Frequency adjustment method and device, electronic equipment and storage medium

Abstract

The invention discloses a frequency adjustment method and device, electronic equipment and a storage medium, and relates to the technical field of quantum, and the method comprises the steps: when any excitation state (target excitation state) of a quantum bit is initialized, a target voltage value, a first frequency value and a pulse duration corresponding to the target excitation state can be obtained firstly, and then the target excitation state is initialized; the frequency adjustment operation can be performed according to the target voltage value, so that the target excitation state of the quantum bit and the target excitation state of the nonlinear superconducting cavity meet the condition of generating a coupling effect. And then, the first frequency and the pulse duration are sent to a pulse generator for applying a driving field to the quantum bits, so that the target excitation state of the quantum bits and the target excitation state of the nonlinear superconducting cavity generate Rabian oscillation under the condition of meeting the coupling effect, and in the Rabian oscillation process, the target excitation state of the quantum bits and the target excitation state of the nonlinear superconducting cavity are subjected to the Rabian oscillation. And after the energy of the target excited state of the quantum bit can be completely transferred to the target excited state of the nonlinear superconducting cavity and released, the initialization of the target excited state of the quantum bit is completed.

Description

Technical Field

[0001] The present application relates to the field of quantum technology, and in particular to a frequency adjustment method, device, electronic device, and storage medium. Background Art

[0002] In the field of quantum technology, quantum state initialization is one of the fundamental requirements for quantum computers to perform computations and quantum simulations. Currently, for some quantum states, initialization is achieved using linear superconducting cavities and sideband transitions. However, sideband transitions simultaneously involve two transitions in opposite directions (for example, a qubit's first excited state transitions to a second excited state, and vice versa), making it impossible to fully initialize the qubit's excited state to the ground state. Summary of the Invention

[0003] The present application provides a frequency adjustment method, device, electronic device, storage medium, and program product to solve the problem that the excited state of a quantum bit cannot be completely initialized to the ground state.

[0004] This application provides a frequency adjustment method, including:

[0005] Obtaining a target voltage value, a first frequency, and a pulse duration corresponding to a target excited state;

[0006] performing a frequency adjustment operation on an energy level corresponding to a target excited state of the quantum bit or an energy level corresponding to a target excited state of the nonlinear superconducting cavity according to a target voltage value, so that the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity meet a condition for generating a coupling effect;

[0007] The first frequency and pulse duration are sent to a pulse generator to apply a driving field to the quantum bit, so that the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity produce Rabi oscillations under the condition of satisfying the coupling effect. During the Rabi oscillation, the energy of the target excited state of the quantum bit is transferred to the target excited state of the nonlinear superconducting cavity and released, thereby completing the initialization of the target excited state of the quantum bit.

[0008] The present application also provides a frequency adjustment device, comprising:

[0009] An acquisition module, configured to acquire a target voltage value, a first frequency, and a pulse duration corresponding to a target excited state;

[0010] An adjustment module is used to perform a frequency adjustment operation on the energy level corresponding to the target excited state of the quantum bit or the energy level corresponding to the target excited state of the nonlinear superconducting cavity according to the target voltage value, so that the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity meet the conditions for generating a coupling effect;

[0011] The sending module is used to send the first frequency and pulse duration to the pulse generator to apply a driving field to the quantum bit so that the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity produce Rabi oscillations under the condition of satisfying the coupling effect. During the Rabi oscillation, the energy of the target excited state of the quantum bit is transferred to the target excited state of the nonlinear superconducting cavity and released, thereby completing the initialization of the target excited state of the quantum bit.

[0012] The present application also provides an electronic device, comprising: a memory for storing a computer program; and a processor for implementing the steps of any of the above-mentioned frequency adjustment methods when executing the computer program.

[0013] The present application also provides a computer-readable storage medium, in which a computer program is stored. When the computer program is executed by a processor, the steps of any of the above-mentioned frequency adjustment methods are implemented.

[0014] The present application also provides a computer program product, including a computer program, which implements the steps of any of the above-mentioned frequency adjustment methods when executed by a processor.

[0015] Through the present application, first of all, for the initialization of any excited state, the voltage value, frequency, and pulse duration corresponding to itself can be obtained. Then, the energy level corresponding to the target excited state of the quantum bit or the frequency of the target excited state corresponding to the nonlinear superconducting cavity can be adjusted through the target voltage value, so that the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity can meet the conditions for generating a coupling effect. Finally, after sending the first frequency and pulse duration to the pulse generator, the pulse generator can apply a driving field to the quantum bit so that the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity generate Rabi oscillations under the conditions of satisfying the coupling effect. In this way, during the Rabi oscillation process, the energy of the target excited state of the quantum bit is transferred to the target excited state of the nonlinear superconducting cavity, completing the initialization of the target excited state of the quantum bit. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0017] Figure 1 An energy level diagram provided in an embodiment of the present application;

[0018] Figure 2 A schematic diagram of the architecture of a quantum state initialization system provided in an embodiment of the present application;

[0019] Figure 3 A schematic structural diagram of a nonlinear superconducting cavity provided in an embodiment of the present application;

[0020] Figure 4 A schematic diagram of the relationship between magnetic flux and frequency provided in an embodiment of the present application;

[0021] Figure 5 Another energy level diagram provided in an embodiment of the present application;

[0022] Figure 6 A schematic diagram of the relationship between probability and the product of frequency and pulse duration provided in an embodiment of the present application;

[0023] Figure 7 A flow chart of a frequency adjustment method provided in an embodiment of the present application;

[0024] Figure 8 Another energy level diagram provided in an embodiment of the present application;

[0025] Figure 9 A schematic structural diagram of a frequency adjustment device provided in an embodiment of the present application;

[0026] Figure 10 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0027] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0028] It should be noted that, in the description of this application, the terms "comprises," "includes," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. The terms "first," "second," etc., in this application are used to distinguish similar objects, and are not used to describe a particular order or sequence.

[0029] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0030] The professional terms involved in this application are explained below.

[0031] Quantum bit: A qubit is the fundamental unit of information in quantum computing. It is a quantum mechanical extension of the classical unit of information, the bit. In classical computing, a bit represents the smallest unit of information and can be either 0 or 1. However, due to the properties of quantum mechanics, a qubit can exist in a superposition of both 0 and 1 simultaneously, enabling quantum computing to far exceed the capabilities of classical computing in certain situations. Qubits can be implemented in a variety of physical systems, such as superconducting circuits.

[0032] Fluxonium qubits: These use a Josephson junction and a circuit consisting of an inductor and capacitor to form an artificial atom. In this setup, the state of the qubit is defined by the current distribution in the circuit, and these states can be manipulated by applying an external magnetic flux.

[0033] Dressed states are a key concept in quantum optics and quantum information. They describe the new states that emerge when a quantum system interacts with a field and its energy level structure changes. The quantum system in this application is composed of a superconducting cavity and quantum bits.

[0034] Quantum state: refers to the state of a quantum object, which can be used to fully describe all physical properties of the quantum object. For example, a quantum state can be a ground state, a first excited state, a second excited state, etc. In this application, a quantum object can be a quantum bit, a nonlinear superconducting cavity, etc.

[0035] Excited state: A higher energy state reached by a quantum object after receiving energy.

[0036] Ground state: The lowest energy state a quantum object can have, and also the most stable state.

[0037] like Figure 1 As shown, the left side is the energy level diagram of the quantum bit, and the right side is the energy level diagram of the linear superconducting cavity. Figure 1 The solid lines in the figure represent actual energy levels, while the bold dashed lines represent temporary states achieved through specific operations (e.g., frequency adjustment). The ground state of the qubit and the ground state of the linear superconducting cavity can both be represented by |g0>. The first excited state of the qubit can be represented by |e0>, and the second excited state of the qubit can be represented by |f0>. The first excited state of the linear superconducting cavity can be represented by |g1>, and the second excited state of the linear superconducting cavity can be represented by |g2>.

[0038] For example, after applying a square wave bias flux pulse to the bias flux line of the quantum bit, the frequency of the energy level corresponding to the second excited state of the quantum bit can be adjusted to be close to the frequency of the energy level corresponding to the first excited state of the linear superconducting cavity. After the adjustment, the difference (frequency detuning) between the frequency of the energy level corresponding to the second excited state of the quantum bit and the frequency of the energy level corresponding to the first excited state of the linear superconducting cavity is less than or equal to a smaller preset threshold, for example, the difference can be 0. In addition, the frequency ω is input to the quantum bit through the control line of the quantum bit. p The driving field of the quantum bit is g. Since the second excited state of the quantum bit has a coupling strength g with the first excited state of the linear superconducting cavity, gr Therefore, under the action of an external driving field, Rabi oscillations can be generated between the second excited state of the qubit and the first excited state of the linear superconducting cavity. Thus, under the action of Rabi oscillations, the energy of the second excited state of the qubit can be transferred to the first excited state of the linear superconducting cavity. The energy of the first excited state of the linear superconducting cavity can then be rapidly decayed through the dissipative channel of the linear superconducting cavity, completing the initialization of the second excited state of the qubit.

[0039] From the first excited state of a quantum bit to a dressed state The transition frequency between the two is related to the frequency of the driving field ω p There is a frequency detuning Δ1=ω0-ω gf =ω ef -ω p , among which, the decorated state Including |f0>, ω0 is the frequency difference between the first excited state and the ground state of the linear superconducting cavity, ω gf is the transition frequency between the second excited state and the ground state of the quantum bit, ω ef The frequency adjustment operation is performed from the first excited state of the quantum bit to the first excited state of the linear superconducting cavity (also called the dressed state). ) between the transition frequency. In the case of weak drive, the efficiency of quantum state exchange through Rabi oscillation is very low. If the frequency of the driving field is increased, the frequency of quantum bit transition from the first excited state to the dressed state can be used. If a driving field with the same frequency as the transition frequency between the two states is used (i.e., reducing frequency detuning and improving exchange efficiency), it is possible to cause energy level transitions in a linear superconducting cavity or qubit. Therefore, the sideband process effect is generally used to initialize the first excited state of the qubit. The sideband transition process simultaneously includes two transitions in opposite directions (for example, the first excited state transitions to the second excited state, and the second excited state transitions to the first excited state), which cannot completely initialize the excited state of the qubit to the ground state.

[0040] In order to solve the above technical problem that the excited state of the quantum bit cannot be completely initialized to the ground state, this application proposes a new quantum state initialization method, which can be achieved by Figure 2 The quantum state initialization system shown in FIG. This system requires no additional components, but only requires converting a linear superconducting cavity into a nonlinear superconducting cavity. For example, the system can include a qubit, a nonlinear superconducting cavity, a superconducting quantum interference device (Squid), a target inductor, a pulse generator, and a controller. The system can be a quantum computer system.

[0041] Among them, the nonlinear superconducting cavity can be grounded at its short-circuit side (reference Figure 3 The nonlinearity of the superconducting cavity can be achieved by increasing defects (on the short-circuit side) or integrating superconducting qubits inside a nonlinear superconducting cavity. The nonlinear superconducting cavity can be used to release energy through its own dissipative channels. A Purcell filter can also be set inside the nonlinear superconducting cavity to accelerate the energy release rate. When the nonlinear superconducting cavity is in the ground state (the first mode), it can be used to read the quantum state of the qubit.

[0042] The superconducting quantum interference device can be set inside a nonlinear superconducting cavity. Figure 3 The positional relationship between the superconducting quantum interference device and the superconducting cavity.

[0043] The target inductor can be used to generate a magnetic field to affect the magnetic flux of the superconducting quantum interference device, so as to further adjust the frequency and frequency spacing of the energy level of the nonlinear superconducting cavity. Figure 3 In, Φ ext Represents the external magnetic flux, that is, the effect of the target inductor on the magnetic flux of the superconducting quantum interference device. Figure 4 As shown, the horizontal axis coordinate is The vertical axis coordinate is Among them, Φ0 is the magnetic flux quantum, which can be expressed as h is Planck's constant, e is the electron charge, and ω1 is the resonant frequency of the first mode of the nonlinear superconducting cavity. For the same applied magnetic flux, the spacing between each curve is inconsistent, indicating that the frequency difference between adjacent energy levels of the nonlinear superconducting cavity is inconsistent. For the same curve, the frequency varies under different applied magnetic fluxes, indicating that the frequency varies periodically with the applied magnetic flux.

[0044] The pulse generator can be used to inject a drive field into the quantum bit.

[0045] The controller can be used to perform frequency adjustment operations, so that the excited state of the quantum bit and the excited state of the nonlinear superconducting cavity are energy-level matched, so as to generate Rabi oscillations under the influence of the driving field and realize energy transfer.

[0046] The following explains the Rabi oscillation process using a simple two-level quantum bit as an example.

[0047] The energy level diagram of a two-level quantum bit can be expressed as Figure 5 As shown, the solid line is the actual energy level, the bold dotted line is the temporary state achieved by a specific operation (applying a driving field), the ground state of the two-level quantum bit can be expressed as |g>, the excited state can be expressed as |e>, the transition frequency between the ground state and the excited state is ω2, and the frequency applied by the control line to the quantum bit is ω p The driving field can generate Rabi oscillations between the ground state and the excited state of the quantum bit. During the Rabi oscillation, the occupation probability of the excited state of the quantum bit can be expressed by the following mathematical expression:

[0048]

[0049] Δ=ω2-ω p (3)

[0050] Among them, P e is the occupation probability of the excited state of the quantum bit, g is the coupling strength between the two quantum states (under the above energy level structure, it is the coupling strength between the ground state and the excited state of the quantum bit), which is a fixed value, ω R is the oscillation frequency of the Rabi oscillation, Δ is the frequency detuning between the transition frequency between the ground state and the excited state of the quantum bit and the frequency of the driving field, ω2 is the frequency of the energy level corresponding to the excited state of the quantum bit, t is the time, ω p is the frequency of the driving field.

[0051] like Figure 6 As shown, the horizontal axis coordinate is ω R t, the vertical axis coordinate is P e The solid line is the curve of probability evolution over time when Δ is equal to 0, the dashed line is the curve of probability evolution over time when Δ is equal to 0.5, and the dotted line is the curve of probability evolution over time when Δ is equal to 1. Figure 6 It can be seen that at the same ω R Under the value of t, the probability corresponding to Δ equal to 0 is higher, that is, when the frequency of the driving field is consistent with the transition frequency between the ground state and the excited state of the quantum bit, P e maximum.

[0052] The embodiment of the present application provides a frequency adjustment method, which can be executed by the above-mentioned controller, such as Figure 7As shown, the specific processing steps of the frequency adjustment method may include:

[0053] Step S701 , obtaining a target voltage value, a first frequency, and a pulse duration corresponding to a target excited state.

[0054] The target excited state may be any excited state, for example, the first excited state and the second excited state mentioned above.

[0055] The quantum bit may be a Fluxonium quantum bit. Since the frequencies of energy levels corresponding to two adjacent excited states of a Fluxonium quantum bit are highly anharmonic, the probability of the quantum state of the quantum bit leaking to a highly excited state can be reduced during the quantum state exchange process.

[0056] The pulse duration corresponding to the target excited state can be Among them, ω R is the oscillation frequency of the Rabi oscillation. It can be seen that the pulse duration determined according to the above expression, when the pulse duration corresponding to the target excited state is substituted into the above formula (1), the value of the trigonometric function is the largest, which is 1. That is, it can be guaranteed that when the Rabi oscillation occurs, the energy of the target excited state of the quantum bit can be efficiently transferred to the target excited state of the nonlinear superconducting cavity, realizing complete initialization.

[0057] Referring to the above formulas (2) and (3), the oscillation frequency of the Rabi oscillation is affected by the transition frequency between the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity, the frequency of the driving field, and the coupling strength between the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity. When the frequency of the driving field is consistent with the transition frequency between the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity, the frequency detuning can be minimized, thereby minimizing the oscillation frequency of the Rabi oscillation. In other words, the oscillation frequency value of the Rabi oscillation is equal to (or approximately equal to) the coupling strength between the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity, maximizing the probability that the quantum system composed of the quantum bit and the nonlinear superconducting cavity is in the target excited state of the nonlinear superconducting cavity. In other words, setting the first frequency to the transition frequency between the energy level corresponding to the target excited state of the quantum bit and the energy level corresponding to the target excited state of the nonlinear superconducting cavity can improve the efficiency of energy transfer to the target excited state of the nonlinear superconducting cavity.

[0058] Specifically, for each excited state initialization operation (initialization to the base state), the controller can obtain the voltage value and frequency corresponding to the excited state. The methods for obtaining the target voltage value may include the following:

[0059] Method 1: directly obtain the target voltage value corresponding to the target excited state.

[0060] Method 2: Obtain the second frequency. Determine the voltage value corresponding to the second frequency based on the second frequency and the corresponding relationship between the voltage value and the frequency.

[0061] The second frequency may be a frequency of an energy level corresponding to a target excited state of the qubit, and the voltage value corresponding to the second frequency is the target voltage value.

[0062] Specifically, the controller can use the original frequency of the energy level of the target excited state of the quantum bit as a reference to adjust the frequency of the energy level corresponding to the target excited state of the nonlinear superconducting cavity, or it can use the original frequency of the energy level corresponding to the target excited state of the nonlinear superconducting cavity as a reference to adjust the frequency of the energy level corresponding to the target excited state of the quantum bit.

[0063] Accordingly, the target voltage value can be the voltage value currently applied to the target inductor. When the voltage corresponding to the target voltage value is applied to the target inductor, current flowing through the inductor generates a magnetic field, which affects the magnetic flux of the superconducting quantum interference device within the nonlinear superconducting cavity, causing the frequency of the energy level corresponding to the target excited state of the nonlinear superconducting cavity to change to the frequency corresponding to the target voltage value. In order to ensure that the frequency of the energy level corresponding to the target excited state of the qubit is consistent with the frequency of the energy level corresponding to the target excited state of the nonlinear superconducting cavity, the controller can obtain the voltage value currently applied to the target inductor, that is, obtain the target voltage value corresponding to the target excited state.

[0064] Alternatively, the controller may obtain the frequency of the energy level corresponding to the target excited state of the quantum bit, and then determine the voltage value corresponding to the second frequency based on the second frequency and the correspondence between the voltage value and the frequency.

[0065] Step S702: performing a frequency adjustment operation on the energy level corresponding to the target excited state of the quantum bit or the energy level corresponding to the target excited state of the nonlinear superconducting cavity according to the target voltage value, so that the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity meet the conditions for generating a coupling effect.

[0066] Corresponding to method 1 in step S701, the controller can apply a voltage equal to the target voltage value to the bias magnetic flux lines of the quantum bit based on the target voltage value, so that the frequency of the energy level corresponding to the target excited state of the quantum bit is consistent with the frequency corresponding to the target voltage value.

[0067] Corresponding to the second method in step S702, a voltage having the same voltage value as the target voltage value is applied to the target inductor, wherein the magnetic field generated by the target inductor affects the magnetic flux of the superconducting quantum interference device in the nonlinear superconducting cavity, so that the frequency of the energy level corresponding to the target excited state of the nonlinear superconducting cavity is consistent with the frequency corresponding to the target voltage value.

[0068] In this way, after adjusting the frequencies of the energy levels corresponding to the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity to be consistent, the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity can meet the conditions for generating coupling.

[0069] Step S703: Send the first frequency and pulse duration to the pulse generator to apply a driving field to the quantum bit, so that the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity produce Rabi oscillations under the condition of satisfying the coupling effect. During the Rabi oscillation, the energy of the target excited state of the quantum bit is transferred to the target excited state of the nonlinear superconducting cavity and released, thereby completing the initialization of the target excited state of the quantum bit.

[0070] Specifically, after the controller sends the first frequency and pulse duration to the pulse generator, the pulse generator can generate a driving field based on the first frequency and pulse duration, and apply a driving field with a frequency of the first frequency and a pulse duration of the above pulse duration to the quantum bit through the control line of the quantum bit. In this way, the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity can produce Rabi oscillations under the influence of the driving field. During the Rabi oscillation process, the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity are exchanged, that is, the target excited state of the quantum bit can be completely transferred to the target excited state of the nonlinear superconducting cavity, and the nonlinear superconducting cavity uses its own dissipative channel to release the energy of its own target excited state, so that the target excited state of the quantum bit is initialized to the ground state, that is, the initialization operation of the target excited state of the quantum bit is completed.

[0071] In some optional embodiments, the first frequency may be less than a preset frequency threshold, which may be the transition frequency between the target excited state of the nonlinear superconducting cavity and its adjacent higher excited state before frequency adjustment. In this way, when the frequency difference between the energy levels corresponding to adjacent excited states of the nonlinear superconducting cavity is large, the probability of the quantum state leaking into the higher excited state can be suppressed. Specifically, after inputting a driving field corresponding to a first frequency less than the preset frequency threshold, the probability of the target excited state of the nonlinear superconducting cavity transitioning to its adjacent higher excited state can be greatly reduced, thereby improving the efficiency of initializing the quantum state of the qubit.

[0072] It should be noted that due to the limitations of the quantum state initialization system, the "consistency" mentioned in this application includes complete consistency and consistency that allows a certain error, that is, the error between the two comparison objects is within a preset error range, and the preset error range can be determined according to the specific situation.

[0073] The frequency adjustment method of the embodiment of the present application, first, for the initialization of any excited state, can obtain the voltage value, frequency, and pulse duration corresponding to itself. Then, the energy level corresponding to the target excited state of the quantum bit or the energy level corresponding to the target excited state of the nonlinear superconducting cavity can be adjusted through the target voltage value, so that the frequency of the energy level corresponding to the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity can meet the conditions for generating coupling. Finally, after the first frequency and pulse duration are sent to the pulse generator, the pulse generator can apply a driving field to the quantum bit so that the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity generate Rabi oscillations under the conditions of satisfying the coupling effect. In this way, during the Rabi oscillation process, the energy of the target excited state of the quantum bit is transferred to the target excited state of the nonlinear superconducting cavity, completing the initialization of the target excited state of the quantum bit.

[0074] The following uses a specific example to describe the quantum state initialization process in detail in combination with the above-mentioned frequency adjustment method.

[0075] like Figure 8 As shown, the solid line is the actual energy level, and the bold dashed line is the temporary state achieved through a specific operation (e.g., frequency adjustment operation). The coupling strength between the first excited state of the fluxonium qubit and the first excited state of the nonlinear superconducting cavity is g a (correspond Figure 8 The coupling strength between the second excited state and the first excited state of the nonlinear superconducting cavity is g b (correspond Figure 8 The coupling strength in 2). Since the main function of the nonlinear superconducting cavity is to perform dispersion reading of the Fluxonium qubit, it is usually in frequency detuning with the Fluxonium qubit. Therefore, before the initialization operation, the voltage is applied by the bias magnetic flux line to adjust the frequency of the corresponding energy level of the first excited state of the Fluxonium qubit to be close to the frequency of the corresponding energy level of the first excited state of the nonlinear cavity (there is a frequency detuning amount 1) or completely consistent with the frequency of the corresponding energy level of the first excited state of the nonlinear cavity, and the frequency of the corresponding energy level of the second excited state of the Fluxonium qubit is adjusted to be close to the frequency of the corresponding energy level of the second excited state of the nonlinear cavity (there is a frequency detuning amount 2) or completely consistent. The specific adjustment process can refer to the specific processing of the above-mentioned step S702, which will not be repeated here. After the adjustment, the frequency detuning amount between the first excited state of the nonlinear superconductor and the first excited state of the Fluxonium qubit is Figure 8 The frequency detuning amount in the nonlinear superconductor is 1, and the frequency detuning amount between the second excited state of the nonlinear superconductor and the second excited state of the Fluxonium quantum bit is Figure 8 The frequency detuning amount in is 2.

[0076] In this way, the first excited state of the Fluxonium qubit can be initialized using the first excited state of the nonlinear superconductor, and the second excited state of the Fluxonium qubit can be initialized using the second excited state of the nonlinear superconductor.

[0077] The controller can then use a pulse generator to apply a pulse of frequency ω to the control line of the Fluxonium qubit. a The driving field is applied to the Fluxonium qubit with a frequency of ω a The field strength of the driving field can be expressed by the following mathematical expression:

[0078]

[0079] Among them, H1 is the frequency ω a The field strength of the driving field is a Hamiltonian, a1 is the annihilation operator, To generate the operator, t a is the pulse duration corresponding to the first excited state.

[0080] ω a and The frequency difference between the transition frequencies can be expressed as Δ a , accordingly, the probability that the quantum system composed of the Fluxonium qubit and the nonlinear superconducting cavity is in the first excited state of the nonlinear superconducting cavity can be expressed by the following expression:

[0081]

[0082] Among them, ω3 is the first excited state |e0> and the dressed state of the Fluxonium quantum bit (can also be the first excited state of the nonlinear superconducting cavity) between the transition frequency, when ω a and The frequency difference between the transition frequencies is Δ a Equal to 0, and the pulse duration When P a The energy of the first excited state of the Fluxonium quantum bit is transferred to the first excited state of the nonlinear superconducting cavity in a maximum and efficient manner, and then the energy is released through the dissipative channel of the nonlinear superconducting cavity, so that the dressed state of the quantum system It can quickly decay to the ground state |00>, completing the initialization operation of the first excited state of the Fluxonium quantum bit.

[0083] The controller can use the pulse generator to apply a driving field with a frequency of ω2 to the control line of the Fluxonium qubit and apply it to the Fluxonium qubit with a frequency of ω bThe field strength of the driving field can be expressed by the following mathematical expression:

[0084]

[0085] Among them, H2 is the frequency ω b The field strength of the driving field is a Hamiltonian, a2 is the annihilation operator, To generate the operator, t b is the pulse duration corresponding to the second excited state.

[0086] ω b and The frequency difference between the transition frequencies is Δ b , accordingly, the probability that the quantum system composed of the Fluxonium qubit and the nonlinear superconducting cavity is in the second excited state of the nonlinear superconducting cavity can be expressed by the following expression:

[0087]

[0088] Among them, ω4 is the second excited state |f0> and the dressed state of the Fluxonium quantum bit (can also be understood as the second excited state of the nonlinear superconducting cavity) between the transition frequency, when ω b and The frequency difference between the transition frequencies is Δ b Equal to 0, and the pulse duration When P b The energy of the second excited state of the Fluxonium quantum bit is transferred to the second excited state of the nonlinear superconducting cavity in a maximum and efficient manner, and then released through the dissipative channel of the nonlinear superconducting cavity, so that the dressed state of the quantum system It can quickly decay to the ground state |00>, completing the initialization operation of the second excited state of the Fluxonium quantum bit.

[0089] In summary, by matching the nonlinear energy levels of the nonlinear superconducting cavity with the energy level anharmonicity of the Fluxonium quantum bit, and controlling the detuning between the frequency of the driving field and the quantum state transition frequency to be small, and controlling the pulse duration of the driving field to be consistent with the pulse duration corresponding to the oscillation frequency of the Rabi oscillation, the initialization operations of the first excited state and the second excited state of the Fluxonium quantum bit can be completed efficiently.

[0090] Through the description of the above implementation methods, those skilled in the art can clearly understand that the method according to the above embodiment can be implemented by means of software plus the necessary general hardware platform, and of course it can also be implemented by hardware, but in many cases the former is a better implementation method.

[0091] The embodiment of the present application also provides a frequency adjustment device, such as Figure 9 Shown, including:

[0092] An acquisition module 910 is configured to acquire a target voltage value, a first frequency, and a pulse duration corresponding to a target excited state;

[0093] An adjustment module 920 is configured to perform a frequency adjustment operation on an energy level corresponding to a target excited state of the qubit or an energy level corresponding to a target excited state of the nonlinear superconducting cavity according to a target voltage value, so that the target excited state of the qubit and the target excited state of the nonlinear superconducting cavity meet a condition for generating a coupling effect;

[0094] The sending module 930 is used to send the first frequency and pulse duration to the pulse generator to apply a driving field to the quantum bit so that the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity produce Rabi oscillations under the condition of satisfying the coupling effect. During the Rabi oscillation, the energy of the target excited state of the quantum bit is transferred to the target excited state of the nonlinear superconducting cavity and released, thereby completing the initialization of the target excited state of the quantum bit.

[0095] In some optional implementations, the acquisition module 910 is specifically configured to:

[0096] Obtaining a second frequency, wherein the second frequency is a frequency of an energy level corresponding to a target excited state of the quantum bit;

[0097] According to the second frequency and the corresponding relationship between the voltage value and the frequency, the voltage value corresponding to the second frequency is determined, wherein the voltage value corresponding to the second frequency is the target voltage value.

[0098] In some optional implementations, the adjustment module 920 is specifically configured to:

[0099] According to the target voltage value, a voltage having the same voltage value as the target voltage value is applied to the target inductor, wherein the magnetic field generated by the target inductor affects the magnetic flux of a superconducting quantum interference device in the nonlinear superconducting cavity so that the frequency of the energy level corresponding to the target excited state of the nonlinear superconducting cavity is consistent with the frequency corresponding to the target voltage value.

[0100] In some optional implementations, the adjustment module 920 is specifically configured to:

[0101] According to the target voltage value, a voltage equal to the target voltage value is applied to the bias magnetic flux line of the quantum bit so that the frequency of the energy level corresponding to the target excited state of the quantum bit is consistent with the frequency corresponding to the target voltage value.

[0102] In some optional embodiments, the pulse duration is Among them, ω Ris the oscillation frequency of the Rabi oscillation, and t0 is the pulse duration corresponding to the target excited state.

[0103] In some optional embodiments, during the Rabi oscillation, the probability that the quantum state of the quantum system composed of the quantum bit and the nonlinear superconducting cavity is in the target excited state of the quantum bit is:

[0104]

[0105] Among them, P m is the probability, g m is the coupling strength between the target excited state of the nonlinear superconducting cavity and the target excited state of the quantum bit, ω R is the oscillation frequency.

[0106] In some optional embodiments, the first frequency is a transition frequency between an energy level corresponding to a target excited state of the quantum bit and an energy level corresponding to a target excited state of the nonlinear superconducting cavity.

[0107] For the description of the features in the embodiment corresponding to the frequency adjustment device, reference can be made to the relevant description of the embodiment corresponding to the frequency adjustment method, and no further details will be given here.

[0108] The embodiment of the present application also provides an electronic device, such as Figure 10 As shown, it includes a memory 10 and a processor 20. The memory 10 stores a computer program, and the processor 20 is configured to run the computer program to execute the steps in any of the above frequency adjustment method embodiments. The electronic device may be the above controller.

[0109] An embodiment of the present application further provides a computer-readable storage medium, in which a computer program is stored. The computer program is configured to execute the steps of any of the above frequency adjustment method embodiments when running.

[0110] In an exemplary embodiment, the computer-readable storage medium may include, but is not limited to, various media that can store computer programs, such as a USB flash drive, a read-only memory (ROM), a random access memory (RAM), a mobile hard disk, a magnetic disk, or an optical disk.

[0111] An embodiment of the present application further provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the steps in any of the above frequency adjustment method embodiments are implemented.

[0112] An embodiment of the present application further provides another computer program product, including a non-volatile computer-readable storage medium, wherein the non-volatile computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps in any of the above frequency adjustment method embodiments are implemented.

[0113] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the above description has generally described the components and steps of each example according to their functions. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0114] The above is a detailed introduction to a frequency adjustment method, device, electronic device, storage medium, and program product provided by the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only intended to help understand the method and core ideas of the present application. It should be noted that for those skilled in the art, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A frequency adjustment method, characterized in that: The method comprises: Obtaining a target voltage value, a first frequency, and a pulse duration corresponding to a target excited state; performing a frequency adjustment operation on an energy level corresponding to a target excited state of the quantum bit or an energy level corresponding to a target excited state of the nonlinear superconducting cavity according to the target voltage value, so that the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity meet a condition for generating a coupling effect; The first frequency and the pulse duration are sent to a pulse generator to apply a driving field to the quantum bit, so that the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity produce Rabi oscillations under the condition that the coupling effect is satisfied. During the Rabi oscillation, the energy of the target excited state of the quantum bit is transferred to the target excited state of the nonlinear superconducting cavity and released, thereby completing the initialization of the target excited state of the quantum bit.

2. The frequency adjustment method according to claim 1, wherein: Obtaining a target voltage value corresponding to the target excited state includes: Acquire a second frequency, wherein the second frequency is a frequency of an energy level corresponding to a target excited state of the quantum bit; According to the second frequency and the corresponding relationship between the voltage value and the frequency, a voltage value corresponding to the second frequency is determined, wherein the voltage value corresponding to the second frequency is the target voltage value.

3. The frequency adjustment method according to claim 2, wherein: Performing a frequency adjustment operation on an energy level corresponding to a target excited state of the nonlinear superconducting cavity according to the target voltage value includes: Based on the target voltage value, a voltage having a voltage value equal to the target voltage value is applied to the target inductor, wherein the magnetic field generated by the target inductor affects the magnetic flux of a superconducting quantum interference device in the nonlinear superconducting cavity so that the frequency of the energy level corresponding to the target excited state of the nonlinear superconducting cavity is consistent with the frequency corresponding to the target voltage value.

4. The frequency adjustment method according to claim 1, wherein: Performing a frequency adjustment operation on an energy level corresponding to a target excited state of the quantum bit according to the target voltage value includes: According to the target voltage value, a voltage having a value equal to the target voltage value is applied to the bias magnetic flux line of the qubit so that the frequency of the energy level corresponding to the target excited state of the qubit is consistent with the frequency corresponding to the target voltage value.

5. The frequency adjustment method according to any one of claims 1 to 4, characterized in that: The pulse duration is Among them, ω R is the oscillation frequency of the Rabi oscillation, and t0 is the pulse duration corresponding to the target excited state.

6. The frequency adjustment method according to claim 5, wherein: During the Rabi oscillation, the probability that the quantum state of the quantum system composed of the quantum bit and the nonlinear superconducting cavity is in the target excited state of the quantum bit is: Among them, P m is the probability, g m is the coupling strength between the target excited state of the nonlinear superconducting cavity and the target excited state of the quantum bit, ω R is the oscillation frequency.

7. The frequency adjustment method according to any one of claims 1 to 4, characterized in that: The first frequency is a transition frequency between an energy level corresponding to a target excited state of the quantum bit and an energy level corresponding to a target excited state of the nonlinear superconducting cavity.

8. A frequency adjustment device, characterized in that: include: An acquisition module, configured to acquire a target voltage value, a first frequency, and a pulse duration corresponding to a target excited state; an adjustment module, configured to perform a frequency adjustment operation on an energy level corresponding to a target excited state of the quantum bit or an energy level corresponding to a target excited state of the nonlinear superconducting cavity according to the target voltage value, so that the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity meet a condition for generating a coupling effect; A sending module is used to send the first frequency and the pulse duration to a pulse generator to apply a driving field to the quantum bit so that the target excited state of the quantum bit and the target excited state of the nonlinear superconducting cavity produce Rabi oscillations under the condition that the coupling effect is satisfied. During the Rabi oscillation, the energy of the target excited state of the quantum bit is transferred to the target excited state of the nonlinear superconducting cavity and released, thereby completing the initialization of the target excited state of the quantum bit.

9. An electronic device, characterized in that: include: memory for storing computer programs; A processor, configured to implement the steps of the frequency adjustment method according to any one of claims 1 to 7 when executing the computer program.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, wherein when the computer program is executed by a processor, the steps of the frequency adjustment method according to any one of claims 1 to 7 are implemented.

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