Time-delay acquisition method and device for frequency control signal in quantum chip

Abstract

The invention discloses a delay acquisition method and device for a frequency control signal in a quantum chip, and the method comprises the steps: obtaining a first resonant frequency and a second resonant frequency according to the modulation spectrums of a first quantum bit and a second quantum bit; and setting the working frequency of the first quantum bit as a first resonant frequency and the working frequency of the second quantum bit as a second resonant frequency. And then performing a state exchange experiment on the first quantum bit and the second quantum bit, and obtaining resonance duration based on a result of the state exchange experiment. And finally, obtaining the time delay of the frequency control signal among the first quantum bit, the second quantum bit and the adjustable coupler. According to the scheme, the time delay of the frequency control signal in the quantum chip can be directly obtained, and compared with the prior art, the time consumed by the whole scheme is greatly shortened, so that the efficiency of executing a quantum computing task by a quantum computer is improved to a certain extent.

Description

Technical Field

[0001] The present invention relates to the field of quantum computing technology, and in particular to a method for executing a measurement and control experiment, a quantum computing measurement and control system, and a quantum computer. Background Art

[0002] Quantum computers are physical devices that follow the laws of quantum mechanics to perform high-speed mathematical and logical operations, store, and process quantum information. Their key characteristics include rapid operation, robust information processing capabilities, and a wide range of applications. Compared to conventional computers, the greater the amount of information they can process, the more advantageous it is for a quantum computer to perform calculations, ensuring greater accuracy.

[0003] A quantum chip is to a quantum computer what a CPU is to a traditional computer; the quantum chip is the core component of a quantum computer. A quantum computer also includes a quantum computing measurement and control system that provides a measurement and control environment for the quantum chip. This system primarily consists of hardware devices located in the room-temperature layer and cryogenic devices and signal transmission lines located within the dilution refrigerator. After the quantum chip is packaged, it is fixed to the lowest, ultra-low-temperature layer of the dilution refrigerator and ultimately connected to the room-temperature hardware devices via coaxial cables between the layers. Two main types of lines are used to control the quantum state of a qubit: a first-class transmission line (quantum state control line) for driving the quantum state of the qubit, and a second-class transmission line (frequency control line) for controlling the frequency of the qubit.

[0004] When conducting a two-qubit experiment, a frequency control signal applied to a second-type transmission line is typically used to adjust the frequency of the corresponding qubit, causing it to resonate with another qubit to achieve a two-qubit gate. However, due to the presence of various microwave devices on the second-type transmission line, and the fact that the lengths of different second-type transmission lines cannot be guaranteed to be exactly the same, the transmission delays of the control signals on different second-type transmission lines vary. This results in different control signals not reaching their corresponding qubits according to the designed timing, seriously affecting the control accuracy of the two-qubit gate. Current approaches to delaying the frequency control signal in quantum chips with adjustable couplers generally involve first calculating the delay between the two qubit quantum state control lines and the frequency control line, then obtaining the delay between the qubit's quantum state control line and the frequency control line of the adjustable coupler, and finally calculating the delay between the qubit frequency control signals through computational conversion. This approach is cumbersome, time-consuming, and inefficient, impacting the efficiency of quantum computers in executing quantum computing tasks.

[0005] Therefore, how to improve the execution efficiency of quantum computers has become a technical problem that needs to be solved urgently in this field.

[0006] It should be noted that the information disclosed in the background technology section of this application is only intended to deepen the understanding of the general background technology of this application, and should not be regarded as an admission or any form of implication that the information constitutes prior art already known to those skilled in the art. Summary of the Invention

[0007] The purpose of the present invention is to provide a method and device for delaying the acquisition of the frequency control signal in a quantum chip, so as to solve the problem that the frequency control signal delay solution of the quantum chip in the prior art consumes a lot of time and has low efficiency.

[0008] In order to solve the above technical problems, the present invention proposes a method for delayed acquisition of frequency control signals in a quantum chip, comprising:

[0009] Obtaining a first resonant frequency and a second resonant frequency according to modulation spectra of a first qubit and a second qubit, and setting an operating frequency of the first qubit to the first resonant frequency and an operating frequency of the second qubit to the second resonant frequency, wherein the first qubit and the second qubit are two qubits in the quantum chip coupled via an adjustable coupler;

[0010] performing a state exchange experiment on the first qubit and the second qubit, and obtaining a resonance duration based on a result of the state exchange experiment, wherein the state exchange experiment utilizes an experiment in which excited states are exchanged back and forth between the two qubits when the two qubits are in resonance;

[0011] The duration of the frequency control signals of the two quantum bits and the adjustable coupler is set based on the resonance duration, and a state exchange experiment is performed on the first quantum bit and the second quantum bit to obtain the delay of the frequency control signal between the first quantum bit, the second quantum bit and the adjustable coupler.

[0012] Optionally, after obtaining the first resonant frequency and the second resonant frequency, the method further includes:

[0013] The first qubit and the second qubit are calibrated respectively using a Ramsey experiment to obtain a first operating voltage corresponding to when the first qubit operates at the first resonant frequency, and a second operating voltage corresponding to when the second qubit operates at the second resonant frequency. When performing the state exchange experiment, the operating voltage of the first qubit is the first operating voltage, and the operating voltage of the second qubit is the second operating voltage.

[0014] Optionally, obtaining the first resonant frequency and the second resonant frequency according to the modulation spectra of the first qubit and the second qubit includes:

[0015] Obtaining a maximum frequency value and a minimum frequency value of the first qubit and a maximum frequency value and a minimum frequency value of the second qubit, respectively, according to the modulation spectra of the first qubit and the second qubit;

[0016] The first resonant frequency and the second resonant frequency are acquired based on the maximum frequency value and the minimum frequency value of the first qubit and the maximum frequency value and the minimum frequency value of the second qubit.

[0017] Optionally, acquiring the first resonant frequency and the second resonant frequency based on the maximum frequency value and the minimum frequency value of the first qubit and the maximum frequency value and the minimum frequency value of the second qubit includes:

[0018] Obtaining an overlapping range of frequencies of the first qubit and the second qubit based on the maximum frequency and the minimum frequency of the first qubit and the maximum frequency and the minimum frequency of the second qubit;

[0019] The first resonant frequency and the second resonant frequency are acquired from frequencies in the overlap range.

[0020] Optionally, the first resonant frequency is equal to the second resonant frequency, wherein any frequency within the overlap range except the current operating frequencies of the first quantum bit and the second quantum bit is the first resonant frequency.

[0021] Optionally, there is the following relationship between the first resonant frequency and the second resonant frequency:

[0022] f1+α=f2;

[0023] Among them, f1 is the first resonant frequency, α is the anharmonicity of the first quantum bit, f2 is the second resonant frequency, the first quantum bit is a high-frequency bit, and the second quantum bit is a low-frequency bit. The high-frequency bit is the quantum bit with a higher operating frequency among the two quantum bits, and the low-frequency bit is the quantum bit with a lower operating frequency among the two quantum bits.

[0024] Optionally, before performing the state exchange experiment on the first qubit and the second qubit and obtaining the resonance duration based on the result of the state exchange experiment, the method further includes:

[0025] The coupling strength between the two quantum bits reaches a preset value by adjusting the operating voltage of the adjustable coupler.

[0026] Optionally, the resonance duration is obtained according to a curve reflecting the change of the probability of the quantum state of the quantum bit with the duration of the frequency control signal in the result of the state exchange experiment.

[0027] Optionally, setting the duration of the frequency control signals of the two qubits and the adjustable coupler based on the resonance duration, and performing a state exchange experiment on the first qubit and the second qubit to obtain the delay of the frequency control signal between the first qubit, the second qubit, and the adjustable coupler includes:

[0028] Setting the duration of the frequency control signals of the first qubit, the second qubit, and the adjustable coupler to the resonance duration;

[0029] Sequentially fixing the delay of the frequency control signal of any two of the first qubit, the second qubit, and the adjustable coupler, and traversing the first delay of the frequency control signal of the remaining one within a first preset range, and performing a state exchange experiment on the first qubit and the second qubit;

[0030] Obtain a first change in the probability of the first qubit or the second qubit being in a first quantum state with a first delay, and obtain a delay of a frequency control signal between the first qubit, the second qubit, and the adjustable coupler based on the first change.

[0031] Based on the same inventive concept, the present invention also proposes a method for calibrating the delay of the frequency control signal in a quantum chip, which uses any one of the methods described above to obtain the delay of the frequency control signal in the quantum chip and perform calibration.

[0032] Based on the same inventive concept, the present invention also proposes a device for obtaining a delayed frequency control signal in a quantum chip, comprising:

[0033] a first working module, configured to obtain a first resonant frequency and a second resonant frequency according to modulation spectra of a first qubit and a second qubit, and set an operating frequency of the first qubit to the first resonant frequency and an operating frequency of the second qubit to the second resonant frequency, wherein the first qubit and the second qubit are two qubits in the quantum chip coupled via an adjustable coupler;

[0034] a second working module, configured to perform a state exchange experiment on the first qubit and the second qubit, and obtain a resonance duration based on a result of the state exchange experiment, wherein the state exchange experiment is an experiment in which excited states are exchanged back and forth between the two qubits when the two qubits are in resonance;

[0035] The third working module is used to set the duration of the frequency control signals of the two quantum bits and the adjustable coupler based on the resonance duration, and perform a state exchange experiment on the first quantum bit and the second quantum bit to obtain the delay of the frequency control signal between the first quantum bit, the second quantum bit and the adjustable coupler.

[0036] Based on the same inventive concept, the present invention also proposes a quantum computing measurement and control system, which utilizes the delayed acquisition method of the frequency control signal in the quantum chip described in any one of the above-mentioned characteristic descriptions, or utilizes the delay calibration method of the frequency control signal in the quantum chip described in the above-mentioned characteristic descriptions, or includes the delayed acquisition device of the frequency control signal in the quantum chip described in the above-mentioned characteristic descriptions.

[0037] Based on the same inventive concept, the present invention also proposes a quantum computer, including the quantum computing measurement and control system described in the above feature description.

[0038] Based on the same inventive concept, the present invention also proposes a readable storage medium storing a computer program. When the computer program is executed by a processor, it can implement the method for obtaining the delayed frequency control signal in a quantum chip described in any one of the above-mentioned feature descriptions, or the method for calibrating the delay of the frequency control signal in the quantum chip described in the above-mentioned feature descriptions.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The present invention proposes a method for obtaining the delay of a frequency control signal in a quantum chip. The method obtains a first resonant frequency and a second resonant frequency based on the modulation spectra of a first quantum bit and a second quantum bit, and sets the operating frequency of the first quantum bit to the first resonant frequency and the operating frequency of the second quantum bit to the second resonant frequency. A state exchange experiment is then performed on the first quantum bit and the second quantum bit, and the resonance duration is obtained based on the results of the state exchange experiment. Finally, the duration of the frequency control signal of the two quantum bits and the adjustable coupler is set based on the resonance duration, and a state exchange experiment is performed on the first quantum bit and the second quantum bit to obtain the delay of the frequency control signal between the first quantum bit, the second quantum bit, and the adjustable coupler. The scheme of the present application can directly obtain the delay of the frequency control signal in the quantum chip. Compared with the existing technology, the time consumed by the entire scheme is greatly reduced, thereby improving the efficiency of the quantum computer in performing quantum computing tasks to a certain extent.

[0041] The method for calibrating the delay of the frequency control signal in a quantum chip, the device for obtaining the delay of the frequency control signal in a quantum chip, the quantum computing measurement and control system, the quantum computer, and the readable storage medium proposed in the present invention belong to the same inventive concept as the method for obtaining the delay of the frequency control signal in the quantum chip, and therefore have the same beneficial effects, and will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Schematic diagram of the structure of a quantum computer system mentioned in this embodiment;

[0043] Figure 2 Schematic diagram of the structure of a quantum chip with an adjustable coupler mentioned in this embodiment;

[0044] Figure 3 A schematic flow chart of a method for delayed acquisition of a frequency control signal in a quantum chip proposed in an embodiment of the present invention;

[0045] Figure 4 This is the waveform timing diagram of the state exchange experiment;

[0046] Figure 5 Schematic diagram of the change of quantum state probability with the duration of the frequency control signal in the experimental results of the state exchange experiment;

[0047] Figure 6 Schematic diagram of a first change in quantum state probability with a first delay in the experimental results of a state exchange experiment;

[0048] Figure 7 This is a simplified structural diagram of a device for delayed acquisition of frequency control signals in a quantum chip proposed in an embodiment of the present invention. DETAILED DESCRIPTION

[0049] The following describes a specific embodiment of the present invention in more detail with reference to schematic diagrams. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that the drawings are greatly simplified and not to exact scale, and are intended solely to facilitate and clearly illustrate the embodiments of the present invention.

[0050] In the description of the present invention, it should be understood that the terms "center", "up", "down", "left", "right", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0051] 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 the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0052] Currently, quantum computer systems can be referenced Figure 1 The quantum chip 2 integrates multiple mutually coupled qubits 21 (two qubits 21 are used as an example in the figure). Each qubit 21 is coupled to an XY signal transmission line for receiving quantum state control signals and a Z signal transmission line for receiving qubit frequency control signals. The XY signal transmission line and the Z signal transmission line are each led to room temperature via the low-temperature circuit of the dilution refrigerator 1. Then, a circuit connected to the corresponding hardware device 4 is established at the room temperature end. When conducting a two-qubit experiment, a qubit frequency control signal is generally applied to the Z signal transmission line to adjust the frequency of the corresponding qubit so that it resonates with another qubit to achieve a two-qubit gate. However, due to the installation of multiple microwave devices on the Z signal transmission line and the fact that the lengths of different Z signal transmission lines cannot be guaranteed to be completely equal, the transmission delays on different Z signal transmission lines vary. As a result, different control signals may not reach their corresponding qubits according to the designed timing, which can seriously affect the control accuracy of the two-qubit gate.

[0053] In the quantum bit expansion architecture based on adjustable couplers, two quantum bits can be coupled through a fixed capacitive coupling and an adjustable coupler with an adjustable coupling coefficient. The structure of the adjustable coupler is similar to that of the quantum bit, except that the adjustable coupler does not have a quantum state control line and a resonant cavity that can directly read information. When we use a quantum chip with an adjustable coupler to perform quantum computing tasks, we need to ensure the synchronization of the signals on the frequency control line of the adjustable coupler and the quantum state control line of the corresponding quantum bit. However, in actual applications, since the lengths of the frequency control line of the adjustable coupler and the quantum state control line of the corresponding quantum bit cannot be guaranteed to be completely equal, the transmission delays of their respective signals are different, resulting in different control signals failing to reach their corresponding quantum bits according to the designed timing, which will seriously affect the control accuracy of the corresponding quantum bit logic gate. The quantum bit expansion architecture based on adjustable couplers can be referenced. Figure 2 , Figure 2The figure is a schematic diagram of the structure of a quantum chip with an adjustable coupler, where C0 is the adjustable coupler, and Q1 and Q2 are two quantum bits coupled to C0. XY1 and XY2 are quantum state control lines, and Z1, Z2, and Z3 are frequency control lines. It will be understood by those skilled in the art that for a quantum chip containing an adjustable coupler, its structure is generally that two adjacent quantum bits are coupled and connected through an adjustable coupler, and the adjustable coupler can adjust the coupling strength of the two quantum bits. The structure of the adjustable coupler is actually similar to that of the quantum bit, the only difference being that the adjustable coupler only has a frequency control line, and does not have a matching quantum state control line or a reading cavity.

[0054] In the prior art, to obtain the delay of the frequency control signal of a quantum chip with an adjustable coupler structure, the adjustable coupler in the quantum chip is used as a transfer medium. First, the first delay between the first quantum state control line of the first qubit and the first frequency control line is obtained. Then, the third delay between the first quantum state control line of the first qubit and the third frequency control line of the adjustable coupler is obtained. The obtained first and third delays are then used to indirectly calculate the fifth delay between the first and third frequency control lines. The delay between the frequency control line of the second qubit and the frequency control line of the adjustable coupler is also obtained according to the above scheme. Then, the delay between the frequency control lines of the first and second qubits is indirectly obtained through computational conversion. This process requires a large number of measurement and control experiments, and the entire solution is cumbersome and time-consuming, which cannot meet the requirements of large-scale quantum chips.

[0055] In the above technical background, this application proposes a solution to improve the delay acquisition efficiency of frequency control signal in quantum chip. Figure 3 , an embodiment of the present invention proposes a method for delayed acquisition of a frequency control signal in a quantum chip, comprising:

[0056] S100: Obtaining a first resonant frequency and a second resonant frequency according to modulation spectra of a first qubit and a second qubit, and setting an operating frequency of the first qubit to the first resonant frequency and an operating frequency of the second qubit to the second resonant frequency, wherein the first qubit and the second qubit are two qubits in the quantum chip coupled via an adjustable coupler;

[0057] S200: performing a state exchange experiment on the first qubit and the second qubit, and obtaining a resonance duration based on a result of the state exchange experiment, wherein the state exchange experiment is an experiment in which excited states are exchanged back and forth between the two qubits when the two qubits are in resonance;

[0058] S300: Setting the duration of the frequency control signals of the two quantum bits and the adjustable coupler based on the resonance duration, performing a state exchange experiment on the first quantum bit and the second quantum bit to obtain the delay of the frequency control signal between the first quantum bit, the second quantum bit and the adjustable coupler.

[0059] The difference from the prior art is that the embodiment of the present invention proposes a method for obtaining the delay of the frequency control signal in a quantum chip, obtaining the first resonant frequency and the second resonant frequency based on the modulation spectrum of the first quantum bit and the second quantum bit, and setting the operating frequency of the first quantum bit to the first resonant frequency and the operating frequency of the second quantum bit to the second resonant frequency. Then, a state exchange experiment is performed on the first quantum bit and the second quantum bit, and the resonance duration is obtained based on the results of the state exchange experiment. Finally, based on the resonance duration, the duration of the frequency control signal of the two quantum bits and the adjustable coupler is set, and a state exchange experiment is performed on the first quantum bit and the second quantum bit to obtain the delay of the frequency control signal between the first quantum bit, the second quantum bit and the adjustable coupler. The scheme of the present application can directly obtain the delay of the frequency control signal in the quantum chip. Compared with the prior art, the entire scheme is simpler and the time required is greatly reduced. Therefore, to a certain extent, the efficiency of the quantum computer in performing quantum computing tasks is improved.

[0060] In order to better understand the technical solution of the present application, the following briefly describes the inventive concept of the present application and the Ramsey experiment involved:

[0061] A Ramsey experiment involves applying two π / 2 quantum logic gates to a qubit, with the time interval between the two operations being τ. A read pulse is then applied to the qubit after the second π / 2 quantum logic gate operation to obtain the qubit's excited state distribution, P1(τ). The time interval τ is then varied to obtain P1(τ). A typical Ramsey experiment results in P1(τ) decaying exponentially with the time interval τ, following the mathematical model shown below:

[0062]

[0063] In formula 1, A and B are fitting coefficients, T0 is the decoherence time of the quantum bit, and f d is the carrier frequency of the microwave pulse signal corresponding to the π / 2 quantum logic gate operation, f0 is the oscillation frequency of the quantum bit, and f0 is related to the real frequency f of the quantum bit. q 、π / 2 quantum logic gate operation carrier frequency f d satisfy:

[0064] f0(f d )=|f q -f d |(2)

[0065] To sum up and combine with Formula 2, we can obtain: the result of the Ramsey experiment, that is, 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 quantum bit. Therefore, in addition to being able to be used to obtain the decoherence time of the quantum bit, the Ramsey experiment can also accurately obtain the true frequency of the quantum bit at the same time.

[0066] Under normal operating conditions, there are many fundamental reasons for qubit frequency changes, but the direct cause is a change in magnetic flux. For example, the presence of an adjustable coupler or crosstalk from surrounding qubits can cause the qubit to deviate from its original operating frequency, which manifests as a shift in the qubit's modulation spectrum. Therefore, if the operating voltage is obtained based on the operating frequency according to the original modulation spectrum, the actual operating frequency obtained is often inaccurate. Using the Ramsey experiment, the real-time frequency of the qubit can be accurately obtained, thus helping us to correct the correspondence between the qubit's operating frequency and operating voltage.

[0067] Furthermore, in order to address the influence of the adjustable coupler or surrounding qubits on the operating frequency of the first qubit and the second qubit, in this embodiment, after we use the modulation spectrum to obtain the first resonant frequency and the second resonant frequency, it is necessary to calibrate the corresponding relationship between the operating frequency and the operating voltage of the first qubit and the second qubit. Specifically, in this embodiment, after obtaining the first resonant frequency and the second resonant frequency, the method further includes:

[0068] The first qubit and the second qubit are calibrated using a Ramsey experiment to obtain a first operating voltage corresponding to when the first qubit operates at the first resonant frequency, and a second operating voltage corresponding to when the second qubit operates at the second resonant frequency. When performing the state exchange experiment, the operating voltage of the first qubit is the first operating voltage, and the operating voltage of the second qubit is the second operating voltage. After the calibration operation, the obtained first operating voltage and second operating voltage are used as the operating voltages of the first qubit and the second qubit, respectively, thereby ensuring that the operating frequency of the first qubit is the first resonant frequency, and the operating frequency of the second qubit is the second resonant frequency.

[0069] It should be noted that the state exchange experiment mentioned in this embodiment refers to an experiment in which the excited state is exchanged back and forth between the two qubits when the two qubits are in resonance. The back-and-forth exchange of excited states in this state exchange experiment can take two forms: the first is the exchange of the 10 state and the 01 state (or the 01 state and the 10 state), that is, the exchange of the excited state |1> between the two qubits; the second is the exchange of the 11 state and the 02 state (or the 11 state and the 20 state), that is, the exchange of the excited state |2> and the excited state |1> between the two qubits. In addition, those skilled in the art will understand that the 10 state here can be simply understood as the first qubit being in the |1> state and the second qubit being in the |0> state; the 02 state can be simply understood as the first qubit being in the |0> state and the second qubit being in the |2> state. The only difference between these two state-exchange experiments lies in the difference in the resonance conditions between the two quantum bits. In the first experiment, the operating frequencies of the two quantum bits are generally set to be equal. In the second experiment, the operating frequencies of the two quantum bits are generally set to differ by the size of the anharmonicity of the high-frequency bit.

[0070] Generally speaking, the waveform timing diagram of the state exchange experiment can be referred to Figure 4 In a quantum chip with an adjustable coupler structure, it is necessary to add a signal timing of the adjustable coupler frequency control line. The signal timing of the adjustable coupler frequency control line is the same as the timing of the two quantum bits, which will not be described here. In the prior art, when we perform state exchange experiments, we often need to traverse two objects. One is the duration of the frequency control signal (the duration of the signal, Figure 4 The other is the amplitude of the frequency control signal. The amplitude of the frequency control signal can be understood as the operating voltage of the quantum bit. The amplitude of the frequency control signal is traversed to obtain the appropriate resonant frequency of the quantum bit. In the solution of the present application, the resonant frequency of the quantum bit is directly obtained by using the modulation spectrum of the quantum bit in step S100. There is no need to traverse the amplitude of the frequency control signal in the state exchange experiment, that is, there is no need to adjust the size of the quantum bit operating voltage. This further reduces the complexity of the entire solution to a certain extent and further improves the execution efficiency of the quantum computer.

[0071] In step S200 of the solution of this application, when performing the state exchange experiment, we fix the frequency of the frequency control signal and scan the duration of the frequency control signal. The results can be referred to Figure 5 As shown, Figure 5 The horizontal axis is the duration of the frequency control signal, in ns, and the vertical axis is the probability. The curve represents the quantum state probability of the two quantum bit system. One curve reflects the probability of the 10 state, and the other curve reflects the probability of the 01 state. Figure 5The time corresponding to point K is the desired resonance duration. In the subsequent step S300, the duration of the frequency control signal for both the qubit and the adjustable coupler is set to this resonance duration. Point K is chosen because the probability of the quantum state at this point changes most sensitively with time, facilitating subsequent analysis of signal delays. The first intersection point is chosen because subsequent intersections would extend the entire experiment time, affecting efficiency.

[0072] Specifically, in this embodiment, obtaining the first resonant frequency and the second resonant frequency according to the modulation spectra of the first qubit and the second qubit includes:

[0073] Obtaining a maximum frequency value and a minimum frequency value of the first qubit and a maximum frequency value and a minimum frequency value of the second qubit, respectively, according to the modulation spectra of the first qubit and the second qubit;

[0074] The first resonant frequency and the second resonant frequency are acquired based on the maximum frequency value and the minimum frequency value of the first qubit and the maximum frequency value and the minimum frequency value of the second qubit.

[0075] Those skilled in the art will understand that, in this embodiment, the modulation spectra of the first quantum bit and the second quantum bit mentioned refer to a data set used to reflect the relationship between the operating voltage and the operating frequency of the first quantum bit and the second quantum bit, which are generally presented in the form of a curve graph. Relevant technicians can directly see the relationship between the operating voltage and the operating frequency in the modulation spectrum graph, and select the required operating point as needed. The operating point here can refer to either the operating frequency or the operating voltage.

[0076] Specifically, in this embodiment, obtaining the first resonant frequency and the second resonant frequency based on the maximum frequency value and the minimum frequency value of the first qubit and the maximum frequency value and the minimum frequency value of the second qubit includes:

[0077] Obtaining an overlapping range of frequencies of the first qubit and the second qubit based on the maximum frequency and the minimum frequency of the first qubit and the maximum frequency and the minimum frequency of the second qubit;

[0078] The first resonant frequency and the second resonant frequency are acquired from frequencies in the overlap range.

[0079] Through the analysis of the state exchange experiment above, it can be seen that when we exchange the first 10 state and the 01 state (or the 01 state and the 10 state), the resonant frequencies of the two quantum bits are equal. Specifically, in this embodiment, the first resonant frequency is equal to the second resonant frequency, wherein any frequency within the overlapping range except the current operating frequency of the first quantum bit and the second quantum bit is the first resonant frequency. It should be noted that the selection of the resonant frequency here needs to avoid the current operating frequency of the two quantum bits, because if the resonant frequency is selected as the current operating frequency, since the frequency has not changed, the amplitude of the frequency control signal has not changed, which is reflected in the timing of the quantum bit. The frequency signal will be presented in the form of a straight line, and what we need to analyze is the delay problem. If it is a straight line, it will be impossible to analyze the delay problem of the signal.

[0080] When we choose the second exchange of the 11 state and the 02 state (or the 11 state and the 20 state), the resonant frequencies of the two qubits need to differ by an anharmonic magnitude. Specifically, in this embodiment, there is the following relationship between the first resonant frequency and the second resonant frequency:

[0081] f1+α=f2;

[0082] Among them, f1 is the first resonant frequency, α is the anharmonicity of the first quantum bit, f2 is the second resonant frequency, the first quantum bit is a high-frequency bit, and the second quantum bit is a low-frequency bit. The high-frequency bit is the quantum bit with a higher operating frequency among the two quantum bits, and the low-frequency bit is the quantum bit with a lower operating frequency among the two quantum bits.

[0083] The magnitude of the coupling strength between the two qubits directly determines how fast a two-bit quantum logic gate is executed on the two qubits, but the coupling strength cannot be too large, otherwise there will be strong residual coupling after the interaction between the two qubits ends, which will cause control errors. In a chip structure with an adjustable coupler, the coupling strength between qubits can be adjusted by adjusting the frequency of the adjustable coupler. We need to configure a suitable coupling strength to achieve the desired effect. Specifically, in this embodiment, before performing the state exchange experiment on the first qubit and the second qubit and obtaining the resonance duration based on the results of the state exchange experiment, the method further includes:

[0084] The coupling strength between the two quantum bits reaches a preset value by adjusting the operating voltage of the adjustable coupler.

[0085] In this embodiment, the preset value of the coupling strength between the two quantum bits can be set to 20 MHz, 25 MHz or 30 MHz.

[0086] Specifically, in this embodiment, the resonance duration is obtained based on the curve of the probability of the quantum state of the quantum bit reflecting the change of the frequency control signal in the result of the state exchange experiment. Figure 5 Analysis of K points.

[0087] Specifically, in this embodiment, setting the duration of the frequency control signals of the two qubits and the adjustable coupler based on the resonance duration, performing a state exchange experiment on the first qubit and the second qubit to obtain the delay of the frequency control signal between the first qubit, the second qubit, and the adjustable coupler includes:

[0088] Setting the duration of the frequency control signals of the first qubit, the second qubit, and the adjustable coupler to the resonance duration;

[0089] Sequentially fixing the delay of the frequency control signal of any two of the first qubit, the second qubit, and the adjustable coupler, and traversing the first delay of the frequency control signal of the remaining one within a first preset range, and performing a state exchange experiment on the first qubit and the second qubit;

[0090] Obtain a first change in the probability of the first qubit or the second qubit being in a first quantum state with a first delay, and obtain a delay of a frequency control signal between the first qubit, the second qubit, and the adjustable coupler based on the first change.

[0091] In the specific implementation process, we fix the delay of the frequency control signal of any two of the first quantum bit, the second quantum bit, and the adjustable coupler each time, and traverse the first delay of the frequency control signal of the remaining one within the first preset range, perform a state exchange experiment on the first quantum bit and the second quantum bit, and then obtain a first change of the quantum state probability with the first delay. The first change can be referred to Figure 6 In the curve shown in , the horizontal axis is the size of the first delay, and the vertical axis is the probability that the first quantum bit or the second quantum bit is in a first quantum state. The first quantum state here can be a |0> state or a |1> state, which can be displayed according to actual needs and is not limited here. It can be understood by those skilled in the art that the curve trends of the |0> state or the |1> state are exactly opposite and mirror-symmetrical. Figure 6 The time corresponding to the extreme point is the delay size we need to obtain.

[0092] It should be noted that in the solution of this embodiment, the delay mentioned refers to the relative delay between the starting positions of the two signals in the timing sequence. Figure 4 As an example of the timing diagram in , assuming that the frequency control signal QH of the high-frequency bit Z The signal starting position in the timing is 100ns, and the frequency control signal QL of the low frequency bit is Z The starting position in the timing is 50ns, so at this time, the delay between the high-frequency bit and the low-frequency bit is 100ns-50ns=50ns.

[0093] Based on the same inventive concept, an embodiment of the present invention further proposes a method for calibrating the delay of a frequency control signal in a quantum chip, which uses any of the methods described above to obtain the delay of the frequency control signal in the quantum chip and perform calibration.

[0094] Based on the same invention concept, please refer to Figure 7 The embodiment of the present invention further provides a device for obtaining a delayed frequency control signal in a quantum chip, comprising:

[0095] A first working module 100 is configured to obtain a first resonant frequency and a second resonant frequency based on modulation spectra of a first qubit and a second qubit, and set an operating frequency of the first qubit to the first resonant frequency and an operating frequency of the second qubit to the second resonant frequency, wherein the first qubit and the second qubit are two qubits in the quantum chip coupled via an adjustable coupler;

[0096] A second working module 200 is configured to perform a state exchange experiment on the first qubit and the second qubit, and obtain a resonance duration based on a result of the state exchange experiment. The state exchange experiment is an experiment in which excited states are exchanged back and forth between the two qubits when the two qubits are in resonance.

[0097] The third working module 300 is used to set the duration of the frequency control signals of the two quantum bits and the adjustable coupler based on the resonance duration, and perform a state exchange experiment on the first quantum bit and the second quantum bit to obtain the delay of the frequency control signal between the first quantum bit, the second quantum bit and the adjustable coupler.

[0098] It is understood that the first working module 100, the second working module 200, and the third working module 300 can be combined into a single device, or any one of the modules can be split into multiple sub-modules, or at least part of the functions of one or more of the first working module 100, the second working module 200, and the third working module 300 can be combined with at least part of the functions of other modules and implemented in a single functional module. According to an embodiment of the present invention, at least one of the first working module 100, the second working module 200, and the third working module 300 can be at least partially implemented as a hardware circuit, 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 a package, an application-specific integrated circuit (ASIC), or can be implemented in hardware or firmware in any other reasonable manner for integrating or packaging circuits, or in an appropriate combination of software, hardware, and firmware. Alternatively, at least one of the first working module 100, the second working module 200 and the third working module 300 can be at least partially implemented as a computer program module, and when the program is executed by a computer, the function of the corresponding module can be executed.

[0099] Based on the same inventive concept, an embodiment of the present invention further proposes a quantum computing measurement and control system, which utilizes the delayed acquisition method of the frequency control signal in a quantum chip described in any one of the above-mentioned characteristic descriptions, or utilizes the delay calibration method of the frequency control signal in the quantum chip described in the above-mentioned characteristic descriptions, or includes the delayed acquisition device of the frequency control signal in the quantum chip described in the above-mentioned characteristic descriptions.

[0100] Based on the same inventive concept, an embodiment of the present invention further proposes a quantum computer, including the quantum computing measurement and control system described in the above feature description.

[0101] Based on the same inventive concept, an embodiment of the present invention further proposes a readable storage medium storing a computer program. When the computer program is executed by a processor, it can implement the method for obtaining the delayed frequency control signal in a quantum chip described in any one of the above-mentioned feature descriptions, or the method for calibrating the delay of the frequency control signal in a quantum chip described in the above-mentioned feature descriptions.

[0102] The readable storage medium can be a tangible device that can keep and store the instruction used by the instruction execution device, such as, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device or any suitable combination thereof. The more specific example (non-exhaustive list) of readable storage medium includes: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a convex structure in a groove having instructions stored thereon, and any suitable combination thereof. The computer program described herein can be downloaded to each computing / processing device from the readable storage medium, or downloaded to an external computer or external storage device by a network, such as the Internet, a local area network, a wide area network and / or a wireless network. The network can include copper transmission cables, optical fiber transmission, wireless transmission, routers, firewalls, switches, gateway computers and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer program from the network and forwards the computer program for storage in a readable storage medium in each computing / processing device. The computer program for performing the operations of the present invention can be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state 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 programming languages. The computer program can be executed entirely on the user's computer, partially on the user's computer, as a separate software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer can be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or can be connected to an external computer (for example, through the Internet using an Internet service provider). In some embodiments, various aspects of the present invention are implemented by utilizing state information of a computer program to personalize an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), which can execute computer-readable program instructions.

[0103] Various aspects of the present invention are described herein with reference to the flowcharts and / or block diagrams of the methods, systems, and computer program products according to embodiments of the present invention. It should be understood that each block of the flowcharts and / or block diagrams, as well as the combination of blocks in the flowcharts and / or block diagrams, can be implemented by computer programs. These computer programs can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, thereby producing a machine such that when these programs are executed by the processor of the computer or other programmable data processing device, a device is generated that implements the functions / actions specified in one or more blocks in the flowcharts and / or block diagrams. These computer programs can also be stored in a readable storage medium, which causes the computer, programmable data processing device, and / or other device to operate in a specific manner, so that the readable storage medium storing the computer program comprises an article of manufacture comprising instructions for implementing various aspects of the functions / actions specified in one or more blocks in the flowcharts and / or block diagrams.

[0104] The computer program may also be loaded onto a computer, other programmable data processing apparatus, or other device so that a series of operational steps are performed on the computer, other programmable data processing apparatus, or other device to produce a computer-implemented process, thereby causing the computer program executed on the computer, other programmable data processing apparatus, or other device to implement the functions / actions specified in one or more blocks in the flowchart and / or block diagram.

[0105] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "example," or "specific example" means that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations 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. Furthermore, those skilled in the art may combine and reconcile different embodiments or examples described in this specification.

[0106] The above description is merely a preferred embodiment of the present invention and does not limit the present invention in any way. Any person skilled in the art who, without departing from the scope of the present invention, makes any equivalent substitution, modification, or other changes to the technical solution and technical content disclosed in the present invention shall be deemed to be within the scope of the present invention and still fall within the scope of protection of the present invention.

Claims

1. A method for delayed acquisition of frequency control signals in a quantum chip, characterized in that: include: Obtaining a first resonant frequency and a second resonant frequency according to modulation spectra of a first qubit and a second qubit, and setting an operating frequency of the first qubit to the first resonant frequency and an operating frequency of the second qubit to the second resonant frequency, wherein the first qubit and the second qubit are two qubits in the quantum chip coupled via an adjustable coupler; performing a state exchange experiment on the first qubit and the second qubit, and obtaining a resonance duration based on a result of the state exchange experiment, wherein the state exchange experiment utilizes an experiment in which excited states are exchanged back and forth between the two qubits when the two qubits are in resonance; The duration of the frequency control signals of the two quantum bits and the adjustable coupler is set based on the resonance duration, and a state exchange experiment is performed on the first quantum bit and the second quantum bit to obtain the delay of the frequency control signal between the first quantum bit, the second quantum bit and the adjustable coupler.

2. The method according to claim 1, wherein After obtaining the first resonant frequency and the second resonant frequency, the method further includes: The first qubit and the second qubit are calibrated respectively using a Ramsey experiment to obtain a first operating voltage corresponding to when the first qubit operates at the first resonant frequency, and a second operating voltage corresponding to when the second qubit operates at the second resonant frequency. When performing the state exchange experiment, the operating voltage of the first qubit is the first operating voltage, and the operating voltage of the second qubit is the second operating voltage.

3. The method according to claim 1, wherein The obtaining of the first resonant frequency and the second resonant frequency according to the modulation spectra of the first qubit and the second qubit includes: Obtaining a maximum frequency value and a minimum frequency value of the first qubit and a maximum frequency value and a minimum frequency value of the second qubit, respectively, according to the modulation spectra of the first qubit and the second qubit; The first resonant frequency and the second resonant frequency are acquired based on the maximum frequency value and the minimum frequency value of the first qubit and the maximum frequency value and the minimum frequency value of the second qubit.

4. The method according to claim 3, wherein The obtaining of the first resonant frequency and the second resonant frequency based on the maximum frequency value and the minimum frequency value of the first qubit and the maximum frequency value and the minimum frequency value of the second qubit includes: Obtaining an overlapping range of frequencies of the first qubit and the second qubit based on the maximum frequency and the minimum frequency of the first qubit and the maximum frequency and the minimum frequency of the second qubit; The first resonant frequency and the second resonant frequency are acquired from frequencies in the overlap range.

5. The method according to claim 4, wherein The first resonant frequency is equal to the second resonant frequency, wherein any frequency within the overlap range except the current operating frequencies of the first qubit and the second qubit is the first resonant frequency.

6. The method according to claim 4, wherein The following relationship exists between the first resonant frequency and the second resonant frequency: f1+α=f2; Among them, f1 is the first resonant frequency, α is the anharmonicity of the first quantum bit, f2 is the second resonant frequency, the first quantum bit is a high-frequency bit, and the second quantum bit is a low-frequency bit. The high-frequency bit is the quantum bit with a higher operating frequency among the two quantum bits, and the low-frequency bit is the quantum bit with a lower operating frequency among the two quantum bits.

7. The method according to claim 1, wherein Before performing the state exchange experiment on the first qubit and the second qubit and obtaining the resonance duration based on the result of the state exchange experiment, the method further includes: The coupling strength between the two quantum bits reaches a preset value by adjusting the operating voltage of the adjustable coupler.

8. The method according to claim 1, wherein The resonance duration is obtained according to a curve reflecting the change of the probability of the quantum state of the quantum bit with the duration of the frequency control signal in the result of the state exchange experiment.

9. The method according to claim 1, wherein The step of setting the duration of the frequency control signals of the two qubits and the adjustable coupler based on the resonance duration, and performing a state exchange experiment on the first qubit and the second qubit to obtain a delay of the frequency control signal between the first qubit, the second qubit, and the adjustable coupler includes: Setting the duration of the frequency control signals of the first qubit, the second qubit, and the adjustable coupler to the resonance duration; Sequentially fixing the delay of the frequency control signal of any two of the first qubit, the second qubit, and the adjustable coupler, and traversing the first delay of the frequency control signal of the remaining one within a first preset range, and performing a state exchange experiment on the first qubit and the second qubit; Obtain a first change in the probability of the first qubit or the second qubit being in a first quantum state with a first delay, and obtain a delay of a frequency control signal between the first qubit, the second qubit, and the adjustable coupler based on the first change.

10. A method for calibrating the delay of a frequency control signal in a quantum chip, characterized in that: The method according to any one of claims 1 to 9 is used to obtain the delay of the frequency control signal in the quantum chip and perform calibration.

11. A device for obtaining a delayed frequency control signal in a quantum chip, characterized in that: include: a first working module, configured to obtain a first resonant frequency and a second resonant frequency according to modulation spectra of a first qubit and a second qubit, and set an operating frequency of the first qubit to the first resonant frequency and an operating frequency of the second qubit to the second resonant frequency, wherein the first qubit and the second qubit are two qubits in the quantum chip coupled via an adjustable coupler; a second working module, configured to perform a state exchange experiment on the first qubit and the second qubit, and obtain a resonance duration based on a result of the state exchange experiment, wherein the state exchange experiment is an experiment in which excited states are exchanged back and forth between the two qubits when the two qubits are in resonance; The third working module is used to set the duration of the frequency control signals of the two quantum bits and the adjustable coupler based on the resonance duration, and perform a state exchange experiment on the first quantum bit and the second quantum bit to obtain the delay of the frequency control signal between the first quantum bit, the second quantum bit and the adjustable coupler.

12. A quantum computing measurement and control system, characterized in that: A method for obtaining a delayed frequency control signal in a quantum chip using any one of claims 1 to 9, or a method for calibrating the delay of a frequency control signal in a quantum chip using claim 10, or a device for obtaining a delayed frequency control signal in a quantum chip including claim 11.

13. A quantum computer, characterized in that: Including the quantum computing measurement and control system described in claim 12.

14. 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 obtaining the delay of the frequency control signal in the quantum chip according to any one of claims 1 to 9, or the method for calibrating the delay of the frequency control signal in the quantum chip according to claim 10.

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