A quantum bit fast reading method based on strict control of resonant cavity field strength

Abstract

The application provides a kind of quantum bit fast reading method based on resonant cavity field strength strict control, belong to quantum computing and quantum information processing technical field, this method includes: extracting the readout resonant cavity coupled with quantum bit, obtains the key parameter of readout resonant cavity;Set driving signal frequency and calculate the detuning of ground state and excited state;Design pulse-maintain two-section type driving signal, determine the matching relationship of two pulse amplitudes, generate two-section type microwave driving signal;Two-section type microwave driving signal is applied to readout resonant cavity, carry out the fast response of resonant cavity field strength;Establish strict stable condition, so that cavity field reaches stable value strictly;Based on the coupling effect of superconducting quantum bit and readout resonant cavity, determine quantum bit state through dispersion model;After reading, quickly empty the photon in cavity to vacuum state, realize fast reset.The application realizes resonant cavity field strength fast response and reset through field strength strict control, realizes the fast, accurate reading of quantum bit.

Description

Technical Field

[0001] This invention relates to the field of quantum computing and quantum information processing technology, and in particular to a method for fast readout of qubits based on strict control of the resonant cavity field strength. Background Technology

[0002] In superconducting quantum computing, the reading of qubits usually adopts the dispersion readout scheme, that is, the state of the qubit is inferred by measuring the microwave transmission or reflection signal of the resonant cavity coupled to the qubit. With the increase in the scale of quantum processors and the increasing demand for error correction algorithms (QEC), the reading speed and fidelity have become the key bottlenecks limiting the system performance.

[0003] Currently, to overcome the inherent ring-up / ring-down time of photons in resonant cavities, two representative technologies have been developed: square-pulse readout technology drives the resonant cavity by applying a square-wave microwave pulse with constant amplitude, and integrates the I / Q components of the output signal to distinguish the state of the qubit. However, this technology is limited by the dynamic characteristics of cavity filling or decay, resulting in low information extraction efficiency within a short time window. Furthermore, residual photons remain after the pulse is turned off, easily introducing additional gate errors, making it difficult to meet the requirements of high-speed, high-fidelity readout. CLEAR pulse technology (Cavity Level Excitation and Reset) achieves rapid injection and extraction of photons by applying high-amplitude short pulses before and after the main pulse. However, this technology has significant drawbacks: the pulse waveform is complex, the specific waveform formula and principle derivation are not publicly disclosed, and the authenticity of the technology is questionable; the experimental curves show unevenness, indicating insufficient stability; and it mainly focuses on the reset function, with limited optimization of response speed.

[0004] Therefore, existing technologies still suffer from problems such as slow response speed, significant transient oscillations, incomplete reset, and low quantum gate fidelity in microsecond-level ultra-fast readout and high photon number working area applications. There is an urgent need for a quantum bit readout technology that can balance fast response, fast reset, and strict control of strength. Summary of the Invention

[0005] The purpose of this invention is to provide a fast quantum bit readout method based on strict control of resonant cavity field strength. Through the design of a two-stage pulse-sustain microwave drive signal and precise parameter matching, a fast response of resonant cavity field strength, oscillation-free stable output and fast reset are achieved, which significantly improves the speed, fidelity and system stability of quantum bit readout and meets the application requirements of large-scale fault-tolerant quantum computing.

[0006] To achieve the above objectives, this invention proposes a method for fast readout of quantum bits based on strict control of the resonant cavity field strength, comprising the following steps:

[0007] Step S1: Extract the readout resonant cavity coupled with the qubit and obtain the key parameters of the readout resonant cavity, including the cavity linewidth, the resonant frequency of the cavity when the qubit is in the ground state, and the resonant frequency of the cavity when the qubit is in the excited state.

[0008] Step S2: Under the rotating wave approximation, based on the Langevin equation to represent the field amplitude evolution of the quantum bit-resonant cavity system in the ground state and excited state, set the frequency of the microwave driving signal, and calculate the detuning of the ground state and excited state;

[0009] Step S3: Design a pulse-sustaining two-stage drive signal, including: a first-stage pulse with an amplitude of Duration from 0 to The second-stage pulse has an amplitude of , started Two microwave drive signals are generated, and the matching relationship between the amplitudes of the two pulse segments is determined by the following formula:

[0010] ;

[0011] ;

[0012] in, for The microwave drive signal at any given moment, The amplitude of the first stage pulse. The amplitude of the second-stage pulse. The duration of the first-stage pulse. It is a step function. For imaginary units, This represents the detuning between the driving frequency and the resonant cavity frequency. The linewidth of the resonant cavity;

[0013] Step S4: Apply the two-stage microwave drive signal to the readout resonant cavity to achieve a fast response of the resonant cavity field strength, specifically as follows:

[0014] exist At that time, the resonant cavity field strength is driven by the first-stage pulse to achieve a fast response of the resonant cavity field strength, as shown in the formula:

[0015] ;

[0016] ;

[0017] in, The amplitude of the ground state step field. To excite the amplitude of the state step field, This is the ground state detuning quantity. For excited-state detuning;

[0018] exist At that time, the resonant cavity field strength is driven by the superposition of the first-stage pulse and the second-stage pulse, resulting in a fast response of the resonant cavity field strength. The formula is as follows:

[0019] ;

[0020] ;

[0021] Step S5: Establish strict stability conditions and eliminate The transient oscillation at time t, which causes the cavity field to strictly reach a stable value, is given by the stability condition formula:

[0022] ;

[0023] Step S6: Use the Hamiltonian to describe the coupling between the superconducting quantum bit and the readout resonant cavity, and use the dispersion model to indirectly determine the state of the quantum bit.

[0024] Step S7: After reading is completed, quickly clear the photons in the cavity to a vacuum state and perform a rapid reset.

[0025] Preferably, in step S2, the driving signal frequency is set, including the frequency of the microwave driving signal, the resonant frequency of the ground-state resonant cavity, and the resonant frequency of the excited-state resonant cavity. The ground-state detuning and excited-state detuning are calculated using the following formula:

[0026] ;

[0027] ;

[0028] in, The resonant frequency of the ground-state resonant cavity. The resonant frequency of the excited-state resonant cavity, The frequency of the microwave drive signal.

[0029] Preferably, the microwave driving signal frequency must meet the dispersion region condition, the frequency of the microwave driving signal, the resonant frequency of the ground state resonant cavity, and the resonant frequency of the excited state resonant cavity do not coincide, and the detuning amount is greater than the coupling strength.

[0030] Preferably, in step S3, the duration of the first-stage pulse... It needs to be adapted to the photon birth and death inertial characteristics of the resonant cavity, and Satisfying the formula:

[0031] ;

[0032] ;

[0033] in, For integer parameters, This is the dispersive frequency shift parameter.

[0034] Preferably, in step S5, the constant value of the cavity field strength is:

[0035] .

[0036] Preferably, step S6 includes the following steps:

[0037] Step S61: Model the qubit as a nonlinear oscillator, read out the resonator as a linear LC circuit, and the two are capacitively coupled. Obtain the coupling strength based on the capacitance value, and define the resonator frequency using the following formula:

[0038] ;

[0039] in, To read the resonant cavity frequency, To read the equivalent inductance of the resonant cavity, To read the equivalent capacitance of the resonant cavity;

[0040] Step S62: Use the Hamiltonian to describe the coupling model between the superconducting quantum bit and the readout resonant cavity, the formula is:

[0041] ;

[0042] in, For Hamiltonian operators, For the free Hamiltonian of the transconducting qubit and the resonant cavity, The Hamiltonian is the interaction quantity between the superconducting quantum bit and the resonator.

[0043] Step S63: By using unitary transformation and expanding the Baker-Campbell-Hausdorff formula, the first-order interaction term is eliminated, and a dispersive frequency shift is introduced to obtain the effective Hamiltonian characterizing the dispersive model, as shown in the formula:

[0044] ;

[0045] ;

[0046] in, For an effective Hamiltonian, To reduce Planck's constant, For the frequency of qubits, For dispersive frequency shift parameters, For Pauli Z Operator, For the generation operator of the resonant cavity field, For the annihilation operator of the resonant cavity field, The detuning parameter;

[0047] Step S64: Establish the correlation between the qubit state and the resonant cavity frequency. Based on the resonant cavity frequency, deduce the qubit state. The resonant cavity frequency includes the resonant cavity frequency corresponding to the qubit's ground state and the resonant cavity frequency corresponding to the qubit's excited state. The formula is:

[0048] ;

[0049] ;

[0050] in, The resonant frequency of the ground-state resonant cavity. The resonant frequency of the excited-state resonant cavity.

[0051] Preferably, in step S63, eliminating the first-order interaction term is achieved by optimizing the generator. The derivation method makes We obtain the generator, eliminate the first-order interaction terms after the Hamiltonian expansion, and retain only the key second-order dispersion effect terms.

[0052] Therefore, this invention proposes a fast quantum bit readout method based on strict control of the resonant cavity field strength, the advantages of which are as follows:

[0053] (1) This invention completely eliminates transient oscillations through a two-stage pulse phase compensation design, ensuring that the field strength of the resonant cavity is within the range of [missing information]. It can quickly reach the target value and maintain it stably, achieving rapid response and strict field strength control, improving information extraction efficiency and significantly shortening reading time.

[0054] (2) This invention enables the rapid reset of the photon number in the resonant cavity to the vacuum state (photon number returns to zero), completely eliminating the interference of residual photons on subsequent quantum gate operations, reducing quantum gate errors, and providing key technical support for fault-tolerant quantum computing.

[0055] (3) Through precise signal design and processing, the signal contrast between the ground state and the excited state is significantly improved, the state distinction fidelity is high, and the reading error rate is effectively reduced. Attached Figure Description

[0056] Figure 1 This is a flowchart of a fast quantum bit readout method based on strict control of the resonant cavity field strength;

[0057] Figure 2 A schematic diagram of the coupling circuit model between the quantum bit and the readout resonant cavity;

[0058] Figure 3A schematic diagram comparing the trajectory of resonant cavity field amplitude change under step drive and pulse hold drive when the qubit is in the ground state;

[0059] Figure 4 A schematic diagram comparing the trajectory of resonant cavity field amplitude change under step drive and pulse hold drive when the qubit is in the excited state;

[0060] Figure 5 This is a schematic diagram comparing the decay curves of the resonant cavity field amplitude in the ground state relative to the steady-state solution over time.

[0061] Figure 6 This is a schematic diagram comparing the decay curves of the deviation of the resonant cavity field amplitude in the excited state relative to the steady-state solution over time.

[0062] Figure 7 This is a schematic diagram comparing the integral evolution trajectory of the resonant cavity field in the ground state;

[0063] Figure 8 A schematic diagram comparing the integral evolution trajectory of the resonant cavity field in the excited state;

[0064] Figure 9 A schematic diagram comparing the variation of the difference between the integral field amplitude of the ground state and the excited state over time under step-driven and pulse-held-driven conditions. Detailed Implementation

[0065] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0066] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0067] Example 1

[0068] like Figure 1 As shown, this invention provides a method for fast readout of quantum bits based on strict control of the resonant cavity field strength, comprising the following steps:

[0069] Step S1: Extract the readout resonant cavity coupled with the qubit and obtain the key parameters of the readout resonant cavity, including the cavity linewidth, the resonant frequency of the cavity when the qubit is in the ground state, and the resonant frequency of the cavity when the qubit is in the excited state.

[0070] Step S2: Under the rotating wave approximation, based on the Langevin equation, the field amplitude evolution of the quantum bit-resonant cavity system in the ground and excited states is represented. The microwave driving signal frequency is set, and the detuning of the ground and excited states is calculated. The set driving signal frequency includes the frequency of the microwave driving signal, the resonant frequency of the ground-state resonant cavity, and the resonant frequency of the excited-state resonant cavity. The microwave driving signal frequency must satisfy the dispersion region condition; the frequencies of the microwave driving signal, the resonant frequency of the ground-state resonant cavity, and the resonant frequency of the excited-state resonant cavity must not coincide, and the detuning must be greater than the coupling strength. Specifically, this includes the following steps:

[0071] Step S21: Under the rotating wave approximation, the field amplitude evolution of the qubit-resonant cavity system in the ground and excited states follows the Langevin equation, as follows:

[0072] ;

[0073] ;

[0074] in, The amplitude of the ground state field. To the amplitude of the excited state field;

[0075] Step S22: Let , Furthermore, the equations are simplified in a rotating coordinate system, resulting in the following simplified formula:

[0076] ;

[0077] ;

[0078] in, The amplitude of the ground state field in the rotating coordinate system. The amplitude of the excited-state field in the rotating coordinate system. This is the ground state detuning quantity. For excited-state detuning;

[0079] The formulas for calculating the ground state detuning and excited state detuning are as follows:

[0080] ;

[0081] ;

[0082] in, The resonant frequency of the ground-state resonant cavity. The resonant frequency of the excited-state resonant cavity, The frequency of the microwave drive signal.

[0083] Step S23: Integrate the simplified formula over time to obtain the following formula:

[0084] ;

[0085] ;

[0086] in, This represents the field amplitude response corresponding to the ground state. The field amplitude response corresponding to the excited state, The amplitude of the driving field, It is a time variable.

[0087] Step S3: Design a pulse-sustaining two-stage drive signal, including: a first-stage pulse with an amplitude of Duration from 0 to The second-stage pulse has an amplitude of , started Two microwave drive signals are generated, and the matching relationship between the amplitudes of the two pulse segments is determined by the following formula:

[0088] ;

[0089] ;

[0090] in, for The microwave drive signal at any given moment, The amplitude of the first stage pulse. The amplitude of the second-stage pulse. The duration of the first-stage pulse is set to... ,and It needs to be adapted to the photon birth and death inertial characteristics of the resonant cavity. It is a step function. For imaginary units, This represents the detuning between the driving frequency and the resonant cavity frequency. denoted as the linewidth of the resonant cavity.

[0091] Step S4: Apply the two-stage microwave drive signal to the readout resonant cavity to achieve a fast response of the resonant cavity field strength, specifically as follows:

[0092] exist At that time, the resonant cavity field strength is driven by the first-stage pulse to achieve a fast response of the resonant cavity field strength, as shown in the formula:

[0093] ;

[0094] ;

[0095] in, The amplitude of the ground state step field. To excite the amplitude of the state step field, This is the ground state detuning quantity. For excited-state detuning;

[0096] exist At that time, the resonant cavity field strength is driven by the superposition of the first-stage pulse and the second-stage pulse, resulting in a fast response of the resonant cavity field strength. The formula is as follows:

[0097] ;

[0098] ;

[0099] Integrating the fast response formula for the resonant cavity field strength over time, we obtain the following formula:

[0100] ;

[0101] ;

[0102] in, This represents the step-driven field amplitude response corresponding to the ground state. This represents the step-driven field amplitude response corresponding to the excited state.

[0103] Step S5: Establish strict stability conditions and eliminate The transient oscillation at time t, which causes the cavity field to strictly reach a stable value, is given by the stability condition formula:

[0104] ;

[0105] When this condition is met, for the rapid response process... The cavity field strength afterward remains constant:

[0106] ;

[0107] This indicates that the system is Not only did the time reach that value, but there was also no subsequent oscillation. The same reasoning applies to the rapid reset process.

[0108] Step S6: Use the Hamiltonian to describe the coupling between the superconducting qubit and the readout resonant cavity, and indirectly determine the state of the qubit using a dispersion model, including the following steps:

[0109] Step S61: Design as follows Figure 2 The circuit model shown for deriving the effective Hamiltonian of the system models the qubit as a nonlinear oscillator and the readout resonator as a linear LC circuit. The two are capacitively coupled, and the coupling strength is obtained based on the capacitance value. The resonator frequency is defined by the following formula:

[0110] ;

[0111] Step S62: Use the Hamiltonian to describe the coupling model between the superconducting quantum bit and the readout resonant cavity, the formula is:

[0112] ;

[0113] in, For the original Hamiltonian of the system, For the free Hamiltonian of the transconducting qubit and the resonant cavity, The Hamiltonian is the interaction quantity between the superconducting quantum bit and the resonator. and The calculation is as follows:

[0114] ;

[0115] ;

[0116] in, This is the first excited state of the qubit. The left vector of the first excited state of the qubit. This is the second excited state of the qubit. The left vector of the first excited state of the qubit. For the first quantum bit State and the first The coupling strength between the state and the resonant cavity, For energy level numbering, Represents taking the conjugate;

[0117] Step S63: Expand using unitary transformation and the Baker-Campbell-Hausdorff formula, the formula is:

[0118] ;

[0119] ;

[0120] in, The effective Hamiltonian after transformation. The original Hamiltonian of the system, , It is a unit positive operator. , for , Hermitian conjugate operator, To generate meta-operators, The target operator is the one subjected to the unitary transformation. To exchange children;

[0121] Substituting the above expression into the effective Hamiltonian and expanding it into a series, the transformed effective Hamiltonian is expressed as:

[0122] ;

[0123] in, For generators, For left-handed unitary operators, It is a right-acting unit operator;

[0124] To simplify the model, appropriate generators are selected. ,make ,Right now , to obtain generator The formula is:

[0125] ;

[0126] in, For coupling strength, For the ground state of a quantum bit, The left vector of the ground state of a quantum bit;

[0127] Will Substituting into the expansion, we get the formula:

[0128] ;

[0129] because: Substituting this into the effective Hamiltonian, we get:

[0130] ;

[0131] Introducing energy level operators The expression can be rewritten as:

[0132] ;

[0133] in, , All are energy level numbers. For the transition operator from the ground state to the first excited state of a quantum bit, For the transition operator from the first excited state to the ground state of a quantum bit, For the transition operator from the first excited state to the second excited state of a quantum bit, For the transition operator from the second excited state to the first excited state of a quantum bit;

[0134] Interacting Hamiltonian:

[0135] ;

[0136] First consideration and The transition between energy levels is defined as follows:

[0137] ;

[0138] Calculate their product:

[0139] ;

[0140] ;

[0141] Obtaining the exchange of pieces: ;

[0142] consider and The transition between energy levels only requires a simple substitution. Replace with ,Will Replace with ,Will Replace with and will Replace with The formula can be obtained as follows: Combining the substitution results, we can obtain the formula:

[0143] ;

[0144] For the ground state Its frequency shift The displacement is given by the following formula:

[0145] ;

[0146] For excited state Its frequency shift The displacement is given by the following formula:

[0147] ;

[0148] Based on the above formula for calculating frequency shift (displacement), the following formula is obtained:

[0149] ;

[0150] To reorganize the frequency shift term, we use the identity:

[0151] ;

[0152] After eliminating the first-order interaction terms from the Hamiltonian expansion and retaining only the crucial second-order dispersion effect terms, a dispersion frequency shift is introduced to obtain the effective Hamiltonian characterizing the dispersion model, as shown in the formula:

[0153] ;

[0154] ;

[0155] in, For an effective Hamiltonian, To reduce Planck's constant, For the frequency of qubits, For dispersion frequency shift, For Pauli Z Operator, For the generation operator of the resonant cavity field, For the annihilation operator of the resonant cavity field;

[0156] Step S64: Establish the correlation between the qubit state and the resonant cavity frequency. Based on the resonant cavity frequency, deduce the qubit state. The resonant cavity frequency includes the resonant cavity frequency corresponding to the qubit's ground state and the resonant cavity frequency corresponding to the qubit's excited state. The formula is:

[0157] ;

[0158] ;

[0159] in, The resonant frequency of the ground-state resonant cavity. The resonant frequency of the excited-state resonant cavity.

[0160] Step S7: After reading is completed, quickly clear the photons in the cavity to a vacuum state and perform a rapid reset.

[0161] like Figure 3 When the qubit shown is in its ground state, the pulse holding drive can accelerate the convergence process of the resonant cavity field; as... Figure 4 As shown, when the quantum bit is in the excited state, pulse holding drive can also accelerate the convergence process of the resonant cavity field, realize the rapid clearing of photons in the cavity to reach the vacuum state, and reduce the reset time.

[0162] like Figure 5 As shown, the curves depict the decay process of the resonant cavity field amplitude relative to the steady-state solution over time. Comparisons show that pulse hold drive can suppress transient oscillations and achieve stable output more quickly, shortening the response time in quantum measurements and thus improving the real-time performance and reliability of quantum readout. Figure 6 As shown, the corresponding situation of the qubit in the excited state is similar to that in the ground state. The pulse holding drive significantly shortens the time for the system to reach a steady state. Regardless of whether the qubit is in the ground state or the excited state, it can achieve fast and stable resonant cavity reset and response.

[0163] like Figure 7As shown in the figure, the integral evolution trajectory of the resonant cavity field under ground state conditions is illustrated. The results indicate that pulse hold-drive can accumulate the required intensity in a shorter time to reach steady state; as... Figure 8 As shown in the figure, the integral evolution trajectory of the resonant cavity field under excited state conditions is displayed. The results show that pulse holding drive can clear the photons in the cavity in a shorter time to achieve a vacuum state.

[0164] like Figure 9 As shown, by integrating over time, the difference between the integral field amplitudes of the ground state and the excited state under the two driving methods is compared with time. The results show that pulse holding drive significantly enhances the signal contrast of the quantum state.

[0165] It is worth noting that all contents not described in detail in this invention are existing technologies and are well known to those skilled in the art.

[0166] Therefore, this invention proposes a fast quantum bit readout method based on strict control of the resonant cavity field strength. By applying a two-stage pulse-sustaining microwave drive signal to the resonant cavity coupled to the quantum bit, the amplitudes of the two pulse stages are strictly controlled to satisfy a specific phase-amplitude relationship. This ensures that the resonant cavity field reaches the target strength stably and without oscillation within a fixed time. After readout, the photons within the cavity are quickly cleared to a vacuum state, achieving rapid response and reset of the resonant cavity field strength. This invention effectively shortens the readout response time, eliminates transient oscillations, and improves readout fidelity and quantum gate operation accuracy.

[0167] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for fast readout of quantum bits based on strict control of resonant cavity field strength, characterized in that, Includes the following steps: Step S1: Extract the readout resonant cavity coupled with the qubit and obtain the key parameters of the readout resonant cavity, including the cavity linewidth, the resonant frequency of the cavity when the qubit is in the ground state, and the resonant frequency of the cavity when the qubit is in the excited state. Step S2: Under the rotating wave approximation, based on the Langevin equation to represent the field amplitude evolution of the quantum bit-resonant cavity system in the ground state and excited state, set the frequency of the microwave driving signal, and calculate the detuning of the ground state and excited state; Step S3: Design a pulse-sustaining two-stage drive signal, including: a first-stage pulse with an amplitude of Duration from 0 to The second-stage pulse has an amplitude of , started Two microwave drive signals are generated, and the matching relationship between the amplitudes of the two pulse segments is determined by the following formula: ； ； in, for The microwave drive signal at any given moment, The amplitude of the first stage pulse. The amplitude of the second-stage pulse. The duration of the first-stage pulse. It is a step function. For virtual part units, This represents the detuning between the driving frequency and the resonant cavity frequency. The linewidth of the resonant cavity; Step S4: Apply the two-stage microwave drive signal to the readout resonant cavity to achieve a fast response of the resonant cavity field strength, specifically as follows: exist At that time, the resonant cavity field strength is driven by the first-stage pulse to achieve a fast response of the resonant cavity field strength, as shown in the formula: ； ； in, The amplitude of the ground state step field. To excite the amplitude of the state step field, This is the ground state detuning quantity. For excited-state detuning; exist At that time, the resonant cavity field strength is driven by the superposition of the first-stage pulse and the second-stage pulse, resulting in a fast response of the resonant cavity field strength. The formula is as follows: ； ； Step S5: Establish strict stability conditions and eliminate The transient oscillation at time t, which causes the cavity field to strictly reach a stable value, is given by the stability condition formula: ； Step S6: Use the Hamiltonian to describe the coupling between the superconducting quantum bit and the readout resonant cavity, and use the dispersion model to indirectly determine the state of the quantum bit. Step S7: After reading is completed, quickly clear the photons in the cavity to a vacuum state and perform a rapid reset.

2. The method for fast readout of quantum bits based on strict control of resonant cavity field strength according to claim 1, characterized in that: In step S2, the driving signal frequency is set, including the frequency of the microwave driving signal, the resonant frequency of the ground-state resonant cavity, and the resonant frequency of the excited-state resonant cavity. The ground-state detuning and excited-state detuning are calculated using the following formula: ； ； in, The resonant frequency of the ground-state resonant cavity. The resonant frequency of the excited-state resonant cavity, The frequency of the microwave drive signal.

3. The method for fast readout of quantum bits based on strict control of resonant cavity field strength according to claim 2, characterized in that: The frequency of the microwave driving signal must meet the dispersion region condition. The frequency of the microwave driving signal, the resonant frequency of the ground state resonant cavity, and the resonant frequency of the excited state resonant cavity do not coincide, and the detuning is greater than the coupling strength.

4. The method for fast readout of quantum bits based on strict control of resonant cavity field strength according to claim 1, characterized in that: In step S3, the duration of the first-stage pulse It needs to be adapted to the photon birth and death inertial characteristics of the resonant cavity, and Satisfying the formula: ； ； in, Integer parameter, This is the dispersive frequency shift parameter.

5. The method for fast readout of quantum bits based on strict control of resonant cavity field strength according to claim 1, characterized in that: In step S5, the cavity field strength is kept constant at the following value: 。 6. The method for fast readout of quantum bits based on strict control of resonant cavity field strength according to claim 1, characterized in that: Step S6 includes the following steps: Step S61: Model the qubit as a nonlinear oscillator, read out the resonator as a linear LC circuit, and the two are capacitively coupled. Obtain the coupling strength based on the capacitance value, and define the resonator frequency using the following formula: ； in, To read the resonant cavity frequency, To read the equivalent inductance of the resonant cavity, To read the equivalent capacitance of the resonant cavity; Step S62: Use the Hamiltonian to describe the coupling model between the superconducting quantum bit and the readout resonant cavity, the formula is: ； in, For Hamiltonian operators, For the free Hamiltonian of the transconducting qubit and the resonant cavity, The Hamiltonian is the interaction quantity between the superconducting quantum bit and the resonator. Step S63: By using unitary transformation and expanding the Baker-Campbell-Hausdorff formula, the first-order interaction term is eliminated, and a dispersive frequency shift is introduced to obtain the effective Hamiltonian characterizing the dispersive model, as shown in the formula: ； ； in, For an effective Hamiltonian, To reduce Planck's constant, For the frequency of qubits, For dispersive frequency shift parameters, For Pauli Z Operator, For the generation operator of the resonant cavity field, For the annihilation operator of the resonant cavity field, The detuning parameter; Step S64: Establish the correlation between the qubit state and the resonant cavity frequency. Based on the resonant cavity frequency, deduce the qubit state. The resonant cavity frequency includes the resonant cavity frequency corresponding to the qubit's ground state and the resonant cavity frequency corresponding to the qubit's excited state. The formula is: ； ； in, The resonant frequency of the ground-state resonant cavity. The resonant frequency of the excited-state resonant cavity.

7. The method for fast readout of quantum bits based on strict control of resonant cavity field strength according to claim 6, characterized in that: In step S63, eliminating the first-order interaction term is achieved by optimizing the generator. The derivation method makes We obtain the generator, eliminate the first-order interaction terms after the Hamiltonian expansion, and retain only the key second-order dispersion effect terms.

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