Photon number information determination method and device, quantum computing equipment, readable storage medium and program product

Abstract

The invention provides a photon number information determination method and device, quantum computing equipment, a computer readable storage medium and a computer program product. The method comprises the following steps: acquiring a target to-be-detected parameter of a quantum bit in a quantum chip; wherein the target to-be-detected parameter comprises dispersion displacement of a resonant cavity coupled with the quantum bit, a change relation parameter between the frequency of the quantum bit and the reading power of a read microwave signal, and the current reading power of the read microwave signal; and determining the current photon number in the resonant cavity based on the target to-be-detected parameter and the target association relationship between the target to-be-detected parameter and the photon number of the resonant cavity. By adopting the method, the precision and accuracy of measuring the photon number in the resonant cavity can be improved.

Description

Technical Field

[0001] The present disclosure relates to the field of quantum information, and in particular to a method and apparatus for determining photon number information, a quantum computing device, a computer-readable storage medium, and a computer program product. Background Art

[0002] With the rapid development of quantum information technology, superconducting quantum chips, as core devices in quantum computing, are facing critical challenges in optimizing and accurately measuring their performance. In superconducting quantum chips, the resonant cavity serves as the medium for interaction between the quantum bit and the external environment. Accurately measuring the number of photons within the cavity is crucial for manipulating quantum states, non-destructively reading quantum information, and maintaining the stability of the quantum bit.

[0003] In related technologies, an attenuator is placed in the measurement and control circuitry of a superconducting quantum chip to estimate the microwave power and photon count entering the chip package. However, this method cannot precisely quantify the number of photons within the superconducting resonant cavity during measurement, resulting in poor measurement accuracy. Summary of the Invention

[0004] In response to the above technical problems, the present disclosure provides a method, apparatus, quantum computing device, computer-readable storage medium and computer program product for determining photon number information to improve the accuracy of measuring photon number information.

[0005] In a first aspect, the present disclosure provides a method for determining photon number information, comprising:

[0006] Obtaining target parameters to be detected of a quantum bit in a quantum chip; wherein the target parameters to be detected include a dispersion shift of a resonant cavity coupled to the quantum bit, a parameter of a change relationship between the frequency of the quantum bit and a read power of a read microwave signal, and a current read power of the read microwave signal;

[0007] Based on the target parameter to be detected and a target correlation between the target parameter to be detected and the photon number of the resonant cavity, a current photon number in the resonant cavity is determined.

[0008] In one embodiment, determining the target association relationship includes:

[0009] Obtaining a first correlation between a frequency change of the quantum bit and a change in the number of photons in the resonant cavity, wherein the first correlation includes a dispersion shift of the resonant cavity;

[0010] Obtaining a second correlation between a frequency change of the quantum bit and a change in a read power of the read microwave signal, wherein the second correlation includes a change relationship parameter;

[0011] The target association relationship is determined according to the first association relationship and the second association relationship.

[0012] In one embodiment, obtaining the dispersion shift of the resonant cavity includes:

[0013] Obtaining a first resonance frequency of the resonant cavity when the quantum state of the quantum bit is a ground state and a second resonance frequency of the resonant cavity when the quantum state of the quantum bit is a first excited state;

[0014] The dispersion shift of the resonant cavity is determined according to the first resonant frequency and the second resonant frequency.

[0015] In one embodiment, obtaining the first resonant frequency of the resonant cavity when the quantum state of the quantum bit is a ground state includes:

[0016] Changing the frequency of the read microwave signal to measure the output signal of the resonant cavity when the quantum state of the qubit is a ground state, wherein the output signal of the resonant cavity changes with the change of the frequency of the read microwave signal;

[0017] Based on the frequency data of the read microwave signal and the data of the output signal of the resonant cavity, fitting the change relationship between the output signal of the resonant cavity and the frequency of the read microwave signal when the quantum state of the qubit is the ground state;

[0018] According to the change relationship, a first resonance frequency of the resonant cavity when the quantum bit is in a ground state is determined.

[0019] In one embodiment, obtaining a parameter of a change relationship between the frequency of the quantum bit and a read power of a microwave signal includes:

[0020] Adjusting the read power of the microwave signal to obtain a plurality of read power values, and obtaining the frequency of the quantum bit at the plurality of read power values;

[0021] The frequency and the read power values ​​are fitted to obtain a parameter of a change relationship between the frequency of the quantum bit and the read power of the read microwave signal.

[0022] In one embodiment, obtaining the frequency of the quantum bit at the plurality of read power values ​​includes:

[0023] Acquiring response data of the output signal of the resonant cavity changing with the frequency of the pump microwave signal under the multiple read power values;

[0024] Based on the correlation between the frequency of the quantum bit and the read power value and the output signal, the response data and the read power value are fitted to obtain the frequency of the quantum bit under the multiple read power values.

[0025] In one embodiment, the method further comprises:

[0026] When the current number of photons is greater than or equal to a preset threshold, adjusting the current reading power of the read microwave signal according to a difference between the current number of photons and the preset threshold until the adjusted number of photons is less than the preset threshold, thereby obtaining an adjusted read microwave signal;

[0027] The quantum state of the quantum bit is read based on the adjusted read microwave signal.

[0028] In a second aspect, the present disclosure further provides a device for determining photon number information, comprising:

[0029] an acquisition module configured to acquire target parameters to be detected of a quantum bit in a quantum chip; wherein the target parameters to be detected include a dispersion shift of a resonant cavity coupled to the quantum bit, a parameter of a change relationship between the frequency of the quantum bit and a read power of a read microwave signal, and a current read power of the read microwave signal;

[0030] The determination module is configured to determine the current number of photons in the resonant cavity based on the target parameter to be detected and a target correlation relationship between the target parameter to be detected and the number of photons in the resonant cavity.

[0031] In one embodiment, the apparatus further includes a target association relationship determination module, and the target association relationship determination module is configured to:

[0032] Obtaining a first correlation between a frequency change of the quantum bit and a change in the number of photons in the resonant cavity, wherein the first correlation includes a dispersion shift of the resonant cavity;

[0033] Obtaining a second correlation between a frequency change of the quantum bit and a change in a read power of the read microwave signal, wherein the second correlation includes a change relationship parameter;

[0034] The target association relationship is determined according to the first association relationship and the second association relationship.

[0035] In one embodiment, the target association relationship determination module is further configured to:

[0036] Obtaining a first resonance frequency of the resonant cavity when the quantum state of the quantum bit is a ground state and a second resonance frequency of the resonant cavity when the quantum state of the quantum bit is a first excited state;

[0037] The dispersion shift of the resonant cavity is determined according to the first resonant frequency and the second resonant frequency.

[0038] In one embodiment, the target association relationship determination module is further configured to:

[0039] Changing the frequency of the read microwave signal to measure the output signal of the resonant cavity when the quantum state of the qubit is a ground state, wherein the output signal of the resonant cavity changes with the change of the frequency of the read microwave signal;

[0040] Based on the frequency data of the read microwave signal and the data of the output signal of the resonant cavity, fitting the change relationship between the output signal of the resonant cavity and the frequency of the read microwave signal when the quantum state of the qubit is the ground state;

[0041] According to the change relationship, a first resonance frequency of the resonant cavity when the quantum bit is in a ground state is determined.

[0042] In one embodiment, the acquisition module is further configured to:

[0043] Adjusting the read power of the microwave signal to obtain a plurality of read power values, and obtaining the frequency of the quantum bit at the plurality of read power values;

[0044] The frequency and the read power values ​​are fitted to obtain a parameter of a change relationship between the frequency of the quantum bit and the read power of the read microwave signal.

[0045] In one embodiment, the acquisition module is further configured to:

[0046] Acquiring response data of the output signal of the resonant cavity changing with the frequency of the pump microwave signal under the multiple read power values;

[0047] Based on the correlation between the frequency of the quantum bit and the read power value and the output signal, the response data and the read power value are fitted to obtain the frequency of the quantum bit under the multiple read power values.

[0048] In one embodiment, the apparatus is further configured to:

[0049] When the current number of photons is greater than or equal to a preset threshold, adjusting the current reading power of the read microwave signal according to a difference between the current number of photons and the preset threshold until the adjusted number of photons is less than the preset threshold, thereby obtaining an adjusted read microwave signal;

[0050] The quantum state of the quantum bit is read based on the adjusted read microwave signal.

[0051] In a third aspect, embodiments of the present disclosure further provide a quantum computing device. The quantum computing device includes a memory, a processor, a signal generator, and a quantum chip. The signal generator is used to read microwave signals. The quantum chip includes a quantum bit and a resonant cavity. The memory stores a computer program. When the processor executes the computer program, the steps of any of the methods described in the embodiments of the present disclosure are implemented.

[0052] In a fourth aspect, embodiments of the present disclosure further provide a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of any one of the methods of the embodiments of the present disclosure.

[0053] In a fifth aspect, embodiments of the present disclosure further provide a computer program product, comprising a computer program that, when executed by a processor, implements the steps of any one of the methods of the embodiments of the present disclosure.

[0054] The aforementioned method, apparatus, quantum computing device, computer-readable storage medium, and computer program product for determining photon number information obtain a target parameter to be detected for a qubit in a quantum chip and, based on the target parameter to be detected and the target correlation between the parameter to be detected and the photon number, determine the current photon number in the resonant cavity, thereby enabling accurate reading of the photon number in the resonant cavity. The target correlation between the parameter to be detected and the photon number in the resonant cavity coupled to the qubit is pre-determined. When reading the photon number, the current photon number in the resonant cavity is determined based on the dispersion shift of the resonant cavity coupled to the qubit, the parameter of the change relationship between the frequency of the qubit and the read power of the read microwave signal, and the current read power of the read microwave signal of the qubit. This effectively improves the accuracy of photon number calculation and measurement. The relationship between the quantum state shift of the qubit and the change in light field intensity is determined based on the AC Stark effect, and the photon number in the resonant cavity is determined. This provides a new means for measuring and manipulating qubits and is applicable to a wider range of application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or related technologies, the following briefly introduces the drawings required for use in the embodiments of the present disclosure or related technical descriptions. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying any creative work.

[0056] Figure 1 Schematic diagram of a flow chart of a method for determining photon number information in one embodiment of the present disclosure;

[0057] Figure 2 Schematic diagram of an output signal curve of a resonant cavity in one embodiment of the present disclosure;

[0058] Figure 3 A schematic diagram showing how the frequency of a quantum bit changes with the power of a read microwave signal in one embodiment of the present disclosure;

[0059] Figure 4 1 is a flow chart of a method for determining photon number information in another embodiment of the present disclosure;

[0060] Figure 5 This is a structural block diagram of a device for determining photon number information in one embodiment of the present disclosure;

[0061] Figure 6 This is a diagram of the internal structure of a quantum computing device in one embodiment of the present disclosure. DETAILED DESCRIPTION

[0062] In order to make the purpose, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present disclosure and are not intended to limit the present disclosure.

[0063] In one embodiment of the present disclosure, the present disclosure provides a method for determining photon number information, including:

[0064] Obtaining target parameters to be detected of a quantum bit in a quantum chip; wherein the target parameters to be detected include a dispersion shift of a resonant cavity coupled to the quantum bit, a parameter of a change relationship between the frequency of the quantum bit and a read power of a read microwave signal, and a current read power of the read microwave signal;

[0065] Based on the target parameter to be detected and a target correlation between the target parameter to be detected and the photon number of the resonant cavity, a current photon number in the resonant cavity is determined.

[0066] The disclosed embodiment obtains the target parameters to be detected of the quantum bits in the quantum chip, and determines the current number of photons in the resonant cavity based on the target parameters to be detected and the target correlation between the parameters to be detected and the number of photons, thereby enabling accurate reading of the number of photons in the resonant cavity. The target correlation between the parameters to be detected and the number of photons in the resonant cavity coupled to the quantum bit is predetermined. When reading the number of photons, the current number of photons in the resonant cavity is determined by the dispersion shift of the resonant cavity coupled to the quantum bit, the parameter of the change relationship between the frequency of the quantum bit and the reading power of the read microwave signal, and the current reading power of the read microwave signal of the quantum bit, thereby effectively improving the accuracy of the photon number calculation and measurement. The relationship between the change of the quantum state movement of the quantum bit and the light field intensity is determined based on the AC Stark effect, and the number of photons in the resonant cavity is determined, providing a new means for the measurement and manipulation of quantum bits, which is applicable to more application scenarios.

[0067] In one embodiment of the present disclosure, Figure 1 As shown, a method for determining photon number information is provided. This embodiment uses the method applied to a terminal as an example for illustration. It is understandable that the method can also be applied to a server, or to a system including a terminal and a server, and implemented through interaction between the terminal and the server. The method includes the following steps:

[0068] Step S110, obtaining target parameters to be detected of the quantum bits in the quantum chip; wherein the target parameters to be detected include the dispersion shift of the resonant cavity coupled to the quantum bit, the change relationship parameter between the frequency of the quantum bit and the reading power of the reading microwave signal, and the current reading power of the reading microwave signal.

[0069] For example, a quantum chip includes a quantum bit and a resonant cavity coupled thereto. Fault-tolerant quantum computing requires non-destructive measurement of the quantum bit. In superconducting quantum computing, the circuit quantum electrodynamics (cQED) method is used for dispersion reading. The number of photons in the resonant cavity cannot exceed the critical photon number. , where Δ is the frequency difference between the qubit and the resonant cavity, and g is the coupling strength between the qubit and the resonant cavity. In some examples, qubits can be implemented based on superconducting circuits, such as those including Josephson junctions and capacitors. The resonant cavity is the medium through which the qubit interacts with the external environment, and there is coupling between the qubit and the resonant cavity. A quantum chip can include multiple qubits, and a qubit can be coupled to one or more resonant cavities, the specific coupling of which can be determined based on the actual application scenario. For example, the state of a qubit (quantum state 0 or 1) is characterized by its interaction with a microwave signal. The microwave signal can include high-frequency electromagnetic waves, which can be used to read the state of the qubit. The qubit is read by detecting the electromagnetic response signal after the qubit is coupled to the resonant cavity to obtain the state of the qubit.

[0070] Optionally, target parameters to be detected are obtained. Target parameters to be detected include the dispersion shift of the resonant cavity. Different resonant cavities and different qubits may correspond to different dispersion shifts. In some examples, the dispersion shift can be measured and determined by adjusting the parameters of the resonant cavity and qubit. In one example, basic parameters characterizing the resonant cavity and qubit are obtained. These basic parameters include, but are not limited to, the resonant cavity frequency of the qubit in the ground state and the parameters of the microwave π pulse that excites the qubit from the ground state to the first excited state. Using these basic parameters, the qubit can be prepared in the ground state or the first excited state to obtain the target parameters to be detected.

[0071] The target parameter to be detected includes a parameter of the variation relationship between the frequency of the qubit and the read power of the read microwave signal. In some examples, the frequency of the qubit and the read power of the read microwave signal are linearly related. The variation relationship parameter may include a linear relationship parameter. The linear relationship between different qubits and the read power of the read microwave signal may vary. Therefore, the variation relationship parameter can be determined by measuring the variation of the qubit frequency with the read power of the read microwave signal. Exemplarily, the frequency of the qubit includes the excitation frequency, i.e., the frequency at which the qubit is excited from the ground state to the first excited state. In one example, the frequency of the qubit can be measured by adjusting the frequency of the pump microwave signal.

[0072] The target parameter to be detected includes the current read power of the qubit's microwave signal. For example, a quantum chip measures qubits by reading the microwave signal. Different read powers of the microwave signal can affect the number of photons in the resonant cavity. Therefore, the number of photons in the resonant cavity can be determined by reading the microwave signal's power. In one example, a signal generator can emit the microwave signal, and the current read power can be determined based on the operating parameters of the signal generator.

[0073] Step S120 : determining the current number of photons in the resonant cavity based on the target parameter to be detected and the target correlation relationship between the target parameter to be detected and the number of photons in the resonant cavity.

[0074] Exemplarily, after determining the target parameter to be detected, a target correlation relationship between the target parameter to be detected and the number of photons in the resonant cavity is obtained, and based on the target correlation relationship and the target parameter to be detected, the number of photons in the resonant cavity is determined.

[0075] Optionally, the target association relationship may be determined based on one or more association relationships between target parameters to be detected and the number of photons. In one example, the target association relationship may be obtained based on multiple association relationships between target parameters to be detected and the number of photons.

[0076] In some embodiments of the present disclosure, if the number of photons is greater than or equal to a preset threshold, the number of photons in the resonant cavity is large, and reading the quantum bit may destroy the quantum state of the quantum bit. Therefore, the number of photons can be adjusted by adjusting the reading power of the microwave signal to avoid destructive reading of the quantum bit.

[0077] The disclosed embodiment obtains the target parameters to be detected of the quantum bits in the quantum chip, and determines the current number of photons in the resonant cavity based on the target parameters to be detected and the target correlation between the parameters to be detected and the number of photons, thereby enabling accurate reading of the number of photons in the resonant cavity. The target correlation between the parameters to be detected and the number of photons in the resonant cavity coupled to the quantum bit is predetermined. When reading the number of photons, the current number of photons in the resonant cavity is determined by the dispersion shift of the resonant cavity coupled to the quantum bit, the parameter of the change relationship between the frequency of the quantum bit and the read power of the read microwave signal, and the current read power of the read microwave signal of the quantum bit, thereby effectively improving the accuracy of the photon number calculation and measurement. The relationship between the change of the quantum state movement of the quantum bit and the light field intensity is determined based on the AC Stark effect, and the number of photons in the resonant cavity is determined, providing a new means for the measurement and manipulation of quantum bits, which is applicable to more application scenarios.

[0078] In one embodiment of the present disclosure, determining the target association relationship includes:

[0079] Obtaining a first correlation between a frequency change of the quantum bit and a change in the number of photons in the resonant cavity, wherein the first correlation includes a dispersion shift of the resonant cavity;

[0080] Obtaining a second correlation between a frequency change of the quantum bit and a change in a read power of the read microwave signal, wherein the second correlation includes a change relationship parameter;

[0081] The target association relationship is determined according to the first association relationship and the second association relationship.

[0082] Exemplarily, when determining the target correlation, a first correlation between a change in the frequency of the qubit and a change in the number of photons in the resonant cavity is obtained. In one example, the relationship between the change in the frequency of the qubit and the change in the number of photons in the resonant cavity is associated with a dispersion shift, and the first correlation includes the dispersion shift of the resonant cavity coupled to the qubit.

[0083] Optionally, a second correlation between the change in the frequency of the qubit and the change in the read power of the microwave signal is obtained. In some examples, the frequency of the qubit changes with the change in the read power of the microwave signal. Therefore, the change in the frequency of the qubit and the change in the read power of the microwave signal exhibit a certain correlation, and this correlation includes a variation relationship parameter. In some possible implementations, the second correlation is obtained by fitting experimentally acquired data, and the variation relationship parameter is determined.

[0084] Exemplarily, after the first correlation relationship and the second correlation relationship are determined, a correlation relationship between the number of photons and the read power is determined based on the first correlation relationship and the second correlation relationship.

[0085] In some possible implementations, the frequency change of the quantum bit is determined based on the AC Stark effect. The change in the number of photons in the resonant cavity The first correlation relationship between them is shown in formula (1).

[0086] (1)

[0087] in, is the dispersion shift.

[0088] For example, the AC Stark effect (alternating current Stark effect) is a phenomenon in which the quantum state of a quantum bit shifts under the influence of an electromagnetic field. In a quantum system, when a quantum bit interacts with a light field, its quantum state shifts, with the amount of shift proportional to the intensity of the light field. In superconducting quantum chips, quantum bits are composed of Josephson junctions, and their quantum states shift under the influence of light fields.

[0089] Frequency change of the quantum bit Reading power variation The relationship is shown in formula (2).

[0090] (2)

[0091] in, is the change relationship parameter.

[0092] Proportional to the number of photons , so the target association relationship can be obtained, as shown in formula (3).

[0093] (3)

[0094] The disclosed embodiment obtains a first correlation between the frequency change of a quantum bit and the change in the number of photons, and a second correlation between the frequency change of a quantum bit and the change in the read power of a microwave signal, thereby obtaining a correlation between the number of photons and the read power. This enables the number of photons to be measured by reading the power, and the target correlation can be quickly and accurately determined, thereby ensuring the accuracy and reliability of the measured number of photons and being suitable for more application scenarios.

[0095] In one embodiment of the present disclosure, obtaining the dispersion shift of the resonant cavity includes:

[0096] Obtaining a first resonance frequency of the resonant cavity when the quantum state of the quantum bit is a ground state and a second resonance frequency of the resonant cavity when the quantum state of the quantum bit is a first excited state;

[0097] The dispersion shift of the resonant cavity is determined according to the first resonant frequency and the second resonant frequency.

[0098] For example, a qubit is placed in a ground state and a first excited state, and a first resonant frequency of the resonant cavity is obtained when the qubit is in the ground state, and a second resonant frequency of the resonant cavity is obtained when the qubit is in the first excited state. In some examples, the resonant frequencies can be determined by fitting a curve showing how the resonant cavity signal changes with the frequency of the read microwave signal. In this example, the ground state is the |0> state, and the first excited state is the |1> state.

[0099] Optionally, a dispersion shift is obtained according to the first resonance frequency and the second resonance frequency. In an example, a frequency difference between the first resonance frequency and the second resonance frequency is the dispersion shift.

[0100] In the embodiment of the present disclosure, the first resonance frequency and the second resonance frequency of the resonant cavity are obtained by placing the quantum bit in the ground state and the first excited state, thereby being able to quickly and accurately obtain the dispersion shift of the resonant cavity.

[0101] In one embodiment of the present disclosure, obtaining the first resonant frequency of the resonant cavity when the quantum state of the quantum bit is a ground state includes:

[0102] Changing the frequency of the read microwave signal to measure the output signal of the resonant cavity when the quantum state of the qubit is a ground state, wherein the output signal of the resonant cavity changes with the change of the frequency of the read microwave signal;

[0103] Based on the frequency data of the read microwave signal and the data of the output signal of the resonant cavity, fitting the change relationship between the output signal of the resonant cavity and the frequency of the read microwave signal when the quantum state of the qubit is the ground state;

[0104] According to the change relationship, a first resonance frequency of the resonant cavity when the quantum bit is in a ground state is determined.

[0105] Exemplarily, the frequency of the microwave reading signal is changed, and the output signal of the resonant cavity when the quantum state of the quantum bit is in the ground state is measured. Based on the output signal, the first resonant frequency can be determined, that is, the resonant frequency of the resonant cavity when the quantum state of the quantum bit is in the ground state.

[0106] Optionally, based on the frequency data of the microwave signal and the output signal of the resonant cavity, a relationship between the output signal of the resonant cavity and the frequency of the microwave signal is fitted, and a first resonant frequency of the resonant cavity when the qubit is in the ground state is determined based on this relationship. In one example, this relationship can be fitted using a preset relationship formula, and the first resonant frequency can be determined.

[0107] In some possible implementations, the quantum state of the quantum bit can be placed in a first excited state in the same manner, and the resonant frequency of the resonant cavity, that is, the second resonant frequency, can be determined.

[0108] In a possible implementation, the output signal of the resonant cavity includes the S 21 Signal, respectively put the quantum bit in the ground state and the first excited state, and measure the data of the output signal of the resonant cavity changing with the frequency of the microwave reading signal, and use formula (4) to fit the output signal curve of the resonant cavity when the quantum bit is in the ground state and the first excited state, as shown in Figure 2 As shown, the resonance frequency of the resonant cavity when the quantum bit is in the ground state is obtained, that is, the first resonance frequency , and the resonant frequency of the resonant cavity when the quantum bit is in the first excited state, that is, the second resonant frequency .Will and Subtraction can be obtained by dispersion shift .

[0109] (4)

[0110] in, is the resonant frequency of the resonant cavity, Indicates the background attenuation amplitude of the measurement circuit, Represents the background phase of the measurement loop, Indicates the frequency of the microwave signal. Indicates the time it takes for the microwave signal to propagate from the transmitter to the receiver. It represents the phase caused by the impedance mismatch between the input and output of the resonant cavity. and are the total quality factor and external quality factor of the resonant cavity, respectively.

[0111] In the embodiment of the present disclosure, the frequency of the read microwave signal is changed and the change of the output signal of the resonant cavity is measured. Based on the frequency data of the read microwave signal and the data of the output signal of the resonant cavity, the first resonant frequency is fitted, so that the dispersion shift of the resonant cavity can be obtained quickly and accurately, and then the first correlation relationship is determined, and the target correlation relationship is obtained, thereby ensuring the reliability and accuracy of the photon number reading.

[0112] In one embodiment of the present disclosure, obtaining a parameter of a change relationship between the frequency of the quantum bit and the read power of the microwave signal includes:

[0113] Adjusting the read power of the microwave signal to obtain a plurality of read power values, and obtaining the frequency of the quantum bit at the plurality of read power values;

[0114] The frequency and the read power values ​​are fitted to obtain a parameter of a change relationship between the frequency of the quantum bit and the read power of the read microwave signal.

[0115] Exemplarily, the reading power of the microwave signal is adjusted to obtain multiple reading power values, the frequency of the quantum bit at each reading power value is obtained respectively, the frequency and reading power values ​​are fitted, and the change relationship parameters between the frequency of the quantum bit and the reading power are obtained.

[0116] In some examples of the present disclosure, frequency and read power values ​​can be fitted using a preset relationship. The frequency of the qubit varies linearly with the read power, and the change in the frequency of the qubit also varies linearly with the change in the read power. The preset relationship can be determined based on a least squares method. The read power and the frequency of the qubit are fitted using the least squares method to obtain a linear change relationship between the two, thereby obtaining a change relationship parameter. Optionally, the change relationship parameter may include a linear change slope.

[0117] The disclosed embodiment can obtain the frequency of the quantum bit under multiple reading power values ​​by adjusting the reading power of the microwave signal, fit the frequency and the reading power value, and obtain the changing relationship parameter between the two, thereby quickly and accurately obtaining the relationship between the reading power value and the frequency of the quantum bit, which is beneficial to the measurement and determination of the number of photons.

[0118] In one embodiment of the present disclosure, obtaining the frequency of the quantum bit at the multiple read power values ​​includes:

[0119] Acquiring response data of the output signal of the resonant cavity changing with the frequency of the pump microwave signal under the multiple read power values;

[0120] Based on the correlation between the frequency of the quantum bit, the read power value, and the output signal, the response data and the read power value are fitted to obtain the frequency of the quantum bit under the multiple read power values.

[0121] Exemplarily, response data is obtained for the resonant cavity output signal as a function of the frequency of the pump microwave signal at multiple read power values. In some examples, the read power data of the microwave signal is fixed, the frequency of the pump microwave signal is adjusted, and response data is obtained for the resonant cavity output signal as a function of the frequency of the pump microwave signal. The response data may include the resonant cavity output signal measured at different pump microwave signal frequencies.

[0122] Optionally, the collected data is fitted based on the correlation between the frequency of the quantum bit and the read power value and the output signal. In some examples, the fitting can be performed using the Lorentz linear formula to determine the frequency of the quantum bit at multiple read power values.

[0123] In some possible implementations, the collected data is fitted using a Lorentz linear formula, such as formula (5), to obtain the frequency of the quantum bit at multiple read power values.

[0124] (5)

[0125] Where f is the frequency of the pump microwave signal, is the frequency of the quantum bit, is the spectral line of the quantum bit (i.e. the output signal S of the resonant cavity 21 where γ is the full width at half maximum of the spectrum line (i.e. the cavity signal measured at different pump microwave frequencies f), and A is the maximum amplitude of the spectrum line.

[0126] According to the frequency of the quantum bit under multiple reading power values, the least squares method is used to fit the linear change of the frequency with the reading power value to obtain the change slope, that is, the change relationship parameter. Figure 3 Schematic diagram showing how the frequency of a quantum bit varies with the power of a read microwave signal according to an exemplary embodiment.

[0127] The disclosed embodiment fits the response data and the read power value based on the correlation between the frequency of the quantum bit and the read power value and the output signal, and quickly and accurately obtains the frequencies corresponding to the quantum bit under multiple read power values.

[0128] In one embodiment of the present disclosure, the method further includes:

[0129] When the current number of photons is greater than or equal to a preset threshold, adjusting the current reading power of the read microwave signal according to a difference between the current number of photons and the preset threshold until the adjusted number of photons is less than the preset threshold, thereby obtaining an adjusted read microwave signal;

[0130] The quantum state of the quantum bit is read based on the adjusted read microwave signal.

[0131] Exemplarily, after determining the number of photons, the control parameters of the quantum chip are dynamically adjusted based on the number of photons, where the control parameters of the quantum chip may include but are not limited to the power of the microwave signal. When the current number of photons is greater than or equal to a preset threshold, it can be considered that the number of photons in the resonant cavity is large, and when the quantum bit is read, the quantum state of the quantum bit may be affected. Therefore, the adjustment of the number of photons is achieved by adjusting the control parameters. The preset threshold can be determined in advance based on the actual application scenario. In some examples, the preset threshold can be determined based on the number of photons that cause damage to the quantum state of the quantum bit in the actual application scenario; in some possible implementations, the critical number of photons can be obtained based on the frequency difference between the quantum bit and the resonant cavity and the coupling strength between the quantum bit and the resonant cavity to determine the preset threshold.

[0132] Optionally, when the number of photons is greater than or equal to a preset threshold, the current reading power of the microwave signal is adjusted. In some examples, the power of the microwave signal is adjusted according to the difference between the number of photons and the preset threshold. For example, the smaller the difference between the number of photons and the preset threshold, the greater the amplitude of the reduction in the power of the microwave signal. Exemplarily, after the adjustment is completed, the number of photons in the resonant cavity is remeasured according to the method described in this embodiment, and compared with the preset threshold again. If the number of photons in the resonant cavity is less than the preset threshold, the quantum bit can be read; if the number of photons in the resonant cavity is still greater than or equal to the preset threshold, the reading power of the microwave signal is continued to be adjusted until the adjusted number of photons is less than the preset threshold, thereby obtaining the adjusted reading microwave signal.

[0133] The quantum state of the quantum bit is read based on the adjusted read microwave signal.

[0134] In some possible implementations, because the quantum state is relatively fragile, when the reading power is too high and the number of photons in the resonant cavity exceeds the critical photon number, the reading of the quantum bit becomes destructive, that is, the reading destroys the quantum state of the quantum bit. This reading method does not meet the conditions for dispersive reading. Therefore, when reading, it is necessary to ensure that the number of photons in the resonant cavity is lower than the critical photon number, that is, the preset threshold. In one example, the expression for the critical photon number is , where Δ is the frequency difference between the quantum bit and the resonant cavity, and g is the coupling strength between the quantum bit and the resonant cavity.

[0135] The disclosed embodiment adjusts the power of the microwave signal for reading to reduce the number of photons in the resonant cavity. By dynamically adjusting the control parameters, the working state of the quantum bit is optimized to ensure non-destructive measurement, which helps maintain the coherence of the quantum bit, improves the reliability of the measurement, avoids the problem of destructive reading caused by excessive number of photons, ensures that the control parameters of the quantum bit are in a better state, and is suitable for more application scenarios.

[0136] Figure 4 This is a flow chart of a method for determining photon number information according to an exemplary embodiment, with reference to Figure 4 As shown, the basic parameter indicators of the resonant cavity and the quantum bit are obtained; the frequency difference of the resonant cavity when the quantum bit is in the ground state and the first excited state is measured to obtain the dispersion shift; the relationship parameter of the quantum bit frequency with the power change of the read microwave signal, that is, the change slope, is measured; the current read power is obtained, and combined with the above-mentioned target parameters to be detected, the current number of photons in the resonant cavity is obtained.

[0137] The disclosed embodiments utilize the AC Stark effect to measure the frequency offset of quantum bits and calculate the number of photons in the resonant cavity, thereby providing higher measurement accuracy. By monitoring the number of photons in the resonant cavity in real time, the control parameters can be dynamically adjusted to optimize the working state of the quantum bits, ensuring non-destructive measurement, helping to maintain the coherence of the quantum bits and improve measurement reliability. The disclosed embodiments are not only applicable to superconducting quantum computing chips, but can also be applied to other superconducting circuits, quantum optical devices, semiconductor quantum dots and other systems with Josephson junctions, providing a new measurement method for quantum information technology.

[0138] It should be understood that, although the various steps in the flowcharts involved in the various embodiments described above are displayed in sequence according to the instructions of the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the flowcharts involved in the various embodiments described above can include multiple steps or multiple stages, and these steps or stages are not necessarily executed and completed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of steps or stages in other steps.

[0139] Based on the same inventive concept, the present disclosure also provides a device for determining photon number information for implementing the aforementioned method for determining photon number information. The solution provided by this device is similar to the solution described in the aforementioned method. Therefore, the specific limitations of one or more embodiments of the device for determining photon number information provided below can be found in the aforementioned method for determining photon number information, and will not be further elaborated here.

[0140] In one embodiment of the present disclosure, Figure 5 As shown, a device 500 for determining photon number information is provided, comprising:

[0141] An acquisition module 510 is configured to acquire target parameters to be detected of a qubit in a quantum chip; wherein the target parameters to be detected include a dispersion shift of a resonant cavity coupled to the qubit, a parameter of a change relationship between the frequency of the qubit and a read power of a read microwave signal, and a current read power of the read microwave signal;

[0142] The determination module 520 is configured to determine the current number of photons in the resonant cavity based on the target parameter to be detected and a target correlation relationship between the target parameter to be detected and the number of photons in the resonant cavity.

[0143] In one embodiment, the apparatus further includes a target association relationship determination module, and the target association relationship determination module is configured to:

[0144] Obtaining a first correlation between a frequency change of the quantum bit and a change in the number of photons in the resonant cavity, wherein the first correlation includes a dispersion shift of the resonant cavity;

[0145] Obtaining a second correlation between a frequency change of the quantum bit and a change in a read power of the read microwave signal, wherein the second correlation includes a change relationship parameter;

[0146] The target association relationship is determined according to the first association relationship and the second association relationship.

[0147] In one embodiment, the target association relationship determination module is further configured to:

[0148] Obtaining a first resonance frequency of the resonant cavity when the quantum state of the quantum bit is a ground state and a second resonance frequency of the resonant cavity when the quantum state of the quantum bit is a first excited state;

[0149] The dispersion shift of the resonant cavity is determined according to the first resonant frequency and the second resonant frequency.

[0150] In one embodiment, the target association relationship determination module is further configured to:

[0151] Changing the frequency of the read microwave signal to measure the output signal of the resonant cavity when the quantum state of the qubit is a ground state, wherein the output signal of the resonant cavity changes with the change of the frequency of the read microwave signal;

[0152] Based on the frequency data of the read microwave signal and the data of the output signal of the resonant cavity, fitting the change relationship between the output signal of the resonant cavity and the frequency of the read microwave signal when the quantum state of the qubit is the ground state;

[0153] According to the change relationship, a first resonance frequency of the resonant cavity when the quantum bit is in a ground state is determined.

[0154] In one embodiment, the acquisition module is further configured to:

[0155] Adjusting the read power of the microwave signal to obtain a plurality of read power values, and obtaining the frequency of the quantum bit at the plurality of read power values;

[0156] The frequency and the read power values ​​are fitted to obtain a parameter of a change relationship between the frequency of the quantum bit and the read power of the read microwave signal.

[0157] In one embodiment, the acquisition module is further configured to:

[0158] Acquiring response data of the output signal of the resonant cavity changing with the frequency of the pump microwave signal under the multiple read power values;

[0159] Based on the correlation between the frequency of the quantum bit and the read power value and the output signal, the response data and the read power value are fitted to obtain the frequency of the quantum bit under the multiple read power values.

[0160] In one embodiment, the apparatus is further configured to:

[0161] When the current number of photons is greater than or equal to a preset threshold, adjusting the current reading power of the read microwave signal according to a difference between the current number of photons and the preset threshold until the adjusted number of photons is less than the preset threshold, thereby obtaining an adjusted read microwave signal;

[0162] The quantum state of the quantum bit is read based on the adjusted read microwave signal.

[0163] Each module in the device for determining the photon number information described above can be implemented in whole or in part through software, hardware, or a combination thereof. Each module can be embedded in or independent of a processor in a quantum computing device in hardware form, or can be stored in a memory in the quantum computing device in software form, so that the processor can call and execute the corresponding operations of each module.

[0164] In one embodiment of the present disclosure, a quantum computing device is provided, which may be a server. The quantum computing device includes a memory, a processor, a signal generator, a quantum chip, an input / output (I / O) interface, and a communication interface. The signal generator is used to read microwave signals. The quantum chip includes qubits and a resonant cavity. The memory stores a computer program, and when the processor executes the computer program, it implements the steps of any of the methods described in any of the embodiments of the present disclosure. The processor, memory, and I / O interface are connected via a system bus, and the communication interface is connected to the system bus via the I / O interface. The processor of the quantum computing device provides computing and control capabilities. The memory of the quantum computing device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operating system and computer program in the non-volatile storage medium. The database of the quantum computing device stores data related to the method described in this embodiment, such as target parameters to be detected. The I / O interface of the quantum computing device is used to exchange information between the processor and external devices. The communication interface of the quantum computing device is used to communicate with external terminals via a network connection. When the computer program is executed by a processor, a method for determining photon number information is implemented.

[0165] In one embodiment of the present disclosure, the signal generator includes a read pulse generator, such as Figure 6 As shown, the present disclosure provides a quantum computing device, including a processor, memory, a pump pulse generator, a read pulse generator, a read pulse collector, and a quantum chip. The pump pulse generator and the read pulse generator are used to generate pulsed output microwave signals based on parameters determined by the processor, which act on the corresponding qubits and resonant cavities of the quantum chip. The read pulse collector is used to collect and analyze the output signals of the quantum chip.

[0166] Those skilled in the art will understand that Figure 6 The structure shown in the figure is merely a block diagram of a portion of the structure related to the disclosed solution and does not constitute a limitation on the quantum computing device to which the disclosed solution is applied. A specific quantum computing device may include more or fewer components than shown in the figure, or combine certain components, or have a different component arrangement.

[0167] In one embodiment, the present disclosure further provides a quantum computing device, including a memory and a processor, wherein a computer program is stored in the memory, and the processor implements the steps in the above-mentioned method embodiments when executing the computer program.

[0168] In one embodiment, the present disclosure provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps in the above-mentioned method embodiments are implemented.

[0169] In one embodiment, the present disclosure provides a computer program product, including a computer program, which implements the steps in the above method embodiments when executed by a processor.

[0170] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this disclosure are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant regulations.

[0171] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the above-mentioned embodiments. In particular, any reference to a memory, database, or other medium used in the embodiments provided in the present disclosure can include at least one of a non-volatile memory and a volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The databases involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the various embodiments provided herein may be, but are not limited to, general-purpose processors, central processing units (CPUs), graphics processing units (GPUs), digital signal processors (DSPs), programmable logic devices (PLDs), quantum computing-based data processing logic devices, artificial intelligence (AI) processors, and the like.

[0172] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this disclosure.

[0173] The above-described embodiments merely represent several implementation methods of the present disclosure. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present disclosure. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present disclosure, all of which fall within the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure shall be determined by the appended claims.

Claims

1. A method for determining photon number information, characterized in that: The method comprises: Obtaining target parameters to be detected of a quantum bit in a quantum chip; wherein the target parameters to be detected include a dispersion shift of a resonant cavity coupled to the quantum bit, a parameter of a change relationship between the frequency of the quantum bit and a read power of a read microwave signal, and a current read power of the read microwave signal; Based on the target parameter to be detected and a target correlation between the target parameter to be detected and the photon number of the resonant cavity, a current photon number in the resonant cavity is determined.

2. The method according to claim 1, characterized in that Determining the target association relationship includes: Obtaining a first correlation between a frequency change of the quantum bit and a change in the number of photons in the resonant cavity, wherein the first correlation includes a dispersion shift of the resonant cavity; Obtaining a second correlation between a frequency change of the quantum bit and a change in a read power of the read microwave signal, wherein the second correlation includes a change relationship parameter; The target association relationship is determined according to the first association relationship and the second association relationship.

3. The method according to claim 1, characterized in that Obtaining the dispersion shift of the resonant cavity, comprising: Obtaining a first resonance frequency of the resonant cavity when the quantum state of the quantum bit is a ground state and a second resonance frequency of the resonant cavity when the quantum state of the quantum bit is a first excited state; The dispersion shift of the resonant cavity is determined according to the first resonant frequency and the second resonant frequency.

4. The method according to claim 3, characterized in that The obtaining of a first resonant frequency of the resonant cavity when the quantum state of the quantum bit is a ground state includes: Changing the frequency of the read microwave signal to measure the output signal of the resonant cavity when the quantum state of the qubit is a ground state, wherein the output signal of the resonant cavity changes with the change of the frequency of the read microwave signal; Based on the frequency data of the read microwave signal and the data of the output signal of the resonant cavity, fitting the change relationship between the output signal of the resonant cavity and the frequency of the read microwave signal when the quantum state of the qubit is a ground state; According to the change relationship, a first resonance frequency of the resonant cavity when the quantum bit is in a ground state is determined.

5. The method according to claim 1, characterized in that Obtaining a parameter of a change relationship between the frequency of the quantum bit and the read power of the microwave signal, including: Adjusting the read power of the microwave signal to obtain a plurality of read power values, and obtaining the frequency of the quantum bit at the plurality of read power values; The frequency and the read power values ​​are fitted to obtain a parameter of a change relationship between the frequency of the quantum bit and the read power of the read microwave signal.

6. The method according to claim 5, characterized in that Obtaining the frequency of the quantum bit at the multiple read power values ​​includes: Acquiring response data of the output signal of the resonant cavity changing with the frequency of the pump microwave signal under the multiple read power values; Based on the correlation between the frequency of the quantum bit and the read power value and the output signal, the response data and the read power value are fitted to obtain the frequency of the quantum bit under the multiple read power values.

7. A device for determining photon number information, characterized in that: The device comprises: an acquisition module configured to acquire target parameters to be detected of a quantum bit in a quantum chip; wherein the target parameters to be detected include a dispersion shift of a resonant cavity coupled to the quantum bit, a parameter of a change relationship between the frequency of the quantum bit and a read power of a read microwave signal, and a current read power of the read microwave signal; The determination module is configured to determine the current number of photons in the resonant cavity based on the target parameter to be detected and a target correlation relationship between the target parameter to be detected and the number of photons in the resonant cavity.

8. A quantum computing device, characterized in that The invention comprises a memory, a processor, a signal generator and a quantum chip, wherein the signal generator is used to read microwave signals, the quantum chip comprises a quantum bit and a resonant cavity, the memory stores a computer program, and the processor implements the steps of the method according to any one of claims 1 to 6 when executing the computer program.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

10. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

Images