Method and device for optimizing quantum state driving signal circuit

Abstract

The invention belongs to the field of quantum computing, and particularly discloses an optimization method and device for a quantum state driving signal circuit, and the method comprises the steps: setting an initial value of a modulation parameter, and obtaining a fidelity average value and a fidelity standard deviation corresponding to a target signal applied by the quantum state driving signal circuit; constructing a loss function based on the fidelity average value and the fidelity standard deviation, wherein the loss function decreases along with the increase of the fidelity average value and increases along with the increase of the fidelity standard deviation; and in response to non-convergence of the loss function, updating an initial value of the modulation parameter, and executing a step of obtaining a fidelity average value and a fidelity standard deviation corresponding to a target signal applied by the quantum state driving signal circuit until the modulation parameter when the loss function is converged is obtained as an optimized value of the quantum state driving signal circuit. According to the invention, the target signal transmitted on the quantum state driving signal is ensured to be optimized.

Description

Technical Field

[0001] This invention belongs to the field of quantum computing, and in particular, it relates to an optimization method and apparatus for quantum state-driven signal circuits. Background Technology

[0002] A quantum computer system comprises a quantum chip system (also called a quantum processor), a quantum computer control system, a quantum computer environment support system (also called a dilution refrigerator), and a quantum computer operating system integrated into a classical computer. The dilution refrigerator provides different temperature zones ranging from room temperature to the lowest temperature using cold plates, which isolate these zones. The quantum chip system is located in the lowest temperature zone of the dilution refrigerator. The quantum computer control system connects to and controls the quantum chip system via a quantum state driving signal circuit. This circuit includes a room temperature link, a room temperature-low temperature link (also called a cross-temperature zone link), and a low temperature link (also called an ultra-low temperature link), connected sequentially. The room temperature link connects the quantum computer control system to the top flange of the dilution refrigerator. The room temperature-low temperature link provides signal connections between the cold plates corresponding to the highest and lowest temperature zones within the dilution refrigerator, while the low temperature link provides signal connections between the cold plate corresponding to the lowest temperature zone and the quantum processor within that zone.

[0003] When transmitting microwave signals, which serve as control signals for quantum state driving, the reflection of these signals causes delays and distortions in amplitude and phase. This severely impacts the fidelity of operations in quantum computing and quantum simulation. Therefore, it is necessary to optimize the quantum state driving signal circuit. Summary of the Invention

[0004] The purpose of this invention is to provide an optimization method and apparatus for quantum state-driven signal circuits to overcome the shortcomings of the prior art.

[0005] One aspect of this application provides an optimization method for a quantum state driving signal circuit, wherein a signal modulation module with adjustable modulation parameters is integrated on the quantum state driving signal circuit, the method comprising:

[0006] The initial values ​​of the modulation parameters are set, including the signal delay modulation parameters, amplitude modulation parameters, and phase modulation parameters of the target signal to be transmitted by the quantum state driving signal circuit. The average fidelity and standard deviation of the target signal applied by the quantum state driving signal circuit are obtained. A loss function is constructed based on the average fidelity and standard deviation, whereby the loss function decreases as the average fidelity increases and increases as the standard deviation of the fidelity increases. In response to the loss function not converging, the initial values ​​of the modulation parameters are updated, and the steps of obtaining the average fidelity and standard deviation of the target signal applied by the quantum state driving signal circuit are executed until the modulation parameters at which the loss function converges are obtained as the optimized values ​​for the quantum state driving signal circuit.

[0007] Optionally, the method further includes: determining the distortion situation when there is no integrated modulation parameter adjustable signal modulation module on the quantum state driving signal circuit, and setting the initial value of the modulation parameter according to the distortion situation.

[0008] In the method described above, optionally, determining the distortion situation when there is no integrated modulation parameter adjustable signal modulation module on the quantum state driving signal circuit includes:

[0009] A fixed delay t is applied to the quantum state driving signal circuit of the qubit. 01 Pulse width t 02 The π logic gate pulse signal; and a frequency pulse signal is applied to the quantum frequency driving signal circuit of the quantum bit, the frequency pulse signal having a first delay t. l1 Pulse width t l2 This is used to adjust the frequency of a qubit from its quantum ratio operating point; the probability of obtaining a qubit's quantum state being in an excited state varies with the first delay t. l1 The change in the frequency pulse signal; in response to the fact that there is a quantum bit in an excited state within the target time interval of the first delay of the π logic gate pulse signal completely covered by the frequency pulse signal, it is determined that there is distortion in the quantum state driving signal circuit.

[0010] In the method described above, optionally, the fixed delay t 01 >Pulse width t l2 >Pulse width t 02 The target time interval is greater than or equal to a fixed delay t. 01 +Pulse width t 02 - Pulse width t l2 And the target time interval is less than or equal to the fixed delay t 01 .

[0011] In the method described above, optionally, the modulation parameters include signal delay modulation parameters, amplitude modulation parameters, and phase modulation parameters of the quantum state driving signal.

[0012] Setting initial values ​​for modulation parameters based on the distortion condition includes setting one or a combination of signal delay modulation parameters, amplitude modulation parameters, and phase modulation parameters based on the distortion condition.

[0013] The method described above, optionally, involves the target signal being a random benchmark sequence; obtaining the average fidelity and standard deviation of the target signal applied by the quantum state driving signal circuit; including: inputting the random benchmark sequence at the input terminal of the quantum state driving signal circuit, and obtaining the fidelity value corresponding to the random benchmark sequence by measuring the quantum state of the qubit coupled at the output terminal of the quantum state driving signal circuit; repeatedly performing the steps of inputting the random benchmark sequence at the input terminal of the quantum state driving signal circuit and obtaining the fidelity value corresponding to the random benchmark sequence by measuring the quantum state of the qubit coupled at the output terminal of the quantum state driving signal circuit, until multiple fidelity values ​​are obtained; and determining the average fidelity and standard deviation of the random benchmark sequence based on the multiple fidelity values.

[0014] In the method described above, optionally, obtaining the average fidelity and standard deviation of the target signal applied by the quantum state driving signal circuit further includes: determining the fidelity error value of a single quantum logic gate in the random benchmark sequence based on the average fidelity of the random benchmark sequence.

[0015] In the method described above, optionally, updating the initial value of the modulation parameter in response to the loss function not converging includes: updating one or a combination of the signal delay modulation parameter, amplitude modulation parameter, and phase modulation parameter.

[0016] In the method described above, optionally, the signal modulation module with adjustable modulation parameters includes: a first digital filter for performing a first delay modulation on the in-phase component signal and the quadrature component signal of the quantum state driving signal circuit; a first signal synthesis device for mixing the in-phase component signal and the quadrature component signal modulated by the first digital filter to obtain a first synthesized signal; a second digital filter for performing a second delay modulation on the in-phase component signal and the quadrature component signal of the quantum state driving signal circuit; a second signal synthesis device for mixing the in-phase component signal and the quadrature component signal modulated by the first digital filter to obtain a second synthesized signal; a digital oscillator for generating a sine signal modulated on the first synthesized signal and a cosine signal modulated on the second synthesized signal; and a third signal synthesis device for synthesizing the first synthesized signal and the second synthesized signal after being respectively mixed and modulated based on the sine signal and the cosine signal; wherein the tap coefficients of the first digital filter and the tap coefficients of the second digital filter determine the modulation parameters.

[0017] Another aspect of this application provides an optimization device for a quantum state driving signal circuit, wherein a signal modulation module with adjustable modulation parameters is integrated on the quantum state driving signal circuit, the device comprising:

[0018] The parameter setting module is used to set the initial values ​​of the modulation parameters, which include the signal delay modulation parameters, amplitude modulation parameters, and phase modulation parameters of the target signal to be transmitted by the quantum state driving signal circuit.

[0019] The experimental module is used to obtain the average fidelity and standard deviation of the target signal applied by the quantum state driving signal circuit;

[0020] The loss module construction module is used to construct a loss function based on the fidelity mean and fidelity standard deviation. The loss function decreases as the fidelity mean increases and increases as the fidelity standard deviation increases.

[0021] An optimization module is used to update the initial value of the modulation parameters in response to the loss function not converging, and to perform the steps of obtaining the average fidelity and standard deviation of the fidelity corresponding to the target signal applied by the quantum state driving signal circuit, until the modulation parameters when the loss function converges are obtained as the optimized values.

[0022] Compared with existing technologies, this invention targets the quantum state driving signal circuit of an integrated adjustable signal modulation module. By applying a target signal to the quantum state driving signal circuit, it obtains the average fidelity and standard deviation of the target signal modulated by the modulation parameters of the modulation module. Then, it optimizes the modulation parameters based on a loss function constructed from the average fidelity and standard deviation, obtaining the optimized value of the modulation parameters with converged loss function. This process optimizes the quantum state driving signal circuit of the integrated adjustable signal modulation module. Throughout the process, the convergence of the loss function based on the average fidelity and standard deviation is used to obtain the optimized quantum state driving signal circuit, thereby ensuring that the target signal transmitted on the quantum state driving signal is optimized. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of an optimization method for a quantum state driving signal circuit provided in an exemplary embodiment;

[0024] Figure 2 This is a schematic diagram of the distortion situation when there is no integrated signal modulation module with adjustable modulation parameters on the deterministic quantum state driving signal circuit, provided by an exemplary embodiment.

[0025] Figure 3 This is a schematic diagram of an exemplary embodiment providing π logic gate pulse signals and frequency pulse signals on the XY and Z lines of a quantum bit, respectively;

[0026] Figure 4 This is a schematic diagram illustrating the changes in the quantum state of a quantum bit according to an embodiment of this application;

[0027] Figure 5 This is a schematic diagram of a device for generating modulated signals according to an embodiment of this application;

[0028] Figure 6 This is a schematic diagram of an embodiment of a device for generating modulated signals provided in this application;

[0029] Figure 7 This is a schematic diagram comparing the results of performing an RB experiment before and after optimization of the quantum state driving signal circuit according to an embodiment of this application;

[0030] Figure 8 This application provides an optimized device for a quantum state driving signal circuit according to one embodiment. Detailed Implementation

[0031] The quantum state driving signal circuit includes XY links (i.e., quantum state driving signal circuits) and z links (i.e., quantum frequency driving signal circuits). When these links transmit quantum signals, they cause distortion of the quantum signals. The applicant has found that the XY links, as the transmission links for quantum state driving control signals, are made even more difficult to guarantee in terms of signal integrity due to the fabrication process of quantum processors. For example, the quantum state driving control signals are high-frequency microwave signals. The manufacturing and packaging technologies of quantum processors, as well as the presence of through-silicon vias (TSVs), increase the probability of impedance mismatch in the XY links. Impedance mismatch increases the reflection of high-frequency microwave signals, leading to distortion of the high-frequency microwave signals, i.e., distortion of the quantum logic gate signals. This distortion, in turn, severely affects the fidelity of operations in quantum computing and quantum simulation.

[0032] The amplitude and duration of the quantum state driving control signal determine the degree of change in the quantum state of the qubit, while the phase of the quantum state driving control signal determines the reference standard for the change in the quantum state of the qubit. Therefore, the calibration of the quantum state driving control signal requires consideration of both amplitude and phase, making distortion calibration difficult.

[0033] Based on the above problems, this application proposes an optimization method for quantum state driving signal circuits. The quantum state driving signal circuit integrates a signal modulation module with adjustable modulation parameters. By optimizing the modulation parameters, the quantum state driving signal circuit obtains the optimized value of the modulation parameters, thereby realizing the calibration of the quantum state driving control signal.

[0034] In implementation, considering that the distortion of the target signal transmitted on the quantum state driving signal circuit will manifest as signal delay, amplitude change or phase change in the target signal, a modulation module is set up. This modulation module is used to modulate the target signal to cause signal delay, amplitude change or phase change. That is, the modulation parameters of the signal modulation module include the signal delay modulation parameters, amplitude modulation parameters and phase modulation parameters of the target signal to be transmitted by the quantum state driving signal circuit.

[0035] During operation, a target signal is applied to the quantum state driving signal circuit. The average fidelity and standard deviation of the target signal modulated by the modulation module are obtained. The modulation parameters are then optimized using a loss function constructed based on the average fidelity and standard deviation. The optimized values ​​of the modulation parameters with convergent loss function are obtained, thereby optimizing the quantum state driving signal circuit of the integrated signal modulation module. Throughout this process, an optimized quantum state driving signal circuit is obtained by constructing a loss function based on the average fidelity and standard deviation, and by assessing the convergence of the loss function, ensuring that the target signal transmitted on the quantum state driving signal is optimized.

[0036] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of this application. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0037] Please refer to Figure 1 , Figure 1 This application provides an embodiment of an optimization method for a quantum state driving signal circuit, wherein the quantum state driving signal circuit integrates a signal modulation module with adjustable modulation parameters, and the method includes the following steps:

[0038] Step S01: Set the initial values ​​of the modulation parameters, which include the signal delay modulation parameters, amplitude modulation parameters, and phase modulation parameters of the target signal to be transmitted by the quantum state driving signal circuit;

[0039] Step S02: Obtain the average fidelity and standard deviation of the target signal applied by the quantum state driving signal circuit;

[0040] Step S03: Construct a loss function based on the mean fidelity and the standard deviation of fidelity. The loss function decreases as the mean fidelity increases and increases as the standard deviation of fidelity increases.

[0041] Step S04: In response to the loss function not converging, update the initial value of the modulation parameter, and perform the step of obtaining the average fidelity and standard deviation of the fidelity corresponding to the target signal applied by the quantum state driving signal circuit, until the modulation parameter when the loss function converges is obtained as the optimized value of the quantum state driving signal circuit.

[0042] In the above process, the modulation parameters of the signal modulation module include the signal delay modulation parameters, amplitude modulation parameters, and phase modulation parameters of the target signal to be transmitted by the quantum state driving signal circuit. That is, this modulation module can be used to modulate the target signal to induce signal delay, amplitude change, or phase change. The target signal is applied to the quantum state driving signal circuit, and the average fidelity and standard deviation of the target signal modulated by the modulation module are obtained. The modulation parameters are then optimized based on a loss function constructed from the average fidelity and standard deviation, obtaining the optimized values ​​of the modulation parameters with convergent loss function. This achieves the optimization of the quantum state driving signal circuit of the integrated adjustable modulation parameter signal modulation module. Throughout the process, by constructing a loss function based on the average fidelity and standard deviation, and by obtaining the optimized quantum state driving signal circuit based on the convergence of the loss function, the optimized target signal transmitted on the quantum state driving signal is ensured.

[0043] As one embodiment of this application, the initial value of the modulation parameter can be set based on experience, experimental results, or application scenarios. For example, the quantum state driving signal circuit causes the signal transmitted on the quantum state driving signal circuit to be distorted due to its own characteristics. Therefore, the distortion situation when there is no integrated signal modulation module with adjustable modulation parameters on the quantum state driving signal circuit can be determined, and the initial value of the modulation parameter can be set according to the distortion situation.

[0044] Figure 2 This is a schematic diagram of the distortion situation when there is no integrated signal modulation module with adjustable modulation parameters on the quantum state driving signal circuit provided in one embodiment of this application; Figure 3 This is a schematic diagram of an embodiment of the present application providing π logic gate pulse signals and frequency pulse signals on the XY and Z lines of a quantum bit, respectively; Figure 4 This is a schematic diagram illustrating the changes in the quantum state of a quantum bit provided in one embodiment of this application.

[0045] like Figure 2 - Figure 4 As shown, the detailed process for determining the distortion when there is no integrated adjustable modulation module on the quantum state driving signal circuit includes:

[0046] Step S201: Apply a fixed delay t to the quantum state driving signal circuit of the qubit. 01 Pulse width t 02 The π logic gate pulse signal; and a frequency pulse signal is applied to the quantum frequency driving signal circuit of the quantum bit, the frequency pulse signal having a first delay t. l1 Pulse width t l2 A frequency pulse signal used to adjust the frequency of a quantum bit from its quantum ratio operating point.

[0047] Specifically, the π-logic gate pulse signal applied to the quantum state driving signal circuit of a qubit enables the qubit at its operating point to jump from the ground state to the excited state. The operating point refers to the qubit's operating frequency being its intrinsic frequency. Conversely, applying a frequency pulse signal to the quantum frequency driving signal circuit of a qubit alters the qubit's frequency, causing it to deviate from its operating point. When the duration of the frequency pulse signal and the duration of the π-logic gate pulse signal do not coincide, the π-logic gate pulse signal effectively excites the qubit's quantum state, resulting in the qubit being in an excited state. When the durations of the frequency pulse signal and the π-logic gate pulse signal coincide, the π-logic gate pulse signal's effect on the qubit's quantum state excitation is affected, resulting in the qubit being in its ground state.

[0048] Step S202: Obtain the probability that the quantum state of the qubit is in an excited state as the first delay t increases. l1 The changes;

[0049] Step S203: In response to the presence of a quantum bit in an excited state within the target time interval of the first delay of the frequency pulse signal completely covering the π logic gate pulse signal, it is determined that there is distortion in the quantum state driving signal circuit.

[0050] Specifically, as mentioned above, when the duration of the frequency pulse signal coincides with the duration of the π logic gate pulse signal, the π logic gate pulse signal affects the quantum state excitation of the qubit, causing the qubit to be in its ground state. Therefore, theoretically, within the target time interval of the first delay of the π logic gate pulse signal completely covered by the frequency pulse signal, there will be no situation where the qubit is in an excited state. If there is an exception, it is due to an additional excitation signal. The additional excitation signal is a distorted signal generated when the π logic gate pulse signal is transmitted on the quantum state driving signal circuit. The time when the qubit generates an excited state corresponds to the time when the additional excitation signal acts on the qubit, and can be regarded as the signal delay of the additional excitation signal relative to the π logic gate pulse signal. Figure 4 As shown in region a, the signal delay of the additional excitation signal relative to the π logic gate pulse signal can be used as the initial value of the delay modulation parameter.

[0051] Therefore, as an embodiment of this application, setting the initial value of the modulation parameter according to the distortion condition includes setting one or a combination of signal delay modulation parameter, amplitude modulation parameter, and phase modulation parameter according to the distortion condition.

[0052] As one embodiment of this application, to ensure that the quantum bit is in an excited state when the frequency pulse signal completely covers the target time interval of the first delay of the π logic gate pulse signal, the fixed delay t is set.01 >Pulse width t l2 >Pulse width t 02 The target time interval is greater than or equal to a fixed delay t. 01 +Pulse width t 02 - Pulse width t l2 And the target time interval is less than or equal to the fixed delay t 01 .

[0053] It should be noted that the target signal applied to the quantum state driving signal circuit is a waveform signal corresponding to a quantum logic gate or a combination of quantum logic gates. This waveform signal is transformed into an analog signal representing a quantum logic gate or a combination of quantum logic gates acting on the qubit by the quantum state driving signal circuit. The fidelity of the signal (also called the fidelity of the quantum logic gate) can be obtained by measuring the quantum state of the qubit. This is a well-known attempt in the field and will not be described in detail further.

[0054] It should be noted that, to improve the accuracy of quantum logic gate fidelity testing, a target signal can be set to correspond to a combination of quantum logic gates. For example, the combination of quantum logic gates can be a random benchmark sequence. A random benchmark sequence is a combination of quantum logic gates used in random benchmarking. Random benchmarking (RB) is a protocol used to evaluate the "average performance" of quantum chip gate operations, aiming to determine the error probability of each gate operation in a computing environment. RB protocol quantum circuits can run on a real quantum chip or be simulated using a quantum simulator. When using a quantum simulator, ideally, the final result after executing the quantum circuit should be exactly the same as the initial state, thus increasing the accuracy of the test.

[0055] It should be noted that the detailed process of random benchmarking is as follows: The qubit is prepared in the |0> state. Then, m group elements C1 are randomly selected from the Clifford group and applied sequentially to the qubit. Any group element C1 can also be called a Clifford gate, which can be obtained by combining basic physical gates, namely the X gate, X / 2 gate, Y gate, and Y / 2 gate. According to the definition of a group, there must exist an inverse in the Clifford group such that this series of operations is equivalent to a unit gate, which is then applied to the bit. If all operations are perfect, the bit should be in the |0> state; the inverse is denoted as Cr. The probability of the bit being in the |0> state is measured as the fidelity of the RB sequence. For each m, the experiment is repeated k times to obtain the average value P_m of the sequence fidelity.

[0056] As one embodiment of this application, to obtain the average fidelity and standard deviation of the target signal, a random benchmark sequence is input to the input terminal of the quantum state driving signal circuit, and the fidelity value corresponding to the random benchmark sequence is obtained by measuring the quantum state of the qubit coupled to the output terminal of the quantum state driving signal circuit. The steps of inputting the random benchmark sequence to the input terminal of the quantum state driving signal circuit and obtaining the fidelity value corresponding to the random benchmark sequence by measuring the quantum state of the qubit coupled to the output terminal of the quantum state driving signal circuit are repeated until multiple fidelity values ​​are obtained. Based on the multiple fidelity values, the average fidelity and standard deviation corresponding to the random benchmark sequence are determined. That is, for each m, the experiment is repeated k times to obtain the average fidelity of the sequence. In this application, the average fidelity is denoted as f. ave，m Let f be the standard deviation of the fidelity. std，m As we know, the mean is the central location of a set of data, while the standard deviation measures the dispersion of the data. Combining the two can comprehensively and accurately reflect the overall characteristics of the data.

[0057] As one implementation of this application, the fidelity error value of a single quantum logic gate in a random benchmark sequence can be determined based on the average fidelity of the random benchmark sequence. Specifically, any group of elements C1 in the random benchmark sequence is also called a Clifford gate, which can be obtained by combining basic physical gates, namely X gate, X / 2 gate, Y gate, and Y / 2 gate. It is known empirically that each Clifford gate contains 1.875 average physical gates. Therefore, the fidelity error value of the quantum logic gate can be determined based on the fidelity of the random benchmark sequence and the average number of physical gates contained in the Clifford gate.

[0058] Specifically, we can obtain the f corresponding to each m. ave，m Then according to f ave，m The fitting relationship between f and m is used to obtain the fitting parameters, where f ave，m The fitting relationship between f and m is as follows: ave，m =AP m +B; where A and B are fitting parameters, and P is the depolarization rate. Then the fidelity error of a single quantum logic gate is (1-f ave，m The fidelity error of the dual quantum logic gate is (1-f) / 2 / 1.875. ave，m ) / 4 / 1.875.

[0059] This application involves reverse measurement and optimization of modulation parameters based on the fidelity of the target signal modulated with the current modulation parameters, based on the average fidelity f. ave，m and the standard deviation of fidelity f std，mA loss function was established, and optimized modulation parameters were found based on the convergence of the loss function. Specifically, the loss function decreases as the average fidelity increases and increases as the standard deviation of the fidelity increases. For example, the loss function is defined as follows:

[0060]

[0061] As one embodiment of this application, updating the initial value of the modulation parameters in response to the loss function not converging includes: updating one or a combination of signal delay modulation parameters, amplitude modulation parameters, and phase modulation parameters. Specifically, different parameter sets can be obtained through combinations, and experiments can be conducted for each different parameter set of the modulation parameters to obtain the corresponding loss function. For example, an optimization algorithm can be used to optimize the modulation parameters and obtain the corresponding fidelity function. For instance, a known differential evolution algorithm can be used to perform iterative optimization between the parameters and the loss function to determine the optimal modulation parameters.

[0062] It should be noted that the quantum state driving signal circuit with an integrated adjustable modulation parameter signal modulation module loads the target signal applied to the quantum state driving signal electrical input terminal with a modulation signal generated by the signal modulation module. This modulation of the target signal ensures that the output terminal of the quantum state driving signal circuit matches the input target signal. The principle behind this is that when the quantum state driving signal circuit transmits electrical signals, the circuit itself alters the signal, commonly referred to as distortion or signal loss. An additional modulation signal can be loaded onto the target signal, and the modulation signal and the target signal satisfy a specific relationship to compensate for the distortion or signal loss of the target signal.

[0063] Since the target signal applied by the quantum state driving signal circuit is a microwave signal, the form of the modulation signal can be determined based on the general form of microwave signals.

[0064] For example, the general form of a microwave signal is as follows:

[0065] s(t)=V I (t)cos(wt)+V Q (t)sin(wt)

[0066] Among them, V I (t) and V Q (t) represents the in-phase component and quadrature component of the microwave signal, respectively; w is the frequency of the microwave signal; wt is the initial phase of the microwave signal;

[0067] Therefore, the modulated signal takes the following form:

[0068]

[0069] Among them, t d A represents the signal delay modulation parameter, and A represents the amplitude modulation parameter. These are the phase modulation parameters.

[0070] Figure 5 This is a schematic diagram of a device for generating modulated signals according to an embodiment of this application. As an embodiment of this application, such as... Figure 5 As shown, the signal modulation module with adjustable modulation parameters for generating the modulation signal includes: a first digital filter, a first signal synthesis device, a second digital filter, a second signal synthesis device, a digitally controlled oscillator, a first mixer, a second mixer, and a third signal synthesis device.

[0071] A first digital filter is used to perform a first delay modulation on the in-phase and quadrature component signals of the quantum state driving signal circuit; a first signal synthesis device is used to mix the in-phase and quadrature component signals modulated by the first digital filter to obtain a first synthesized signal; a second digital filter is used to perform a second delay modulation on the in-phase and quadrature component signals of the quantum state driving signal circuit; a second signal synthesis device is used to mix the in-phase and quadrature component signals modulated by the first digital filter to obtain a second synthesized signal; a digital oscillator is used to generate a sine signal modulated by the first synthesized signal and a cosine signal modulated by the second synthesized signal; a second signal synthesis device is used to synthesize the first synthesized signal and the second synthesized signal after being respectively mixed and modulated by the sine signal and the cosine signal. The tap coefficients of the first digital filter and the second digital filter determine the modulation parameters.

[0072] Specifically, a digital filter can generally be represented by a linear constant-coefficient difference equation as follows:

[0073]

[0074] Where x(n) is the input signal of the digital filter, g(n) is the output signal of the digital filter, and the variable n is an integer value representing a discrete instance. n can be converted to a continuous-time variable t using t = nTs. M is the total order of the filter, b... m These are the tap coefficients of the m-th order filter, a k These are the tap coefficients of the k-th order filter. The difference is that b... m It is the feedforward tap coefficient, a k It is the feedback tap coefficient.

[0075] when a kWhen =0, the digital filter represented by the above linear constant coefficient difference equation is an FIR filter, also called a forward feedback filter. Among them, the FIR (Finite Impulse Response) filter, that is, the finite-length unit impulse response filter, is also called a non-recursive filter.

[0076] The linear constant coefficient difference equation for an FIR filter is:

[0077]

[0078] The above formula represents the time delay step *m* between the input and output signals, therefore, digital filters have the function of adjusting signal delay. This can be achieved using t... d =n d Ts will equal n d Transform m into a continuous time variable t d ,Right now: That is, the input and output signals of a digital filter have a t. d Signal delay.

[0079] Figure 6 This is a schematic diagram illustrating an embodiment of a modulated signal generation device provided in this application. As one embodiment of this application, as... Figure 6 As shown, the first digital filter includes a first sub-filter and a second sub-filter. The first sub-filter is used to modulate one of the in-phase component signal and the quadrature component signal, and the second sub-filter is used to modulate the other of the in-phase component signal and the quadrature component signal. The second digital filter includes a third sub-filter and a fourth sub-filter. The third sub-filter is used to modulate one of the in-phase component signal and the quadrature component signal, and the fourth sub-filter is used to modulate the other of the in-phase component signal and the quadrature component signal. The first sub-filter, the second sub-filter, the third sub-filter, and the fourth sub-filter are all referred to as sub-filters.

[0080] The sub-filter that modulates the in-phase component signal in the first digital filter is denoted as the first sub-filter, and its m (m = n) d The tap coefficients of order ) are recorded as The sub-filter that modulates the quadrature phase component signal in the first digital filter is denoted as the second sub-filter, whose m (m = n) d The tap coefficients of order ) are recorded as

[0081] The sub-filter that modulates the in-phase component signal in the second digital filter is denoted as the third sub-filter, whose m (m = n) d The tap coefficients of order ) are recorded as The sub-filter that modulates the quadrature phase component signal in the second digital filter is denoted as the fourth sub-filter, whose m (m = n) d The tap coefficients of order ) are recorded as

[0082] Set the tap coefficients of the first sub-filter Tap coefficients of the second sub-filter Tap coefficients of the third sub-filter Tap coefficients of the fourth sub-filter Additionally, simplify the settings. but:

[0083] The modulation signal corresponding to the above process is:

[0084]

[0085] The optimized quantum state driving signal circuit based on the above embodiments, when used to perform the RB experiment, yields the following comparison results with those before optimization: Figure 7 As shown, the optimized quantum state driving signal circuit improves both the fidelity and the standard deviation of the RB sequence for each m when performing the RB experiment.

[0086] Based on the same inventive concept, such as Figure 8 As shown, one embodiment of this application provides an optimization device for a quantum state driving signal circuit. The quantum state driving signal circuit integrates a signal modulation module with adjustable modulation parameters. The device includes a parameter setting module, an experimental module, a loss module construction module, and an optimization module.

[0087] The system includes a parameter setting module for setting initial values ​​for modulation parameters, including signal delay modulation parameters, amplitude modulation parameters, and phase modulation parameters for the target signal to be transmitted by the quantum state driving signal circuit; an experimental module for obtaining the average fidelity and standard deviation of the fidelity corresponding to the target signal applied by the quantum state driving signal circuit; a loss function construction module for constructing a loss function based on the average fidelity and standard deviation, wherein the loss function decreases as the average fidelity increases and increases as the standard deviation of the fidelity increases; and an optimization module for updating the initial values ​​of the modulation parameters in response to the loss function not converging, and performing the steps of obtaining the average fidelity and standard deviation of the fidelity corresponding to the target signal applied by the quantum state driving signal circuit until the modulation parameters at which the loss function converges are obtained as the optimized values.

[0088] The systems, devices, modules, or units described in the above embodiments can be implemented by computer chips or entities, or by products with certain functions. A typical implementation device is a computer, which can take the form of a personal computer, laptop computer, cellular phone, camera phone, smartphone, personal digital assistant, media player, navigation device, email sending and receiving device, game console, tablet computer, wearable device, or any combination of these devices.

[0089] In a typical configuration, a computer includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0090] Memory may include non-persistent storage in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0091] Computer-readable media include both permanent and non-permanent, removable and non-removable media that can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, disk storage, quantum memory, graphene-based storage media or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0092] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0093] The foregoing has described specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims may be performed in a different order than that shown in the embodiments and may still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired result. In some embodiments, multitasking and parallel processing are possible or may be advantageous.

[0094] The terminology used in one or more embodiments of this specification is for the purpose of describing particular embodiments only and is not intended to limit the one or more embodiments of this specification. The singular forms “a,” “described,” and “the” used in one or more embodiments of this specification and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more associated listed items. It should be understood that although the terms first, second, third, etc., may be used to describe various information in one or more embodiments of this specification, such information should not be limited to these terms. These terms are used only to distinguish information of the same type from one another. For example, first information may also be referred to as second information without departing from the scope of one or more embodiments of this specification, and similarly, second information may also be referred to as first information. Depending on the context, the word “if” as used herein may be interpreted as “when,” “when,” or “in response to a determination.” The above descriptions are merely preferred embodiments of one or more embodiments of this specification and are not intended to limit the one or more embodiments of this specification. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments of this specification should be included within the scope of protection of one or more embodiments of this specification.

[0095] The above description, based on the embodiments shown in the figures, details the structure, features, and effects of the present invention. The above description is only a preferred embodiment of the present invention, but the present invention is not limited to the scope of implementation shown in the figures. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, that do not exceed the spirit covered by the specification and figures, should be within the protection scope of the present invention.

Claims

1. An optimization method for a quantum state-driven signal circuit, characterized in that, A signal modulation module with adjustable modulation parameters is integrated on a quantum state driving signal circuit, the method comprising: The initial values ​​of the modulation parameters are set, including the signal delay modulation parameters, amplitude modulation parameters, and phase modulation parameters of the target signal to be transmitted by the quantum state driving signal circuit. Obtain the average fidelity and standard deviation of the target signal applied by the quantum state driving signal circuit; A loss function is constructed based on the mean fidelity and the standard deviation of fidelity. The loss function decreases as the mean fidelity increases and increases as the standard deviation of fidelity increases. In response to the loss function not converging, the initial value of the modulation parameter is updated, and the steps of obtaining the average fidelity and standard deviation of the target signal applied by the quantum state driving signal circuit are performed until the modulation parameter at which the loss function converges is obtained as the optimized value of the quantum state driving signal circuit.

2. The method according to claim 1, characterized in that, The method further includes: determining the distortion situation when there is no integrated modulation parameter adjustable signal modulation module on the quantum state driving signal circuit, and setting the initial value of the modulation parameter according to the distortion situation.

3. The method according to claim 2, characterized in that, The distortion situation when there is no integrated adjustable modulation parameter signal modulation module on the quantum state driving signal circuit includes: A fixed delay t is applied to the quantum state driving signal circuit of the qubit. 01 Pulse width t 02 The π logic gate pulse signal; and a frequency pulse signal is applied to the quantum frequency driving signal circuit of the quantum bit, the frequency pulse signal having a first delay t. l1 Pulse width t l2 This is used to adjust the frequency of the qubits from the quantum ratio operating point; The probability of obtaining a quantum bit in an excited state varies with the first delay t. l1 The changes; In response to the presence of a quantum bit in an excited state within a target time interval where the frequency pulse signal completely covers the first delay of the π logic gate pulse signal, it is determined that there is distortion in the quantum state driving signal circuit.

4. The method according to claim 3, characterized in that, The fixed delay t 01 >Pulse width t l2 >Pulse width t 02 ; The target time interval is greater than or equal to a fixed delay t. 01 +Pulse width t 02 - Pulse width t l2 And the target time interval is less than or equal to the fixed delay t 01 .

5. The method according to claim 4, characterized in that, The modulation parameters include the signal delay modulation parameters, amplitude modulation parameters, and phase modulation parameters of the quantum state driving signal; Setting initial values ​​for modulation parameters based on the distortion condition includes setting one or a combination of signal delay modulation parameters, amplitude modulation parameters, and phase modulation parameters based on the distortion condition.

6. The method according to claim 1, characterized in that, The target signal is a random benchmark test sequence; Obtain the average fidelity and standard deviation of the target signal applied by the quantum state driving signal circuit; including: A random benchmark sequence is input into the input terminal of the quantum state driving signal circuit, and the fidelity value corresponding to the random benchmark sequence is obtained by measuring the quantum state of the quantum bit coupled at the output terminal of the quantum state driving signal circuit. Repeat the steps of inputting a random benchmark test sequence at the input terminal of the quantum state driving signal circuit and obtaining the fidelity value corresponding to the random benchmark test sequence by measuring the quantum state of the qubit coupled at the output terminal of the quantum state driving signal circuit, until multiple fidelity values ​​are obtained; The mean fidelity and standard deviation of the corresponding random benchmark sequence are determined based on multiple fidelity values.

7. The method according to claim 6, characterized in that, The method for obtaining the average fidelity and standard deviation of the target signal applied by the quantum state driving signal circuit also includes: The fidelity error of a single quantum logic gate in a random benchmark sequence is determined based on the average fidelity of the random benchmark sequence.

8. The method according to claim 1, characterized in that, The step of updating the initial value of the modulation parameter in response to the loss function not converging includes: Update one or a combination of the signal delay modulation parameters, amplitude modulation parameters, and phase modulation parameters.

9. The method according to any one of claims 1-8, characterized in that, The adjustable modulation parameter signal modulation module includes: The first digital filter is used to perform a first delay modulation on the in-phase component signal and the quadrature component signal of the quantum state driving signal circuit; The first signal synthesis device is used to mix the in-phase component signal and the quadrature component signal modulated by the first digital filter to obtain a first synthesized signal. The second digital filter is used to perform a second delay modulation on the in-phase component signal and the quadrature component signal of the quantum state driving signal circuit; The second signal synthesis device is used to mix the in-phase component signal and the quadrature component signal modulated by the first digital filter to obtain the second synthesized signal. A digital oscillator is used to generate a sine signal that modulates a first synthesized signal and a cosine signal that modulates a second synthesized signal. The third signal synthesis device is used to synthesize the first and second synthesized signals based on the frequency mixing and modulation of sine and cosine signals, respectively. The modulation parameters are determined by the tap coefficients of the first digital filter and the tap coefficients of the second digital filter.

10. An optimization device for a quantum state-driven signal circuit, characterized in that, A signal modulation module with adjustable modulation parameters is integrated on a quantum state driving signal circuit. The device includes: The parameter setting module is used to set the initial values ​​of the modulation parameters, which include the signal delay modulation parameters, amplitude modulation parameters, and phase modulation parameters of the target signal to be transmitted by the quantum state driving signal circuit. The experimental module is used to obtain the average fidelity and standard deviation of the target signal applied by the quantum state driving signal circuit; The loss module construction module is used to construct a loss function based on the fidelity mean and fidelity standard deviation. The loss function decreases as the fidelity mean increases and increases as the fidelity standard deviation increases. An optimization module is used to update the initial value of the modulation parameters in response to the loss function not converging, and to perform the steps of obtaining the average fidelity and standard deviation of the fidelity corresponding to the target signal applied by the quantum state driving signal circuit, until the modulation parameters when the loss function converges are obtained as the optimized values.

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