A method and device for detecting a quantum state

Abstract

The present application discloses a method and apparatus for quantum state detection, including: performing a first operation on a qubit array to make the photon distributions of any qubits independent of each other; calibrating the bright-state photon distribution and dark-state photon distribution of each qubit in the qubit array for the qubits after the first operation; irradiating the qubit array to be detected for quantum state with detection laser, and determining the bright / dark state of each qubit based on the bright-state photon distribution and dark-state photon distribution of each qubit according to the likelihood function of the photon distribution of the qubit array; and obtaining the state of the qubit array according to the determined bright / dark state of each qubit. The embodiment of the present disclosure determines the bright / dark state through the likelihood function, reduces the influence of crosstalk on the quantum state detection result, and improves the fidelity of quantum state detection.

Description

Technical Field

[0001] This application relates to, but is not limited to, quantum computing technology, and in particular, to a method and apparatus for quantum state detection. Background Art

[0002] Quantum state detection is a crucial part of quantum computing and quantum information processing; quantum state detection is usually based on the statistics of the number of fluorescent photons and the photon distribution information; through quantum state detection, the information of qubits can be effectively extracted. However, with the expansion of the scale of quantum computing, the requirements for quantum state detection are also getting higher and higher, especially in terms of fast and high-fidelity detection, which is crucial for the effective implementation of quantum computing.

[0003] In the quantum state detection of single qubits, the detection by a photomultiplier tube (PMT) is a commonly used detection method; the PMT detector has the advantages of high sensitivity and fast response, and can detect weak optical signals in a short time. However, the PMT detection lacks spatial resolution ability and can only provide overall photon counting information; this limitation becomes particularly obvious when facing large-scale qubit detection and cannot efficiently handle complex qubit arrays.

[0004] To achieve the quantum state detection of large-scale qubits, there are several different methods in related technologies: 1. Array PMT detection: Using multiple PMT detection units with fixed spacing, arranged in an array form for detection; although multiple qubits can be detected simultaneously, its electrical crosstalk is large, and the spacing of the PMT detection units is fixed, requiring the distance between qubits to be strictly controlled; this rigid limitation makes it not flexible enough and difficult to expand in practical applications. 2. Fiber array detection: Using a fiber array to collect fluorescent photons, each fiber corresponding to a PMT detector; the fiber array can effectively reduce electrical crosstalk; but this method is still limited by the fiber spacing and requires qubits to be arranged at specific intervals; for non-equidistant and irregularly arranged two-dimensional qubit arrays, there are still inconveniences. 3. Two-dimensional array camera detection: Cameras such as electron-multiplying charge-coupled device (EMCCD) and complementary metal-oxide semiconductor device (CMOS) use a two-dimensional array structure and can obtain detailed spatial distribution information of the qubit array, Figure 1 which is a schematic diagram of the two-dimensional distribution of the fluorescence emitted by qubits in related technologies, as Figure 1 shown, the two-dimensional distribution of the fluorescence emitted by a one-dimensional 92-qubit chain on the EMCCD; this detection method has high flexibility and can handle two-dimensional qubit arrays with arbitrary arrangements, whether equidistant or irregularly arranged, which makes the two-dimensional array camera an ideal choice for large-scale qubit detection.

[0005] Quantum state detection is usually achieved by accumulating the number of photons. The dark state |0> theoretically does not emit fluorescence, that is, the number of emitted photons is 0. However, due to the scattered light generated by the laser irradiation during the detection process being collected, the actual number of photons is actually a number close to 0. The bright state |1> emits more fluorescence and can collect photons through a quantum state detector. The photon distribution of qubits follows a Poisson distribution. When the average count difference between the photons in the bright state and the dark state is large enough, these two states can be distinguished by statistical methods, thereby realizing the detection of the bright and dark states; Figure 2 is a schematic diagram of the photon distribution of qubits in related technologies, as Figure 2 shown. The dotted envelope is the photon distribution of the dark state, the solid envelope is the photon distribution of the bright state, and the black vertical line is the threshold n for distinguishing the bright state and the dark state th , when the number of photons in a single acquisition is greater than n th it is the bright state. Conversely, when the number of photons in a single acquisition is less than or equal to n th it is the dark state. This method is theoretically efficient and accurate. Although the above detection method performs excellently under ideal conditions, in practical applications, the imperfection of optical imaging will introduce a large number of crosstalk photons; the crosstalk photons, detector noise, and signal photons cannot be effectively distinguished, resulting in a decrease in the signal-to-noise ratio of the detection signal and limiting the high-fidelity quantum state detection.

[0006] In summary, how to reduce crosstalk in the actual quantum state detection process and improve the fidelity of quantum state detection is still an urgent problem to be solved. Summary of the Invention

[0007] The following is an overview of the subject matter described in detail in this application. This overview is not intended to limit the scope of protection of the claims.

[0008] Embodiments of the present disclosure provide a method and device for quantum state detection, which can reduce the influence of crosstalk in the actual quantum state detection process and improve the fidelity of quantum state detection.

[0009] Embodiments of the present disclosure provide a method for quantum state detection, including:

[0010] Performing a first operation on a qubit array to make the photon distributions of any qubits independent of each other;

[0011] Calibrating the bright-state photon distribution and dark-state photon distribution of each qubit in the qubit array for the qubits that have undergone the first operation;

[0012] Irradiating the qubit array to be detected for quantum state detection with detection laser, and determining the bright and dark states of each qubit based on the bright-state photon distribution and dark-state photon distribution of each qubit according to the likelihood function of the photon distribution of the qubit array;

[0013] Based on the determined bright and dark states of each qubit, the state of the qubit array is obtained.

[0014] On the other hand, an embodiment of the present disclosure further provides a quantum state detection device, including: an operation unit, a calibration unit, a determination unit, and a determination unit; wherein,

[0015] The operation unit is configured to: perform a first operation on the qubit array so that the photon distributions of any qubits are independent of each other;

[0016] The calibration unit is configured to: calibrate the bright-state photon distribution and the dark-state photon distribution of each qubit in the qubit array for the qubits that have undergone the first operation;

[0017] The determination unit is configured to: irradiate the qubit array to be detected for quantum state with detection laser light, and based on the bright-state photon distribution and the dark-state photon distribution of each qubit, determine the bright and dark states of each qubit according to the likelihood function of the photon distribution of the qubit array;

[0018] The determination unit is configured to: obtain the state of the qubit array according to the determined bright and dark states of each qubit.

[0019] When calibrating the bright-state and dark-state photon distributions of qubits in the embodiments of the present disclosure, the photon distributions of each qubit are independent of each other, reducing the timing complexity; the bright and dark states are judged through the likelihood function, reducing the influence of crosstalk on the quantum state detection result and improving the fidelity of quantum state detection.

[0020] Other features and advantages of the present application will be described in the subsequent specification, and part of them will become obvious from the specification, or be understood by implementing the present application. Other advantages of the present application can be realized and obtained through the solutions described in the specification and the drawings. Description of the Drawings

[0021] The drawings are used to provide an understanding of the technical solutions of the present application, and constitute a part of the specification. They are used together with the embodiments of the present application to explain the technical solutions of the present application, and do not constitute a limitation to the technical solutions of the present application.

[0022] Figure 1 It is a schematic diagram of the two-dimensional distribution of fluorescence emitted by qubits in the related art;

[0023] Figure 2 It is a schematic diagram of the photon distribution of qubits in the related art;

[0024] Figure 3 It is a flowchart of the method for quantum state detection in the embodiments of the present disclosure;

[0025] Figure 4Structural block diagram of the device for quantum state detection according to an embodiment of the present disclosure. Detailed implementation manners

[0026] This application describes multiple embodiments, but the description is exemplary rather than restrictive, and it will be obvious to those of ordinary skill in the art that there can be more embodiments and implementation solutions within the scope covered by the embodiments described in this application. Although many possible feature combinations are shown in the drawings and discussed in the detailed implementation manners, many other combination ways of the disclosed features are also possible. Unless specifically restricted, any feature or element of any embodiment can be combined with any other feature or element in any other embodiment, or can replace any other feature or element in any other embodiment.

[0027] This application includes and contemplates combinations with features and elements known to those of ordinary skill in the art. The embodiments, features, and elements already disclosed in this application can also be combined with any conventional features or elements to form unique inventive solutions defined by the claims. Any feature or element of any embodiment can also be combined with features or elements from other inventive solutions to form another unique inventive solution defined by the claims. Therefore, it should be understood that any feature shown and / or discussed in this application can be implemented alone or in any suitable combination. Therefore, the embodiments are not subject to other restrictions except those made according to the appended claims and their equivalent replacements. In addition, various modifications and changes can be made within the scope of the protection of the appended claims.

[0028] In addition, when describing representative embodiments, the specification may have presented the method and / or process as a specific sequence of steps. However, to the extent that the method or process does not depend on the specific order of the steps described herein, the method or process should not be limited to the specific order of steps described. As will be understood by those of ordinary skill in the art, other step sequences are possible. Therefore, the specific order of steps set forth in the specification should not be construed as a limitation on the claims. In addition, the claims directed to the method and / or process should not be limited to performing their steps in the order written, and those skilled in the art can easily understand that these orders can be changed and still remain within the spirit and scope of the embodiments of this application.

[0029] To facilitate the understanding of the embodiments of the present disclosure, the following defines the Bayesian estimation and independent component analysis (ICA) methods that appear in the examples of the embodiments of the present disclosure; among them, Bayesian estimation is a statistical method that updates the belief distribution of parameters by combining prior knowledge and observed data, and the basic formula is:

[0030]

[0031] In the formula, P(θ|D) is the posterior distribution of parameter θ after the given data D; P(D|θ) is the likelihood function of data D under the given parameter θ; P(θ) is the prior distribution of parameter θ; P(D) is the marginal likelihood of data D; in the case of non-informative prior, a uniform distribution is usually used as the prior distribution to make the Bayesian estimation consistent with the maximum likelihood estimation.

[0032] ICA is a statistical and computational technique used to decompose an observed multivariate signal into independent non-Gaussian signal components; the basic model is x = As, where x is the observed signal vector, A is the unknown mixing matrix, and s is the independent component vector. The goal of ICA is to find the demixing matrix W such that s = Wx, making the components of the independent component s statistically independent of each other.

[0033] To achieve efficient quantum state detection, the embodiments of the present disclosure use the method of Bayesian estimation, utilize the spatial distribution of photons to assist in the detection of quantum states, and use independent component analysis to quickly calibrate the parameters of Bayesian estimation; as Figure 1 shown in the measurement of qubits based on EMCCD, a two-dimensional spatial distribution of fluorescence can be obtained, and this distribution provides more spatial information compared to detectors such as PMT; if simply adding up the pixel counts near each qubit degenerates into single-pixel detection, but compared to PMT arrays and fiber arrays, etc., it still has better programmability and scalability because EMCCD and CMOS generally have millions or tens of millions of pixels, and each pixel can be photosensitive, that is, the embodiments of the present disclosure can obtain a photon matrix distribution I(x, y) for qubit detection, where (x, y) represents the row and column numbers of the pixels; the photon distribution of the bright state of the qubit is B(x, y), and the photon distribution of the dark state is D(x, y). For the convenience of subsequent scheme introduction, the embodiments of the present disclosure uniformly use the letter B and its extensions (B′ and B〞) to distinguish and represent the bright-state photon distribution, and use the letter D and its extensions (D′ and D〞) to distinguish and represent the dark-state photon distribution. For the measurement of unknown quantum states, it belongs to non-informative prior, that is, P(B) = P(D) = 0.5. Therefore, the embodiments of the present disclosure can use the maximum likelihood estimation to calculate the probabilities of the bright and dark states; the likelihood function depends on the detection device, and the related parameter Θ can be calibrated through a single dark exposure image.

[0034] Figure 3 is the flowchart of the method for quantum state detection in the embodiments of the present disclosure, as Figure 3 shown, including:

[0035] Step 301, perform a first operation on the qubit array to make the photon distributions of any qubits independent of each other;

[0036] Step 302: For the qubits that have undergone the first operation, calibrate the bright-state photon distribution and dark-state photon distribution of each qubit in the qubit array.

[0037] Step 303: Irradiate the qubit array for which quantum state detection is to be performed with a detection laser. Based on the bright-state photon distribution and dark-state photon distribution of each qubit, determine the bright and dark states of each qubit according to the likelihood function of the photon distribution of the qubit array.

[0038] Step 304: Obtain the state of the qubit array according to the determined bright and dark states of each qubit.

[0039] The qubit types in the embodiments of the present disclosure include atomic qubits, ion qubits, etc.

[0040] When the embodiments of the present disclosure perform calibration on the bright-state and dark-state photon distributions of qubits, the photon distributions of each qubit are independent of each other, reducing the timing complexity; the embodiments of the present disclosure use the likelihood function to judge the bright and dark states, reducing the influence of crosstalk on the quantum state detection result and improving the fidelity of the quantum state detection. Since the spatial distributions of detector noise and scattering noise are different from those of signal photons, the embodiments of the present disclosure effectively distinguish detector noise, scattering noise from signal photons, providing an operation basis for improving the fidelity of quantum state detection.

[0041] In the embodiments of the present disclosure, the photon distributions of any two qubits are independent of each other, which can be achieved in the following ways:

[0042] For the qubit array, illuminate only one qubit at a time;

[0043] For the qubit array, illuminate only some qubits at a time, and the illuminated qubits satisfy that there is at least one qubit between any two qubits;

[0044] Initialize all qubits in the dark state, and then prepare all qubits in the superposition state of the bright state and the dark state through a π / 2 pulse, where |0> represents the dark state of the qubit and |1> represents the bright state of the qubit.

[0045] In an exemplary example, the photon distributions of any two qubits in the embodiments of the present disclosure are independent of each other, including: for any i-th qubit and j-th qubit where the matrix represents the spin component operator of the i-th qubit in the z direction, the matrix represents the spin component operator of the j-th qubit in the z direction.

[0046] In an exemplary instance, the first operation of the embodiments of the present disclosure includes:

[0047] Initializing all qubits in the dark state;

[0048] Preparing all qubits in a superposition state of the bright state and the dark state through a π / 2 pulse; where |0> represents the dark state of the qubit and |1> represents the bright state of the qubit.

[0049] Corresponding to the above first operation, in an exemplary instance, the bright state photon distribution of each qubit in the qubit array of the embodiments of the present disclosure is calibrated through the following processing:

[0050]

[0051] Irradiating the qubit array that has undergone the first operation with a preset detection laser to obtain the photon distribution of the qubit array, and obtaining the bright state photon distribution of each qubit by using the independent component analysis method.

[0052] In an exemplary instance, the first operation in the embodiments of the present disclosure includes: initializing all qubits in the dark state. Correspondingly, the dark state photon distribution of each qubit in the qubit array is calibrated through the following processing: irradiating the qubit array that has undergone the first operation with a preset detection laser to obtain the photon distribution of the qubit array; obtaining the dark state photon distribution of each qubit by using the independent component analysis method; or irradiating the qubit array that has undergone the first operation with a preset detection laser to obtain the photon distribution of the qubit array, and taking the photon distribution in the pixel matrix corresponding to each qubit in the photon distribution of the qubit array as the dark state photon distribution of the corresponding qubit.

[0053] The embodiments of the present disclosure determine the bright and dark states of each qubit through the likelihood function of the photon distribution of the qubit array, and can be obtained in three ways; the following will make corresponding descriptions for the three ways respectively.

[0054] The embodiments of the present disclosure determine the bright and dark states of each qubit according to the likelihood function of the photon distribution of the qubit array. The first method includes:

[0055] Based on the bright state photon distribution and the dark state photon distribution of each qubit, determining the bright and dark states of each qubit according to the likelihood function of the photon distribution of the qubit array, including:

[0056] Calculating the likelihood functions of the bright state and the dark state of the i-th qubit based on the following formula:

[0057] P(I i (x,y)|B​i (x,y),Θ) = Π j B ij (n ij );

[0058] P(I i (x,y)|D i (x,y),Θ) = Π j D ij (n ij );

[0059] where P(I i (x,y)|B i (x,y),Θ) is the likelihood function of the bright state of the i-th qubit, P(I i (x,y)|D i (x,y),Θ) is the likelihood function of the dark state of the i-th qubit, j is the j-th pixel of the pixel matrix corresponding to the i-th qubit, B ij (n ij ) represents the probability of detecting n ij photons at the j-th pixel calculated according to the calibrated bright state photon distribution of the i-th qubit, D ij (n ij ) represents the probability of detecting n ij photons at the j-th pixel calculated according to the calibrated dark state photon distribution of the i-th qubit; the above formula for calculating the likelihood function is only to illustrate the meaning of the likelihood function and the most essential calculation method. In the specific implementation process, it can also be calculated by other deformation formulas of the formula. For example, to reduce the calculation complexity, the formula can be taken logarithmically;

[0060] When , it is determined that the qubit is in the bright state;

[0061] When , it is determined that the qubit is in the dark state.

[0062] The most core purpose of quantum state detection is to determine the probability P(B i (x,y)|I i (x,y),Θ) that the i-th qubit is in the bright state and the probability P(D i (x,y)|I i (x,y),Θ) that it is in the dark state according to the detected photon distribution I i (x,y),Θ). According to Bayes' formula

[0063] P(B i (x,y)|I i (x,y),Θ) = P(I i (x,y)|Bi (x,y), Θ)P(B i (x,y)) / P(I i (x,y)

[0064] P(D i (x,y)|I i (x,y), Θ) = P(I i (x,y)|D i (x,y), Θ)P(D i (x,y)) / P(I i (x,y))

[0065] where P(I i (x,y)) is the marginal likelihood of the observation result I i (x,y), and P(B i (x,y)) = P(D i (x,y)) = 0.5 corresponds to no prior distribution, and I i (x,y) is the photon matrix distribution of qubit i, and (x,y) is the pixel matrix corresponding to qubit i, then

[0066]

[0067] Therefore, it is only necessary to calculate the likelihood function to determine the bright and dark states of qubit i, that is, the maximum likelihood estimation.

[0068] In the embodiments of the present disclosure, by calculating the likelihood functions of the bright and dark states of each qubit, the bright and dark states of each qubit are determined. The second method includes:

[0069] For S(x,y) = ∑ i B i (x,y) × s i , according to the method of multivariable optimization, the photon distribution matrix I(x,y) of the detected qubit is restored as much as possible, and s = (s 1 , s 2 , … s i …, s N ) is obtained to maximize the likelihood function P(I(x,y)|S(x,y), Θ), where s i ≥0;

[0070] Compare s = (s 1 , s 2 , … s i …, s N ) with the threshold n th for distinguishing the bright and dark states to calibrate the bright and dark states of each qubit;

[0071] Wherein, S(x, y) represents a photon distribution matrix formed by superimposing the states of all qubits and the independent photon distribution, and s i represents the magnitude contributed by the bright-state photon distribution B i (x, y) corresponding to the i-th qubit, and P(I(x, y)|S(x, y), Θ) represents the posterior distribution given S(x, y) and the detector parameters Θ. Here, the states of all qubits include: bright state and dark state.

[0072] For the processing of Method 2, the method of this embodiment of the present disclosure further includes:

[0073] By pre-collecting M sets of calibration data of the dark state |ψ> D =|000…0> and calibration data of the bright state |ψ> B =|111…1>, using a multivariate optimization method to calculate M sets of corresponding and where i represents the qubit serial number, B represents the bright-state data set, D represents the dark-state data set, represents the magnitude contributed by the bright-state photon distribution B i (x, y) of the i-th qubit in the m-th set of bright-state data, represents the magnitude contributed by the dark-state photon distribution D i (x, y) of the i-th qubit in the m-th set of dark-state data;

[0074] According to the calculated and Calibrate the threshold for distinguishing the bright state and the dark state according to the following method

[0075] Select the threshold according to the following expression to minimize the error: where, is the number of times less than in is the number of times greater than in The optimization objective of B is to minimize ∈=(∈ D ) / 2.

[0076] The method 2 of this embodiment of the present disclosure ignores the contribution of the dark state (close to the background), assuming that the photon distribution matrix obtained by a single measurement is I(x, y), and this matrix is determined by the states corresponding to N qubits. For example, only the first qubit is in the bright state and the remaining qubits are in the dark state and do not emit light, then I(x, y) is mainly composed of B 1(x, y) is composed. However, since each pixel in a single measurement is independently distributed, P(B 1 (x, y)|I(x, y), Θ) has the largest proportion among all posterior distributions. That is, the probability of the state |ψ> = |100…0> is the largest, corresponding to the maximum likelihood estimation of Method 1. Therefore, the embodiments of the present disclosure can optimize through a multi-variable approach by S(x, y) = ∑ i B i (x, y) × s i to restore I(x, y) with the greatest possibility and obtain s = (s 1 , s 2 , …, s N ) such that the likelihood function P(I(x, y)|S(x, y), Θ) is the largest, where s i ≥0; then, using the threshold n th for distinguishing the bright state and the dark state in related technologies, when then the state of qubit i is the bright state c i = 1. Conversely, when then the state of qubit i is the dark state c i = 0.

[0077] The embodiments of the present disclosure determine the bright and dark states of each qubit by calculating the likelihood functions of the bright and dark states of each qubit. Method 3 includes:

[0078] Using the result of the π / 2 pulse, perform the following processing for a second preset number of times to obtain s = (s 1 , s 2 , … s i …, s N ): Optimize through a multi-variable approach by S(x, y) = ∑ i B i (x, y) × s i to restore the photon distribution matrix I(x, y) with the greatest possibility and obtain s = (s 1 , s 2 , … s i …, s N ) such that the likelihood function P(I(x, y)|S(x, y), Θ) is the largest, where s i ≥0;

[0079] Take the average of all the obtained s = (s 1 , s 2 , … s i …, s N ) to obtain

[0080] Normalize B i (x,y) to

[0081] For the photon distribution matrix I(x,y) obtained from a single measurement, determine S(x,y) = ∑ i B′ i (x,y) × p i +(1 - p i )D i (x,y), where 0 ≤ p i ≤ 1, indicating that the photon distribution matrix is composed of the superposition of the bright state with probability p i and the dark state with probability (1 - p i ) (i.e., the probability that qubit i is in the bright state is p i ), and the likelihood function is P(I(x,y)|S(x,y), Θ);

[0082] According to the method of multivariate optimization, maximize the likelihood function P(I(x,y)|S(x,y), Θ) by restoring the photon distribution matrix I(x,y) as much as possible through S(x,y) = ∑ i B′ i (x,y) × p i +(1 - p i )D i (x,y), and obtain p = (p 1 , p 2 , …, p 3 );

[0083] If p i ≥ 0.5, determine that qubit i is in the bright state; otherwise, if p i < 0.5, determine that qubit i is in the dark state.

[0084] Method three in the embodiments of the present disclosure considers the contribution of the dark state, uses the result of the π / 2 pulse, and refers to s = (s 1 , s 2 , …, s N ) obtained in method two. For the s = (s 1 , s 2 , …, s N ) repeatedly calculated for the third preset number of times, take the average to obtain Then the embodiments of the present disclosure can normalize B i (x,y) to Such normalization does not require additional calibration operations; assume that the fluorescence matrix obtained from a single measurement is I(x,y), and this matrix is determined by the modes corresponding to N qubits, that is, S(x,y) = ∑ i B i(x,y)×p i +(1-p i )D i (x,y)(previous text), where 0≤p i ≤1, the likelihood function is P(C(x,y)|S(x,y),Θ), and the embodiment of the present disclosure can obtain p=(p 1 ,p 2 ,…,p 3 ), so that the likelihood function is maximized, if p i If ≥0.5, it is judged as bright state, otherwise it is dark state.

[0085] In an exemplary embodiment, after obtaining the state of the quantum bit array by the above method 1, method 2 or method 3, the method of the embodiment of the present disclosure further includes:

[0086] When there are bright-state qubits in the qubit array state, for each qubit i+1 adjacent to the bright-state qubit i, the bright or dark state of qubit i+1 is re-determined according to the following processing: according to the photon distribution of qubit i and the photon distribution generated by qubit i at qubit i+1, the bright-state and dark-state photon distributions of qubit i+1 are updated; according to the updated bright-state and dark-state photon distributions of qubit i+1, the bright or dark state of qubit i+1 is determined according to the likelihood function of the photon distribution of the qubit array;

[0087] According to the determined light and dark states of quantum bit i+1, the state of the new quantum bit array is obtained.

[0088] The newly obtained quantum bit array state is the same as the quantum bit array state obtained in the previous time, and the quantum bit array state is determined to be the final quantum bit array state;

[0089] When the newly obtained qubit array state is different from the qubit array state obtained in the previous time, and the number of times the new qubit array state is obtained is less than the first preset number, a process of re-determining the bright and dark states of qubit i+1 is performed on the qubit i+1 adjacent to each bright-state qubit i in the newly obtained qubit array state, and a new qubit array state is obtained according to the result of the re-determination of the bright and dark states of qubit i+1, until the newly obtained qubit array state is the same as the qubit array state obtained in the previous time, and the qubit array state is determined to be the final qubit array state;

[0090] The state of the newly obtained qubit array is different from the state of the qubit array obtained in the previous time. However, when the number of times of obtaining the new qubit array state reaches the first preset number of times, the state of the last newly obtained qubit array is determined as the final state of the qubit array. In an exemplary instance, the expressions for the bright state and dark state photon distributions of qubit i+1 in the embodiments of the present disclosure are as follows:

[0091] B′ i+1 (x,y) = B i+1 (x,y) + C i,i+1 (x,y);

[0092] D′ i+1 (x,y) = D i+1 (x,y) + C i,i+1 (x,y);

[0093] Wherein, B i+1 (x,y) is the photon distribution of the bright state of qubit i+1 when crosstalk is ignored, D i+1 (x,y) is the photon distribution of the dark state of qubit i+1 when crosstalk is ignored, B′ i+1 (x,y) is the photon distribution of the bright state of qubit i+1 when crosstalk is considered, D′ i+1 (x,y) is the photon distribution of the dark state of qubit i+1 when crosstalk is considered, C i,i+1 (x,y) is the photon distribution generated by qubit i at the position adjacent to qubit i+1, and (x,y) is the coordinate of the pixel matrix.

[0094] In an exemplary instance, the pixel matrix corresponding to each qubit in the embodiments of the present disclosure may be circular or rectangular.

[0095] The following describes the update operation of the qubit array state after obtaining the qubit array state through Method 1.

[0096] In the embodiments of the present disclosure, for a qubit array including N qubits, the state of the qubit array can be represented by N bits. For example, it is represented by |ψ> = |c 1 …c N >>, where c i ∈{0,1} represents the state of the i-th qubit. It is assumed in the embodiments of the present disclosure that the fluorescence of the qubit is only distributed in a small range. For example, when the qubit position is (x i ,y i ), its photon distribution is mainly within its photon distribution radius R i . Referring to the related art, (x i - R i ,y i - R i ) → (xi +R i ,y i +R i ) The rectangular pixel array where the four top corners are located calculates the likelihood functions of the bright and dark states for all qubits. Based on the likelihood functions of the bright and dark states of the qubits obtained through calculation, the state of each qubit is judged as c i ∈{0,1}, and then the state ψ of the qubit array is obtained 1 , if the state ψ of the qubit array 1 =|0000…00>, since very few photons are generated by the dark state, the influence of crosstalk can be ignored, and the state ψ of the qubit array is returned 1 . On the contrary, if there are bright-state qubits in the qubit array, the state of the qubit array needs to be updated through the following operations: In the embodiments of the present disclosure, the fluorescence emitted by the bright-state qubits may generate crosstalk photons at the positions of the surrounding qubits. To reduce the detection errors caused by the crosstalk photons, the embodiments of the present disclosure take crosstalk into consideration, that is, qubit i will also generate a photon distribution C i,i+1 (x,y) at the position adjacent to qubit i+1. Then, the bright and dark state photon distributions in the region where qubit i+1 is located need to be updated to B′ i+1 (x,y)=B i+1 (x,y)+C i,i+1 (x,y) and D′ i+1 (x,y)=D i+1 (x,y)+C i,i+1 (x,y). Using the likelihood function P(I i+1 (x,y)|B′ i+1 (x,y),Θ) / P(I i+1 (x,y)|D′ i+1 (x,y),Θ) of the qubits considering crosstalk, the bright and dark state results are calculated. The above steps are repeated a preset number of times for all the qubits surrounding the bright-state qubits. Each time a new state ψ of the qubit array is obtained n When, if ψ n =ψ n-1 , the state ψ of the qubit array is returned n . Otherwise, the above steps are continued to be repeated until the number of repetitions reaches the first preset number, and the state ψ of the qubit array obtained in the last time is output n ; For example, the state ψ of the qubit array is obtained 2 . Suppose ψ 2 =ψ 1 , the result ψ 2 is returned. On the contrary, the above steps are repeated for the third time until ψ n =ψ n-1 , and the result ψ n, or when the number of repetitions reaches the first preset number, output the state ψ of the qubit array obtained last time n .

[0097] In an exemplary instance, when performing quantum state detection, the method of the embodiments of the present disclosure further includes:

[0098] Select one or more calibration points from one or more preset positions of the qubit array; initialize the calibration points to the bright state and keep the qubits of the calibration points in the bright state; perform the following one or any combination of processes:

[0099] Before determining the bright and dark states of each qubit by calculating the likelihood functions of the bright and dark states of each qubit, when it is determined that the position of the qubit relative to the detector has changed, use one or more calibration points to correct the position of the photon distribution of each qubit and the intensity change ratio P;

[0100] Adjust the position of the laser for quantum state detection or the laser for quantum operation according to one or more calibration points;

[0101] Monitor whether the qubit structure has changed according to one or more calibration points.

[0102] The laser for quantum operation in the embodiments of the present disclosure includes lasers for performing the following functions: cooling, quantum logic gate manipulation, coherent transfer, etc.

[0103] In an exemplary instance, the embodiments of the present disclosure can correct the photon distribution of the bright state of the qubit and the photon distribution of the dark state of the qubit according to the following formula:

[0104] B i ″(x,y) = P·B i (x + Δx, y + Δy);

[0105] D i ″(x,y) = P·D i (x + Δx, y + Δy).

[0106] For the qubit array in the embodiments of the present disclosure, 1 to 2 qubits can be selected as calibration points. For example, the two outermost qubits of a long qubit array are initialized to the bright state and no quantum operation is performed on them, so they always remain in the bright state. If the position of the qubit relative to the detector changes due to temperature drift or other reasons during the experiment, then these two calibration points can be used as indicators to correct the position (Δx, Δy) of the distribution of each qubit and the intensity change ratio P in real time. Before performing any one of the above methods 1 to 3, the bright and dark state distributions B i ″(x,y) = P·B i(x + Δx, y + Δy), D' i (x, y) = P·D i (x + Δx, y + Δy).

[0107] In the embodiments of the present disclosure, the above calibration points can be used as indicators for rapid calibration. Only by calibrating the relationship between the laser and the qubit position once, subsequent rapid feedback can be achieved (the position of the laser can be adjusted through an acousto-optic deflector AOD, an electric displacement stage, etc.); for example, the one-to-one correspondence between the laser deflection coordinates and the qubit plane coordinates is denoted as wherein, (x L , y L ) represents the parameters for controlling the laser position, and (x, y) represents the position on the detector. Suppose the qubit position has shifted by (Δx L , Δy L ), then the laser position also needs to be adjusted accordingly by (Δx L , Δy L ), where the laser offset and the qubit position offset satisfy the corresponding relationship obtained through calibration

[0108] In the embodiments of the present disclosure, the above calibration points can also be used as indicators for monitoring the qubit crystal structure; for example, the two calibration points respectively correspond to displacements of (Δx 1 , Δy 1 ) and (Δx 2 , Δy 2 ). If they are not equal and the difference is outside the detection accuracy, the embodiments of the present disclosure can determine that the qubit crystal structure has changed and corresponding feedback operations need to be performed.

[0109] Figure 4 is the structural block diagram of the quantum state detection device in the embodiments of the present disclosure. As Figure 4 shown, it includes: an operation unit, a calibration unit, a determination unit, and a determination unit; wherein

[0110] The operation unit is configured to: perform a first operation on the qubit array to make the photon distributions of any qubits independent of each other;

[0111] The calibration unit is configured to: calibrate the bright-state photon distribution and the dark-state photon distribution of each qubit in the qubit array for the qubits that have undergone the first operation;

[0112] The determination unit is configured to: irradiate the qubit array to be subjected to quantum state detection with a detection laser, and based on the bright-state photon distribution and the dark-state photon distribution of each qubit, determine the bright and dark states of each qubit according to the likelihood function of the photon distribution of the qubit array;

[0113] The determination unit is configured to: obtain the state of the qubit array according to the bright and dark states of each determined qubit.

[0114] In an exemplary example, the photon distributions of any qubits in the embodiments of the present disclosure are independent of each other, including:

[0115] For any i-th qubit and j-th qubit

[0116] where The matrix represents the spin component operator of the i-th qubit in the z direction, The matrix represents the spin component operator of the j-th qubit in the z direction.

[0117] In an exemplary example, the calibration unit in the embodiments of the present disclosure is configured to: calibrate the bright state photon distribution of each qubit in the qubit array through the following processing:

[0118] Irradiate the qubit array that has undergone the first operation with a preset detection laser to obtain the photon distribution of the qubit array, and use the independent component analysis method to obtain the bright state photon distribution of each qubit.

[0119] In an exemplary example, the operation unit in the embodiments of the present disclosure is configured to:

[0120] Initialize all qubits in The dark state;

[0121] Prepare all qubits in The superposition state of the bright state and the dark state;

[0122] where |0> represents the dark state of the qubit, and |1> represents the bright state of the qubit.

[0123] In an exemplary example, the operation unit in the embodiments of the present disclosure is configured to: Initialize all qubits in The dark state. Correspondingly, the calibration unit is configured to: calibrate the dark state photon distribution of each qubit in the qubit array through the following processing:

[0124] Irradiate the qubit array that has undergone the first operation with a preset detection laser to obtain the photon distribution of the qubit array; use the independent component analysis method to obtain the dark state photon distribution of each qubit; or,

[0125] Irradiate the qubit array that has undergone the first operation with a preset detection laser to obtain the photon distribution of the qubit array, and use the photon distribution in the pixel matrix corresponding to each qubit in the photon distribution of the qubit array as the dark state photon distribution of the corresponding qubit.

[0126] In an exemplary instance, the determination unit of the embodiments of the present disclosure is configured to determine the bright and dark states of each qubit based on the bright-state photon distribution and the dark-state photon distribution of each qubit, according to the likelihood function of the qubit array photon distribution, including:

[0127] Calculate the likelihood functions of the bright and dark states of the i-th qubit based on the following formula:

[0128] P(I i (x,y)|B i (x,y),Θ)=Π j B ij (n ij );

[0129] P(I i (x,y)|D i (x,y),Θ)=Π j D ij (n ij );

[0130] Where P(I i (x,y)|B i (x,y),Θ) is the likelihood function of the bright state of the i-th qubit, P(I i (x,y)|D i (x,y),Θ) is the likelihood function of the dark state of the i-th qubit, j is the j-th pixel point of the pixel matrix corresponding to the i-th qubit, B ij (n ij ) represents the probability of detecting n ij photons at the j-th pixel point calculated according to the calibrated bright-state photon distribution of the i-th qubit, D ij (n ij ) represents the probability of detecting n ij photons at the j-th pixel point calculated according to the calibrated dark-state photon distribution of the i-th qubit;

[0131] When , determine that the qubit is in the bright state;

[0132] When , determine that the qubit is in the dark state.

[0133] In an exemplary instance, the determination unit of the embodiments of the present disclosure is configured to determine the bright and dark states of each qubit by calculating the likelihood functions of the bright and dark states of each qubit, including:

[0134] For S(x,y)=∑ i B i(x,y)×s i , according to the multi-variable optimization method, the photon distribution matrix I(x,y) detected is restored as much as possible, and s = (s 1 , s 2 , … s i …, s N ) is obtained to maximize the likelihood function P(I(x,y)|S(x,y),Θ), where s i ≥0;

[0135] s = (s 1 , s 2 , … s i …, s N ) is compared with the threshold n th for distinguishing bright and dark states to calibrate the bright and dark states of each qubit;

[0136] In the formula, S(x,y) represents the photon distribution matrix formed by the states of all qubits and the superposition of independent photon distributions, and s i represents the contribution of the bright-state photon distribution B i (x,y) corresponding to the i-th qubit, and P(I(x,y)|S(x,y),Θ) represents the posterior distribution given S(x,y) and the detector parameters Θ.

[0137] In an exemplary instance, the determination unit of the present disclosure is further configured to:

[0138] By pre-collecting M sets of dark-state |ψ> D = |000…0> calibration data and bright-state |ψ> B = |111…1> calibration data, using the multi-variable optimization method to calculate M sets of and corresponding to the bright and dark state data, where i represents the qubit serial number, B represents the bright-state data set, D represents the dark-state data set, represents the contribution of the bright-state photon distribution B i (x,y) of the i-th qubit in the m-th set of bright-state data, represents the contribution of the dark-state photon distribution D i (x,y) of the i-th qubit in the m-th set of dark-state data;

[0139] According to the calculated and calibrate the threshold for distinguishing bright and dark states according to the following method

[0140] Select the threshold according to the following expression to minimize the error: Among them, is the number of times less than in is the number of times greater than in The optimization objective is to minimize ∈=(∈ B +∈ D ) / 2.

[0141] In an exemplary instance, the determination unit of the embodiments of the present disclosure is configured to determine the bright and dark states of each qubit by calculating the likelihood functions of the bright and dark states of each qubit, including:

[0142] Using the result of the π / 2 pulse, perform the second preset number of calculations through the following processing to obtain s=(s 1 ,s 2 ,…s i …,s N ): According to the multivariate optimization method, maximize the photon distribution matrix I(x,y) that can be restored most likely through S(x,y)=∑ i B i (x,y)×s i to obtain s=(s 1 ,s 2 ,…s i …,s N ), making the likelihood function P(I(x,y)|S(x,y),Θ) maximum, where s i ≥0;

[0143] Take the average of all the obtained s=(s 1 ,s 2 ,…s i …,s N ) to obtain

[0144] Renormalize B i (x,y) to

[0145] For the photon distribution matrix I(x,y) obtained by a single measurement, determine S(x,y)=∑ i B′ i (x,y)×p i +(1 - p i )D i (x,y) according to the modes corresponding to N qubits, where 0≤p i ≤1, indicating that this photon distribution matrix consists of the bright state with probability p i and the (1 - p i) is formed by superimposing dark states, and the likelihood function is P(I(x,y)|S(x,y),Θ);

[0146] According to the multi-variable optimization method, S(x,y) = ∑ i B′ i (x,y)×p i +(1 - p i )D i (x,y) maximally restores the photon distribution matrix I(x,y) as much as possible, and obtains p = (p 1 , p 2 , …, p 3 ) to maximize the likelihood function P(I(x,y)|S(x,y),Θ);

[0147] If p i ≥0.5, it is determined that qubit i is in the bright state; conversely, if p i <0.5, it is determined that qubit i is in the dark state.

[0148] In an exemplary instance, after the determination unit of the present disclosure embodiment obtains the state of the qubit array, it is further set as:

[0149] When there is a bright-state qubit in the qubit array state, for each qubit i + 1 adjacent to the bright-state qubit i, the bright and dark states of qubit i + 1 are re-determined according to the following processing: According to the photon distribution of qubit i and the photon distribution generated by qubit i in qubit i + 1, update the bright-state and dark-state photon distributions of qubit i + 1; According to the updated bright-state and dark-state photon distributions of qubit i + 1, calculate the likelihood functions of the bright state and dark state of qubit i + 1; According to the calculated likelihood functions of the bright state and dark state of qubit i + 1, determine the bright and dark states of qubit i + 1;

[0150] According to the determined bright and dark states of qubit i + 1, obtain a new qubit array state;

[0151] If the newly obtained qubit array state is the same as the qubit array state obtained in the previous time, determine this qubit array state as the final qubit array state;

[0152] When the state of the newly obtained qubit array is different from the state of the qubit array obtained in the previous time, and the number of times of obtaining the new qubit array state is less than the first preset number of times, for the qubits with bright states in the newly obtained qubit array state, the qubits i + 1 adjacent to each bright-state qubit i are processed to re-determine the bright / dark state of qubit i + 1, and according to the result of re-determining the bright / dark state of qubit i + 1, a new qubit array state is obtained until the newly obtained qubit array state is the same as the qubit array state obtained in the previous time, and then the qubit array state is determined as the final qubit array state;

[0153] When the state of the newly obtained qubit array is different from the state of the qubit array obtained in the previous time, but the number of times of obtaining the new qubit array state reaches the first preset number of times, the last newly obtained qubit array state is determined as the final qubit array state.

[0154] In the embodiments of the present disclosure, the expressions for the bright-state and dark-state photon distributions of qubit i + 1 are:

[0155] B′ i+1 (x,y) = B i (x,y) + C i,i+1 (x,y);

[0156] D′ i+1 (x,y) = D i (x,y) + C i,i+1 (x,y);

[0157] Wherein, B i (x,y) is the photon distribution of the bright state of qubit i, D i (x,y) is the photon distribution of the dark state of qubit i, B′ i+1 (x,y) is the photon distribution of the bright state of qubit i + 1, D′ i+1 (x,y) is the photon distribution of the dark state of qubit i + 1, C i,i+1 (x,y) is the photon distribution generated by qubit i at the position adjacent to qubit i + 1, and (x,y) is the coordinate of the pixel matrix.

[0158] In an exemplary example, the device in the embodiments of the present disclosure further includes a calibration unit, which is configured to:

[0159] Select one or more calibration points from one or more preset positions of the qubit array; initialize the calibration points to the bright state and keep the qubits of the calibration points in the bright state; perform the following one or any combination of processes:

[0160] Before determining the bright and dark states of each qubit according to the likelihood function of the photon distribution of the qubit array, when it is determined that the position of the qubit relative to the detector changes, the position and the intensity change ratio P of the photon distribution of each qubit are corrected by using more than one calibration point;

[0161] The position of the laser for quantum state detection or the laser for quantum operation is adjusted according to more than one calibration point;

[0162] Whether the qubit structure changes is monitored according to more than one calibration point.

[0163] Those of ordinary skill in the art can understand that all or some of the steps in the methods disclosed above, and the functional modules / units in the systems and devices, can be implemented as software, firmware, hardware, and their appropriate combinations. In the hardware implementation, the division of the functional modules / units mentioned above does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be executed by several physical components in cooperation. Some components or all components can be implemented as software executed by a processor, such as a digital signal processor or a microprocessor, or implemented as hardware, or implemented as an integrated circuit, such as an application-specific integrated circuit. Such software can be distributed on a computer-readable medium, which can include a computer storage medium (or a non-transitory medium) and a communication medium (or a transitory medium). As is well known to those of ordinary skill in the art, the term computer storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information, such as computer-readable instructions, data structures, program modules, or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disc (DVD) or other optical disc storage, magnetic cassette, tape, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and can be accessed by a computer. In addition, as is well known to those of ordinary skill in the art, a communication medium typically contains computer-readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transmission mechanism, and can include any information delivery medium.

Claims

1. A method for quantum state detection, characterized in that: include: Performing a first operation on the quantum bit array so that the photon distributions of any quantum bits are independent of each other; For the quantum bit that has undergone the first operation, calibrate the bright state photon distribution and the dark state photon distribution of each quantum bit in the quantum bit array; Irradiate the quantum bit array that needs to be detected for quantum state with a detection laser, and determine the bright and dark states of each quantum bit based on the distribution of bright and dark photons of each quantum bit and the likelihood function of the photon distribution of the quantum bit array; According to the determined light and dark states of each quantum bit, the state of the quantum bit array is obtained.

2. The method according to claim 1, characterized in that The photon distributions of the arbitrary quantum bits are independent of each other, including: Any ith qubit and jth qubit in, The matrix represents the spin component operator of the i-th quantum bit in the z direction, The matrix represents the spin component operator of the j-th quantum bit in the z direction.

3. The method according to claim 1, characterized in that The bright state photon distribution of each qubit in the qubit array is calibrated by the following process: The quantum bit array that has undergone the first operation is irradiated with a preset detection laser to obtain the photon distribution of the quantum bit array, and the bright state photon distribution of each quantum bit is obtained using an independent component analysis method.

4. The method according to claim 1, characterized in that: The first operation includes: Initialize all qubits in The dark state; All qubits are prepared by π / 2 pulses The superposition state of the bright state and the dark state; Among them, |0> represents the dark state of the quantum bit, |1> represents the light state of the quantum bit, and N represents the number of quantum bits.

5. The method according to claim 1, characterized in that The first operation includes: Initialize all qubits in The dark state of , where N represents the number of quantum bits.

6. The method according to claim 5, characterized in that The dark state photon distribution of each qubit in the qubit array is calibrated by the following process: Irradiating the quantum bit array after the first operation with a preset detection laser to obtain the photon distribution of the quantum bit array; using the independent component analysis method to obtain the dark state photon distribution of each quantum bit; or, The quantum bit array that has undergone the first operation is irradiated with a preset detection laser to obtain the photon distribution of the quantum bit array, and the photon distribution in the pixel matrix corresponding to each quantum bit in the photon distribution of the quantum bit array is used as the dark state photon distribution of the corresponding quantum bit.

7. The method according to any one of claims 1 to 6, characterized in that: Determining the light and dark state of each quantum bit according to the likelihood function of the photon distribution of the quantum bit array includes: The likelihood function of the bright and dark states of the ith qubit is calculated based on the following formula: P(I i (x,y)|B i (x,y),Θ)=Π j B ij (n ij ); P(I i (x,y)|D i (x,y),Θ)=Π j D ij (n ij ); Where i represents the quantum bit number, B represents the bright state data set, D represents the dark state data set, (x, y) represents the coordinates of the pixel matrix, and I i (x, y) represents the detected photon distribution, B i (x,y) represents the photon distribution of quantum bit i in the bright state, D i (x,y) represents the photon distribution of quantum bit i in the dark state, Θ represents the detector parameters, P(I i (x,y)|B i (x,y),Θ) is the likelihood function of the bright state of the i-th quantum bit, P(I i (x,y)|D i (x,y),Θ) is the likelihood function of the dark state of the ith qubit, j is the jth pixel in the pixel matrix corresponding to the ith qubit, B ij (n ij ) represents the number of n detected at the jth pixel point calculated based on the bright state photon distribution of the calibrated i-th quantum bit. ij The probability of a photon, D ij (n ij ) represents the number of n detected at the jth pixel point calculated based on the dark state photon distribution of the calibrated i-th quantum bit. ij The probability of a photon; when When , the quantum bit is determined to be in a bright state; when , the quantum bit is determined to be in a dark state.

8. The method according to any one of claims 1 to 6, characterized in that: Determining the light and dark state of each quantum bit according to the likelihood function of the photon distribution of the quantum bit array includes: For S(x,y)=∑ i B i (x,y)×s i , according to the multivariable optimization method, the photon distribution matrix I(x,y) of the detected quantum bit is restored to the maximum extent possible, and s=(s1,s2,…s i …,s N ), so that the likelihood function P(I(x,y)|S(x,y),Θ) is maximized, where s i ≥0; Let s=(s1,s2,…s i …,s N ) and the threshold n for distinguishing between bright and dark states th Compare and calibrate the light and dark states of each quantum bit; In the formula, S(x,y) represents the photon distribution matrix formed by the superposition of the states of all quantum bits and independent photon distributions, and s i Indicates the bright state photon distribution B corresponding to the i-th quantum bit i The contribution of (x,y) is expressed as P(I(x,y)|S(x,y),Θ) which represents the posterior distribution given S(x,y) and the detector parameters Θ.

9. The method according to claim 8, characterized in that The method further comprises: Through the pre-collected M dark states |ψ> D =|000…0>Calibration data and bright state|ψ> B =|111…1> calibration data, and multivariable optimization is used to calculate the corresponding M groups of bright state and dark state data and Where i represents the quantum bit number, B represents the bright state data group, and D represents the dark state data group. represents the bright state photon distribution B of the i-th quantum bit in the m-th group of bright state data i The size contributed by (x,y), represents the dark state photon distribution D of the i-th quantum bit in the m-th group of dark state data i The size of the contribution of (x,y); Obtained based on calculation and The threshold for distinguishing between bright and dark states is calibrated according to The threshold is selected according to the following expression Minimize the error: in, yes Smaller than The number of times yes Medium to large The number of times The optimization goal is to make ∈=(∈ B +∈ D ) / 2 is the smallest.

10. The method according to any one of claims 1 to 6, characterized in that: Determining the light and dark state of each quantum bit according to the likelihood function of the photon distribution of the quantum bit array includes: Using the result of the π / 2 pulse, the second preset number of calculations is performed through the following processing to obtain s=(s1, s2, ...s i …,s N ): According to the multivariable optimization method, S(x,y)=∑ i B i (x,y)×s i The photon distribution matrix I(x,y) can be restored to its maximum possible value, and s=(s1,s2,…s i …,s N ), so that the likelihood function P(I(x,y)|S(x,y),Θ) is maximized, where s i ≥0, Θ represents the detector parameters; For all s=(s1,s2,…s i …,s N ) take the average, and we get B i (x,y) is renormalized to For the photon distribution matrix I(x,y) obtained from a single measurement, S(x,y)=∑ i B′ i (x,y)×p i +(1-p i )D i (x,y), where 0≤p i ≤1, indicating that the photon distribution matrix is ​​composed of probability p i The bright state and (1-p i ) is composed of the dark states of the original image, and the likelihood function is P(I(x,y)|S(x,y),Θ); According to the multivariable optimization method, S(x,y)=∑ i B′ i (x,y)×p i +(1-p i )D i (x, y) restores the photon distribution matrix I(x, y) to the maximum extent possible, and obtains p = (p1, p2, ..., p3), so that the likelihood function P(I(x, y) | S(x, y), Θ) is maximized; If p i ≥0.5, the quantum bit i is judged to be in the bright state; otherwise, if p i <0.5, the quantum bit i is judged to be in dark state; In the formula, S(x,y) represents the photon distribution matrix formed by the superposition of the states of all quantum bits and independent photon distributions, and s i Indicates the bright state photon distribution B corresponding to the i-th quantum bit i The size of the contribution of (x,y), N represents the number of quantum bits.

11. The method according to claim 7, characterized in that After obtaining the state of the quantum bit array, the method further includes: When there are bright-state quantum bits in the quantum bit array state, for each quantum bit i+1 adjacent to the quantum bit i in the bright state, the bright and dark states of the quantum bit i+1 are re-determined according to the following processing: according to the photon distribution of the quantum bit i and the photon distribution generated by the quantum bit i at the quantum bit i+1, the bright and dark state photon distribution of the quantum bit i+1 is updated; according to the updated bright and dark state photon distribution of the quantum bit i+1, the bright and dark state of the quantum bit i+1 is determined according to the likelihood function of the quantum bit array photon distribution; Obtaining a new state of the quantum bit array according to the determined light or dark state of the quantum bit i+1; The newly obtained quantum bit array state is the same as the quantum bit array state obtained last time, and the quantum bit array state is determined to be the final quantum bit array state; When the newly obtained qubit array state is different from the qubit array state obtained last time, and the number of times the new qubit array state is obtained is less than the first preset number, the process of re-determining the bright and dark states of the qubit i+1 is performed on the qubit i+1 adjacent to each bright-state qubit i in the newly obtained qubit array state, and the new qubit array state is obtained according to the result of the re-determination of the bright and dark states of the qubit i+1, until the newly obtained qubit array state is the same as the qubit array state obtained last time, and the qubit array state is determined to be the final qubit array state; The newly obtained qubit array state is different from the qubit array state obtained last time, but when the number of times the new qubit array state is obtained reaches a first preset number, the last newly obtained qubit array state is determined as the final qubit array state; The distribution of the bright and dark photons of the quantum bit i+1 is expressed as follows: i ′ +1 (x,y)=B i+1 (x,y)+C i,i+1 (x,y);D i ′ +1 (x,y)=D i+1 (x,y)+C i,i+1 (x,y); B i+1 (x, y) is the photon distribution of the bright state of the quantum bit i+1 when crosstalk is ignored, D i+1 (x, y) is the photon distribution of the dark state of the quantum bit i+1 when crosstalk is ignored, B i ′ +1 (x, y) is the photon distribution of the bright state of the quantum bit i+1 when crosstalk is considered, D i ′ +1 (x, y) is the photon distribution of the dark state of the quantum bit i+1 when crosstalk is considered, C i,i+1 (x, y) is the photon distribution generated by quantum bit i at the position adjacent to quantum bit i+1, and (x, y) is the coordinate of the pixel matrix corresponding to the quantum bit.

12. The method according to claim 8, characterized in that After obtaining the state of the quantum bit array, the method further includes: When there are bright-state quantum bits in the quantum bit array state, for each quantum bit i+1 adjacent to the quantum bit i in the bright state, the bright and dark states of the quantum bit i+1 are re-determined according to the following processing: according to the photon distribution of the quantum bit i and the photon distribution generated by the quantum bit i at the quantum bit i+1, the bright and dark state photon distribution of the quantum bit i+1 is updated; according to the updated bright and dark state photon distribution of the quantum bit i+1, the bright and dark state of the quantum bit i+1 is determined according to the likelihood function of the quantum bit array photon distribution; Obtaining a new state of the quantum bit array according to the determined light or dark state of the quantum bit i+1; The newly obtained quantum bit array state is the same as the quantum bit array state obtained last time, and the quantum bit array state is determined to be the final quantum bit array state; When the newly obtained qubit array state is different from the qubit array state obtained last time, and the number of times the new qubit array state is obtained is less than the first preset number, the process of re-determining the bright and dark states of the qubit i+1 is performed on the qubit i+1 adjacent to each bright-state qubit i in the newly obtained qubit array state, and the new qubit array state is obtained according to the result of the re-determination of the bright and dark states of the qubit i+1, until the newly obtained qubit array state is the same as the qubit array state obtained last time, and the qubit array state is determined to be the final qubit array state; The newly obtained qubit array state is different from the qubit array state obtained last time, but when the number of times the new qubit array state is obtained reaches a first preset number, the last newly obtained qubit array state is determined as the final qubit array state; The distribution of the bright and dark photons of the quantum bit i+1 is expressed as follows: i ′ +1 (x,y)=B i+1 (x,y)+C i,i+1 (x,y);D i ′ +1 (x,y)=D i+1 (x,y)+C i,i+1 (x,y); B i+1 (x, y) is the photon distribution of the bright state of the quantum bit i+1 when crosstalk is ignored, D i+1 (x, y) is the photon distribution of the dark state of the quantum bit i+1 when crosstalk is ignored, B i ′ +1 (x, y) is the photon distribution of the bright state of the quantum bit i+1 when crosstalk is considered, D i ′ +1 (x, y) is the photon distribution of the dark state of the quantum bit i+1 when crosstalk is considered, C i,i+1 (x, y) is the photon distribution generated by quantum bit i at the position adjacent to quantum bit i+1, and (x, y) is the coordinate of the pixel matrix corresponding to the quantum bit.

13. The method according to claim 10, characterized in that After obtaining the state of the quantum bit array, the method further includes: When there are bright-state quantum bits in the quantum bit array state, for each quantum bit i+1 adjacent to the quantum bit i in the bright state, the bright and dark states of the quantum bit i+1 are re-determined according to the following processing: according to the photon distribution of the quantum bit i and the photon distribution generated by the quantum bit i at the quantum bit i+1, the bright and dark state photon distribution of the quantum bit i+1 is updated; according to the updated bright and dark state photon distribution of the quantum bit i+1, the bright and dark state of the quantum bit i+1 is determined according to the likelihood function of the quantum bit array photon distribution; Obtaining a new state of the quantum bit array according to the determined light or dark state of the quantum bit i+1; The newly obtained quantum bit array state is the same as the quantum bit array state obtained last time, and the quantum bit array state is determined to be the final quantum bit array state; When the newly obtained qubit array state is different from the qubit array state obtained last time, and the number of times the new qubit array state is obtained is less than the first preset number, the process of re-determining the bright and dark states of the qubit i+1 is performed on the qubit i+1 adjacent to each bright-state qubit i in the newly obtained qubit array state, and the new qubit array state is obtained according to the result of the re-determination of the bright and dark states of the qubit i+1, until the newly obtained qubit array state is the same as the qubit array state obtained last time, and the qubit array state is determined to be the final qubit array state; The newly obtained qubit array state is different from the qubit array state obtained last time, but when the number of times the new qubit array state is obtained reaches a first preset number, the last newly obtained qubit array state is determined as the final qubit array state; The distribution of the bright and dark photons of the quantum bit i+1 is expressed as follows: i ′ +1 (x,y)=B i+1 (x,y)+C i,i+1 (x,y);D i ′ +1 (x,y)=D i+1 (x,y)+C i,i+1 (x,y); B i+1 (x, y) is the photon distribution of the bright state of the quantum bit i+1 when crosstalk is ignored, D i+1 (x, y) is the photon distribution of the dark state of the quantum bit i+1 when crosstalk is ignored, B i ′ +1 (x, y) is the photon distribution of the bright state of the quantum bit i+1 when crosstalk is considered, D i ′ +1 (x, y) is the photon distribution of the dark state of the quantum bit i+1 when crosstalk is considered, C i,i+1 (x, y) is the photon distribution generated by quantum bit i at the position adjacent to quantum bit i+1, and (x, y) is the coordinate of the pixel matrix corresponding to the quantum bit.

14. The method according to any one of claims 1 to 6, characterized in that: The method further comprises: Select one or more calibration points from one or more preset positions of the quantum bit array; initialize the calibration points to a bright state and keep the quantum bits of the calibration points in a bright state; perform one or any combination of the following processing: Before determining the bright or dark state of each quantum bit according to the likelihood function of the photon distribution of the quantum bit array, when it is determined that the position of the quantum bit relative to the detector has changed, the position of the photon distribution of each quantum bit and the intensity change ratio P are corrected using the one or more calibration points; According to the one or more calibration points, adjusting the position of a laser used for quantum state detection or a laser used for quantum operation; Based on the one or more calibration points, monitor whether the quantum bit structure changes.

15. A device for quantum state detection, comprising: An operation unit, a calibration unit, a judgment unit and a determination unit; wherein, The operation unit is configured to: perform a first operation on the quantum bit array so that the photon distributions of any quantum bits are independent of each other; The calibration unit is configured to: calibrate the bright state photon distribution and the dark state photon distribution of each quantum bit in the quantum bit array for the quantum bit that has undergone the first operation; The determination unit is configured to: illuminate the quantum bit array that needs to be detected for quantum state with a detection laser, determine the bright and dark states of each quantum bit based on the bright state photon distribution and the dark state photon distribution of each quantum bit and according to the likelihood function of the photon distribution of the quantum bit array; The determination unit is set to: obtain the state of the quantum bit array according to the determined bright and dark states of each quantum bit.

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