CN116484964A

CN116484964A - Quantum bit operation method and device based on pulse, electronic equipment and medium

Info

Publication number: CN116484964A
Application number: CN202310333885.6A
Authority: CN
Inventors: 王贺; 孟则霖
Original assignee: Beijing Baidu Netcom Science and Technology Co Ltd
Current assignee: Beijing Baidu Netcom Science and Technology Co Ltd
Priority date: 2023-03-30
Filing date: 2023-03-30
Publication date: 2023-07-25

Abstract

The present disclosure provides a method, apparatus, electronic device, computer readable storage medium and computer program product for pulse-based qubit operation, and relates to the field of computers, in particular to the technical field of quantum computers. The implementation scheme is as follows: determining a plurality of sets of data comprising a pair of pulse amplitude values and a pulse duration value; determining a change curve of probability of the quantum bit in a first state along with pulse driving frequency based on multiple groups of data respectively so as to determine a quantum bit frequency value; determining an optimal qubit frequency value as a first qubit frequency value and setting a pulse drive frequency value equal to the optimal qubit frequency value; fitting the probability of the qubit being in the first state as a function of pulse amplitude based on one or more second pulse duration values to determine a pulse duration value and a pulse amplitude value and to determine a pulse drive coefficient value; and scanning at least one parameter of the pulse amplitude, the pulse duration and the drive frequency.

Description

Quantum bit operation method and device based on pulse, electronic equipment and medium

Technical Field

The present disclosure relates to the field of computers, and more particularly to the field of quantum computer technology, and in particular to a pulse-based qubit operation method, apparatus, electronic device, computer-readable storage medium, and computer program product.

Background

Quantum computers have powerful information processing capabilities. Currently, scientists have experimentally demonstrated that quantum computers are far more computationally efficient than classical supercomputers, i.e. have quantum advantages, on specific problems. Developing a practical quantum computer, demonstrating the application with industrial value, is a major difficulty facing the current quantum computing industry. However, developing a practical quantum computer is a complex and laborious project pushing the quantum computer to practical industrial applications, and a great number of technical challenges need to be solved, one of which is the problem of automated characterization and calibration of the quantum computer.

Disclosure of Invention

The present disclosure provides a method, apparatus, electronic device, computer readable storage medium, and computer program product for pulse-based qubit operation.

According to an aspect of the present disclosure, there is provided a pulse-based qubit operation method including: determining a plurality of sets of data, each set of data comprising a pair of pulse amplitude values and pulse duration values; determining a change curve of probability of the quantum bit in a first state along with pulse driving frequency based on the plurality of groups of data respectively to determine quantum bit frequency values corresponding to the plurality of groups of data respectively, wherein the probability is determined based on pulse amplitude, pulse duration, pulse driving frequency, quantum bit frequency and pulse driving coefficient; determining an optimal qubit frequency value to take the optimal qubit frequency value as a first qubit frequency value and setting a pulse drive frequency value equal to the optimal qubit frequency value; fitting the probability of the quantum bit in a first state along with the change of the pulse amplitude according to each of the pulse driving frequency value and one or more preset first pulse duration values so as to determine a first pulse duration value with the optimal fitting effect and a corresponding first pulse amplitude value; determining a pulse drive coefficient value based on the optimal first pulse duration value and the corresponding first pulse amplitude value; and scanning at least one parameter of the pulse amplitude, the pulse duration and the driving frequency within a preset corresponding first value range based on the pulse driving coefficient value and the first qubit frequency value, and determining values of other parameters of the pulse amplitude, the pulse duration and the driving frequency except the at least one parameter to determine the value of each of the at least one parameter based on a variation curve of the probability with the at least one parameter.

According to another aspect of the present disclosure, there is provided a pulse-based qubit operation apparatus including: a first determining unit configured to determine a plurality of sets of data, each set of data including a pair of pulse amplitude values and pulse duration values; a second determining unit configured to determine a variation curve of probability of the quantum bit in a first state with a pulse driving frequency based on the plurality of sets of data, respectively, so as to determine a quantum bit frequency value corresponding to each of the plurality of sets of data, wherein the probability is determined based on a pulse amplitude, a pulse duration, a pulse driving frequency, a quantum bit frequency, and a pulse driving coefficient; a third determination unit configured to determine an optimal qubit frequency value to take the optimal qubit frequency value as a first qubit frequency value, and to set a pulse drive frequency value equal to the optimal qubit frequency value; the first fitting unit is configured to fit the probability of the quantum bit in a first state along with the change of the pulse amplitude according to each of the pulse driving frequency value and one or more preset first pulse duration values so as to determine a first pulse duration value with the best fitting effect and a corresponding first pulse amplitude value; a fourth determination unit configured to determine a pulse drive coefficient value based on the optimal first pulse duration value and the corresponding first pulse amplitude value; and a first scanning unit configured to scan at least one parameter of the pulse amplitude, the pulse duration, and the driving frequency within a preset corresponding first value range based on the pulse driving coefficient value and the first qubit frequency value, and determine values of other parameters of the pulse amplitude, the pulse duration, and the driving frequency than the at least one parameter, so as to determine a value of each of the at least one parameter based on a variation curve of the probability with the at least one parameter.

According to another aspect of the present disclosure, there is provided an electronic device including: at least one processor; and a memory communicatively coupled to the at least one processor; the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the methods described in the present disclosure.

According to another aspect of the present disclosure, there is provided a non-transitory computer-readable storage medium storing computer instructions for causing a computer to perform the method described in the present disclosure.

According to another aspect of the present disclosure, there is provided a computer program product comprising a computer program which, when executed by a processor, implements the method described in the present disclosure.

According to one or more embodiments of the present disclosure, a full range scan of each pulse parameter is not required and the pulse parameters can be automatically selected, thereby improving the efficiency and accuracy of qubit characterization and calibration.

It should be understood that the description in this section is not intended to identify key or critical features of the embodiments of the disclosure, nor is it intended to be used to limit the scope of the disclosure. Other features of the present disclosure will become apparent from the following specification.

Drawings

The accompanying drawings illustrate exemplary embodiments and, together with the description, serve to explain exemplary implementations of the embodiments. The illustrated embodiments are for exemplary purposes only and do not limit the scope of the claims. Throughout the drawings, identical reference numerals designate similar, but not necessarily identical, elements.

FIG. 1 illustrates a flow chart of a method of pulse-based qubit operation according to an embodiment of the disclosure;

FIG. 2 illustrates a flow chart for further determining pulse parameter values in accordance with an embodiment of the present disclosure;

FIG. 3 illustrates a schematic diagram of determining line widths according to an embodiment of the present disclosure;

FIG. 4 shows a schematic diagram of results obtained from a two-dimensional scan experiment in step 240, according to an embodiment of the present disclosure;

FIG. 5 shows a schematic diagram of fitting results based on a theoretical model in accordance with an embodiment of the disclosure;

FIGS. 6A and 6B are diagrams illustrating experimental results obtained by scanning pulse duration and driving frequency, respectively, according to embodiments of the present disclosure;

FIGS. 7A and 7B are diagrams showing experimental results of scanning pulse amplitudes and pulse durations according to embodiments of the present disclosure;

FIG. 8 illustrates a block diagram of a pulse-based qubit manipulation device according to an embodiment of the disclosure; and

fig. 9 illustrates a block diagram of an exemplary electronic device that can be used to implement embodiments of the present disclosure.

Detailed Description

Exemplary embodiments of the present disclosure are described below in conjunction with the accompanying drawings, which include various details of the embodiments of the present disclosure to facilitate understanding, and should be considered as merely exemplary. Accordingly, one of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the present disclosure. Also, descriptions of well-known functions and constructions are omitted in the following description for clarity and conciseness.

In the present disclosure, the use of the terms "first," "second," and the like to describe various elements is not intended to limit the positional relationship, timing relationship, or importance relationship of the elements, unless otherwise indicated, and such terms are merely used to distinguish one element from another. In some examples, a first element and a second element may refer to the same instance of the element, and in some cases, they may also refer to different instances based on the description of the context.

The terminology used in the description of the various illustrated examples in this disclosure is for the purpose of describing particular examples only and is not intended to be limiting. Unless the context clearly indicates otherwise, the elements may be one or more if the number of the elements is not specifically limited. Furthermore, the term "and/or" as used in this disclosure encompasses any and all possible combinations of the listed items.

Embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

To date, various types of computers in use are based on classical physics as the theoretical basis for information processing, known as traditional or classical computers. Classical information systems store data or programs using binary data bits that are physically easiest to implement, each binary data bit being represented by a 0 or a 1, called a bit or a bit, as the smallest unit of information. Classical computers themselves have the inevitable weakness: first, the most basic limitation of energy consumption in the calculation process. The minimum energy required by the logic element or the memory cell should be more than several times of kT to avoid malfunction under thermal expansion; secondly, information entropy and heating energy consumption; thirdly, when the wiring density of the computer chip is large, the uncertainty of momentum is large when the uncertainty of the electronic position is small according to the uncertainty relation of the Hessenberg. Electrons are no longer bound and there is a quantum interference effect that can even destroy the performance of the chip.

Quantum computers (QWs) are a class of physical devices that perform high-speed mathematical and logical operations, store and process quantum information, following quantum mechanical properties, laws. When a device processes and calculates quantum information and a quantum algorithm is operated, the device is a quantum computer. Quantum computers follow unique quantum dynamics (particularly quantum interferometry) to achieve a new model of information processing. For parallel processing of computational problems, quantum computers have an absolute advantage in speed over classical computers. The transformation implemented by the quantum computer on each superposition component is equivalent to a classical computation, all of which are completed simultaneously and are superimposed according to a certain probability amplitude to give the output result of the quantum computer, and the computation is called quantum parallel computation. Quantum parallel processing greatly improves the efficiency of quantum computers so that they can perform tasks that classical computers cannot do, such as factorization of a large natural number. Quantum coherence is essentially exploited in all quantum ultrafast algorithms. Therefore, quantum parallel computation with quantum state instead of classical state can reach incomparable operation speed and information processing function of classical computer, and save a large amount of operation resources.

Quantum computer uses quantum bit as most basic information processing unit, when executing specific calculation task, it usually uses quantum circuit to write quantum algorithm, the quantum circuit is formed from quantum logic gate and quantum measurement, these quantum operations can be used for controlling state of quantum bit so as to implement specific calculation task. The last essential step in the practical use of quantum devices is the characterization (calibration) and calibration (calibration). The characterization is to obtain basic information of the quantum equipment by a specific technical means, and only after the basic information is obtained, the quantum operation can be realized. The calibration is to obtain accurate control parameters through a specific technology, so that the quantum operation with high fidelity can be performed on the quantum bit. Researchers also unify characterization and calibration into device calibration. After characterization and calibration of the quantum device, the quantum device can be used. Since qubits are the basic information units of a quantum computer, accurate characterization and calibration of the qubits is critical.

For example, in a superconducting quantum computer, in order to enable the superconducting quantum computer to work normally, the superconducting quantum computer needs to be characterized to obtain basic information such as the frequency of a quantum bit, and then pulse parameters of various quantum operations are obtained through calibration, so that accurate control of the quantum bit is realized. When the number of qubits is not high, one can manually perform characterization and calibration of the quantum device. With the continuous expansion of quantum computer scale, fully automated characterization and calibration is becoming the dominant approach.

Among the physical routes of quantum computation, the technical routes of superconducting quantum computation and the like require the use of pulses to achieve quantum operations. When a completely new quantum device is obtained, little is generally known about the information already present in the device, and for characterization, it is necessary to manipulate the qubit with pulses to obtain relevant information. However, in the case of insufficient initial information, it is difficult to know how a set of pulse parameters should be selected to complete the corresponding quantum operation. To break this contradiction, manual experience is often required to assist. For example, in order to realize the excitation of the qubit, a quantum logic gate such as an X gate needs to be realized, at this time, a set of experience parameters are generally selected manually, and after the result is obtained, the judgment is successful according to the manual experience, or the parameters are continuously adjusted to carry out experiments again until the purpose is finally achieved. In the process of quantum equipment characterization and calibration, a large number of experiments need to select different pulse parameters, and the number of the pulse parameters is large, so that the failure of automatic characterization and calibration can be caused by unsuitable pulse parameters.

Thus, according to an embodiment of the present disclosure, a pulse-based qubit operation method is provided. Fig. 1 shows a flow chart of a pulse-based qubit operation method according to an embodiment of the present disclosure, as shown in fig. 1, method 100 includes: determining a plurality of sets of data, each set of data comprising a pair of pulse amplitude values and pulse duration values (step 110); determining a change curve of probability of the quantum bit in a first state along with a pulse driving frequency based on the plurality of groups of data respectively to determine quantum bit frequency values corresponding to the plurality of groups of data respectively, wherein the probability is determined based on pulse amplitude, pulse duration, pulse driving frequency, quantum bit frequency and pulse driving coefficient (step 120); determining an optimal qubit frequency value to take the optimal qubit frequency value as a first qubit frequency value and setting a pulse drive frequency value equal to the optimal qubit frequency value (step 130); fitting the probability of the qubit in a first state along with the change of the pulse amplitude according to each of the pulse driving frequency value and one or more preset first pulse duration values to determine a first pulse duration value with the best fitting effect and a corresponding first pulse amplitude value (step 140); determining a pulse drive coefficient value based on the optimal first pulse duration value and the corresponding first pulse amplitude value (step 150); and scanning at least one parameter of the pulse amplitude, the pulse duration, and the drive frequency over a preset corresponding first range of values based on the pulse drive coefficient value and the first qubit frequency value, and determining values of other parameters of the pulse amplitude, the pulse duration, and the drive frequency than the at least one parameter to determine a value of each of the at least one parameter based on a profile of the probability with the at least one parameter (step 160).

According to the embodiment of the disclosure, full-range scanning of each pulse parameter is not required, and the pulse parameters can be automatically selected, so that the efficiency and accuracy of qubit characterization and calibration are improved.

In superconducting quantum computing, the scenario of pulses used mainly includes two types, one of which is a pulse applied to a read resonator, called a read pulse, and one of which is a pulse applied to a qubit for exciting the qubit. For reading the resonant cavity, the information to be characterized is the frequency of the resonant cavity, and the amplitude and duration of the used pulse are optimized to obtain the optimal pulse parameters when the reading calibration is carried out, so that the method is relatively simple. Whereas for qubits, the information that needs to be characterized and calibrated includes the qubit frequency, the amplitude and duration of Pi pulses, the curve between the Z line voltage and the qubit frequency, the coupling strength of the XY line, etc. For example, a plot between the Z-line voltage and the qubit frequency means that changing the Z-line voltage can be used to change the qubit frequency, and the information that needs to be obtained is the true frequency of the qubit when setting the Z-line voltage of the qubit. For each voltage value point, the corresponding quantum bit frequency needs to be obtained, and a lookup table is made for use.

In superconducting quantum computation, the qubit is initially at |0>After a pulse with a certain parameter is applied to the state, the quantum bit is excited to be |1 with a certain probability>In the state of being in a state,record the qubit at |1>Probability of state P ₁ . A special pulse Pi pulse is to excite the quantum bit to |1>Pulse in state, i.e. P ₁ Pulse of =1. It will be appreciated that the Pi pulse parameters are not exclusive and that different pulse parameters are required in different scenarios, the pulses of these parameters all meeting P ₁ =1. For example, the basic parameters of the pulse may include amplitude, start time, center position, duration, etc.

Laratio oscillation, which means that when a pulse of a certain parameter is applied, the parameter of the scanned pulse, such as amplitude A or duration D, is observed to be in 1>Probability of states P ₁ The periodic oscillations between 0 and 1 are called the rabi oscillations. With the Rabbet oscillation, the Pi pulse is naturally obtained. In qubit characterization and calibration, the actual resulting change in IQ values, not the direct probability P, is before the readout calibration ₁ . But IQ value represents P ₁ Can unify the size of the probability P ₁ To represent that the effect is equivalent to IQ values.

Thus, according to some embodiments, the first state is |1>State, and the probability P ₁ The determination is made according to the following equation:

wherein omega ₁ Coef, where Coef is the drive factor (which is constant), a is the pulse amplitude,wherein f _d For the driving frequency f _q For the qubit frequency, t is a time determined based on the pulse duration. For example, when there is no time delay for the pulse device, t=d, where D is the pulse duration.

The square wave pulse is to modulate the square wave amplitude of a sine wave with a certain frequency, and the frequency of the sine wave is recorded as the driving frequency f _d To a rough extentIn other words, the drive frequency is near the qubit frequency to excite the qubit. For square wave pulses, only amplitude and duration need be of interest. But for other pulses, such as gaussian pulses, attention is also paid to the center position of the pulse, the standard deviation of the pulse, etc.

Since the pulse duration used in quantum computation is much longer than the qubit period, the integrated area of the pulse from the start time to the end time can be considered to affect the qubit excitation probability. Although the parameters of the different types of pulses are different, for other types of pulses, the integration area may be equivalent to the corresponding square wave pulse as long as it is uniform. Thus, in some examples, respective pulse parameters may be determined in accordance with embodiments of the present disclosure, after being converted to respective other types of pulses.

In this disclosure, therefore, only square wave pulses may be considered for ease of description, and further only the amplitude and duration of the pulses. And further, the pulse amplitude can be normalized to a real number between 0 and 1, denoted as a; the pulse duration is noted as D.

According to some embodiments, the probability that the qubit is in the first state is further determined based on a pulse delay time. Thus, determining the plurality of sets of data may further comprise: a preset pulse delay time value is determined.

In practice, the device used to pulse may have a delay of some time due to the effects of the pulse device sensitivity and pulse start time calibration. Thus, in this embodiment, the impact of pulse delay time may be further considered in the characterization and calibration of the qubit, thereby improving the accuracy of the qubit characterization and calibration.

In some examples, the pulse delay time value may be predetermined based on the corresponding pulse device, e.g., 0.1s or 0s.

Further, in the first state, is |1>In the example of the state, this time t=delay+d. Delay is a constant, representing a pulse Delay time value, typically 0, and there is a Delay value if the starting time is not well calibrated. Probability P ₁ And pulse parametersIs referred to as an a-ratio V-shaped pattern (Rabi chevron pattern).

According to some embodiments, in the plurality of sets of data, there is a ratio of a first data between at least two sets of data being an irrational number, wherein the first data is a product of a pulse amplitude value and a pulse duration value in the same set of data.

Note that the qubit frequency and the drive coefficient are non-tunable parameters, the values of which are constant. When the drive frequency value is equal to the qubit frequency value, the probability that the qubit is in the first state is determined by the pulse amplitude and pulse duration, the other values being constant. Reference to the first state being |1>In the embodiment of the state (when considering the pulse delay time, the value of the pulse delay time may be a predetermined constant, for example, 0), there is a probability P when a×coef×d is a positive integer ₁ =0. To avoid probability P at this time ₁ For 0, in the determined plurality of sets of data, there may be a irrational number as a ratio of first data between at least two sets of data, the first data being a product of a pulse amplitude value and a pulse duration value in the same set of data.

In particular, multiple sets of pulse amplitude values and pulse duration values, e.g., { A }, may be set ₁ ,D ₁ }、{A ₂ ,D ₂ }、{A ₃ ,D ₃ And the like, and the ratio of the a x D values of the at least two sets of pulse parameters is irrational. For example, (A) ₁ *D ₁ )/(A ₂ *D ₂ ) =irrational number. Thus, when f _d ＝f _q Even if P is under a certain set of pulse parameters ₁ =0, and must satisfy P under another set of pulse parameters ₁ Not equal to 0. I.e. with at least one set of pulse parameters, the observation probability P ₁ With the driving frequency f _d Is signaled.

After the multiple sets of pulse amplitude values and pulse duration values are determined, a probability of the qubit being in the first state can be determined as a function of the pulse drive frequency. Specifically, the observation probability P ₁ With the driving frequency f _d Fitting the curve or taking the middle position of the signal according to symmetry to obtain the quantityFrequency f of sub-bit _q . Fitting the probability of the qubit being in the first state with the change of the pulse driving frequency can be conveniently achieved, and will not be described here again.

In step 130, determining an optimal qubit frequency value to take the optimal qubit frequency value as a first qubit frequency value and setting a pulse drive frequency value equal to the optimal qubit frequency value; and in step 140, fitting the probability of the qubit being in the first state with the change of the pulse amplitude according to each of the pulse driving frequency value and one or more preset first pulse duration values to determine the first pulse duration value with the best fitting effect and the corresponding first pulse amplitude value { A } ₄ ,D ₄ }。

Specifically, the driving frequency is set such that f _d ＝f _q One or more pulse duration values, such as 100ns, 200ns, are arbitrarily chosen. Scanning pulse amplitude in a full range of 0 to 1 (the pulse delay time value may be a preset constant when considering the pulse delay time, such as 0), fitting the curve of the Rate oscillation to obtain the pulse amplitude value corresponding to the Pi pulse at each pulse duration value to determine the pulse duration value and the pulse amplitude value with the best fitting effect as the first pulse duration value and the first pulse amplitude value { A } ₄ ,D ₄ }。

In some examples, the first pulse duration value with the best fit is not necessarily the selected pulse duration value, since it is possible that no complete period of the ratio oscillation is scanned, at which point the pulse duration needs to be calculated according to theory.

After the Pi pulse parameters are obtained, the driving coefficient cofe=1/(a) can be calculated ₄ *D ₄ ) As the pulse drive coefficient value. At this point, a set of pulse drive coefficient values, qubit frequency values, have been obtained (i.e., step 130). The pulse delay time value may be a preset constant, for example, 0 when considering the pulse delay time. At this time, a scan experiment can be performed based on the set of values to determine a set of values by observing the qubit spectral lines Adjustable pulse parameter values including their amplitude a, duration D and drive frequency f _d 。

In some embodiments, forward prediction may be advanced when determining the value of each of the at least one parameter based on the probability as a function of the at least one parameter (i.e., step 160). That is, an arbitrary pulse is input according to its amplitude A, duration D and driving frequency f _d The excitation probability of the qubit in a certain state, such as P, can be obtained ₁ . The excitation probability P of the qubit can be predicted for any pulse ₁ . This can also be used to predict the outcome of a scan experiment, i.e. as a look-up table for use.

In some examples, a fixed pulse amplitude, a scan pulse duration D, and a drive frequency f may be predicted _d The experimental results of these two dimensions, such as the fixed driving frequency, the scanning pulse amplitude a and the pulse duration D, can be predicted. These experiments are also often used in the characterization and calibration of quantum devices. After the corresponding scanning result is obtained, appropriate pulse parameters can be automatically provided in the scanning result according to the user requirement.

Illustratively, the user wishes to scan the pulse drive frequency f _d When the obtained quantum bit spectral line has only one peak, and the line width of the peak is a certain set value, pulse amplitude and duration parameters meeting the conditions can be given according to the scanning result, which is very useful in representing the curve between the Z line voltage and the quantum bit frequency. Alternatively, where the user wishes to scan the pulse amplitude or pulse duration from zero, a certain number of periods of the ratio oscillation can be seen, and pulse parameters meeting the conditions can be given from the scan results, which is very useful in the subsequent accurate characterization and calibration of Pi pulses.

According to some embodiments, as shown in fig. 2, before scanning at least one parameter of the pulse amplitude, the pulse duration and the driving frequency within a preset corresponding first value range, the method 200 further includes: determining a second pulse duration value and a second pulse amplitude value based on the drive coefficient value, a preset number of pull-up oscillation cycles (step 210); fitting a probability of the qubit being in a first state as a function of drive frequency based on the second pulse duration value, second pulse amplitude value, and the drive coefficient value to determine a linewidth of a qubit spectral line (step 220); determining a second scan range corresponding to the qubit frequency based on the line width, and determining a third scan range corresponding to the pulse amplitude based on the second pulse amplitude value (step 230); and scanning based on the second pulse duration value and based on the second scanning range and the third scanning range, respectively, fitting a probability that the qubit is in a first state with a change in the qubit frequency and the pulse amplitude to redetermine the pulse drive coefficient value and the first qubit frequency value based on a fitting result (step 240).

In some examples, the pulse drive coefficient value and the qubit frequency value determined based on the fitting result may be used as the new pulse drive coefficient value and the first qubit frequency value. Thus, at least one parameter of the pulse amplitude, pulse duration and said driving frequency is scanned within a preset corresponding first range of values based on the new pulse drive coefficient value and the first qubit frequency value, and values of the other parameters of the pulse amplitude, pulse duration and driving frequency than the at least one parameter are determined to determine the value of each of the at least one parameter based on the probability as a function of the at least one parameter, i.e. based on the new pulse drive coefficient value and the first qubit frequency value, said step 160 is performed.

In this embodiment, the preset number of pull-up oscillation cycles N is constant, typically greater than 1, e.g., n=2.5, 3, 4, etc. Based on the calculated drive coefficient value Coef and the preset ratio oscillation period number N, a third pulse duration value D can be determined ₅ And a third pulse amplitude value A ₅ Satisfy A ₅ *Coef*D ₅ =n. Based on the above parameters, probability P can be obtained ₁ With driving frequency f _d The change curve of (a) is calculated to obtain a lineWide Width.

According to some embodiments, the linewidth of the qubit spectral line is determined according to the following operations: determining a half-height line based on half of the peak-to-peak value of the qubit spectral line; and determining a maximum distance between two intersections of the quantum bit spectral line based on the intersections of the quantum bit spectral line and the half-height line, to take the maximum distance as the line width.

As shown in fig. 3, half of the height H between the peaks and troughs of the spectral line is determined as the half-height line, i.e. L. The half-height line and the spectral line form a plurality of intersection points, and the maximum distance between the two intersection points can be used as the line Width.

It will be appreciated that the line width may be determined by the user based on any suitable means, and is not limited in this regard.

According to some embodiments, the second scan range includes [ f _q1 -Width,f _q1 +Width]Wherein Width is the line Width, f _q1 Representing the first qubit frequency value.

According to some embodiments, the third scan range includes [0, A ₅ ]Wherein A is ₅ And the third pulse amplitude value.

In this embodiment, some pulse initial values, including the qubit frequency f, can be roughly obtained through steps 110-150 and 210 _q The drive coefficient Coef, the determined line Width of the qubit line, and a set of third pulse duration values and third pulse amplitude values (the pulse delay time values may be preset constants, e.g. 0, when considering the pulse delay time). Based on the initial values, the number of scanning points required by the follow-up process can be greatly reduced, so that the representation and calibration efficiency of the quantum bit are improved; and, these initial values can be used as the initial fitting values in the fitting process of step 240, thereby improving the fitting success rate.

It will be appreciated that the second and third scan ranges described above are exemplary only and are not limiting herein.

FIG. 4 shows a schematic representation of the results of a two-dimensional scan experiment in step 240 according to an embodiment of the present disclosureA drawing. As shown in FIG. 4, the schematic color represents the probability that the qubit is in the first state, e.g., P ₁ . FIG. 5 shows a schematic diagram of fitting results based on a theoretical model, wherein goodness of fit r, according to an embodiment of the present disclosure ² ＝0.93。

To verify the predictive effect of the model, the pulse amplitude a=0.6, the scan pulse duration as the first dimension, the scan drive frequency as the second dimension, the predicted IQ value (i.e. corresponding to the probability P ₁ ) The results are shown in the graph of fig. 6A, and the experiment is carried out on the real machine, and the obtained experimental results are shown in the graph of fig. 6B, so that the experimental results are very consistent with the predicted results. And it is noted that the theoretical prediction results herein are mostly not in the experimental data in fig. 4, and belong to new experimental data, indicating that the model can predict experimental results other than the fitted experimental data.

To further verify the correctness of the model predictions, the driving frequency is fixed such that f _d ＝f _q The pulse amplitude and duration are scanned, the IQ value is predicted, the result is shown in the graph of FIG. 7A, and an experiment is carried out on a real machine, the obtained experimental result is shown in the graph of FIG. 7B, so that the result is very consistent with the predicted result. Also here, most of the data are new experimental data different from the above two experiments, indicating that the model can predict experimental results other than the fitted experimental data.

With continued reference to FIG. 2, more accurate constant parameters, including the qubit frequency f, can generally be further obtained by the steps shown in FIG. 2 _q Driving coefficient Coef. According to some embodiments, redefining the second pulse drive coefficient value and the first qubit frequency value based on the fitting result includes: the second pulse drive coefficient value, the first qubit frequency value, and the pulse delay time value are redetermined based on the fitting result. That is, when considering the pulse Delay time, a more accurate pulse Delay time Delay can be further obtained by fitting. In this way, pulse parameters with smaller errors can be provided automatically.

According to some embodiments, fitting the probability of the qubit being in the first state as a function of the qubit frequency and the pulse amplitude to redetermine the second pulse drive coefficient value and the first qubit frequency value based on the fitting result comprises: in response to determining that the goodness of fit is greater than a preset threshold, taking the pulse drive coefficient value and the qubit frequency value redetermined based on the fitting result as new pulse drive coefficient value and the first qubit frequency value; and in response to determining that the goodness of fit is not greater than the preset threshold, leaving the pulse drive coefficient value and the first qubit frequency value unchanged.

That is, a goodness of fit may be further determined in step 240 to further determine whether to perform a scan experiment based on the original pulse drive coefficient value and the original first qubit frequency value or whether to perform a scan experiment based on the pulse drive coefficient value and the first qubit frequency value that were redetermined by the fit.

There is also provided, in accordance with an embodiment of the present disclosure, as in fig. 8, a pulse-based qubit manipulation device 800 comprising: a first determining unit 810 configured to determine a plurality of sets of data, each set of data including a pair of pulse amplitude values and pulse duration values; a second determining unit 820 configured to determine, based on the plurality of sets of data, a variation curve of probability of the qubit in the first state with a pulse driving frequency, respectively, so as to determine a qubit frequency value corresponding to each of the plurality of sets of data, wherein the probability is determined based on a pulse amplitude, a pulse duration, a pulse driving frequency, a qubit frequency, and a pulse driving coefficient; a third determining unit 830 configured to determine an optimal qubit frequency value to take the optimal qubit frequency value as a first qubit frequency value and set a pulse drive frequency value equal to the optimal qubit frequency value; a first fitting unit 840 configured to fit the probability of the qubit being in the first state with the change of the pulse amplitude according to each of the pulse driving frequency value and one or more preset first pulse duration values, so as to determine a first pulse duration value with the best fitting effect and a corresponding first pulse amplitude value; a fourth determining unit 850 configured to determine a pulse drive coefficient value based on the optimal first pulse duration value and the corresponding first pulse amplitude value; and a first scanning unit 860 configured to scan at least one parameter of the pulse amplitude, the pulse duration, and the driving frequency over a preset corresponding first range of values based on the pulse driving coefficient value and the first qubit frequency value, and to determine values of other parameters of the pulse amplitude, the pulse duration, and the driving frequency than the at least one parameter, to determine values of each of the at least one parameter based on a variation curve of the probability with the at least one parameter.

Here, the operations of the above-described units 810 to 860 of the pulse-based qubit operation apparatus 800 are similar to the operations of the steps 110 to 160 described above, respectively, and are not repeated here.

According to embodiments of the present disclosure, there is also provided an electronic device, a readable storage medium and a computer program product.

Referring to fig. 9, a block diagram of an electronic device 900 that may be a server or a client of the present disclosure, which is an example of a hardware device that may be applied to aspects of the present disclosure, will now be described. Electronic devices are intended to represent various forms of digital electronic computer devices, such as laptops, desktops, workstations, personal digital assistants, servers, blade servers, mainframes, and other suitable computers. The electronic device may also represent various forms of mobile devices, such as personal digital processing, cellular telephones, smartphones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions, are meant to be exemplary only, and are not meant to limit implementations of the disclosure described and/or claimed herein.

As shown in fig. 9, the electronic device 900 includes a computing unit 901 that can perform various appropriate actions and processes according to a computer program stored in a Read Only Memory (ROM) 902 or a computer program loaded from a storage unit 908 into a Random Access Memory (RAM) 903. In the RAM 903, various programs and data required for the operation of the electronic device 900 can also be stored. The computing unit 901, the ROM 902, and the RAM 903 are connected to each other by a bus 904. An input/output (I/O) interface 905 is also connected to the bus 904.

A number of components in the electronic device 900 are connected to the I/O interface 905, including: an input unit 906, an output unit 907, a storage unit 908, and a communication unit 909. The input unit 906 may be any type of device capable of inputting information to the electronic device 900, the input unit 906 may receive input numeric or character information and generate key signal inputs related to user settings and/or function control of the electronic device, and may include, but is not limited to, a mouse, a keyboard, a touch screen, a trackpad, a trackball, a joystick, a microphone, and/or a remote control. The output unit 907 may be any type of device capable of presenting information and may include, but is not limited to, a display, speakers, video/audio output terminals, vibrators, and/or printers. Storage unit 908 may include, but is not limited to, magnetic disks, optical disks. The communication unit 909 allows the electronic device 900 to exchange information/data with other devices through a computer network such as the internet and/or various telecommunications networks, and may include, but is not limited to, modems, network cards, infrared communication devices, wireless communication transceivers and/or chipsets, such as bluetooth devices, 802.11 devices, wiFi devices, wiMax devices, cellular communication devices, and/or the like.

The computing unit 901 may be a variety of general and/or special purpose processing components having processing and computing capabilities. Some examples of computing unit 901 include, but are not limited to, a Central Processing Unit (CPU), a Graphics Processing Unit (GPU), various specialized Artificial Intelligence (AI) computing chips, various computing units running machine learning model algorithms, a Digital Signal Processor (DSP), and any suitable processor, controller, microcontroller, etc. The computing unit 901 performs the various methods and processes described above, such as method 100. For example, in some embodiments, the method 100 may be implemented as a computer software program tangibly embodied on a machine-readable medium, such as the storage unit 908. In some embodiments, part or all of the computer program may be loaded and/or installed onto the electronic device 900 via the ROM 902 and/or the communication unit 909. When the computer program is loaded into RAM 903 and executed by computing unit 901, one or more steps of method 100 described above may be performed. Alternatively, in other embodiments, the computing unit 901 may be configured to perform the method 100 by any other suitable means (e.g., by means of firmware).

Various implementations of the systems and techniques described here above may be implemented in digital electronic circuitry, integrated circuit systems, field Programmable Gate Arrays (FPGAs), application Specific Integrated Circuits (ASICs), application Specific Standard Products (ASSPs), systems On Chip (SOCs), complex Programmable Logic Devices (CPLDs), computer hardware, firmware, software, and/or combinations thereof. These various embodiments may include: implemented in one or more computer programs, the one or more computer programs may be executed and/or interpreted on a programmable system including at least one programmable processor, which may be a special purpose or general-purpose programmable processor, that may receive data and instructions from, and transmit data and instructions to, a storage system, at least one input device, and at least one output device.

Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program code may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus such that the program code, when executed by the processor or controller, causes the functions/operations specified in the flowchart and/or block diagram to be implemented. The program code may execute entirely on the machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of this disclosure, a machine-readable medium may be a tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. The machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. The machine-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of a machine-readable storage medium would include an electrical connection based on one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

To provide for interaction with a user, the systems and techniques described here can be implemented on a computer having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to a user; and a keyboard and pointing device (e.g., a mouse or trackball) by which a user can provide input to the computer. Other kinds of devices may also be used to provide for interaction with a user; for example, feedback provided to the user may be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user may be received in any form, including acoustic input, speech input, or tactile input.

The systems and techniques described here can be implemented in a computing system that includes a background component (e.g., as a data server), or that includes a middleware component (e.g., an application server), or that includes a front-end component (e.g., a user computer having a graphical user interface or a web browser through which a user can interact with an implementation of the systems and techniques described here), or any combination of such background, middleware, or front-end components. The components of the system can be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include: local Area Networks (LANs), wide Area Networks (WANs), the internet, and blockchain networks.

The computer system may include a client and a server. The client and server are typically remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other. The server may be a cloud server, a server of a distributed system, or a server incorporating a blockchain.

It should be appreciated that various forms of the flows shown above may be used to reorder, add, or delete steps. For example, the steps recited in the present disclosure may be performed in parallel, sequentially or in a different order, provided that the desired results of the disclosed aspects are achieved, and are not limited herein.

Although embodiments or examples of the present disclosure have been described with reference to the accompanying drawings, it is to be understood that the foregoing methods, systems, and apparatus are merely exemplary embodiments or examples, and that the scope of the present invention is not limited by these embodiments or examples but only by the claims following the grant and their equivalents. Various elements of the embodiments or examples may be omitted or replaced with equivalent elements thereof. Furthermore, the steps may be performed in a different order than described in the present disclosure. Further, various elements of the embodiments or examples may be combined in various ways. It is important that as technology evolves, many of the elements described herein may be replaced by equivalent elements that appear after the disclosure.

Claims

1. A method of pulse-based qubit operation, comprising:

Determining a plurality of sets of data, each set of data comprising a pair of pulse amplitude values and pulse duration values;

determining a change curve of probability of the quantum bit in a first state along with pulse driving frequency based on the plurality of groups of data respectively to determine quantum bit frequency values corresponding to the plurality of groups of data respectively, wherein the probability is determined based on pulse amplitude, pulse duration, pulse driving frequency, quantum bit frequency and pulse driving coefficient;

determining an optimal qubit frequency value to take the optimal qubit frequency value as a first qubit frequency value and setting a pulse drive frequency value equal to the optimal qubit frequency value;

fitting the probability of the quantum bit in a first state along with the change of the pulse amplitude according to each of the pulse driving frequency value and one or more preset first pulse duration values so as to determine a first pulse duration value with the optimal fitting effect and a corresponding first pulse amplitude value;

determining a pulse drive coefficient value based on the optimal first pulse duration value and the corresponding first pulse amplitude value; and

Scanning at least one parameter of the pulse amplitude, the pulse duration and the driving frequency within a preset corresponding first value range based on the pulse driving coefficient value and the first qubit frequency value, and determining values of other parameters of the pulse amplitude, the pulse duration and the driving frequency except the at least one parameter to determine the value of each of the at least one parameter based on a variation curve of the probability with the at least one parameter.

2. The method of claim 1, wherein among the plurality of sets of data, there is a irrational number of a ratio of first data between at least two sets of data, wherein the first data is a product of a pulse amplitude value and a pulse duration value in the same set of data.

3. The method of claim 1, wherein scanning at least one parameter of the pulse amplitude, the pulse duration, and the drive frequency over a preset corresponding first range of values further comprises:

determining a second pulse duration value and a second pulse amplitude value based on the drive coefficient value and a preset ratio oscillation period number;

Fitting the probability of the qubit being in a first state with a change in drive frequency based on the second pulse duration value, a second pulse amplitude value and the drive coefficient value to determine a linewidth of a qubit spectral line;

determining a second scanning range corresponding to the quantum bit frequency based on the line width, and determining a third scanning range corresponding to the pulse amplitude based on the second pulse amplitude value; and

and respectively scanning based on the second pulse duration value and the second scanning range and the third scanning range, and fitting the probability of the qubit in a first state along with the change of the qubit frequency and the pulse amplitude so as to redetermine the pulse drive coefficient value and the first qubit frequency value based on fitting results.

4. A method as claimed in claim 3, wherein fitting the probability of the qubit being in the first state as a function of the qubit frequency and the pulse amplitude to redetermine the pulse drive coefficient value and the first qubit frequency value based on the fitting result comprises:

in response to determining that the goodness of fit is greater than a preset threshold, taking the pulse drive coefficient value and the qubit frequency value redetermined based on the fitting result as new pulse drive coefficient value and the first qubit frequency value; and

In response to determining that the goodness of fit is not greater than the preset threshold, leaving the pulse drive coefficient value and the first qubit frequency value unchanged.

5. A method as claimed in claim 3, wherein the linewidth of the qubit spectral line is determined in accordance with:

determining a half-height line based on half of the peak-to-peak value of the qubit spectral line; and

based on the intersection of the qubit spectral line and the half-height line, determining the maximum distance between two intersection points of the qubit spectral line, and taking the maximum distance as the line width.

6. The method of claim 3, wherein the probability that the qubit is in the first state is further determined based on a pulse delay time, and wherein determining the plurality of sets of data comprises: a preset pulse delay time value is determined.

7. The method of claim 6, wherein redefining the pulse drive coefficient value and the first qubit frequency value based on fitting results comprises: the pulse drive coefficient value, the first qubit frequency value, and the pulse delay time value are redetermined based on the fitting result.

8. The method of any one of claims 1-7, wherein the first state is |1 >State, and the probability P ₁ The determination is made according to the following equation:

wherein omega ₁ Coef, where Coef is the drive factor, a is the pulse amplitude,wherein f _d For the driving frequency f _q For the qubit frequency, t is a time determined based on the pulse duration.

9. A method as claimed in claim 3, wherein the second scan range comprises [ f ] _q1 -Width,f _q1 +Width]Wherein Width is the line Width, f _q1 Representing the first quantumBit frequency values.

10. The method of claim 3, wherein the third scan range comprises [0, a ] ₁ ]Wherein A is ₁ And the third pulse amplitude value.

11. A pulse-based qubit manipulation device comprising:

a first determining unit configured to determine a plurality of sets of data, each set of data including a pair of pulse amplitude values and pulse duration values;

a second determining unit configured to determine a variation curve of probability of the quantum bit in a first state with a pulse driving frequency based on the plurality of sets of data, respectively, so as to determine a quantum bit frequency value corresponding to each of the plurality of sets of data, wherein the probability is determined based on a pulse amplitude, a pulse duration, a pulse driving frequency, a quantum bit frequency, and a pulse driving coefficient;

A third determination unit configured to determine an optimal qubit frequency value to take the optimal qubit frequency value as a first qubit frequency value, and to set a pulse drive frequency value equal to the optimal qubit frequency value;

the first fitting unit is configured to fit the probability of the quantum bit in a first state along with the change of the pulse amplitude according to each of the pulse driving frequency value and one or more preset first pulse duration values so as to determine a first pulse duration value with the best fitting effect and a corresponding first pulse amplitude value;

a fourth determination unit configured to determine a pulse drive coefficient value based on the optimal first pulse duration value and the corresponding first pulse amplitude value; and

a first scanning unit configured to scan at least one parameter of the pulse amplitude, the pulse duration, and the driving frequency within a preset corresponding first value range based on the pulse driving coefficient value and the first qubit frequency value, and determine values of other parameters of the pulse amplitude, the pulse duration, and the driving frequency than the at least one parameter, so as to determine a value of each of the at least one parameter based on a variation curve of the probability with the at least one parameter.

12. The apparatus of claim 11, wherein among the plurality of sets of data, there is a irrational number of a ratio of first data between at least two sets of data, wherein the first data is a product of a pulse amplitude value and a pulse duration value in the same set of data.

13. The apparatus of claim 11, further comprising:

a fifth determining unit configured to determine a second pulse duration value and a second pulse amplitude value based on the drive coefficient value and a preset ratio oscillation period number before scanning at least one parameter of the pulse amplitude, the pulse duration, and the drive frequency within a preset corresponding first value range;

a second fitting unit configured to fit a probability of the qubit being in a first state with a change in a driving frequency based on the second pulse duration value, a second pulse amplitude value, and the driving coefficient value, to determine a linewidth of a qubit spectral line;

a sixth determining unit configured to determine a second scanning range corresponding to the qubit frequency based on the line width, and determine a third scanning range corresponding to the pulse amplitude based on the second pulse amplitude value; and

And a second scanning unit configured to scan based on the second pulse duration value and based on the second scanning range and the third scanning range, respectively, and fit a probability of the qubit being in a first state to a change of the qubit frequency and the pulse amplitude, so as to redetermine the pulse drive coefficient value and the first qubit frequency value based on a fitting result.

14. The apparatus of claim 13, wherein the second scanning unit comprises:

a first response subunit configured to, in response to determining that the goodness of fit is greater than a preset threshold, take as new said pulse drive coefficient value and said first qubit frequency value a pulse drive coefficient value and a qubit frequency value redetermined based on the fitting result; and

a second response subunit configured to leave the pulse drive coefficient value and the first qubit frequency value unchanged in response to determining that the goodness of fit is not greater than the preset threshold.

15. The apparatus of claim 13, wherein a linewidth of the qubit spectral line is determined according to:

16. The apparatus of claim 13, wherein the probability that the qubit is in the first state is further determined based on a pulse delay time, and wherein determining the plurality of sets of data comprises: a preset pulse delay time value is determined.

17. The apparatus of claim 16, wherein the second scanning unit comprises a determination subunit configured to: the pulse drive coefficient value, the first qubit frequency value, and the pulse delay time value are redetermined based on the fitting result.

18. The apparatus of any one of claims 11-17, wherein the first state is |1>State, and the probability P ₁ The determination is made according to the following equation:

19. The apparatus of claim 13, wherein the second scan range comprises [ f ] _q1 -Width,f _q1 +Width]Wherein Width is the line Width, f _q1 Representing the first qubit frequency value.

20. The apparatus of claim 13, wherein the third scan range comprises [0, a ₁ ]Wherein A is ₁ And the third pulse amplitude value.

21. An electronic device, comprising:

at least one processor; and

a memory communicatively coupled to the at least one processor; wherein the method comprises the steps of

The memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method of any one of claims 1-10.

22. A non-transitory computer readable storage medium storing computer instructions for causing the computer to perform the method of any one of claims 1-10.

23. A computer program product comprising a computer program, wherein the computer program, when executed by a processor, implements the method of any of claims 1-10.