Method and device for determining quantum bit high-energy state control signal and quantum computer

Abstract

This application discloses a method, device, and quantum computer for determining a high-energy-state control signal for a quantum bit. By sequentially applying a π pulse and the high-energy-state control signal, the quantum bit is continuously excited. This allows the quantum bit, already possessing quantum state information in the {|0>, |1>} subspace, to acquire quantum state information in the {|1>, |2>} subspace through the high-energy-state control signal. A Rabi oscillation experiment is then performed on this quantum bit, traversing the amplitude of the high-energy-state control signal throughout the entire process. The optimal high-energy-state control signal is determined by measuring the first signal obtained from the final state information of the quantum bit and the applied π pulse. The high-energy-state control signal for the quantum bit obtained using this method can precisely control the quantum state of the quantum bit to the |2> state, providing a foundation for achieving high-energy-state control of the quantum bit and improving the read fidelity of the quantum bit, thus filling a gap in the relevant art.

Description

Technical Field

[0001] The present application relates to the field of quantum computing, and in particular to a method and device for determining a quantum bit high-energy state control signal, and a quantum computer. Background Art

[0002] Quantum bits are the carriers of information processing in quantum computing. Related technologies use artificial multi-level systems to implement quantum bits. Common artificial multi-level systems include superconducting Josephson junctions, semiconductor quantum dots, ion traps, etc. Figure 1 In the multi-level system shown, because the spacing between adjacent energy levels is unequal, the qubit's ground state and first excited state (i.e., the |0> and |1> states) can be isolated from other higher-excited states, forming a {|0>, |1>} subspace. However, in actual bit manipulation, such as the common CZ two-bit gate operation, the qubit is excited to a higher energy state, the second excited state |2>. This high-energy state leakage reduces the qubit readout fidelity, thereby affecting the accuracy of quantum computing.

[0003] In order to study this high-energy state leakage error and optimize it, it is necessary to realize the high-energy state control and reading of quantum bits.

[0004] Based on this, there is an urgent need to provide a method for determining the high-energy state control signal of a quantum bit to determine the high-energy state control signal of the quantum bit with high precision, so as to realize the high-energy state control of the quantum bit, thereby filling the relevant technical gaps. Summary of the Invention

[0005] The purpose of this application is to provide a method, device and quantum computer for determining the high-energy state control signal of a quantum bit to address the deficiencies in the prior art. It can provide a method for determining the high-energy state control signal of a quantum bit, which is used to determine the high-energy state control signal for controlling the high-energy state of the quantum bit, so as to fill the gap in the relevant technology.

[0006] In one aspect, the present application provides a method for determining a quantum bit high-energy state control signal.

[0007] The high-energy state control signal is used to adjust the state of the quantum bit to flip between two adjacent excited states, and the determination method includes:

[0008] Adjusting the amplitude of the high-energy-state control signal within a preset amplitude sweep range, and sequentially applying a π pulse, the high-energy-state control signal, and a π pulse to the sub-bit to be measured after each adjustment of the amplitude of the high-energy-state control signal to perform a Rabi oscillation experiment, respectively obtaining a first signal corresponding to the sub-bit to be measured, wherein the first signal is a measured signal containing final state information of the sub-bit to be measured;

[0009] Based on the amplitude data or phase data of all the first signals, the amplitude of the high-energy-state control signal corresponding to when the sub-bit to be measured is in a high excited state of two adjacent excited states is obtained as the optimal amplitude of the high-energy-state control signal.

[0010] In the method for determining the quantum bit high-energy state control signal as described above, preferably, the frequency of the read waveform used to obtain each first signal is set to the cavity frequency of the read resonant cavity coupled to the quantum bit to be measured when the quantum bit to be measured is in the ground state.

[0011] In the above-described method for determining a qubit high-energy-state control signal, preferably, the high-energy-state control signal and the π pulse are output through the same signal output channel. In the above-described method for determining a qubit high-energy-state control signal, preferably, the amplitude sweep range is determined based on the amplitude of the π pulse, and the amplitude of the high-energy-state control signal is greater than the amplitude of the π pulse.

[0012] The method for determining the quantum bit high energy state control signal as described above, wherein preferably,

[0013] The adjusting the amplitude of the high-energy state control signal within a preset amplitude scanning range includes:

[0014] An initial amplitude is selected within a preset amplitude scanning range, and the amplitude of the high-energy state control signal can be adjusted by increasing or decreasing the initial amplitude based on a preset step size.

[0015] In the above-mentioned method for determining the high-energy state control signal of a quantum bit, preferably, the amplitude of the high-energy state control signal corresponding to the quantum bit being in the higher excited state of two adjacent excited states is the amplitude of the high-energy state control signal corresponding to the extreme value of the amplitude data or phase data of all the first signals. In the above-mentioned method for determining the high-energy state control signal of a quantum bit, preferably,

[0016] The acquiring, based on the amplitude data or phase data of all the first signals, the amplitude of the high-energy state control signal corresponding to when the sub-bit to be measured is in a high excited state of two adjacent excited states, includes:

[0017] Fitting the amplitude data or the phase data to obtain amplitude fitting data or phase fitting data;

[0018] Identify the extreme value of the amplitude fitting data or the phase fitting data, and obtain the amplitude of the high-energy state control signal corresponding to the extreme value, which is the amplitude of the high-energy state control signal corresponding to when the quantum bit is in the higher excited state of two adjacent excited states.

[0019] The method for determining the quantum bit high-energy state control signal as described above, wherein preferably, the determination method further includes:

[0020] The power and pulse width of the high energy state control signal are determined based on the power and pulse width of the π pulse.

[0021] In the above-mentioned method for determining the high-energy state control signal of a quantum bit, preferably, determining the power and pulse width of the high-energy state control signal based on the power and pulse width of the π pulse includes:

[0022] The power and pulse width of the high-energy state control signal are the same as the power and pulse width of the π pulse.

[0023] The method for determining the quantum bit high-energy state control signal as described above, wherein preferably, the determination method further includes:

[0024] The operating frequency of the high energy state control signal is determined based on the operating frequency of the π pulse.

[0025] In the method for determining the high-energy-state control signal of a quantum bit as described above, preferably, the operating frequency of the high-energy-state control signal is obtained based on the frequency spectrum curve of the quantum bit to be measured.

[0026] In another aspect, an embodiment of the present application provides a device for determining a high-energy state control signal of a quantum bit, wherein the high-energy state control signal is used to adjust the state of the quantum bit to flip between two adjacent excited states. The device includes:

[0027] an experimental measurement module, configured to adjust the amplitude of the high-energy-state control signal within a preset amplitude sweep range, and sequentially apply a π pulse, the high-energy-state control signal, and a π pulse to the sub-bit to be measured after each adjustment of the amplitude of the high-energy-state control signal to perform a Rabi oscillation experiment, thereby obtaining a first signal corresponding to the sub-bit to be measured, wherein the first signal is a measured signal containing final-state information of the sub-bit to be measured;

[0028] A parameter acquisition module is used to obtain, based on the amplitude data or phase data of all the first signals, the amplitude of the high-energy state control signal corresponding to when the sub-bit to be measured is in a high excited state among two adjacent excited states, which is the optimal amplitude of the high-energy state control signal.

[0029] Another embodiment of the present application provides a quantum computer, including the above-mentioned device for determining the high-energy state control signal of a quantum bit or using any of the above-mentioned methods to determine the high-energy state control signal of a quantum bit.

[0030] Another embodiment of the present application provides a computer storage medium, wherein the computer storage medium stores a computer program, wherein the computer program is configured to execute any of the above methods when running.

[0031] Another embodiment of the present application provides an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to execute any of the methods described above.

[0032] Compared to the prior art, the present invention discloses a method for determining a high-energy-state control signal for a quantum bit. By sequentially applying a π pulse and the high-energy-state control signal, the quantum bit is continuously excited. This allows the quantum bit to acquire quantum state information in the {|0>, |1>} subspace through the high-energy-state control signal. A Rabi oscillation experiment is then performed on the quantum bit, traversing the amplitude of the quantum bit's high-energy-state control signal throughout the process. The optimal high-energy-state control signal is determined by measuring the first signal obtained from the quantum bit's final state information and the π pulse used. When the high-energy-state control signal fully excites the quantum bit to the |2> state, the corresponding high-energy-state control signal amplitude is the optimal high-energy-state control signal amplitude. The quantum bit high-energy-state control signal obtained using the present invention's method can precisely control the quantum state of the quantum bit to the |2> state, providing a foundation for achieving high-energy-state control of the quantum bit and improving the read fidelity of the quantum bit, thus filling a gap in the relevant art.

[0033] These and other aspects of the present application will become more readily apparent from the description of the following embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application and should not be regarded as limiting the scope. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0035] Figure 1 A schematic diagram of the energy level distribution of a multi-level structure system for realizing quantum bits in related technologies;

[0036] Figure 2 This is a flow chart of a method for determining a quantum bit high-energy state control signal according to an embodiment of the present application;

[0037] Figure 3 This is a schematic diagram of a quantum state control and reading circuit according to an embodiment of the present application;

[0038] Figure 4 This is a flow chart of a method for determining a quantum bit high-energy state control signal according to another embodiment of the present application;

[0039] Figure 5 This is a flow chart of a method for determining a quantum bit high-energy state control signal according to another embodiment of the present application;

[0040] Figure 6 This is a structural block diagram of a device for determining a quantum bit high-energy state control signal according to an embodiment of the present application;

[0041] Figure 7 FIG. 1 is a structural block diagram of an electronic device according to an embodiment of the present application. DETAILED DESCRIPTION

[0042] Qubits on superconducting quantum chips are carriers of quantum states, carrying quantum information. Superconducting quantum computing boasts rapid speeds and is widely used. Controlling and reading qubits on superconducting quantum chips is crucial for the physical realization of quantum computing. High-precision quantum state control and reading technologies can improve the accuracy of quantum computing results.

[0043] See Figure 1 Currently, qubits on superconducting quantum chips are multi-level nonlinear resonators, whose quantum states are primarily distinguished by the energy levels. In related technologies, qubits used in quantum computing employ a two-level structure consisting of a ground state |0> and a first excited state |1> within the multi-level structure, forming a {|0>, |1>} subspace. In this case, the qubit is limited to two energy states: the ground state |0> and the first excited state |1>, resulting in the qubit possessing only quantum state information within the {|0>, |1>} subspace. However, the short relaxation time for the qubit from the first excited state |1> to the ground state |0> shortens the qubit's decoherence time, resulting in low fidelity in reading the quantum state. This makes it difficult to achieve ideal quantum computing results in practical applications.

[0044] Furthermore, in actual qubit quantum state manipulation, such as the common CZ two-bit gate operation, the qubit may be excited to a higher energy state than the first excited state, namely the second excited state |2>. This high-energy state leakage also reduces the qubit readout fidelity, thereby affecting the accuracy of quantum computing results.

[0045] Therefore, based on the above analysis, the present application discloses a method, device and quantum computer for determining the high-energy state control signal of a quantum bit, which is used to determine the high-energy state control signal for realizing high-energy state control of the quantum bit, providing a basis for realizing high-energy state control of the quantum bit and improving the reading fidelity of the quantum bit, and filling the gap in related technologies.

[0046] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific embodiments. Obviously, the embodiments described are only a part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making any creative efforts are within the scope of protection of the present application.

[0047] Please refer to Figure 2 In an embodiment of the present application, a method for determining a high-energy state control signal of a quantum bit, wherein the high-energy state control signal is used to adjust the state of the quantum bit to flip between two adjacent excited states, includes:

[0048] S101: Adjust the amplitude of the high-energy state control signal within a preset amplitude scanning range, and apply a π pulse, the high-energy state control signal, and a π pulse to the sub-bit to be measured in sequence after each adjustment of the amplitude of the high-energy state control signal to perform a Rabi oscillation experiment, and obtain a first signal corresponding to the sub-bit to be measured, respectively, wherein the first signal is a measured signal containing final state information of the sub-bit to be measured.

[0049] It should be noted that the π pulse, also known as a π-pulse or Pauli-X gate, is a Rabi drive signal that can excite the subbit to the |1> state. The first π pulse applied to the subbit is used to drive the subbit from the |0> state to the |1> state, while the second π pulse applied to the subbit is used to drive the subbit back to the |0> state if the high-energy state control signal fails. The aforementioned excited states are concepts corresponding to the ground state; both the first excited state and higher energy states with higher energy levels than the first excited state are considered excited states. Two adjacent excited states are excited states with adjacent energy levels, such as the first excited state |1> and the second excited state |2>, the second excited state |2> and the third excited state |3>, the third excited state |3> and the fourth excited state |4>, and so on. Adjusting the state of the quantum bit to flip between two adjacent excited states means that the state of the quantum bit can be transitioned from the low excited state of two adjacent excited states to the high excited state, and the state of the quantum bit can be relaxed from the high excited state of two adjacent excited states to the low excited state.

[0050] The control signal of the quantum bit can be expressed by the following formula:

[0051]

[0052] A(t) represents the amplitude of the quantum bit control signal, w represents the frequency of the quantum bit control signal, Represents the phase of the quantum bit control signal.

[0053] For quantum bits on a superconducting quantum chip, the typical quantum bit control signal is generated by an arbitrary waveform generator (AWG), a microwave local oscillator source and an IQ mixer.

[0054] In this embodiment of the present application, the high-energy-state control signal and the π pulse can be output from the same signal output channel of the IQ mixer. Therefore, the channel drive power of the two is the same, the amplitude sweep range can be determined based on the amplitude of the π pulse, and the amplitude of the high-energy-state control signal must be greater than the amplitude of the π pulse.

[0055] In addition, the high-energy state control signal and the π pulse may adopt a flat-top Gaussian wave or a DRAG waveform.

[0056] The adjusting the amplitude of the high-energy state control signal within a preset amplitude scanning range includes:

[0057] The amplitude of the high-energy-state control signal can be adjusted by selecting an initial amplitude within a preset amplitude sweep range and increasing or decreasing the initial amplitude based on a preset step size. For example, if the amplitude of the π pulse is less than 0.5V, the amplitude sweep range of the high-energy-state control signal can be set to [0.5V, 1V], the initial amplitude can be selected arbitrarily within [0.5V, 1V], and the step size can also be set according to actual application needs, without limitation herein.

[0058] The operating results of the superconducting quantum chip, that is, the calculation results of the quantum information processing process, are contained in the quantum state of the quantum bit. In order to accurately obtain the operating results of the superconducting quantum chip, it is necessary to read (or measure) the quantum state of the quantum bit on the quantum chip after the quantum information processing process.

[0059] See Figure 3In this embodiment of the present application, after a Rabi oscillation experiment is performed on a subbit to be measured by sequentially applying a π pulse (denoted as X01), the high-energy-state control signal (denoted as X12), and a π pulse (denoted as X01), the final state of the subbit to be measured has two possibilities: one is that if the high-energy-state control signal X12 with a specific amplitude can completely excite the subbit to be measured from the |1> state to the |2> state (i.e., the high-energy-state control signal is effective), the final state of the subbit to be measured is the |2> state; the other is that if the high-energy-state control signal X12 with a specific amplitude cannot completely excite the subbit to be measured from the |1> state to the |2> state (i.e., the high-energy-state control signal is ineffective), the final state of the subbit to be measured is the |0> state. Therefore, the final state information of the subbit to be measured contained in the first signal has two possibilities: one is that the first signal contains information that the subbit to be measured is in the |2> state, and the other is that the first signal contains information that the subbit to be measured is in the |0> state.

[0060] Dispersion reading technology is often used to read the quantum state information of qubits. Dispersion reading technology obtains the quantum state by state projection, without completely destroying the quantum state. Specifically, a reading resonant cavity is nonlinearly coupled next to the qubit, and a reading waveform is applied to the reading resonant cavity. The quantum state information of the qubit is obtained by quickly exciting the number of photons in the reading resonant cavity through the reading waveform. The fundamental reason why the reading resonant cavity can read the quantum state of the qubit is that the different quantum states of the qubit produce different dispersion frequency shifts on the reading resonant cavity. As a result, when the frequency of the reading waveform applied to the reading resonant cavity for different quantum states of the qubit is very close to the cavity frequency (also called resonant frequency or natural frequency) of the reading resonant cavity, the reading resonant cavity will have obvious differences in response to the reading waveform due to the qubit being in different quantum states, that is, the qubit reading waveform has maximum distinguishability.

[0061] Preferably, the frequency of the read waveform used to obtain each first signal is set to the cavity frequency of the read resonant cavity coupled to the subbit to be measured when the subbit to be measured is in the ground state (|0> state). This allows all final state information of the subbit to be measured to be projected into the {|0>, |1>} subspace for quantum state reading, and the first signal is obtained by reading the quantum bit in the |1> state.

[0062] S102: Based on the amplitude data or phase data of all the first signals, obtaining the optimal amplitude of the high-energy-state control signal corresponding to when the sub-bit to be measured is in a high excited state of two adjacent excited states.

[0063] In one embodiment, the high-energy state control signal is a signal that adjusts the state of the quantum bit to flip between the first excited state |1> and the second excited state |2>. In this step, the amplitude of the high-energy state control signal corresponding to when the quantum bit to be measured is in the second excited state |2> is obtained, which is the optimal amplitude of the high-energy state control signal.

[0064] Those skilled in the art will appreciate that the parameters of the first signal obtained by measuring and reading the resonant cavity include amplitude and phase, and in practical applications, one of the parameters may be selected for acquisition.

[0065] Preferably, the amplitude of the high-energy state control signal corresponding to the quantum bit being in the higher excited state of two adjacent excited states is the amplitude of the high-energy state control signal corresponding to the extreme value of the amplitude data or phase data of all the first signals.

[0066] The amplitude data or phase data of each first signal has a one-to-one correspondence with the amplitude of the high-energy-state control signal. That is, the amplitude of the high-energy-state control signal is adjusted to a specific amplitude, and a Rabi oscillation experiment is performed on the sub-bit to be measured based on the high-energy-state control signal of this amplitude to obtain the corresponding amplitude data or phase data. Furthermore, when the high-energy-state control signal with a certain amplitude is able to excite the sub-bit to be measured from the |1> state to the |2> state, the amplitude or phase of the corresponding first signal undergoes a sudden change, resulting in an extreme value of the amplitude data or phase data of the first signal. Therefore, by obtaining the extreme value of the amplitude data or phase data of the first signal, the amplitude of the high-energy-state control signal corresponding to the sub-bit to be measured in the second excited state |2> can be inferred. This amplitude is the target amplitude and is the optimal amplitude of the high-energy-state control signal.

[0067] In addition, the amplitude data or the phase data is oscillation data. In order to further improve the accuracy of solving the data extreme value, the amplitude data or phase data of the first signal can be fitted, and the extreme value obtained based on the fitted amplitude fitting data or phase fitting data can be reversely deduced that the amplitude of the high-energy state control signal corresponding to the extreme value is the amplitude of the high-energy state control signal corresponding to the extreme value when the quantum bit is in the high-excited state among two adjacent excited states.

[0068] In practical applications, a fitting function such as a sine function, a Fourier basis function, etc. may be used to perform fitting calculation on the amplitude data or the phase data, which is not limited here.

[0069] The method for determining a qubit high-energy-state control signal provided in an embodiment of the present application achieves continuous excitation of the qubit by sequentially applying a π pulse and the high-energy-state control signal, so that the qubit, based on the quantum state information of the {|0>, |1>} subspace, is excited by the high-energy-state control signal to have quantum state information of the {|1>, |2>} subspace. A Rabi oscillation experiment is performed on this qubit, and the amplitude of the high-energy-state control signal of the qubit is traversed throughout the process. The optimal high-energy-state control signal is determined by measuring the first signal obtained from the final state information of the qubit and the π pulse used. When the high-energy-state control signal completely excites the qubit to the |2> state, the corresponding high-energy-state control signal amplitude is the optimal high-energy-state control signal amplitude. The qubit high-energy-state control signal obtained based on the method of the present application can accurately control the quantum state of the qubit to the |2> state, providing a foundation for realizing high-energy-state control of the qubit and improving the read fidelity of the qubit, filling a gap in the relevant technology.

[0070] The specific content of the method for determining the quantum bit high-energy state control signal provided in this application will be introduced in detail in the following embodiments.

[0071] See Figure 4 In an embodiment of the present application, a method for determining a quantum bit high-energy state control signal includes:

[0072] S201: Adjust the amplitude of the high-energy state control signal within a preset amplitude scanning range, and apply a π pulse, the high-energy state control signal, and a π pulse to the sub-bit to be measured in sequence after each adjustment of the amplitude of the high-energy state control signal to perform a Rabi oscillation experiment, and obtain a first signal corresponding to the sub-bit to be measured, respectively, wherein the first signal is a measured signal containing final state information of the sub-bit to be measured.

[0073] S202: Based on the amplitude data or phase data of all the first signals, obtaining the optimal amplitude of the high-energy-state control signal corresponding to when the sub-bit to be measured is in a high excited state of two adjacent excited states.

[0074] S203: Determine the power and pulse width of the high-energy state control signal based on the power and pulse width of the π pulse.

[0075] In this step, the high-energy-state control signal and the π pulse can be output from the same signal output channel of the IQ mixer, with the same channel drive power. Therefore, the power of the two is the same. Furthermore, to facilitate experimental operation, the pulse width of the high-energy-state control signal can be set to be the same as the pulse width of the π pulse.

[0076] Steps S201 and S202 are basically the same as S101 and S102 in the above-mentioned embodiment of the present application. Please refer to the above-mentioned embodiment of the present application for details, and no further details will be given here.

[0077] It should be noted that the above S203 can be executed in parallel with the above S201 to S202, or can be executed after S202, which is not specifically limited in the embodiments of the present application.

[0078] The method for determining a qubit high-energy-state control signal provided in an embodiment of the present application achieves continuous excitation of the qubit by sequentially applying a π pulse and the high-energy-state control signal, so that the qubit, based on the quantum state information of the {|0>, |1>} subspace, is excited by the high-energy-state control signal to have quantum state information of the {|1>, |2>} subspace. A Rabi oscillation experiment is performed on this qubit, and the amplitude of the high-energy-state control signal of the qubit is traversed throughout the process. The optimal high-energy-state control signal is determined by measuring the first signal obtained from the final state information of the qubit and the π pulse used. When the high-energy-state control signal completely excites the qubit to the |2> state, the corresponding high-energy-state control signal amplitude is the optimal high-energy-state control signal amplitude. The qubit high-energy-state control signal obtained based on the method of the present application can accurately control the quantum state of the qubit to the |2> state, providing a foundation for realizing high-energy-state control of the qubit and improving the read fidelity of the qubit, filling a gap in the relevant technology.

[0079] See Figure 5 In an embodiment of the present application, a method for determining a quantum bit high-energy state control signal includes:

[0080] S301: Adjust the amplitude of the high-energy state control signal within a preset amplitude scanning range, and apply a π pulse, the high-energy state control signal, and a π pulse to the sub-bit to be measured in sequence after each adjustment of the amplitude of the high-energy state control signal to perform a Rabi oscillation experiment, and obtain a first signal corresponding to the sub-bit to be measured, respectively, wherein the first signal is a measured signal containing final state information of the sub-bit to be measured.

[0081] S302: Based on the amplitude data or phase data of all the first signals, obtaining the optimal amplitude of the high-energy-state control signal corresponding to when the sub-bit to be measured is in a high excited state of two adjacent excited states.

[0082] S303: Determine the operating frequency of the high-energy state control signal based on the operating frequency of the π pulse.

[0083] Those skilled in the art will appreciate that the sub-bit to be measured can only be excited from the |1> state to the |2> state when the operating frequency of the high-energy-state control signal is very close to the transition frequency of the sub-bit to be measured from the |1> state to the |2> state. Therefore, the operating frequency of the high-energy-state control signal can be selected to be the transition frequency of the sub-bit to be measured from the |1> state to the |2> state.

[0084] In one embodiment, the transition frequency f of the subbit to be measured from the |1> state to the |2> state is 12 The transition frequency of the sub-bit to be measured from the |0> state to the |1> state (ie, the operating frequency of the π pulse) f 01 The anharmonicity α of the sub-bit to be measured is determined, that is, f 12 =f 01 +α.

[0085] In another embodiment, the transition frequency f of the subbit to be measured from the |1> state to the |2> state is 12 It can also be obtained by performing an energy spectrum measurement experiment on the sub-bit to be measured. Specifically, a spectrum measurement experiment is performed by applying a driving waveform of a certain power and amplitude to the sub-bit to be measured to obtain the spectrum curve of the sub-bit to be measured, and the two-photon excitation frequency is obtained from the spectrum curve. Finally, according to the relationship f 12 =f 02 -f 01 The transition frequency f of the quantum bit to be measured from the |1> state to the |2> state is calculated. 12 .

[0086] Preferably, in another embodiment, the operating frequency of the high-energy state control signal can also be obtained based on the spectrum curve of the subbit to be measured. Specifically, a first control signal is applied to the subbit to be measured to control the subbit to be measured to the |1> state. The frequency of a second control signal is then scanned within an appropriate frequency sweep range, and the second control signal having a predetermined frequency is applied to the subbit to further excite the subbit to transition from the |1> state to the |2> state. The quantum state of the subbit to be measured is then read and the spectrum curve of the subbit to be measured is obtained. If the frequency of the second control signal resonates with the transition frequency of the subbit to be measured from the |1> state to the |2> state, a resonance peak corresponding to the transition of the subbit to be measured from the |1> state to the |2> state will exist in the spectrum curve, i.e., an extreme value in the spectrum curve. Finally, the frequency of the second control signal corresponding to the extreme value of the spectrum curve is identified as the transition frequency of the subbit to be measured from the |1> state to the |2> state.

[0087] Steps S301 and S302 are basically the same as S101 and S102 in the above-mentioned embodiment of the present application. Please refer to the above-mentioned embodiment of the present application for details, and no further details will be given here.

[0088] It should be noted that the above S303 can be executed in parallel with the above S301 to S302, or can be executed after S302, which is not specifically limited in the embodiments of the present application.

[0089] The method for determining a qubit high-energy-state control signal provided in an embodiment of the present application achieves continuous excitation of the qubit by sequentially applying a π pulse and the high-energy-state control signal, so that the qubit, based on the quantum state information of the {|0>, |1>} subspace, is excited by the high-energy-state control signal to have quantum state information of the {|1>, |2>} subspace. A Rabi oscillation experiment is performed on this qubit, and the amplitude of the high-energy-state control signal of the qubit is traversed throughout the process. The optimal high-energy-state control signal is determined by measuring the first signal obtained from the final state information of the qubit and the π pulse used. When the high-energy-state control signal completely excites the qubit to the |2> state, the corresponding high-energy-state control signal amplitude is the optimal high-energy-state control signal amplitude. The qubit high-energy-state control signal obtained based on the method of the present application can accurately control the quantum state of the qubit to the |2> state, providing a foundation for realizing high-energy-state control of the qubit and improving the read fidelity of the qubit, filling a gap in the relevant technology.

[0090] The following is an introduction to a device for determining a quantum bit high-energy state control signal provided in an embodiment of the present application. The determination device described below and the determination method described above can be referenced to each other.

[0091] Please refer to Figure 6 , Figure 6 This is a block diagram of a device for determining a qubit high-energy state control signal provided in an embodiment of the present application. The device for determining a qubit high-energy state control signal may include:

[0092] Experimental measurement module 001, configured to adjust the amplitude of the high-energy-state control signal within a preset amplitude sweep range, and after each adjustment of the amplitude of the high-energy-state control signal, sequentially apply a π pulse, the high-energy-state control signal, and a π pulse to the sub-bit to be measured to perform a Rabi oscillation experiment, thereby obtaining a first signal corresponding to the sub-bit to be measured, wherein the first signal is a measured signal containing final-state information of the sub-bit to be measured;

[0093] The parameter acquisition module 002 is used to obtain the optimal amplitude of the high-energy state control signal when the sub-bit to be measured is in the high excited state of two adjacent excited states based on the amplitude data or phase data of all the first signals.

[0094] The device for determining the quantum bit high-energy state control signal of the embodiment of the present application is used to implement the aforementioned method for determining the quantum bit high-energy state control signal. Therefore, the specific implementation method of the device for determining the quantum bit high-energy state control signal can be seen in the embodiment part of the method for determining the quantum bit high-energy state control signal in the previous text. For example, the experimental measurement module 001 and the parameter acquisition module 002 are respectively used to implement steps S101 and S102 in the above-mentioned method for determining the quantum bit high-energy state control signal. Therefore, its specific implementation method can refer to the description of the corresponding embodiments of each part and will not be repeated here.

[0095] This application also provides a quantum computer, comprising the apparatus for determining a qubit high-energy-state control signal according to the aforementioned embodiments of this application, or employing a method for determining a qubit high-energy-state control signal described in any of the aforementioned embodiments of this application to determine the qubit high-energy-state control signal. The remaining details may be referred to the prior art and will not be further described here.

[0096] An electronic device provided in an embodiment of the present application is introduced below. The electronic device described below and the method for determining the quantum bit high-energy state control signal and the device for determining the quantum bit high-energy state control signal described above can be referenced to each other.

[0097] Please refer to Figure 7 , Figure 7 This is a structural block diagram of an electronic device provided in an embodiment of the present application.

[0098] Reference Figure 7 , the electronic device may include a processor 11 and a memory 12.

[0099] The memory 12 is used to store computer programs; the processor 11 is used to implement the method for determining the quantum bit high-energy state control signal described in the above-mentioned embodiment of the present application when executing the computer program.

[0100] In the device for determining a qubit high-energy-state control signal of this embodiment, processor 11 is used to install the device for determining a qubit high-energy-state control signal described in the embodiments of the present application. At the same time, processor 11, in combination with memory 12, can implement the method for determining a qubit high-energy-state control signal described in any of the embodiments of the present application. Therefore, the specific implementation of the device for determining a qubit high-energy-state control signal can be found in the embodiment section of the method for determining a qubit high-energy-state control signal described above. The specific implementation can be referred to the description of each corresponding embodiment and will not be repeated here.

[0101] This application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the method for determining a qubit high-energy state control signal described in any of the aforementioned embodiments of this application. The remaining content can be referenced to the prior art and will not be further described here.

[0102] The embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the same or similar parts between the embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple. For relevant parts, refer to the method description.

[0103] 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.

[0104] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in a random access memory (RAM), internal memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0105] Finally, it should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," 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. In the absence of further limitations, an element defined by the phrase "comprising a..." does not exclude the presence of additional identical elements in the process, method, article, or device comprising the element.

[0106] It should be noted that the terms "first excited state", "second excited state", "third excited state" and so on in the full text are commonly used technical terms in this field. They are names in sequence according to the energy levels and have a definite energy level order. The first excited state refers to the first excited state energy level adjacent to the ground state, the second excited state refers to the second excited state energy level adjacent to the first excited state, the third excited state refers to the third excited state energy level adjacent to the second excited state, and so on.

[0107] The above is a detailed introduction to a method for determining a quantum bit high-energy state control signal, a device for determining a quantum bit high-energy state control signal, a quantum computer, an electronic device, and a computer-readable storage medium 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 used to help understand the method of the present application and its core idea. It should be pointed out that for ordinary technicians in this technical field, 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 method for determining a quantum bit high-energy state control signal, characterized in that: The high-energy state control signal is used to adjust the state of the quantum bit to flip between two adjacent excited states, and the determination method includes: Adjusting the amplitude of the high-energy-state control signal within a preset amplitude sweep range, and sequentially applying a π pulse, the high-energy-state control signal, and a π pulse to the sub-bit to be measured after each adjustment of the amplitude of the high-energy-state control signal to perform a Rabi oscillation experiment, thereby obtaining a first signal corresponding to the sub-bit to be measured, wherein the first signal is a measured signal containing final-state information of the sub-bit to be measured; Based on the amplitude data or phase data of all the first signals, the amplitude of the high-energy-state control signal corresponding to when the sub-bit to be measured is in a high excited state of two adjacent excited states is obtained as the optimal amplitude of the high-energy-state control signal.

2. The method according to claim 1, wherein The frequency of the read waveform used to obtain each first signal is set to the cavity frequency of the read resonant cavity coupled to the subbit to be measured when the subbit to be measured is in a ground state.

3. The method according to claim 1, wherein The high-energy state control signal and the π pulse are outputted through the same signal output channel.

4. The method according to claim 1, wherein The amplitude scanning range is determined based on the amplitude of the π pulse, and the amplitude of the high-energy state control signal is greater than the amplitude of the π pulse.

5. The method according to claim 4, wherein The adjusting the amplitude of the high-energy state control signal within a preset amplitude scanning range includes: An initial amplitude is selected within a preset amplitude scanning range, and the amplitude of the high-energy state control signal can be adjusted by increasing or decreasing the initial amplitude based on a preset step size.

6. The method according to claim 1, wherein When the quantum bit is in a higher excited state among two adjacent excited states, the amplitude of the high energy state control signal corresponding to the extreme value of the amplitude data or phase data of all the first signals is the amplitude of the high energy state control signal corresponding to the extreme value of the amplitude data or phase data of all the first signals.

7. The method according to claim 1, wherein The acquiring, based on the amplitude data or phase data of all the first signals, the amplitude of the high-energy state control signal corresponding to when the sub-bit to be measured is in a high excited state of two adjacent excited states, includes: Fitting the amplitude data or the phase data to obtain amplitude fitting data or phase fitting data; Identify the extreme value of the amplitude fitting data or the phase fitting data, and obtain the amplitude of the high-energy state control signal corresponding to the extreme value, which is the amplitude of the high-energy state control signal corresponding to when the quantum bit is in the higher excited state of two adjacent excited states.

8. The method according to claim 1, wherein The determination method further includes: The power and pulse width of the high energy state control signal are determined based on the power and pulse width of the π pulse.

9. The method according to claim 8, wherein The determining the power and pulse width of the high-energy-state control signal based on the power and pulse width of the π pulse includes: The power and pulse width of the high-energy state control signal are the same as the power and pulse width of the π pulse.

10. The method according to claim 1, wherein The determination method further includes: The operating frequency of the high energy state control signal is determined based on the operating frequency of the π pulse.

11. The method according to claim 1, wherein The operating frequency of the high-energy state control signal is obtained based on the frequency spectrum curve of the sub-bit to be measured.

12. A device for determining a quantum bit high-energy state control signal, characterized in that: The high-energy state control signal is used to adjust the state of the quantum bit to flip between two adjacent excited states, and the determining device includes: an experimental measurement module, configured to adjust the amplitude of the high-energy-state control signal within a preset amplitude sweep range, and sequentially apply a π pulse, the high-energy-state control signal, and a π pulse to the sub-bit to be measured after each adjustment of the amplitude of the high-energy-state control signal to perform a Rabi oscillation experiment, thereby obtaining a first signal corresponding to the sub-bit to be measured, wherein the first signal is a measured signal containing final-state information of the sub-bit to be measured; A parameter acquisition module is used to obtain, based on the amplitude data or phase data of all the first signals, the amplitude of the high-energy state control signal corresponding to when the sub-bit to be measured is in a high excited state among two adjacent excited states, which is the optimal amplitude of the high-energy state control signal.

13. A quantum computer, characterized in that: The method comprises the device as claimed in claim 12 or uses the method as claimed in any one of claims 1 to 11 to determine the high-energy state control signal of the quantum bit.

14. A computer storage medium, characterized in that The computer storage medium stores a computer program, wherein the computer program is configured to execute the method according to any one of claims 1 to 11 when run.

15. An electronic device, characterized in that: The method comprises a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to perform the method according to any one of claims 1 to 11.

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