Quantum computer system latency calibration method, calibration device, and quantum computer

Abstract

The application provides a quantum computer system delay calibration method, a calibration device and a quantum computer. First, a first delay and a second delay between quantum state control signal transmission lines connected with a first quantum bit and a second quantum bit coupled with each other are obtained, respectively. Then, a third delay between frequency control signal transmission lines connected with the first quantum bit and the second quantum bit is obtained. Finally, a fourth delay between the quantum state control signal transmission lines connected with the first quantum bit and the second quantum bit is obtained based on the first delay, the second delay and the third delay, and delay calibration is performed based on the fourth delay, so as to eliminate the transmission delays on different quantum state control signal transmission lines, so that the frequency control signals on different quantum state control signal transmission lines can reach the corresponding quantum bits at the same time according to the designed timing, the corresponding quantum bits are excited at the same time, respectively, and the control precision of the two quantum bit gates is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of quantum chip measurement and control, and particularly relates to a quantum computer system delay calibration method, a calibration device and a quantum computer. BACKGROUND

[0002] Quantum computing is a new computing method that combines quantum mechanics and computers, and performs computation by controlling quantum information units in accordance with quantum mechanical laws. It uses quantum bits as basic units, has quantum superposition and entanglement, and can realize information encoding and computation storage through controlled evolution of quantum states, thus having a huge amount of information carrying capacity and super strong parallel computing processing capacity that cannot be matched by classical computing.

[0003] The quantum computer core is a quantum chip, which is provided with a plurality of quantum bits. Each quantum bit is composed of a specific hardware circuit provided on the quantum chip, and each quantum bit has at least two distinguishable logic states. Based on quantum algorithms, the logic states of the quantum bits can be controllably changed, thereby realizing quantum computing.

[0004] The quantum computer also includes a measurement and control system that provides a measurement and control environment for the quantum chip. The measurement and control system mainly includes hardware devices located at room temperature and low-temperature devices and signal transmission lines located in a dilution refrigerator. After the quantum chip is packaged, it is fixed to the extremely low-temperature layer at the bottom of the dilution refrigerator and finally connected to the hardware devices at room temperature through coaxial lines between layers. In the measurement and control system, two types of lines are mainly used when regulating the quantum states of the quantum bits. One is a first type of transmission line for regulating the quantum states of the quantum bits, and the other is a second type of transmission line for regulating the frequency of the quantum bits.

[0005] The coupling between the plurality of quantum bits on the quantum chip is realized by inter-coupling through a coupling structure. When performing a two-quantum-bit experiment, the quantum states of the corresponding two quantum bits need to be adjusted to the quantum states required for the two-quantum-bit gate to be implemented while a control signal is applied on the first type of transmission line. However, since a plurality of microwave devices are provided on the first type of transmission line, and the lengths of different first type of transmission lines cannot be guaranteed to be completely equal, the transmission delays of the control signals on different first type of transmission lines are different, which causes different control signals to not reach their corresponding quantum bits at the designed timing, and this will cause the quantum state of one of the two quantum bits to be excited in advance, deviating from the preset quantum state, and will seriously affect the regulation accuracy of the two-quantum-bit gate. Therefore, how to calibrate the line delay on the first type of transmission line of different quantum bits to ensure that different control signals reach their corresponding quantum bits at the designed timing and improve the regulation accuracy of the two-quantum-bit gate is a problem that needs to be solved at present. SUMMARY

[0006] The present application aims to provide a quantum computer system delay calibration method, a calibration device and a quantum computer to solve the problem that in the prior art, when two-qubit experiments are performed, the transmission delays on the first-type transmission lines of different qubits are different, resulting in different control signals not being able to reach their corresponding qubits at the designed timing, and the regulation accuracy of the two-qubit gate being very low. The present application can improve the regulation accuracy of the two-qubit gate.

[0007] To achieve the above-mentioned purpose, in a first aspect, the present application provides a quantum computer system delay calibration method, the quantum computer system comprising a quantum chip, the quantum chip being provided with a plurality of qubits, each qubit being connected with a quantum state regulation signal transmission line and a frequency regulation signal transmission line, the calibration method comprising:

[0008] acquiring a first delay between the quantum state regulation signal transmission line and the frequency regulation signal transmission line connected to a first qubit and a second delay between the quantum state regulation signal transmission line and the frequency regulation signal transmission line connected to a second qubit, wherein the first qubit and the second qubit are coupled to each other;

[0009] acquiring a third delay between the frequency regulation signal transmission lines connected to the first qubit and the second qubit, respectively;

[0010] acquiring a fourth delay between the quantum state regulation signal transmission lines connected to the first qubit and the second qubit based on the first delay, the second delay and the third delay, and performing delay calibration based on the fourth delay.

[0011] Optionally, the acquiring of the first delay between the quantum state regulation signal transmission line and the frequency regulation signal transmission line connected to the first qubit and the second delay between the quantum state regulation signal transmission line and the frequency regulation signal transmission line connected to the second qubit specifically comprises:

[0012] acquiring the first delay between the quantum state regulation signal transmission line and the frequency regulation signal transmission line connected to the first qubit and the second delay between the quantum state regulation signal transmission line and the frequency regulation signal transmission line connected to the second qubit based on a representation that the quantum state evolution of a qubit is affected by changes in its quantum state regulation signal and frequency regulation signal.

[0013] Optionally, the acquiring of the third delay between the frequency regulation signal transmission lines connected to the first qubit and the second qubit, respectively, specifically comprises:

[0014] The quantum state evolution of two quantum bits based on mutual coupling is influenced by changes in quantum state control signals and frequency control signals, and a third delay between frequency control signal transmission lines connected to the first quantum bit and the second quantum bit is obtained.

[0015] Optionally, the fourth delay between quantum state control signal transmission lines connected to the first quantum bit and the second quantum bit is obtained based on the first delay, the second delay, and the third delay, and specifically includes:

[0016] The duration of the quantum state control signal applied to the quantum state control signal transmission line connected to the first quantum bit is a first time;

[0017] The duration of the frequency control signal applied to the frequency control signal transmission line connected to the first quantum bit is determined to be a second time based on the first time and the first delay;

[0018] The duration of the frequency control signal applied to the frequency control signal transmission line connected to the second quantum bit is determined to be a third time based on the second time and the third delay;

[0019] The duration of the quantum state control signal applied to the quantum state control signal transmission line connected to the second quantum bit is determined to be a fourth time based on the third time and the second delay;

[0020] The fourth delay between quantum state control signal transmission lines connected to the first quantum bit and the second quantum bit is determined based on the first time and the fourth time.

[0021] Optionally, the first delay between quantum state control signal transmission lines and frequency control signal transmission lines connected to the first quantum bit is obtained based on the quantum state evolution of a quantum bit being influenced by changes in quantum state control signals and frequency control signals, and specifically includes:

[0022] A first control signal is applied to the first quantum bit through the quantum state control signal transmission line connected to the first quantum bit, and a second control signal with a first preset delay is applied to the first quantum bit through the frequency control signal transmission line connected to the first quantum bit; wherein the first control signal is used to control the quantum state of the first quantum bit to the eigenstate, and the second control signal is used to control the frequency of the first quantum bit, and the change in the frequency of the first quantum bit will affect the probability of its quantum state being in the eigenstate;

[0023] updating the first preset delay in a first preset range in turn, and applying the second control signal after updating the first preset delay to the first qubit to obtain a first curve of probability of quantum state of the first qubit being eigenstate varying with the first preset delay; wherein the first preset range is set according to lengths of the quantum state regulation signal transmission line and the frequency regulation signal transmission line connected with the first qubit;

[0024] determining whether the first curve has a trough; if yes, determining the first delay based on the first preset delay corresponding to the trough of the first curve.

[0025] Optionally, after the determination of whether the first curve has a trough, the method further comprises:

[0026] if no, delaying the first control signal by a first fixed time length, and returning to the step of applying the first control signal through the quantum state regulation signal transmission line connected with the first qubit to the first qubit.

[0027] Optionally, after the first control signal is delayed by the first fixed time length, when the first curve has a trough, the determination of the first delay based on the first preset delay corresponding to the trough of the first curve comprises:

[0028] respectively acquiring the first preset delay corresponding to the trough of the first curve;

[0029] respectively determining the first delay based on the first preset delay and the first fixed time length.

[0030] Optionally, the acquisition of the representation of quantum state evolution of the two qubits coupled with each other being affected by changes of quantum state regulation signals and frequency regulation signals connected with the two qubits comprises:

[0031] respectively presetting quantum states of the first qubit and the second qubit as excited states and ground states, and acquiring a first amplitude and a second amplitude of the frequency regulation signals respectively applied to the frequency regulation signal transmission lines connected with the first qubit and the second qubit based on a resonance test of the first qubit and the second qubit; wherein the resonance test is an experiment of measuring coupling strength of the first qubit and the second qubit varying with the amplitudes of the frequency regulation signals.

[0032] obtain a first width of the frequency control signal based on a first amplitude and a second amplitude of the frequency control signal applied on a frequency control signal transmission line connected with the first qubit and the second qubit, and a quantum state oscillation test of the first qubit and the second qubit; wherein the quantum state oscillation test is an experiment of measuring quantum state of the first qubit and the second qubit changing with the width of the frequency control signal;

[0033] apply a first frequency control signal with the first amplitude and the first width to the frequency control signal transmission line connected with the first qubit, and sequentially update a second preset delay within a second preset range, apply a second frequency control signal with the second amplitude and the first width after the second preset delay is updated to the frequency control signal transmission line connected with the second qubit, and obtain a second curve of probability of quantum state of the first qubit and the second qubit being excited state and ground state respectively changing with the second preset delay;

[0034] determine whether the second curve has a trough, and if yes, determine the third delay based on the second preset delay corresponding to the trough of the second curve.

[0035] Optionally, after the determination of whether the second curve has a trough, the method further comprises:

[0036] if no, delay the first frequency control signal by a second fixed time length, and return to apply the first frequency control signal with the first amplitude and the first width to the frequency control signal transmission line connected with the first qubit.

[0037] Optionally, after the first frequency control signal is delayed by the second fixed time length, when the second curve has a trough, the determination of the third delay based on the second preset delay corresponding to the trough of the second curve comprises:

[0038] obtain the second preset delay corresponding to the trough of the second curve;

[0039] determine the third delay based on the second preset delay and the second fixed time length.

[0040] In a second aspect, the present application provides a calibration device for a quantum computer system delay, comprising:

[0041] The first acquisition module is configured to acquire a first delay between quantum state control signal transmission lines connected with a first qubit and a second delay between quantum state control signal transmission lines connected with a second qubit based on a representation of quantum state evolution of the first qubit and the second qubit affected by changes in quantum state control signals and frequency control signals, wherein the first qubit and the second qubit are coupled with each other.

[0042] The second acquisition module is configured to acquire a third delay between frequency control signal transmission lines connected with the first qubit and the second qubit based on a representation of quantum state evolution of the two qubits affected by changes in quantum state control signals and frequency control signals.

[0043] The calibration module is configured to acquire a fourth delay between quantum state control signal transmission lines connected with the first qubit and the second qubit based on the first delay, the second delay, and the third delay, and to perform delay calibration based on the fourth delay.

[0044] In a third aspect, the present application provides a quantum computer, which comprises a quantum chip and a quantum computer system delay calibration device as described in the second aspect, wherein the quantum chip is provided with a plurality of qubits coupled with each other, each of the qubits is connected with quantum state control signal transmission lines and frequency control signal transmission lines, and the quantum computer system delay calibration device is connected with the quantum state control signal transmission lines and the frequency control signal transmission lines, and is configured to implement the quantum computer system delay calibration method as described in the third aspect.

[0045] Compared with the prior art, the quantum computer system delay calibration method, the calibration device and the quantum computer provided by the application have the following beneficial effects: the quantum computer system comprises a quantum chip, the quantum chip is provided with a plurality of quantum bits, each quantum bit is connected with a quantum state regulation signal transmission line and a frequency regulation signal transmission line, in the implementation of the calibration method, firstly, a first delay between the quantum state regulation signal transmission line and the frequency regulation signal transmission line connected with a first quantum bit and a second delay between the quantum state regulation signal transmission line and the frequency regulation signal transmission line connected with a second quantum bit are obtained, then a third delay between the frequency regulation signal transmission lines connected with the first quantum bit and the second quantum bit is obtained, finally, a fourth delay between the quantum state regulation signal transmission lines connected with the first quantum bit and the second quantum bit is obtained based on the first delay, the second delay and the third delay, and delay calibration is performed based on the fourth delay, so that the transmission delays of different quantum state regulation signal transmission lines caused by the arrangement of a plurality of microwave devices and the different lengths are eliminated, so that different frequency regulation signals reach the corresponding quantum bits according to the designed timing, and the corresponding quantum bits are excited at the same time, and the control precision of the two quantum bit gates is improved. BRIEF DESCRIPTION OF DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0047] Figure 1 It is a hardware structure block diagram of a computer terminal of a quantum computer system delay calibration method provided by an embodiment of the present application.

[0048] Figure 2 It is a low-temperature measurement and control circuit schematic diagram of a dilution refrigerator provided by an embodiment of the present application.

[0049] Figure 3 It is a flowchart of a quantum computer system delay calibration method provided by an embodiment of the present application.

[0050] Figure 4 It is a flowchart of a method for obtaining a fourth delay between quantum state regulation signal transmission lines connected with a first quantum bit and a second quantum bit based on a first delay, a second delay and a third delay provided by an embodiment of the present application.

[0051] Figure 5is a flowchart of a method for acquiring a first delay between a quantum state control signal transmission line and a frequency control signal transmission line connected with a first quantum bit according to an embodiment of the present application;

[0052] Figure 6 is a first curve showing the probability of the quantum state of the first quantum bit being an eigenstate as the first preset delay changes according to an embodiment of the present application;

[0053] Figure 7 is a flowchart of a method for acquiring a third delay between frequency control signal transmission lines connected with the first quantum bit and the second quantum bit according to an embodiment of the present application;

[0054] Figure 8 is a second curve showing the probability of the quantum state of the first quantum bit being an excited state and the probability of the quantum state of the second quantum bit being a ground state as the second preset delay changes according to an embodiment of the present application;

[0055] Figure 9 is a structural diagram of a calibration device for a quantum computer system according to an embodiment of the present application.

[0056] Legend:

[0057] 100-computer terminal; 101-processor; 102-power supply; 103-transmission device; 104-input / output device; 105-memory, 200-calibration device; 201-first acquisition module; 202-second acquisition module; 203-calibration module; 1-dilution refrigerator; 2-quantum chip; 21-quantum bit; 3-microwave device; 4-hardware device. DETAILED DESCRIPTION

[0058] The present application provides a calibration method and calibration device for a quantum computer system and a quantum computer. The advantages and features of the present application will be more apparent from the following description. It should be noted that the drawings are very simplified and the proportions are not accurate, which are only used to facilitate and clarify the purpose of illustrating the embodiments of the present application.

[0059] In the description of this invention, 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 indicated technical features. 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] The method provided in this embodiment can be executed on a computer terminal or similar computing device. For example, to run on a computer terminal, please refer to [link to example]. Figure 1 The computer terminal 100 includes a power supply 102 and may include one or more ( Figure 1 Only one is shown in the diagram. A processor 101 (which may include, but is not limited to, a microprocessor MCU or a programmable logic device FPGA, etc.) and a memory 105 for storing data are also shown. Optionally, the computer terminal 100 may further include a transmission device 103 for communication functions and an input / output device 104. Those skilled in the art will understand that... Figure 1 The structure shown is for illustrative purposes only and does not limit the structure of the computer terminal described above. For example, the computer terminal may also include components that are more complex than those described above. Figure 1 The more or fewer components shown, or having the same Figure 1 The different configurations shown.

[0061] The memory 105 can be used to store software programs and modules for application software, such as the program instructions / modules corresponding to the method for determining multi-qubit measurement results provided in this application. The processor 101 executes various functional applications and data processing by running the software programs and modules stored in the memory 105, thereby implementing the above-described method. The memory 105 may include high-speed random access memory and may also include non-volatile solid-state memory. In some embodiments, the memory 105 may further include memory remotely located relative to the processor, and these remote memories can be connected to a computer terminal via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0062] The transmission device 103 is used to receive or send data via a network. Specific examples of the network described above may include a wireless network provided by a communication provider for the computer terminal. In one embodiment, the transmission device 103 includes a Network Interface Controller (NIC), which can connect to other network devices via a base station to communicate with the Internet. In another embodiment, the transmission device 103 may be a Radio Frequency (RF) module for wireless communication with the Internet.

[0063] The method provided by the embodiment can be applied to the computer terminal or quantum computer system.

[0064] Please refer to Figure 2 In the quantum computer system, a plurality of quantum bits 21 (two quantum bits 21 are taken as an example in the figure) are integrated on the quantum chip 2 and are coupled to each other, and each quantum bit 21 is coupled to an XY signal transmission line for receiving a quantum state control signal and a Z signal transmission line for receiving a quantum bit frequency control signal. The XY signal transmission line and the Z signal transmission line are respectively led out to room temperature through the low-temperature line of the dilution refrigerator 1, and then connected to the corresponding hardware device 4 at the room temperature end. When performing a two-quantum-bit experiment, it is necessary to adjust the quantum state of the corresponding two quantum bits to the quantum state required by the two-quantum-bit gate to be implemented by applying a control signal on the XY signal transmission line. However, since a plurality of microwave devices are arranged on the XY signal transmission line, and the lengths of different XY signal transmission lines cannot be guaranteed to be completely equal, the transmission delays of different control signals on different XY signal transmission lines are different, so that different control signals cannot simultaneously reach the corresponding quantum bits according to the designed timing, which can cause the quantum state of one of the two quantum bits to be excited in advance, deviating from the preset quantum state, and seriously affecting the control accuracy of the two-quantum-bit gate.

[0065] The core idea of the application is to provide a quantum computer system delay calibration method, a calibration device and a quantum computer. First, the first delay and the second delay between the quantum state control signal transmission lines (i.e. the above-mentioned XY signal transmission lines) and the frequency control signal transmission lines (i.e. the above-mentioned Z signal transmission lines) connected to the first quantum bit and the second quantum bit coupled to each other are obtained, respectively. Then, the third delay between the frequency control signal transmission lines connected to the first quantum bit and the second quantum bit is obtained. Finally, the fourth delay between the quantum state control signal transmission lines connected to the first quantum bit and the second quantum bit is obtained based on the first delay, the second delay and the third delay, and the delay calibration is performed based on the fourth delay, so as to eliminate the transmission delays on different quantum state control signal transmission lines, so that the frequency control signals on different quantum state control signal transmission lines can simultaneously reach the corresponding quantum bits according to the designed timing, respectively, and the corresponding quantum bits are excited simultaneously, thereby improving the control accuracy of the two-quantum-bit gate.

[0066] Therefore, the application provides a quantum computer system delay calibration method, the quantum computer system includes a quantum chip, the quantum chip is provided with a plurality of quantum bits, each quantum bit is connected to a quantum state control signal transmission line and a frequency control signal transmission line, please refer to Figure 3 , the calibration method includes the following steps:

[0067] Step S1, obtaining a first delay between a quantum state control signal transmission line connected to a first quantum bit and a frequency control signal transmission line and a second delay between a quantum state control signal transmission line connected to a second quantum bit and a frequency control signal transmission line; wherein the first quantum bit and the second quantum bit are coupled to each other.

[0068] Specifically, based on the characterization that the quantum state evolution of a quantum bit is affected by the changes of its quantum state control signal and frequency control signal, the first delay between the quantum state control signal transmission line connected to the first quantum bit and the frequency control signal transmission line and the second delay between the quantum state control signal transmission line connected to the second quantum bit and the frequency control signal transmission line are obtained.

[0069] Step S2, obtaining a third delay between the frequency control signal transmission lines connected to the first quantum bit and the second quantum bit respectively.

[0070] Specifically, based on the characterization that the quantum state evolution of two quantum bits coupled to each other is affected by the changes of their quantum state control signals and frequency control signals, the third delay between the frequency control signal transmission lines connected to the first quantum bit and the second quantum bit respectively is obtained.

[0071] Step S3, obtaining a fourth delay between the quantum state control signal transmission lines connected to the first quantum bit and the second quantum bit based on the first delay, the second delay, and the third delay, and performing delay calibration based on the fourth delay.

[0072] Specifically, after obtaining the fourth delay, in actual application, initially, the quantum state control signal on the quantum state control signal transmission line connected to the first quantum bit or the quantum state control signal on the quantum state control signal transmission line connected to the second quantum bit is compensated by an empty signal with a duration of the absolute value of the fourth delay to eliminate the transmission delays of both, so as to realize delay calibration between the quantum state control signal transmission line connected to the first quantum bit and the quantum state control signal transmission line connected to the second quantum bit.

[0073] Wherein, the signal sources of the quantum state control signal and the frequency control signal are provided by hardware devices in the room temperature layer outside the dilution refrigerator, including but not limited to a vector network analyzer, a radio frequency signal generator, etc. The quantum state control signal is used to control the quantum state of the corresponding quantum bit to the required quantum state in the experiment, and the frequency control signal is used to control the frequency of the corresponding quantum bit.

[0074] It should be noted that the first delay in the embodiment is the delay of the quantum state control signal transmission line connected with the first qubit relative to the frequency control signal transmission line connected therewith; the second delay is the delay of the quantum state control signal transmission line connected with the second qubit relative to the frequency control signal transmission line connected therewith; and the third delay is the delay of the frequency control signal transmission line connected with the first qubit relative to the frequency control signal transmission line connected with the second qubit.

[0075] For example, referring to Figure 4 , the fourth delay between the quantum state control signal transmission lines connected with the first qubit and the second qubit is obtained based on the first delay, the second delay and the third delay, specifically comprising the following steps:

[0076] In step S31, the duration of the quantum state control signal applied on the quantum state control signal transmission line connected with the first qubit is the first time.

[0077] Specifically, in the embodiment, the first time is set to be 10 ns, and the first time is denoted as T XY1 .

[0078] In step S32, the duration of the frequency control signal applied on the frequency control signal transmission line connected with the first qubit is determined to be the second time based on the first time and the first delay.

[0079] Specifically, the second time is denoted as T Z1 , for example, in the embodiment, the first delay obtained in step S1 is 5 ns, i.e. T XY1 -T Z1 = 5 ns, and it can be obtained that when T XY1 = 10, T Z1 = 5 ns.

[0080] In step S33, the duration of the frequency control signal applied on the frequency control signal transmission line connected with the second qubit is determined to be the third time based on the second time and the third delay.

[0081] Specifically, the third time is denoted as T Z2 , for example, in the embodiment, the third delay obtained in step S2 is 1 ns, i.e. T Z1 -T Z2 = 1 ns, and it can be obtained that when T Z1 = 5 ns, T Z2 = 4 ns.

[0082] Step S34: Based on the third time and the second delay, determine the duration of the quantum state control signal applied to the quantum state control signal transmission line of the second quantum bit connection as the fourth time.

[0083] Specifically, let the fourth time be denoted as T. XY2 For example, in this embodiment, the second delay obtained through step S1 is 8ns, i.e., T XY2 -T Z2 =8ns, therefore, when T Z2 When T = 4ns, XY2 =12ns.

[0084] Step S35: Determine the fourth delay between the quantum state control signal transmission lines to which the first quantum bit and the second quantum bit are respectively connected, based on the first time and the fourth time.

[0085] Specifically, as can be seen from the above, when T XY1 =10ns, T XY2 When = 12ns, T can be obtained XY1 -T XY2 = -2ns, that is, the fourth delay is -2ns, which means that the quantum state control signal on the quantum state control signal transmission line connected to the first quantum bit arrives at the first quantum bit 2ns later than the quantum state control signal on the quantum state control signal transmission line connected to the second quantum bit.

[0086] For example, please refer to Figure 5 The characterization of the quantum state evolution based on qubits, which is affected by changes in their quantum state control signals and frequency control signals, and the acquisition of the first delay between the quantum state control signal transmission line and the frequency control signal transmission line connected to the first qubit, specifically includes:

[0087] Step S11: A first control signal is applied to the first quantum bit through the quantum state modulation signal transmission line connected to the first quantum bit, and a second control signal after a first preset delay is applied to the first quantum bit through the frequency modulation signal transmission line connected to the first quantum bit; wherein, the first control signal is used to modulate the quantum state of the first quantum bit to an eigenstate, and the second control signal is used to modulate the frequency of the first quantum bit, and the change in the frequency of the first quantum bit will affect the probability that its quantum state is an eigenstate.

[0088] The first control signal enters the first quantum bit from one end of the quantum state control signal transmission line connected with the first quantum bit, and is used for exciting the first quantum bit and controlling the quantum state of the first quantum bit to an eigenstate. Specifically, the quantum state of the first quantum bit includes two eigenstates of |0> state and |1> state. In this embodiment, a pi pulse quantum bit control signal is applied to the quantum state control signal transmission line connected with the first quantum bit, that is, the first control signal is a pi pulse quantum bit control signal, which is used for controlling the quantum state of the first quantum bit to |1> state. At this time, the probability of the quantum state of the first quantum bit being |1> state is 1 or an approximate 1 probability value.

[0089] The second control signal applied after the preset delay enters the first quantum bit on the quantum chip from one end of the frequency control signal transmission line connected with the first quantum bit, and is used for controlling the frequency of the first quantum bit.

[0090] It should be noted that the frequency of the first quantum bit refers to the energy level transition frequency between the ground state (i.e., |0> state) and the excited state (i.e., |1> state) of the first quantum bit. Only when the frequency of the first control signal is equal to or close to the frequency of the first quantum bit, the first quantum bit produces a resonance effect with the first control signal, and then the first quantum bit connected with the quantum state control signal transmission line applies the first control signal to control the quantum state of the first quantum bit. When the frequency of the first quantum bit is very different from the frequency of the first control signal, the quantum state of the first quantum bit will not respond to the first control signal. In this embodiment, the second control signal applied to the first quantum bit will control the frequency of the quantum bit, and then will affect the control effect of the first control signal on the quantum state of the first quantum bit. That is, as the frequency of the first quantum bit changes, the probability of the quantum state being an eigenstate will also change.

[0091] In step S12, the first preset delay is sequentially updated within a first preset range, and the second control signal after the first preset delay is updated is applied to the first quantum bit, to obtain a first curve of the probability of the quantum state of the first quantum bit being an eigenstate changing with the first preset delay; wherein the first preset range is set according to the lengths of the quantum state control signal transmission line and the frequency control signal transmission line connected with the first quantum bit.

[0092] Specifically, within a preset range, the first preset delay is updated sequentially in increments of 0.5 ns. With each increment, the second control signal after updating the first preset delay is applied to the first qubit, and the probability of the first qubit's quantum state being an eigenstate is measured as a function of the first preset delay. Then, all the data is plotted with the first preset delay on the horizontal axis and the probability of the first qubit's quantum state on the vertical axis to create a first curve showing the probability of the first qubit's quantum state being an eigenstate as a function of the first preset delay. Figure 6 As shown.

[0093] The first preset range is set according to the length of the quantum state control signal transmission line and the frequency control signal transmission line connected to the first quantum bit, so as to ensure that the first preset delay takes a value within the first preset range, and can obtain all the effective data information, so that the first curve is complete.

[0094] Step S13: Determine whether the first curve has a trough. If so, proceed to step S14.

[0095] Specifically, it can be seen from Figure 6 Intuitively, it can be seen whether the change curve has troughs. The actual situation at a trough is that when a second control signal with a preset delay is applied to the frequency control signal transmission line connected to the first qubit, and the first and second control signals are transmitted to the first qubit via the quantum state control signal transmission line and the frequency control signal transmission line respectively, the waveforms of the first and second control signals are aligned. As mentioned earlier, when the frequency of the first qubit changes, the quantum state of the first qubit also changes accordingly. When the waveforms of the first and second control signals are aligned, that is, when the second control signal applied to the frequency control signal transmission line connected to the first qubit adjusts the frequency of the first qubit to deviate from the maximum value of the target operating point frequency, the first control signal applied to the quantum state control signal transmission line connected to the first qubit has the worst effect on the quantum state of the first qubit, and the probability that the quantum state of the first qubit is an eigenstate is the lowest.

[0096] Step S14: Determine the first delay based on the first preset delay corresponding to the trough of the first curve.

[0097] Similarly, the second delay can be obtained by following the above method.

[0098] For example, after determining whether the first curve has a trough, the method further includes:

[0099] If not, the first control signal is delayed for a first fixed time length, and the step S11 is returned.

[0100] Specifically, if the change curve with the wave trough cannot be obtained by only delaying the second control signal, it indicates that the transmission speed on the frequency control signal transmission line connected with the first quantum bit is less than the transmission speed on the quantum state control signal transmission line connected with the first quantum bit. At this time, the first control signal needs to be delayed for a first fixed time length with a certain length, so as to ensure the implementability of the subsequent scheme.

[0101] Exemplarily, when the first curve has the wave trough after the first control signal is delayed for the first fixed time length, the first preset delay corresponding to the wave trough of the first curve is used to determine the first delay, specifically including:

[0102] The first preset delay corresponding to the wave trough of the first curve is obtained respectively.

[0103] The first delay is determined based on the first preset delay and the first fixed time length respectively.

[0104] Exemplarily, please refer to Figure 7 The third delay between the frequency control signal transmission lines connected with the first quantum bit and the second quantum bit is obtained based on the representation of the quantum state evolution of the two quantum bits coupled with each other and influenced by the change of the quantum state control signal and the frequency control signal, specifically including:

[0105] In step S21, the quantum state of the first quantum bit and the quantum state of the second quantum bit are respectively preset as the excited state and the ground state, and the first amplitude and the second amplitude of the frequency control signal respectively applied on the frequency control signal transmission lines connected with the first quantum bit and the second quantum bit are obtained based on the resonance test of the first quantum bit and the second quantum bit; wherein, the resonance test is an experiment of measuring the coupling strength of the first quantum bit and the second quantum bit changing with the amplitude of the frequency control signal.

[0106] Specifically, a pi-pulse quantum state regulation signal is applied to the first quantum bit through the quantum state regulation signal transmission line connected to the first quantum bit, for regulating the quantum state of the first quantum bit to an excited state; and a 0-pulse quantum state regulation signal is applied to the second quantum bit through the quantum state regulation signal transmission line connected to the second quantum bit, for regulating the quantum state of the second quantum bit to a ground state. Based on this, a resonance experiment is performed on the first quantum bit and the second quantum bit to respectively obtain a first amplitude of the frequency regulation signal applied to the frequency regulation signal transmission line connected to the first quantum bit and a second amplitude of the frequency regulation signal applied to the frequency regulation signal transmission line connected to the second quantum bit when the first quantum bit and the second quantum bit resonate and the coupling strength is maximum (the frequencies of the two quantum bits are equal).

[0107] It should be noted that the frequency regulation of the first quantum bit and the second quantum bit will affect each other and further affect the quantum states thereof. When the frequencies of the first quantum bit and the second quantum bit are regulated to be equal, the coupling strength of the first quantum bit and the second quantum bit is maximum, and the quantum states of the first quantum bit and the second quantum bit will be exchanged, i.e., the first quantum bit will decay from the excited state to the ground state, and the second quantum bit will decay from the ground state to the excited state. It can be seen that the coupling strength of the first quantum bit and the second quantum bit will affect the quantum states thereof. In the embodiment, the resonance experiment is an experiment for measuring the coupling strength of the first quantum bit and the second quantum bit as the amplitude of the frequency regulation signal changes. Specifically, it is an experiment for measuring the probability of the quantum state of the first quantum bit and the second quantum bit being an eigenstate (including the ground state and the eigenstate) as the amplitude of the frequency regulation signal changes.

[0108] In step S22, a first width of the frequency regulation signal is obtained based on the first amplitude and the second amplitude of the frequency regulation signal applied to the frequency regulation signal transmission lines connected to the first quantum bit and the second quantum bit, and a quantum state oscillation experiment of the first quantum bit and the second quantum bit. The quantum state oscillation experiment is an experiment for measuring the quantum state of the first quantum bit and the second quantum bit as the width of the frequency regulation signal changes.

[0109] Specifically, the frequency control signal transmission line connected with the first qubit applies the frequency control signal with the first amplitude to the first qubit, and the frequency control signal transmission line connected with the second qubit applies the frequency control signal with the second amplitude to the second qubit. As known from step S1, at this time, the first qubit and the second qubit resonate and the coupling strength is maximum (the frequencies of the two qubits are equal). Based on this, the quantum state oscillation experiment is performed on the first qubit and the second qubit to obtain the first width of the frequency control signal applied to the first qubit and the second qubit when the probability change of the quantum state of the first qubit and the second qubit as the eigenstate is most sensitive to the width of the frequency control signal in the exchange process.

[0110] It should be noted that the width of the frequency control signal applied to the first qubit and the second qubit is equal and synchronously changed throughout, that is, the duration of the frequency control signal applied to the first qubit and the second qubit is equal and synchronously changed.

[0111] Step S23: The first frequency control signal with the first amplitude and the first width is applied to the frequency control signal transmission line connected with the first qubit, and the second preset delay is sequentially updated in a second preset range. The second frequency control signal with the second amplitude and the first width after the second preset delay is updated is applied to the frequency control signal transmission line connected with the second qubit, to obtain a second curve of the probability change of the quantum state of the first qubit and the second qubit being the excited state and the ground state, respectively, with the change of the second preset delay.

[0112] Specifically, the frequency control signal transmission line connected with the first qubit applies the frequency control signal with the first amplitude and the first width to the first qubit, and the frequency control signal transmission line connected with the second qubit applies the frequency control signal with the second amplitude and the first width to the second qubit. As known from steps S1 and S2, at this time, the first qubit and the second qubit resonate, the coupling strength is maximum, and the probability change of the quantum state of the first qubit and the second qubit as the eigenstate is most sensitive to the duration of the frequency control signal.

[0113] More specifically, within the second preset range, the second preset delay is updated sequentially in 1ns increments. With each increment, a frequency modulation signal with the second amplitude and the first width, updated to the second preset delay, is applied to the second qubit. The probability of the first and second qubits being in excited and ground states, respectively, is measured as a function of the second preset delay. Then, all the data is plotted with the second preset delay on the horizontal axis and the probability of the first and second qubits being in excited and ground states, respectively, on the vertical axis, forming a second curve showing the probability of the first and second qubits being in excited and ground states as a function of the second preset delay. Figure 8 As shown.

[0114] The second preset range is set according to the length of the frequency-controlled signal transmission line connecting the first quantum bit and the second quantum bit, respectively, so as to ensure that the second preset delay takes a value within the second preset range, and can obtain all the effective data information, so that the second change curve is complete.

[0115] Step S24: Determine whether the second curve has a trough. If so, proceed to step S25.

[0116] Specifically, from Figure 8 Intuitively, it can be seen whether the second curve has a trough. The actual situation at the trough is that, after delay calibration of the frequency control signal transmission line connecting the first and second qubits based on the second preset delay corresponding to that point, when the two frequency control signals are transmitted to the first and second qubits respectively through their corresponding frequency control signal transmission lines, the waveform widths of the two frequency control signals are aligned (i.e., the start and end points of the waveforms of the two frequency control signals are aligned). As described above, when the waveforms of the frequency control signals of the first and second qubits are aligned (i.e., the widths of the frequency control signals of the first and second qubits are equal, i.e., the durations are equal), the mutual influence between the first and second qubits is greatest, and the probability change of the quantum state of the first and second qubits being an eigenstate is most sensitive to the change in the duration of the frequency control signal. This results in the lowest and equal probability that the quantum states of the first and second qubits are respectively an excited state and a ground state, specifically both around 50%.

[0117] Step S25: Determine the third delay based on the second preset delay corresponding to the trough of the second curve.

[0118] Exemplarily, after judging whether the second curve has a trough, the method further comprises:

[0119] If no, the first frequency control signal is delayed for a second fixed time length, and the step S23 is performed again.

[0120] Specifically, if the first curve with a trough cannot be obtained by only delaying the second frequency control signal, it indicates that the transmission speed of the frequency control signal transmission line connected to the second quantum bit is less than the transmission speed of the frequency control signal transmission line connected to the first quantum bit. At this time, the first frequency control signal needs to be delayed for a second fixed time length with a certain length, so as to ensure the implementability of the subsequent scheme.

[0121] Exemplarily, after the first frequency control signal is delayed for a second fixed time length, when the second curve has a trough, the third delay is determined based on a second preset delay corresponding to the trough of the second curve, and specifically comprises:

[0122] obtaining the second preset delay corresponding to the trough of the second curve.

[0123] determining the third delay based on the second preset delay and the second fixed time length.

[0124] Based on the same inventive concept, the embodiment also provides a calibration device for time delay of a quantum computer system, please refer to Figure 9 , the calibration device 200 specifically comprises:

[0125] The first acquisition module 201 is configured to acquire a first time delay between a quantum state control signal transmission line and a frequency control signal transmission line connected to a first quantum bit and a second time delay between a quantum state control signal transmission line and a frequency control signal transmission line connected to a second quantum bit based on a representation of quantum state evolution of the quantum bit affected by changes in the quantum state control signal and the frequency control signal, wherein the first quantum bit and the second quantum bit are coupled to each other.

[0126] The second acquisition module 202 is configured to acquire a third time delay between frequency control signal transmission lines connected to the first quantum bit and the second quantum bit based on a representation of quantum state evolution of the two quantum bits affected by changes in the quantum state control signal and the frequency control signal.

[0127] The calibration module 203 is configured to acquire a fourth time delay between quantum state control signal transmission lines connected to the first quantum bit and the second quantum bit based on the first time delay, the second time delay, and the third time delay, and perform time delay calibration based on the fourth time delay.

[0128] Based on the same inventive concept, the embodiment further provides a quantum computer, which comprises a quantum chip and the quantum computer system delay calibration device as described above, wherein the quantum chip is provided with a plurality of quantum bits coupled with each other, each of the quantum bits is connected with a quantum state regulation signal transmission line and a frequency regulation signal transmission line, and the quantum computer system delay calibration device is connected with the quantum state regulation signal transmission line and the frequency regulation signal transmission line, and is used for realizing the quantum computer system delay calibration method as described above.

[0129] In conclusion, the quantum computer system delay calibration method, calibration device and quantum computer provided by the application have the following advantages: the quantum computer system comprises a quantum chip, the quantum chip is provided with a plurality of quantum bits, each of the quantum bits is connected with a quantum state regulation signal transmission line and a frequency regulation signal transmission line, in the calibration method, first, a first delay between the quantum state regulation signal transmission line and the frequency regulation signal transmission line connected with a first quantum bit and a second delay between the quantum state regulation signal transmission line and the frequency regulation signal transmission line connected with a second quantum bit are obtained, then, a third delay between the frequency regulation signal transmission lines connected with the first quantum bit and the second quantum bit is obtained, finally, a fourth delay between the quantum state regulation signal transmission lines connected with the first quantum bit and the second quantum bit is obtained based on the first delay, the second delay and the third delay, and delay calibration is performed based on the fourth delay, so that the transmission delays of different quantum state regulation signal transmission lines caused by the arrangement of a plurality of microwave devices and the different lengths are eliminated, so that different frequency regulation signals reach the corresponding quantum bits according to the designed timing, and the corresponding quantum bits are excited at the same time, and the control precision of the two quantum bit gates is improved.

[0130] The above description is only a description of the preferred embodiments of the application, and does not limit the scope of the application in any way, and any modification or modification of the application by a person skilled in the art based on the above disclosure is within the protection scope of the claims.

Claims

1. A method for calibrating the delay of a quantum computer system, the quantum computer system comprising a quantum chip, the quantum chip being provided with a plurality of quantum bits, each of the quantum bits being connected with a quantum state control signal transmission line and a frequency control signal transmission line, characterized in that, The calibration method comprises: obtaining a first delay between a quantum state control signal transmission line connected with a first qubit and a frequency control signal transmission line and a second delay between a quantum state control signal transmission line connected with a second qubit and the frequency control signal transmission line, wherein the first qubit and the second qubit are coupled with each other; obtaining a third delay between the frequency control signal transmission lines connected with the first qubit and the second qubit respectively; obtaining a fourth delay between the quantum state control signal transmission lines connected with the first qubit and the second qubit based on the first delay, the second delay and the third delay, and performing delay calibration based on the fourth delay.

2. The method of calibrating latency for a quantum computer system of claim 1, wherein, The obtaining of the first delay and the second delay comprises: obtaining the first delay and the second delay based on a representation of quantum state evolution of a qubit affected by changes in quantum state control signals and frequency control signals.

3. The method of calibrating latency for a quantum computer system of claim 2, wherein, The obtaining of the third delay comprises: obtaining the third delay based on a representation of quantum state evolution of two qubits coupled with each other affected by changes in quantum state control signals and frequency control signals.

4. The method of calibrating latency for a quantum computer system of claim 1, wherein, The obtaining of the fourth delay comprises: a duration of quantum state control signals applied on the quantum state control signal transmission line connected with the first qubit is a first time; a duration of frequency control signals applied on the frequency control signal transmission line connected with the first qubit is determined to be a second time based on the first time and the first delay; a duration of frequency control signals applied on the frequency control signal transmission line connected with the second qubit is determined to be a third time based on the second time and the third delay; a duration of quantum state control signals applied on the quantum state control signal transmission line connected with the second qubit is determined to be a fourth time based on the third time and the second delay; the fourth delay between the quantum state control signal transmission lines connected with the first qubit and the second qubit respectively is determined based on the first time and the fourth time.

5. The method of calibrating the latency of a quantum computer system of claim 3, wherein, The obtaining of the first delay based on the representation of quantum state evolution of the qubit affected by changes in the quantum state control signals and the frequency control signals comprises: The first control signal is applied to the first qubit through the quantum state regulation signal transmission line connected with the first qubit, and the second control signal with a first preset delay is applied to the first qubit through the frequency regulation signal transmission line connected with the first qubit; wherein, the first control signal is used to regulate the quantum state of the first qubit to an eigenstate, and the second control signal is used to regulate the frequency of the first qubit, and the change of the frequency of the first qubit will affect the probability of the quantum state of the first qubit being the eigenstate; The first preset delay is updated in a first preset range in sequence, and the second control signal with the updated first preset delay is applied to the first qubit, to obtain a first curve of the probability of the quantum state of the first qubit being the eigenstate changing with the first preset delay; wherein, the first preset range is set according to the lengths of the quantum state regulation signal transmission line and the frequency regulation signal transmission line connected with the first qubit; It is judged whether the first curve has a wave trough; if yes, the first delay is determined based on the first preset delay corresponding to the wave trough of the first curve.

6. The method of calibrating the latency of a quantum computer system of claim 5, wherein, After the judgment of whether the first curve has a wave trough, the method further comprises: If no, the first control signal is delayed for a first fixed time length, and the step of applying the first control signal to the first qubit through the quantum state regulation signal transmission line connected with the first qubit is performed again.

7. The method of calibrating the latency of a quantum computer system of claim 6, wherein, After the first control signal is delayed for the first fixed time length, when the first curve has a wave trough, the first delay is determined based on the first preset delay corresponding to the wave trough of the first curve, and specifically comprises: The first preset delay corresponding to the wave trough of the first curve is obtained respectively; The first delay is determined based on the first preset delay and the first fixed time length respectively.

8. The method of calibrating the latency of a quantum computer system of claim 3, wherein, The representation of the quantum state evolution of the two qubits coupled with each other being affected by the changes of the quantum state regulation signal and the frequency regulation signal is used to obtain a third delay between the frequency regulation signal transmission lines connected with the first qubit and the second qubit, and specifically comprises: The quantum states of the first qubit and the second qubit are respectively preset to an excited state and a ground state, and the first amplitude and the second amplitude of the frequency regulation signal applied to the frequency regulation signal transmission lines connected with the first qubit and the second qubit are obtained based on a resonance test of the first qubit and the second qubit; wherein, the resonance test is an experiment of measuring the coupling strength of the first qubit and the second qubit changing with the amplitude of the frequency regulation signal; The first width of the frequency regulation signal is obtained based on the first amplitude and the second amplitude of the frequency regulation signal applied to the frequency regulation signal transmission lines connected with the first qubit and the second qubit, and a quantum state oscillation test of the first qubit and the second qubit; wherein, the quantum state oscillation test is an experiment of measuring the quantum state of the first qubit and the second qubit changing with the width of the frequency regulation signal. applying a first frequency control signal with the first amplitude and the first width to the frequency control signal transmission line connected with the first qubit, and sequentially updating a second preset delay within a second preset range, applying a second frequency control signal with the second amplitude and the first width after the second preset delay is updated to the frequency control signal transmission line connected with the second qubit, to obtain a second curve of the probability that the quantum state of the first qubit and the second qubit is excited state and ground state respectively with the second preset delay changing; determining whether the second curve has a trough, and if so, determining the third delay based on the second preset delay corresponding to the trough of the second curve.

9. The method of calibrating the latency of a quantum computer system of claim 8, wherein, After the determination of whether the second curve has a trough, the method further comprises: if not, delaying the first frequency control signal by a second fixed time length, and returning to the step of applying the first frequency control signal with the first amplitude and the first width to the frequency control signal transmission line connected with the first qubit.

10. The method of calibrating the latency of a quantum computer system of claim 9, wherein, After the first frequency control signal is delayed by the second fixed time length, when the second curve has a trough, the determination of the third delay based on the second preset delay corresponding to the trough of the second curve comprises: obtaining the second preset delay corresponding to the trough of the second curve; determining the third delay based on the second preset delay and the second fixed time length.

11. A calibration device for delay in a quantum computer system, characterized in that, The method comprises: a first obtaining module configured to obtain a first delay between a quantum state control signal transmission line and a frequency control signal transmission line connected with a first qubit and a second delay between a quantum state control signal transmission line and a frequency control signal transmission line connected with a second qubit based on a representation of quantum state evolution of the qubits being affected by changes in quantum state control signals and frequency control signals; wherein the first qubit and the second qubit are coupled to each other; a second obtaining module configured to obtain a third delay between frequency control signal transmission lines connected with the first qubit and the second qubit based on a representation of quantum state evolution of the two qubits being affected by changes in quantum state control signals and frequency control signals; a calibration module configured to obtain a fourth delay between quantum state control signal transmission lines connected with the first qubit and the second qubit based on the first delay, the second delay, and the third delay, and to perform delay calibration based on the fourth delay.

12. A quantum computer, comprising: The quantum computer comprises a quantum chip, and a quantum computer system delay calibration device as claimed in claim 11, wherein the quantum chip is provided with a plurality of qubits coupled to each other, each of the qubits is connected with a quantum state control signal transmission line and a frequency control signal transmission line, and the quantum computer system delay calibration device is connected with the quantum state control signal transmission line and the frequency control signal transmission line, and is configured to implement the quantum computer system delay calibration method as claimed in any one of claims 1-10.

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