatus, or other device to produce a computer-implemented process, thereby causing the computer program executing on the computer, other programmable data processing apparatus, or other device to perform the functions / actions specified in one or more boxes of a flowchart and / or block diagram.

[0081] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," or "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0082] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.

Claims

1. A method of controlling coupling between quantum bits, characterized by, include: The energy level of the third qubit is adjusted to be far away from the energy levels of the first and second qubits. Either the first or second qubit is set to the |0> state and the |1> state, respectively. The frequency of the other qubit is obtained using a Ramsey experiment. Based on the two frequencies, the difference between the two frequencies is divided by two as the coupling strength between the first and second qubits. When the result is zero, the magnetic flux of the first tunable coupler is the first magnetic flux. The first and second qubits are coupled together via the first tunable coupler. The magnetic flux of the first tunable coupler is set to the first magnetic flux, and the energy level of the third qubit is set to the initial state. Either the second qubit or the third qubit is set to the |0> state and the |1> state, respectively. The frequency of the second qubit and the other qubit of the third qubit is obtained using a Ramsey experiment. Based on the two obtained frequencies, the difference between the two frequencies divided by two is taken as the coupling strength between the second qubit and the third qubit. When the result is zero, the magnetic flux of the second tunable coupler is determined to be the second magnetic flux. The second qubit and the third qubit are coupled together via the second tunable coupler. The magnetic flux magnitude of the first adjustable coupler is set to the first magnetic flux, and the magnetic flux magnitude of the second adjustable coupler is set to the second magnetic flux, so as to shut off the coupling between the first qubit, the second qubit, and the third qubit.

2. The method of claim 1, wherein, The energy level of the third qubit is adjusted by the bit frequency of the third qubit.

3. The method of claim 1, wherein, The method further includes obtaining the result of dividing the difference between two frequencies by two as the coupling strength between the first qubit and the second qubit, and determining that when the result is zero, the magnetic flux magnitude of the first tunable coupler is the first magnetic flux. If the result of dividing the difference between the two frequencies by two is not zero, then adjust the magnetic flux of the first adjustable coupler and return to the process of setting one of the two qubits to the |0> state and the |1> state respectively, and using the Ramsey experiment to obtain the frequency of the other qubit, until the result of dividing the difference between the two frequencies by two is zero.

4. The method of claim 1, wherein, The method further includes obtaining the result of dividing the difference between two frequencies by two as the coupling strength between the second qubit and the third qubit, and determining that when the result is zero, the magnetic flux magnitude of the second tunable coupler is the second magnetic flux. If the result of dividing the difference between the two frequencies by two is not zero, then adjust the magnetic flux of the second adjustable coupler and return to the process of setting one of the two qubits to the |0> state and the |1> state respectively, and using the Ramsey experiment to obtain the frequency of the other qubit, until the result of dividing the difference between the two frequencies by two is zero.

5. The method of claim 1, wherein, After setting the magnetic flux magnitude of the first adjustable coupler to a first magnetic flux and the magnetic flux magnitude of the second adjustable coupler to a second magnetic flux, the method further includes: Obtain the coupling strength between the first qubit and the second qubit. If the coupling strength between the first qubit and the second qubit is not 0 at this time, update the value of the first magnetic flux and return to execute the step of setting the magnetic flux size of the first adjustable coupler to the first magnetic flux and the magnetic flux size of the second adjustable coupler to the second magnetic flux.

6. An apparatus for controlling coupling between quantum bits, characterized by include: A first flux acquisition unit is configured to adjust the energy level of a third qubit to be away from the energy levels of the first and second qubits, set either the first or second qubit to the |0> state and the |1> state respectively, obtain the frequency of the other qubit using a Ramsey experiment, and, based on the two obtained frequencies, obtain the result of dividing the difference between the two frequencies by two as the coupling strength between the first and second qubits. When the result is zero, the flux magnitude of the first tunable coupler is the first flux; wherein the first and second qubits are coupled together via the first tunable coupler. The second magnetic flux acquisition unit is configured to set the magnetic flux of the first tunable coupler to the first magnetic flux, set the energy level of the third qubit to an initial state, set either the second qubit or the third qubit to the |0> state and the |1> state respectively, obtain the frequency of the second qubit and the other qubit of the third qubit using a Ramsey experiment, obtain the difference between the two frequencies divided by two as the coupling strength between the second qubit and the third qubit, and determine the magnetic flux magnitude of the second tunable coupler as the second magnetic flux when the result is zero; wherein the second qubit and the third qubit are coupled together through the second tunable coupler. A coupling shutdown unit is configured to set the magnetic flux magnitude of the first adjustable coupler to a first magnetic flux and the magnetic flux magnitude of the second adjustable coupler to a second magnetic flux to shut off the coupling between the first qubit, the second qubit, and the third qubit.

7. A quantum control system, characterized by, The method for controlling the coupling relationship between qubits as described in any one of claims 1-5, or the device for controlling the coupling relationship between qubits as described in claim 6.

8. A quantum computer, characterized in that, Including the quantum control system as described in claim 7.

9. A readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it can implement the method for controlling the coupling relationship between qubits as described in any one of claims 1 to 5.

Images