Method and device for controlling quantum bits, quantum control system, quantum computer

Abstract

The application discloses a quantum bit control method and device, a quantum control system, and a quantum computer. When a two-qubit logic gate is executed on a first quantum bit and a second quantum bit, the phase of the first quantum bit is a first initial phase, and the phase of the second quantum bit is a second initial phase. The phase of the first quantum bit and / or the second quantum bit is obtained within a specified preset range by using a QST experiment, and the change of the state accuracy of the first quantum bit and / or the second quantum bit is obtained. Based on the change, the phase corresponding to the maximum state accuracy of the first quantum bit and / or the second quantum bit is obtained as a target phase, and finally, the phase of the first quantum bit and / or the second quantum bit is updated based on the target phase. The scheme can effectively improve the fidelity of the two-qubit logic gate by optimizing the phase of the quantum bit used to execute the two-qubit logic gate.

Description

Technical Field

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

[0002] A quantum computer is a physical device that performs high-speed mathematical and logical operations, stores and processes quantum information, following the laws of quantum mechanics. The main characteristics of quantum computers include high operating speed, strong information processing capabilities, and a wide range of applications. Compared to conventional computers, the greater the amount of information processed, the more advantageous it is for quantum computers to perform calculations, and the more accurately the calculations can be ensured.

[0003] Quantum chips are to quantum computers what CPUs are to traditional computers; they are the core components of quantum computers. With the continuous advancement of quantum computing technologies, the number of qubits on quantum chips is increasing year by year. It is foreseeable that larger-scale quantum chips will emerge in the future, containing even more qubits, and quantum computers will incorporate larger-scale quantum chips. Similar to classical bits, when using qubits to perform quantum computing, it is inevitable to apply qubit logic gates. For qubits, qubit logic gates actually refer to a series of control signals. Qubit logic gates mainly consist of two types: single-qubit logic gates and two-qubit logic gates. Two-qubit logic gates include CNOT, SWAP, and CZ. For two-qubit logic gates, fidelity is a crucial parameter. If the fidelity is too low, it can lead to deviations or even serious errors during the execution of quantum computing tasks.

[0004] Therefore, a scheme is needed to improve the fidelity 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 and device for controlling qubits, a quantum control system, and a quantum computer, for improving the fidelity of two-qubit logic gates.

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

[0008] When performing a two-qubit logic gate on the first qubit and the second qubit, the phase of the first qubit is the first initial phase, and the phase of the second qubit is the second initial phase.

[0009] Using QST experiments, the changes in the state precision of the first qubit and / or the second qubit within a specified preset range are obtained, wherein the specified preset range is determined based on the first initial phase and / or the second initial phase;

[0010] Based on the aforementioned changes, the phase corresponding to the maximum state precision of the first qubit and / or the second qubit is taken as the target phase.

[0011] The phases of the first qubit and / or the second qubit are updated based on the target phase.

[0012] Optionally, the step of using QST experiments to obtain the change in the state precision of the first qubit and / or the second qubit within a specified preset range includes:

[0013] Using QST experiments, the first change in the state precision of the first qubit within a first range is obtained.

[0014] Optionally, the step of determining the target phase as the phase corresponding to the maximum state precision of the first qubit and / or the second qubit based on the changes includes:

[0015] Based on the first change, the phase of the first qubit is the first target phase when the maximum state precision of the first qubit is obtained.

[0016] Optionally, updating the phase of the first qubit and / or the second qubit based on the target phase includes:

[0017] The phase of the first qubit is updated based on the first target phase.

[0018] Optionally, the step of using QST experiments to obtain the change in state precision of the first qubit and / or the second qubit within a specified preset range further includes:

[0019] Using QST experiments, the phase of the second qubit and the second variation in the state precision of the second qubit within a second range are obtained.

[0020] Optionally, the step of determining the target phase as the phase corresponding to the maximum state precision of the first qubit and / or the second qubit based on the changes further includes:

[0021] Based on the second change, the phase of the second qubit is the second target phase when the maximum state precision of the second qubit is obtained.

[0022] Optionally, updating the phase of the first qubit and / or the second qubit based on the target phase further includes:

[0023] The phase of the second qubit is updated based on the second target phase.

[0024] Optionally, the step of using QST experiments to obtain the change in state precision of the first qubit and / or the second qubit within a specified preset range further includes:

[0025] Using QST experiments, the first change in the state precision of the first qubit within a first range is obtained;

[0026] Using QST experiments, the phase of the second qubit and the second variation in the state precision of the second qubit within a second range are obtained.

[0027] Optionally, the step of determining the target phase as the phase corresponding to the maximum state precision of the first qubit and / or the second qubit based on the changes further includes:

[0028] Based on the first change, the phase of the first qubit is the first target phase when the maximum state precision of the first qubit is obtained;

[0029] Based on the second change, the phase of the second qubit is the second target phase when the maximum state precision of the second qubit is obtained.

[0030] Optionally, updating the phase of the first qubit and / or the second qubit based on the target phase further includes:

[0031] The phase of the first qubit is updated based on the first target phase;

[0032] The phase of the second qubit is updated based on the second target phase.

[0033] Optionally, after obtaining the first target phase and / or the second target phase, the method further includes using random benchmark tests to obtain the fidelity of the two-qubit logic gate.

[0034] Optionally, obtaining the fidelity of the two-qubit logic gate using random benchmark testing includes:

[0035] Perform random benchmark tests on the first and second qubits to obtain a first fidelity;

[0036] The two-qubit logic gate is applied to the first qubit and the second qubit, and a random benchmark test is performed on the first qubit and the second qubit to obtain the second fidelity.

[0037] The fidelity of the two-qubit logic gate is obtained based on the first fidelity and the second fidelity.

[0038] Optionally, the state precision is included in the following ways:

[0039] Perform a QST experiment on the first qubit and / or the second qubit to obtain the actual quantum state information of the first qubit and / or the second qubit;

[0040] Based on the actual quantum state information and the theoretical quantum state information, the state precision is obtained, wherein the theoretical quantum state information is the theoretical result of performing a QST experiment on the first quantum bit and / or the second quantum bit.

[0041] Based on the same inventive concept, the present invention also proposes a control device for qubits, comprising:

[0042] An initial phase acquisition unit is configured to acquire, when performing a two-qubit logic gate on the first qubit and the second qubit, the phase of the first qubit is a first initial phase and the phase of the second qubit is a second initial phase.

[0043] A state precision acquisition unit is configured to use a QST experiment to acquire the change in the state precision of the first qubit and / or the second qubit within a specified preset range, wherein the specified preset range is determined based on the first initial phase and / or the second initial phase.

[0044] A target phase acquisition unit is configured to acquire, based on the changes, the phase corresponding to the maximum state precision of the first qubit and / or the second qubit as the target phase;

[0045] A phase update unit is configured to update the phase of the first qubit and / or the second qubit based on the target phase.

[0046] Based on the same inventive concept, the present invention also proposes a quantum control system, which utilizes the control method of the qubit described in any one of the above-described features, or a control device including the qubit described in the above-described features.

[0047] 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.

[0048] 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 control method of the qubit described in any of the above features.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] This invention proposes a method for controlling qubits. When executing a two-qubit logic gate on a first qubit and a second qubit, the phase of the first qubit is determined as a first initial phase, and the phase of the second qubit as a second initial phase. Using a QST experiment, the change in state precision of the first and / or second qubits within a specified preset range is obtained. Based on this change, the phase corresponding to the maximum state precision of the first and / or second qubits is determined as the target phase. Finally, the phases of the first and / or second qubits are updated based on the target phase. This solution effectively improves the fidelity of two-qubit logic gates by optimizing the phase of the qubits used to execute them.

[0051] The quantum bit control device, quantum control system, quantum computer, and readable storage medium proposed in this invention belong to the same inventive concept as the quantum bit control method, and therefore have the same beneficial effects, which will not be elaborated here. Attached Figure Description

[0052] Figure 1 This is a flowchart illustrating a quantum bit control method proposed in an embodiment of the present invention;

[0053] Figure 2 A schematic diagram showing the results of a random benchmark test in the initial state;

[0054] Figure 3 A schematic diagram of the results of a random benchmark test after updating the phase of the first qubit;

[0055] Figure 4 A schematic diagram of the results of a random benchmark test after updating the phases of the first and second qubits;

[0056] Figure 5 This is a simplified structural diagram of a quantum bit control device proposed in another embodiment of the present invention. Detailed Implementation

[0057] 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.

[0058] 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.

[0059] 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.

[0060] To facilitate understanding of the scheme in this application, a brief introduction to several physical terms involved in this application is provided first. QST (Quantum State Tomography) experiment: When performing a two-qubit logic gate operation, it is necessary to know the initial state of the bit and the bit state after the two-qubit logic gate operation. Then, the information of the two-qubit logic gate is obtained based on the changes in the bit state. First, the state of the bit needs to be described using a density matrix. The density matrix can be represented as: ρ = ∑ i p i |φ i ><φ i |, where p i This represents the state φ of the system. i The probability of a two-qubit system is known. For a two-qubit system with a known initial state, its system state can be described by the density matrix. However, when the two qubits are operated on by an unknown two-qubit logic gate, it is impossible to determine the state of the two-qubit system. In this case, quantum state tomography can be used to analyze the state of this unknown system.

[0061] Randomized Benchmarking (RB testing): RB testing includes single-bit RB and two-bit RB. Single-bit RB is a randomized benchmark based on the Clifford group. The single-bit Clifford group has 24 elements. We can construct the elements in the Clifford group using several basic gate operations, which are the logic gates of the qubit to be characterized. The set of basic gate operations is S = {I, ±X, ±Y, ±X / 2, ±Y / 2}. We randomly select m group elements (m is also called the gate depth) from the Clifford group and apply them to the qubit sequentially. According to the definition of a group, there must exist an inverse element in the Clifford group such that this series of operations is equivalent to a unit gate, which is then applied to the qubit. If all operations are perfect, then the qubit should be in the |0> state. The probability of the qubit being in the |0> state is measured as the guarantee of the sequence. For each m, the average value of the sequence guarantee is P obtained by repeating the experiment k times. m Change the value of m and repeat the above steps to obtain a set {P}. m}. {P m}Use formula P m =Ap m The initial state preparation and measurement errors are included in the fitting results A and B, obtained by fitting the parameters p. The error of a Clifford operation, r = 0.5*(1-p), can be calculated based on the fitting parameter p. Since a Clifford operation contains 1.875 basic gates in S, the average fidelity of the basic gate operations in S is 1-r / 1.875. Thus, we can obtain the average fidelity of a single-bit gate. The execution process of a single-bit RB is similar to that of a two-bit RB, the difference being that the Clifford in the single-bit RB experiment consists entirely of single-bit gates, while the Clifford in the two-bit RB experiment contains both single-bit and two-bit gates.

[0062] Please refer to Figure 1 This invention proposes a method for controlling qubits, including:

[0063] S100: When performing a two-qubit logic gate on the first qubit and the second qubit, the phase of the first qubit is the first initial phase, and the phase of the second qubit is the second initial phase;

[0064] S200: Using a QST experiment, obtain the change in the state precision of the first qubit and / or the second qubit within a specified preset range, wherein the specified preset range is determined based on the first initial phase and / or the second initial phase;

[0065] S300: Based on the changes, the phase corresponding to the maximum state precision of the first qubit and / or the second qubit is the target phase;

[0066] S400: Update the phase of the first qubit and / or the second qubit based on the target phase.

[0067] Unlike existing technologies, this embodiment proposes a qubit control method that obtains the phase of the first qubit as a first initial phase and the phase of the second qubit as a second initial phase when executing a two-qubit logic gate on the first and second qubits. Using QST experiments, the method obtains the changes in the state precision of the first and / or second qubits within a specified preset range of their phases. Based on these changes, the phase corresponding to the maximum state precision of the first and / or second qubits is obtained as the target phase. Finally, the phases of the first and / or second qubits are updated based on the target phase. This application's solution, by optimizing the phase of the qubits used to execute the two-qubit logic gate, can effectively improve the fidelity of the two-qubit logic gate. Experimental verification by the applicant shows that the fidelity can be improved by at least two percentage points.

[0068] This application proposes to improve the fidelity of two-qubit logic gates by optimizing the phase of qubits. To achieve this, three schemes are proposed in this embodiment. The first scheme optimizes only the phase of the first qubit. In this embodiment, the first qubit is a high-frequency qubit, and the second qubit is a low-frequency qubit. Specifically, high-frequency and low-frequency qubits refer to the first qubit operating at a higher frequency than the second qubit when executing a two-qubit logic gate. Specifically, in this embodiment, the step of using QST experiments to obtain the change in the state precision of the first qubit and / or the second qubit within a specified preset range includes:

[0069] Using a QST experiment, the phase of the first qubit is measured within a first range, and the first change in the state precision of the first qubit is obtained. It should be noted that the first range is determined based on the first initial phase, and in this embodiment, the first range can be set near the first initial phase as needed.

[0070] As described in the preceding basic introduction to QST experiments, QST experiments can be used to obtain detailed information about qubits. In this embodiment, a QST experiment is performed on the first qubit to obtain the actual quantum state information of the first qubit. Then, based on the actual quantum state information and the theoretical quantum state information, the state precision is obtained. The theoretical quantum state information is the theoretical result of performing the QST experiment on the first qubit. It can be understood that the state precision refers to the ratio of the actual quantum state information to the theoretical quantum state information. The closer the state precision value is to 1, the more accurate the result of the QST experiment, and the more precise the calibrated quantum state information.

[0071] Specifically, when only the phase of the first qubit is optimized, the step of obtaining the phase corresponding to the maximum state precision of the first qubit and / or the second qubit based on the changes as the target phase includes:

[0072] Based on the first change, the phase of the first qubit is the first target phase when the maximum state precision of the first qubit is obtained.

[0073] After obtaining the first target phase, updating the phase of the first qubit using the first target phase, that is, updating the phase of the first qubit and / or the second qubit based on the target phase, includes:

[0074] The phase of the first qubit is updated based on the first target phase.

[0075] Please refer to 2 and Figure 3 , Figure 2 When the phase of the first qubit has not been updated, i.e., in the initial state, the fidelity of the two-qubit logic gate obtained by random benchmark testing is 94.69%. Figure 3 After updating the phase of the first qubit using the first target phase, the fidelity of the two-qubit logic gate obtained through random benchmark testing is 94.73%. Random benchmark testing verifies whether the proposed solution can effectively improve the fidelity of the two-qubit logic gate.

[0076] In this embodiment, a two-bit Restricted Behavior (RB) test is performed on the first and second qubits, both with and without the two-qubit logic gate executed. The fidelity of the two-qubit logic gate is obtained by comparing the fidelity ratio obtained from the two RB tests. Specifically, the fidelity of the two-qubit logic gate is obtained as follows: First, a random benchmark test is performed on the first qubit to obtain a first fidelity.

[0077] Then, the two-qubit logic gate is applied to the first qubit, and a random benchmark test is performed on the first qubit to obtain the second fidelity.

[0078] Finally, the fidelity of the two-qubit logic gate is obtained based on the first fidelity and the second fidelity. The fidelity of the two-qubit logic gate is the ratio of the second fidelity to the first fidelity.

[0079] The second approach is to optimize only the phase of the second qubit. In this embodiment, the first qubit is a high-frequency qubit, and the second qubit is a low-frequency qubit. Specifically, high-frequency and low-frequency qubits refer to the first qubit operating at a higher frequency than the second qubit when executing a two-qubit logic gate. Specifically, in this embodiment, the step of using QST experiments to obtain the change in the state precision of the first and / or second qubits within a specified preset range, further includes:

[0080] Using QST experiments, the phase of the second qubit is determined within a second range, and the state precision of the second qubit is observed to exhibit a second variation. It should be noted that the second range is determined based on the second initial phase, and in this embodiment, the second range can be set near the second initial phase as needed.

[0081] As described in the preceding basic introduction to QST experiments, QST experiments can be used to obtain detailed information about qubits. In this embodiment, a QST experiment is performed on the second qubit to obtain its actual quantum state information. Then, based on the actual quantum state information and the theoretical quantum state information, the state precision is obtained. The theoretical quantum state information is the theoretical result of performing the QST experiment on the second qubit. It can be understood that the state precision refers to the ratio of the actual quantum state information to the theoretical quantum state information. The closer the state precision value is to 1, the more accurate the result of the QST experiment, and the more precise the calibrated quantum state information.

[0082] Specifically, in this embodiment, the step of determining the phase corresponding to the maximum state precision of the first qubit and / or the second qubit based on the changes as the target phase further includes:

[0083] Based on the second change, the phase of the second qubit is the second target phase when the maximum state precision of the second qubit is obtained.

[0084] After obtaining the second target phase, updating the phase of the second qubit using the second target phase, that is, updating the phase of the first qubit and / or the second qubit based on the target phase, further includes:

[0085] The phase of the second qubit is updated based on the second target phase.

[0086] Similar to the first approach, in this embodiment, two-bit RB is performed on the first and second qubits respectively, both when the two-qubit logic gate is not executed and when it is executed. The fidelity of the two-qubit logic gate is obtained by the fidelity ratio obtained from the two two-bit RBs.

[0087] The third approach is to optimize the phases of the first and second qubits. In this embodiment, the first qubit is a high-frequency qubit, and the second qubit is a low-frequency qubit. Specifically, the high-frequency and low-frequency qubits refer to the fact that when executing a two-qubit logic gate, the operating frequency of the first qubit is higher than that of the second qubit. It should be noted that in this embodiment, the phase of the first qubit can be optimized first, or the phase of the second qubit can be optimized first; there is no limitation on this. Optionally, the step of using QST experiments to obtain the change in the state precision of the first and / or second qubits within a specified preset range of phase of the first and / or second qubits further includes:

[0088] Using QST experiments, the first change in the state precision of the first qubit is obtained within a first range. It should be noted that the first range is determined based on the first initial phase. In this embodiment, the first range can be set near the first initial phase as needed.

[0089] Using QST experiments, the phase of the second qubit is determined within a second range, and the state precision of the second qubit is observed to exhibit a second variation. It should be noted that the second range is determined based on the second initial phase, and in this embodiment, the second range can be set near the second initial phase as needed.

[0090] Optionally, the step of determining the target phase as the phase corresponding to the maximum state precision of the first qubit and / or the second qubit based on the changes further includes:

[0091] Based on the first change, the phase of the first qubit is the first target phase when the maximum state precision of the first qubit is obtained;

[0092] Based on the second change, the phase of the second qubit is the second target phase when the maximum state precision of the second qubit is obtained.

[0093] After obtaining the first target phase and the second target phase, the phases of the first qubit and the second qubit are updated using the first target phase and the second target phase. The step of updating the phases of the first qubit and / or the second qubit based on the target phase further includes:

[0094] The phase of the first qubit is updated based on the first target phase;

[0095] The phase of the second qubit is updated based on the second target phase.

[0096] Please refer to 2 and Figure 4 , Figure 2 When the phase of the first qubit has not been updated, i.e., in the initial state, the fidelity of the two-qubit logic gate obtained by random benchmark testing is 94.69%. Figure 4 After updating the phases of the first and second qubits using the first and second target phases, a two-qubit logic gate with a fidelity of 96.75% obtained through random benchmark testing was achieved. Random benchmark testing verifies whether the proposed solution can improve the fidelity of the two-qubit logic gate. As described in the above three schemes, simultaneously optimizing the phases of both the first and second qubits significantly improves the fidelity of the two-qubit logic gate compared to optimizing only one qubit. Therefore, these three schemes can be selected based on the specific fidelity requirements of each scenario.

[0097] Specifically, in this embodiment, after obtaining the first target phase and / or the second target phase, the fidelity of the two-qubit logic gate is obtained using a random benchmark test.

[0098] Specifically, in this embodiment, obtaining the fidelity of the two-qubit logic gate using random benchmark testing includes:

[0099] Perform random benchmark tests on the first and second qubits to obtain a first fidelity;

[0100] The two-qubit logic gate is applied to the first qubit and the second qubit, and a random benchmark test is performed on the first qubit and the second qubit to obtain the second fidelity.

[0101] The fidelity of the two-qubit logic gate is obtained based on the first fidelity and the second fidelity.

[0102] Specifically, in this embodiment, the state precision is included in the following ways:

[0103] Perform a QST experiment on the first qubit and / or the second qubit to obtain the actual quantum state information of the first qubit and / or the second qubit;

[0104] Based on the actual quantum state information and the theoretical quantum state information, the state precision is obtained, wherein the theoretical quantum state information is the theoretical result of performing a QST experiment on the first quantum bit and / or the second quantum bit.

[0105] It should be noted that the two-qubit logic gate described in this embodiment can be a CZ gate, or other types of two-qubit logic gates, and there are no restrictions here.

[0106] Please refer to Figure 5 Based on the same inventive concept, embodiments of the present invention also propose a control device for qubits, comprising:

[0107] The initial phase acquisition unit 100 is configured to acquire, when performing a two-qubit logic gate on the first qubit and the second qubit, the phase of the first qubit is a first initial phase and the phase of the second qubit is a second initial phase.

[0108] The state precision acquisition unit 200 is configured to use a QST experiment to acquire the change in the state precision of the first qubit and / or the second qubit within a specified preset range of phase, wherein the specified preset range is determined based on the first initial phase and / or the second initial phase.

[0109] The target phase acquisition unit 300 is configured to acquire the phase corresponding to the maximum state precision of the first qubit and / or the second qubit as the target phase based on the changes.

[0110] A phase update unit 400 is configured to update the phase of the first qubit and / or the second qubit based on the target phase.

[0111] It is understood that the initial phase acquisition unit 100, the state precision acquisition unit 200, the target phase acquisition unit 300, and the phase update unit 400 can be implemented in a single device, or any one of these modules can be split into multiple sub-modules. Alternatively, at least some of the functions of one or more modules of the initial phase acquisition unit 100, the state precision acquisition unit 200, the target phase acquisition unit 300, and the phase update unit 400 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 initial phase acquisition unit 100, the state precision acquisition unit 200, the target phase acquisition unit 300, and the phase update unit 400 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 circuitry, or implemented in hardware or firmware, or in a suitable combination of software, hardware, and firmware implementations. Alternatively, at least one of the initial phase acquisition unit 100, the state accuracy acquisition unit 200, the target phase acquisition unit 300, and the phase update unit 400 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.

[0112] Based on the same inventive concept, embodiments of the present invention also propose a quantum control system, which utilizes the control method for qubits described in any of the above-described features, or a control device including the qubits described in the above-described features.

[0113] 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.

[0114] 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 control method of the qubit described in any of the above features.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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 for controlling a quantum bit, characterized in that, include: When performing a two-qubit logic gate on the first qubit and the second qubit, the phase of the first qubit is the first initial phase, and the phase of the second qubit is the second initial phase. Using a QST experiment, the change in the state precision of the first qubit and / or the second qubit within a specified preset range is obtained. The specified preset range is determined based on the first initial phase and / or the second initial phase. The state precision is the ratio of actual quantum state information to theoretical quantum state information. The actual quantum state information is obtained by performing a QST experiment on the first qubit and / or the second qubit. The theoretical quantum state information is the theoretical result of performing a QST experiment on the first qubit and / or the second qubit. Based on the aforementioned changes, the phase corresponding to the maximum state precision of the first qubit and / or the second qubit is taken as the target phase. The phases of the first qubit and / or the second qubit are updated based on the target phase.

2. The method as described in claim 1, characterized in that, The step of using QST experiments to obtain the changes in the state precision of the first qubit and / or the second qubit within a specified preset range includes: Using QST experiments, the first change in the state precision of the first qubit within a first range is obtained.

3. The method as described in claim 2, characterized in that, The step of determining the target phase as the phase corresponding to the maximum state precision of the first qubit and / or the second qubit based on the aforementioned changes includes: Based on the first change, the phase of the first qubit is the first target phase when the maximum state precision of the first qubit is obtained.

4. The method as described in claim 3, characterized in that, Updating the phase of the first qubit and / or the second qubit based on the target phase includes: The phase of the first qubit is updated based on the first target phase.

5. The method as described in claim 1, characterized in that, The step of using QST experiments to obtain the changes in the state precision of the first qubit and / or the second qubit within a specified preset range also includes: Using QST experiments, the phase of the second qubit and the second variation in the state precision of the second qubit within a second range are obtained.

6. The method as described in claim 5, characterized in that, The step of determining the target phase as the phase corresponding to the maximum state precision of the first qubit and / or the second qubit based on the aforementioned changes further includes: Based on the second change, the phase of the second qubit is the second target phase when the maximum state precision of the second qubit is obtained.

7. The method as described in claim 6, characterized in that, The step of updating the phase of the first qubit and / or the second qubit based on the target phase further includes: The phase of the second qubit is updated based on the second target phase.

8. The method as described in claim 1, characterized in that, The step of using QST experiments to obtain the changes in the state precision of the first qubit and / or the second qubit within a specified preset range also includes: Using QST experiments, the first change in the state precision of the first qubit within a first range is obtained; Using QST experiments, the phase of the second qubit and the second variation in the state precision of the second qubit within a second range are obtained.

9. The method as described in claim 8, characterized in that, The step of determining the target phase as the phase corresponding to the maximum state precision of the first qubit and / or the second qubit based on the aforementioned changes further includes: Based on the first change, the phase of the first qubit is the first target phase when the maximum state precision of the first qubit is obtained; Based on the second change, the phase of the second qubit is the second target phase when the maximum state precision of the second qubit is obtained.

10. The method as described in claim 9, characterized in that, The step of updating the phase of the first qubit and / or the second qubit based on the target phase further includes: The phase of the first qubit is updated based on the first target phase; The phase of the second qubit is updated based on the second target phase.

11. The method as described in claim 9, characterized in that, After obtaining the first target phase and / or the second target phase, the method further includes using random benchmark tests to obtain the fidelity of the two-qubit logic gate.

12. The method as described in claim 11, characterized in that, The method of obtaining the fidelity of the two-qubit logic gate using random benchmark testing includes: Perform random benchmark tests on the first and second qubits to obtain a first fidelity; The two-qubit logic gate is applied to the first qubit and the second qubit, and a random benchmark test is performed on the first qubit and the second qubit to obtain the second fidelity. The fidelity of the two-qubit logic gate is obtained based on the first fidelity and the second fidelity.

13. A control device for qubits, characterized in that, include: An initial phase acquisition unit is configured to acquire, when performing a two-qubit logic gate on the first qubit and the second qubit, the phase of the first qubit is a first initial phase and the phase of the second qubit is a second initial phase. A state precision acquisition unit is configured to use a QST experiment to acquire the change in state precision of the first qubit and / or the second qubit within a specified preset range of phase, wherein the specified preset range is determined based on the first initial phase and / or the second initial phase, the state precision is the ratio of actual quantum state information to theoretical quantum state information, the actual quantum state information is obtained by performing a QST experiment on the first qubit and / or the second qubit, and the theoretical quantum state information is the theoretical result of performing a QST experiment on the first qubit and / or the second qubit; A target phase acquisition unit is configured to acquire, based on the changes, the phase corresponding to the maximum state precision of the first qubit and / or the second qubit as the target phase; A phase update unit is configured to update the phase of the first qubit and / or the second qubit based on the target phase.

14. A quantum control system, characterized in that, The control method of the qubit according to any one of claims 1-12, or the control device including the qubit according to claim 13.

15. A quantum computer, characterized in that, Includes the quantum control system described in claim 14.

16. 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 control method for the qubits according to any one of claims 1 to 12.

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