Parallel quantum gate correlation error detection method and detection device

Abstract

The present application provides a parallel quantum gate correlation error detection method and detection device, the method comprising obtaining a plurality of quantum bit combinations in each error detection case, wherein the quantum bit combination includes two quantum bits with an initial quantum state; performing quantum state excitation processing on a quantum bit with an initial quantum state in at least one quantum bit combination to obtain a quantum bit with an intermediate quantum state; performing multiple target gate operations on each quantum bit with an initial quantum state and each quantum bit with an intermediate quantum state to obtain a quantum bit with a target quantum state; measuring the multiple quantum bits with a target quantum state obtained after each error detection to obtain a measurement data set; and determining whether there is a correlation error between different quantum bit combinations based on multiple measured combination probabilities and multiple state probabilities.

Description

Technical Field

[0001] The present application relates to the field of quantum computing technology, and more specifically, to a detection method and a detection device for parallel quantum gate correlation errors. Background Art

[0002] In superconducting quantum computing, high-fidelity single-bit gate and two-bit gate operations are the basis for realizing universal quantum computing. At present, the fidelity of single serial single-bit gate and two-bit gate operations can exceed 99.9%. However, in large-scale quantum bits, due to the limitation of quantum bit decoherence performance, quantum gates need to be completed in the shortest possible time. The commonly used method is to run multiple gate operations at the same time, that is, parallel gate operations. For parallel single-bit gate operations, it is only necessary to stagger the frequency of quantum bits, reduce the coupling between quantum bits, and perform XY drive crosstalk correction to achieve more than 99.9% of parallel single-bit gate operations. For parallel two-bit gate operations, due to the influence of residual coupling and signal crosstalk, even for the same set of gate parameters, the fidelity relative to a single (serial) two-bit gate operation may be greatly affected. Therefore, how to quickly and accurately calibrate this correlation error is a necessary means to improve parallel two-bit gates.

[0003] In order to detect correlation errors, a common method is to determine whether there is a correlation error by comparing the difference in fidelity between the serial two-bit gate and the parallel two-bit. However, this method requires a large number of experiments to be run. For n groups of parallel two-bit gates, if they are compared one by one, (n^2 / 2-n) calibration fidelity experiments are required. As the number of bits and the number of parallel two-bit gates increase, this time consumption is unacceptable. Summary of the invention

[0004] In view of this, the present application provides a method and a device for detecting correlation errors of parallel quantum gates.

[0005] One aspect of the present application provides a method for detecting correlation errors of parallel quantum gates, comprising:

[0006] In each error detection case, a plurality of quantum bit combinations are obtained, wherein the quantum bit combination includes two quantum bits having an initial quantum state, and the number of error detections is n times;

[0007] Performing quantum state excitation processing on one of the above-mentioned quantum bits with the initial quantum state in at least one of the above-mentioned quantum bit combinations to obtain a quantum bit with an intermediate quantum state, wherein the quantum bit with the intermediate quantum state has a target excited state;

[0008] Performing multiple target gate operations on each of the above-mentioned qubits having the initial quantum state and each of the above-mentioned qubits having the intermediate quantum state to obtain qubits having the target quantum state;

[0009] Measuring the plurality of qubits having the target quantum state obtained after each error detection to obtain a measurement data set, wherein the measurement data set includes a plurality of measured combination probabilities of at least two qubits having the target quantum state being in different first target states and a state probability of each qubit having the target quantum state being in a second target state, wherein the at least two qubits having the target quantum state belong to different qubit combinations;

[0010] Based on the multiple measured combination probabilities and the multiple state probabilities, determine whether there is a correlation error between different quantum bit combinations.

[0011] According to an embodiment of the present application, when the target gate operation is to control a Z gate, a quantum state excitation process is performed on one of the quantum bits with an initial quantum state in one of the quantum bit combinations.

[0012] According to an embodiment of the present application, determining whether there is a correlation error between different quantum bit combinations based on the multiple measured combination probabilities and the multiple state probabilities includes:

[0013] When the number of the quantum bit combinations is two, determining a first combination probability threshold and a second combination probability threshold according to the two state probabilities respectively belonging to different quantum bit combinations;

[0014] According to the above-mentioned measured combination probability, the above-mentioned first combination probability threshold and the above-mentioned second combination probability threshold, the degree of correlation that characterizes whether there is correlation error between the above-mentioned different quantum bit combinations is determined.

[0015] According to an embodiment of the present application, determining the degree of correlation that characterizes whether there is a correlation error between different quantum bit combinations according to the measured combination probability, the first combination probability threshold, and the second combination probability threshold includes:

[0016] Calculate a first absolute difference between the measured combined probability and the first combined probability threshold;

[0017] Calculate a second absolute difference between the measured combined probability and the second combined probability threshold;

[0018] According to the first absolute difference and the second absolute difference, a correlation degree is determined, which characterizes whether there is a correlation error between different combinations of the quantum bits.

[0019] According to an embodiment of the present application, determining the degree of correlation that characterizes whether there is a correlation error between different quantum bit combinations according to the first absolute difference and the second absolute difference includes:

[0020] When the first absolute difference is less than the second absolute difference, determining a first correlation probability indicating that there is a correlation error between different quantum bit combinations;

[0021] When the first absolute difference is greater than the second absolute difference, a second correlation probability is determined, which characterizes the existence of correlation errors between different quantum bit combinations.

[0022] According to an embodiment of the present application, when the target gate operation is an Iswap-like gate, quantum state excitation processing is performed on one of the quantum bits with the initial quantum state in each of the quantum bit combinations.

[0023] According to an embodiment of the present application, determining whether there is a correlation error between different quantum bit combinations based on the multiple measured combination probabilities and the multiple state probabilities includes:

[0024] When the number of the above-mentioned quantum bit combinations is two, determining a third combination probability threshold and a fourth combination probability threshold according to the above-mentioned four state probabilities respectively belonging to the above-mentioned different quantum bit combinations;

[0025] According to the above-mentioned measured combination probability, the above-mentioned third combination probability threshold and the above-mentioned fourth combination probability threshold, the degree of correlation that characterizes whether there is correlation error between different above-mentioned quantum bit combinations is determined.

[0026] According to an embodiment of the present application, determining the degree of correlation that characterizes whether there is a correlation error between different quantum bit combinations according to the measured combination probability, the third combination probability threshold, and the fourth combination probability threshold includes:

[0027] Calculating a third absolute difference between the measured combined probability and the third combined probability threshold;

[0028] Calculating a fourth absolute difference between the measured combined probability and the fourth combined probability threshold;

[0029] According to the third absolute difference and the fourth absolute difference, a correlation degree is determined, which characterizes whether correlation errors exist between different combinations of the quantum bits.

[0030] According to an embodiment of the present application, determining the degree of correlation that characterizes whether there is a correlation error between different quantum bit combinations according to the third absolute difference and the fourth absolute difference includes:

[0031] When the third absolute difference is less than the fourth absolute difference, determining a third correlation probability representing the existence of correlation errors between different quantum bit combinations;

[0032] When the third absolute difference is greater than the fourth absolute difference, a fourth correlation probability is determined, which characterizes the existence of correlation errors between different quantum bit combinations.

[0033] Another aspect of the present application provides a parallel quantum gate correlation error detection device, comprising:

[0034] An acquisition module, used for acquiring a plurality of quantum bit combinations in each error detection, wherein the quantum bit combination includes two quantum bits in an initial quantum state, and the number of error detections is n times;

[0035] an excitation module, configured to perform quantum state excitation processing on one of the above-mentioned quantum bits with the initial quantum state in at least one of the above-mentioned quantum bit combinations to obtain a quantum bit with an intermediate quantum state, wherein the above-mentioned quantum bit with the intermediate quantum state has a target excited state;

[0036] An obtaining module is used to perform multiple target gate operations on each of the above-mentioned quantum bits with the initial quantum state and each of the above-mentioned quantum bits with the intermediate quantum state to obtain a quantum bit with a target quantum state;

[0037] A measurement module, configured to measure the plurality of qubits having the target quantum state obtained after each error detection to obtain a measurement data set, wherein the measurement data set includes a plurality of measured combination probabilities of at least two qubits having the target quantum state being in different first target states and a state probability of each qubit having the target quantum state being in a second target state, wherein the at least two qubits having the target quantum state belong to different qubit combinations;

[0038] A determination module is used to determine whether there is a correlation error between different quantum bit combinations based on the multiple measured combination probabilities and the multiple state probabilities.

[0039] According to an embodiment of the present application, a quantum bit with an initial quantum state in at least one quantum bit combination is subjected to quantum state excitation processing to obtain a quantum bit with an intermediate quantum state, and multiple target gate operations are performed on each quantum bit with an initial quantum state and each quantum bit with an intermediate quantum state to obtain a quantum bit with a target quantum state, and multiple quantum bits with a target quantum state obtained after each error detection are measured to obtain a measurement data set, and based on multiple measured combination probabilities and multiple state probabilities in the measurement data set, it is determined whether there is a correlation error between different quantum bit combinations. The detection method of the present application can effectively calibrate whether there is a correlation error between parallel quantum gates, thereby improving the detection efficiency of correlation errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The above and other objects, features and advantages of the present application will become more apparent through the following description of the embodiments of the present application with reference to the accompanying drawings, in which:

[0041] Figure 1 A flow chart of a method for detecting correlation errors of parallel quantum gates according to an embodiment of the present application is shown;

[0042] Figure 2 A schematic diagram of a parallel two-bit quantum gate according to an embodiment of the present application is shown;

[0043] Figure 3 A schematic diagram of a |01> and |10> interaction detection circuit according to an embodiment of the present application is shown;

[0044] Figure 4 A schematic diagram of a detection circuit for interaction between |11> and |02> (or |20>) according to an embodiment of the present application is shown;

[0045] Figure 5 A block diagram of a parallel quantum gate correlation error detection device according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0046] Below, embodiments of the present application will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present application. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present application. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present application.

[0047] The terms used herein are only for describing specific embodiments and are not intended to limit the present application. The terms "include", "comprising", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0048] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0049] When using expressions such as "at least one of A, B, and C, etc.", they should generally be interpreted according to the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0050] In the embodiments of this application, the collection, updating, analysis, processing, use, transmission, provision, disclosure, storage, etc. of the data involved (for example, including but not limited to user personal information) are in compliance with the provisions of relevant laws and regulations, are used for legitimate purposes, and do not violate public order and good morals. In particular, necessary measures are taken for user personal information to prevent illegal access to user personal information data and maintain the security of user personal information and network security.

[0051] Figure 1 A flow chart of a method for detecting correlation errors of parallel quantum gates according to an embodiment of the present application is shown.

[0052] Figure 2 A schematic diagram of a parallel two-bit quantum gate according to an embodiment of the present application is shown. Figure 2 The solid line in the middle indicates that the two bits act as a two-bit gate, and the proximity in spatial position is more likely to produce residual coupling.

[0053] Figure 3 A schematic diagram of a |01> and |10> interaction detection circuit according to an embodiment of the present application is shown. In the figure, the detection of correlation errors between two quantum bit combinations Q1-Q2 and Q5-Q6 is taken as an example. Before the circuit starts, it is assumed that all bits are reset to the 0 state. The X-gate operation in the figure indicates that Q1 is excited to the |1> state, and errors are subsequently accumulated by superimposing multiple layers of two-bit gates.

[0054] like Figure 1 As shown, the parallel quantum gate correlation error detection method includes operations S101 to S105.

[0055] In operation S101, in each error detection, a plurality of quantum bit combinations are obtained, wherein the quantum bit combination includes two quantum bits having an initial quantum state, and the number of error detections is n times;

[0056] In operation S102, a quantum state excitation process is performed on a quantum bit having an initial quantum state in at least one quantum bit combination to obtain a quantum bit having an intermediate quantum state, wherein the quantum bit having the intermediate quantum state has a target excited state;

[0057] In operation S103, a target gate operation is performed multiple times on each qubit having an initial quantum state and each qubit having an intermediate quantum state to obtain a qubit having a target quantum state;

[0058] In operation S104, a plurality of qubits having a target quantum state obtained after each error detection are measured to obtain a measurement data set, wherein the measurement data set includes a plurality of measured combination probabilities of at least two qubits having a target quantum state being in different first target states and a state probability of each qubit having a target quantum state being in a second target state, wherein the at least two qubits having a target quantum state belong to different qubit combinations respectively;

[0059] In operation S105, it is determined whether there is a correlation error between different quantum bit combinations based on the multiple measured combination probabilities and the multiple state probabilities.

[0060] According to an embodiment of the present application, the target gate operation may be any type of gate operation, such as a controlled Z (CZ) gate and an iswap-like gate. The first target state and the second target state may both be a 0 state, a 1 state, or a 2 state.

[0061] According to the embodiments of the present application, residual coupling and signal crosstalk when two-bit gates are in parallel are the main sources of correlation errors. The present application designs quantum circuits to detect the correlation between quantum bit states and analyze the types of error sources. Figure 2 This is a schematic diagram of a parallel two-bit gate. The two bits connected by a straight line in the figure represent the execution of a two-bit gate in this parallel combination. The residual coupling mainly causes the quantum states of the two related bits to produce |11> and |20> (or |02>, depending on the frequency difference between the two bits) and the interactions of |01> and |10>. For these two interactions, different quantum circuits need to be prepared to distinguish them.

[0062] According to the embodiments of the present application, Figure 3 Multiple quantum bit combinations are input into the quantum circuit shown. Figure 3Q1-Q2 are two qubits with initial quantum states in a qubit combination, and Q5-Q6 are two qubits with initial quantum states in another qubit combination. At this time, Q1 or Q2 (or Q5 or Q6) is selected to be excited to obtain a qubit with an intermediate quantum state, wherein the qubit with the intermediate quantum state has the target excited state 1 state, i.e., the |1> state, and the other bits remain in the 0 state. All parallel two-bit gate operations are performed in the subsequent circuit to obtain a qubit with a target quantum state, and it is measured, for example, by using a dispersion reading method to obtain the measured combination probability and state probability.

[0063] According to an embodiment of the present application, whether there is a correlation error between different quantum bit combinations is determined based on multiple measured combination probabilities and multiple state probabilities.

[0064] According to the embodiments of the present application, the parallel quantum gate correlation error detection method of the present application requires a maximum of n experiments for n groups of parallel two-bit gates, which greatly reduces the number of experiments required and can directly analyze the source of the error, facilitating subsequent adjustment of the two-bit gate parameters to avoid the error.

[0065] According to an embodiment of the present application, a quantum bit with an initial quantum state in at least one quantum bit combination is subjected to quantum state excitation processing to obtain a quantum bit with an intermediate quantum state, and multiple target gate operations are performed on each quantum bit with an initial quantum state and each quantum bit with an intermediate quantum state to obtain a quantum bit with a target quantum state, and multiple quantum bits with a target quantum state obtained after each error detection are measured to obtain a measurement data set, and based on multiple measured combination probabilities and multiple state probabilities in the measurement data set, it is determined whether there is a correlation error between different quantum bit combinations. The detection method of the present application can effectively calibrate whether there is a correlation error between parallel quantum gates, thereby improving the detection efficiency of correlation errors.

[0066] According to an embodiment of the present application, when the target gate operation is a control Z gate (CZ), a quantum state excitation process is performed on a quantum bit having an initial quantum state in a quantum bit combination.

[0067] According to an embodiment of the present application, determining whether there is a correlation error between different quantum bit combinations based on multiple measured combination probabilities and multiple state probabilities includes:

[0068] When the number of quantum bit combinations is two, determining a first combination probability threshold and a second combination probability threshold according to two state probabilities respectively belonging to different quantum bit combinations;

[0069] The degree of correlation of correlation errors between different quantum bit combinations is characterized based on the measured combination probability, the first combination probability threshold and the second combination probability threshold.

[0070] According to an embodiment of the present application, characterizing the degree of correlation of correlation errors between different qubit combinations based on the measured combination probability, the first combination probability threshold, and the second combination probability threshold includes:

[0071] Calculating a first absolute difference between the measured combined probability and a first combined probability threshold;

[0072] Calculating a second absolute difference between the measured combined probability and a second combined probability threshold;

[0073] A correlation degree of correlation error is determined based on the first absolute difference and the second absolute difference, which characterizes whether there is correlation error between different combinations of quantum bits.

[0074] According to an embodiment of the present application, determining, according to the first absolute difference and the second absolute difference, whether there is a correlation error correlation degree between different quantum bit combinations includes:

[0075] When the first absolute difference is greater than the second absolute difference, determining a first correlation probability characterizing that there is a correlation error between different quantum bit combinations;

[0076] When the first absolute difference is greater than the second absolute difference, a second correlation probability is determined, which indicates that there is a correlation error between different quantum bit combinations.

[0077] According to an embodiment of the present application, the first correlation probability represents that there is a larger correlation error between different quantum bit combinations, and the second correlation probability represents that there is a smaller correlation error between different quantum bit combinations.

[0078] In a first specific embodiment, in the error detection of the interaction between |01> and |10>, according to the attached Figure 3 For a quantum circuit, it will be necessary to verify whether the quantum bit combination corresponding to the interacting two-bit gates excites a single quantum bit with an initial quantum state in any of the groups. For example, it is necessary to verify whether there is interaction between |01> and |10> between the two groups of CZ gates Q1-Q2 and Q5-Q6. In this case, Q1 (or Q2) needs to be excited, and the other bits remain in the 0 state. All parallel two-bit gates are executed in the subsequent circuit. Similarly, the number of layers of parallel two-bit gates can be increased to accumulate errors and read P01 (or P012) for all bits.

[0079] If the two-bit gates under test interact with each other, the accumulation of the |1> state can be measured in the corresponding bit, that is, assuming that Q1 is excited, the probability of Q5 and Q6 being in the 1 state can be counted to detect whether Q1 interacts with Q5 and Q6. There is no problem in directly using the probability of Q5 and Q6 reaching the |1> state as the correlation statistic when only Q1 is excited, but in order to reduce the total number of running experiments, the bits in other two-bit gates can be excited at the same time. That is, assuming that it is necessary to test whether Q1-Q2 and Q3-Q4 have an impact on Q5-Q6 respectively, Q1 and Q3 can be excited at the same time, and the bit states of Q1, Q3, Q5, and Q6 can be read. For example, if it is necessary to detect whether Q1 is associated with Q5, the following analysis can be performed. Assuming that a total of n error detections are performed, the probability of Q1 being in P1 can be counted as P1_Q1, and the probability of Q5 being in P1 can be counted as P1_Q5.

[0080] According to an embodiment of the present application, if the excitation of Q1 is not associated with the excitation of Q5, then the measured combined probabilities of Q1-Q5 being |01> and |10> are closer to the second combined probability threshold as shown in formula (1), that is, the first absolute difference is greater than the second absolute difference:

[0081] P01 = (1-P1_Q1) * P1_Q5

[0082] P10 = (1-P1_Q5)*P1_Q1 (1)

[0083] The statistical standard deviation corresponds to sqrt((1-P01)*P01) / n) and sqrt((1-P10)*P10) / n). In principle, the statistical standard deviation can be reduced by increasing the number of measurements.

[0084] According to an embodiment of the present application, if the excitation of Q5 comes from Q1, under ideal reading, the measured combination probability of |01> and |10> is closer to the first combination probability threshold as shown in formula (2), that is, the first absolute difference is less than the second absolute difference:

[0085] P01 = P1_Q5, P10 = P1_Q1 (2)

[0086] At this time, there will be obvious differences from the unrelated data. Considering the reading error and decoherence error, formula (2) cannot be strictly established, but it will deviate from the second combination probability threshold shown in formula (1).

[0087] According to the embodiment of the present application, the deviation from the first combination probability threshold, that is, the excitation of Q5 is correlated with the excitation of Q1. In general, it should be possible to analyze the excitation correlation of the bit pairs between 01 in any team of initial states, so as to determine whether there is a correlation error between |01> and |10>.

[0088] Figure 4 A schematic diagram of a detection circuit for interaction between |11> and |02> (or |20>) according to an embodiment of the present application is shown, and Figure 3 It is similar, except that at the beginning of the quantum circuit, X gates are implemented on Q1 and Q5 at the same time, so that the initial state of Q1-Q5 is prepared to be |11>.

[0089] In a second specific embodiment, for the error detection of the interaction between |11> and |20> (or |02>), according to the attached Figure 4 For the circuit, it will be necessary to check whether the bits corresponding to the interacting two-bit gates are all excited to the 1 state. For example, it is necessary to detect whether there is |11> and |20> (or |02>) interaction between the two groups of CZ gates Q1-Q2 and Q5-Q6. In this case, Q1 (or Q2) and Q5 (or Q6) need to be excited to the 1 state, and the other bits need to remain in the 0 state. Then, all parallel two-bit gates are executed in the circuit. In order to accumulate errors, the number of layers of parallel two-bit gates here needs to be sufficient, and then P012 reading is performed on all bits.

[0090] According to the embodiments of the present application, if the two-bit gates being detected interact with each other, the accumulation of the 2-state can be measured on the corresponding bit. It should be noted that when Q1-Q2 and Q5-Q6 perform gate operations in series, |11> and |20> interactions between their own two bits will also occur, and these are often the main items of state leakage errors. Therefore, it is necessary to avoid the simultaneous excitation of two bits in the same group of two-bit gates. When only checking the influence between two groups of CZ gates, the probability of the corresponding bit's |2> state can be directly used as an indicator of correlation. For more groups of CZ gates, we can analyze it in the same way as when detecting the interaction between |01> and |10>. For example, detect the error of the interaction between |11> and |20> between Q1-Q5. Assuming that a total of n error detections are performed, the individual statistical probabilities of this pair of bits are counted, P0_Q1, P1_Q1, P2_Q1, P0_Q5, P1_Q5, P2_Q5. If there is no interaction between this pair of bits, then the appearance of the 0 state and the 2 state is not correlated (that is, there is no correlation error). The measured combination probability should be closer to the second combination probability threshold shown in formula (3), that is, the first absolute difference is greater than the second absolute difference:

[0091] P02_Q1Q5 = P0_Q1* P2_Q5, P20_Q1Q5 = P2_Q1*P0_Q5 (3)

[0092] If the reading and decoherence errors are not considered, 02 comes entirely from the interaction between the pair of bits (i.e., there is a correlation error). In this case, the measured combination probability should be closer to the first combination probability threshold as shown in formula (4), that is, the first absolute difference is smaller than the second absolute difference:

[0093] P02_Q1Q5 = P0_Q1 = P2_Q5, P20_Q1Q5 =P2_Q1= P0_Q5 (4)

[0094] According to an embodiment of the present application, when the target gate operation is an Iswap-like gate, a quantum state excitation process is performed on a quantum bit with an initial quantum state in each quantum bit combination.

[0095] According to an embodiment of the present application, for another two-bit gate Iswap-like gate, the principle is to exchange |01> and |10> between two bits, so for Figure 3 and Figure 4 In the quantum circuit, even if only one qubit with an initial quantum state is stimulated, since the Iswap-like gate will exchange the layout numbers of two qubits with initial quantum states, it is necessary to consider the combination of two groups of qubits corresponding to all qubits with initial quantum states when analyzing the data.

[0096] According to an embodiment of the present application, determining whether there is a correlation error between different quantum bit combinations based on multiple measured combination probabilities and multiple state probabilities includes:

[0097] When the number of quantum bit combinations is two, determining a third combination probability threshold and a fourth combination probability threshold according to four state probabilities respectively belonging to different quantum bit combinations;

[0098] According to the measured combination probability, the third combination probability threshold and the fourth combination probability threshold, the degree of correlation that characterizes whether there is a correlation error between different quantum bit combinations is determined.

[0099] According to an embodiment of the present application, determining the degree of correlation that characterizes whether there is a correlation error between different quantum bit combinations according to the measured combination probability, the third combination probability threshold, and the fourth combination probability threshold includes:

[0100] Calculating a third absolute difference between the measured combined probability and a third combined probability threshold;

[0101] calculating a fourth absolute difference between the measured combined probability and a fourth combined probability threshold;

[0102] A correlation degree characterizing whether correlation errors exist between different quantum bit combinations is determined according to the third absolute difference and the fourth absolute difference.

[0103] According to an embodiment of the present application, determining the degree of correlation that characterizes whether there is a correlation error between different quantum bit combinations according to the third absolute difference and the fourth absolute difference includes:

[0104] When the third absolute difference is greater than the fourth absolute difference, determining a third correlation probability characterizing the existence of correlation errors between different quantum bit combinations;

[0105] When the third absolute difference is greater than the fourth absolute difference, a fourth correlation probability is determined, which characterizes the existence of correlation errors between different quantum bit combinations.

[0106] According to an embodiment of the present application, the third correlation probability represents that there is a larger correlation error between different quantum bit combinations, and the fourth correlation probability represents that there is a smaller correlation error between different quantum bit combinations.

[0107] In a first specific embodiment, for the interaction between |01> and |10>, similar to the CZ gate, according to the attached Figure 3 For a quantum circuit, it will be necessary to verify whether there are multiple quantum bit combinations corresponding to interacting two-bit gates that excite a single quantum bit with an initial quantum state in any group. Taking Q1-Q2 and Q5-Q6 as examples, assuming that Q1 is excited, after N rounds of Iswap-like gates, Q1, Q2, Q5, and Q6 are measured to obtain a measurement data set.

[0108] According to an embodiment of the present application, if there is no correlation error between Q1-Q2 and Q5-Q6, the measured combined probability is closer to the fourth combined probability threshold as shown in formula (5), that is, the third absolute difference is greater than the fourth absolute difference:

[0109] ;

[0110] (5)

[0111] If there is a correlation between the two groups of two-bit gates, then ideally the measured combination probability is closer to the third combination probability threshold as shown in formula (6), that is, the third absolute difference is smaller than the fourth absolute difference:

[0112] P1000_Q1Q2Q5Q6+P0100_Q1Q2Q5Q6 = (P10_Q1Q2+P01_Q1Q2)

[0113] P0010_Q1Q2Q5Q6+P0001_Q1Q2Q5Q6 = (P10_Q5Q6+P01_Q5Q6) (6)

[0114] According to an embodiment of the present application, it is determined whether there are correlation errors of |01> and |10> between two groups of quantum bit combinations according to formulas (5) and (6).

[0115] In a second specific embodiment, for the error detection of the interaction between |11> and |20> (or |02>), according to the attached Figure 4 For a quantum circuit, we need to select one quantum bit with an initial quantum state from each of the two groups of quantum bits to excite, for example, to excite Q1 and Q5. After n rounds of two-bit gates, we measure Q1, Q2, Q5, and Q6 to obtain a measurement data set.

[0116] According to an embodiment of the present application, if there is no correlation error between Q1-Q2 and Q5-Q6, the measured combined probability is closer to the fourth combined probability threshold as shown in formula (7), that is, the third absolute difference is greater than the fourth absolute difference:

[0117] P0200_Q1Q2Q5Q6+P2000_Q1Q2Q5Q6=(P20_Q1Q2+P02_Q1Q2)*P00_Q5Q6;

[0118] P0002_Q1Q2Q5Q6+P0020_Q1Q2Q5Q6=(P20_Q5Q6+P02_Q5Q6)*P00_Q1Q2 (7)

[0119] According to an embodiment of the present application, if there is a correlation between the two groups of quantum bit combinations, then ideally the measured combination probability is closer to the third combination probability threshold as shown in formula (8), that is, the third absolute difference is less than the fourth absolute difference:

[0120] P0200_Q1Q2Q5Q6+P2000_Q1Q2Q5Q6 = (P20_Q1Q2+P02_Q1Q2),

[0121] P0002_Q1Q2Q5Q6+P0020_Q1Q2Q5Q6 = (P20_Q5Q6+P02_Q5Q6) (8)

[0122] According to an embodiment of the present application, it is determined whether there are correlation errors of |01> and |10> between two groups of quantum bit combinations according to formulas (7) and (8).

[0123] According to the embodiments of the present application, since different two-bit gates are implemented in different principles, the specific circuits will be different, but the principles of the inspection ideas are similar. The present application takes the mainstream CZ gate and iswap-like gate as examples, and designs corresponding schemes and specific circuits for detecting associated errors, but does not limit the present application to only detect the target gate operations as CZ gates and iswap-like gates.

[0124] It should be noted that in the above specific example, Pefgh_QaQbQcQd represents the probability that the quantum bit Qa is in the e state, Qb is in the f state, Qc is in the g state, and Qd is in the h state in n detections, where e, f, g, and h can all be quantum states such as 0, 1, and 2, and a, b, c, and d represent the numbers of the quantum bits in the quantum circuit. The QaQbQcQd in the above probability can be two, three, or four quantum bits, and there is no limit to the number.

[0125] Figure 5 A block diagram of a parallel quantum gate correlation error detection device according to an embodiment of the present application is shown.

[0126] like Figure 5 As shown, the parallel quantum gate correlation error detection device 500 includes an acquisition module 510, an excitation module 520, a obtaining module 530, a measurement module 540, and a determination module 550.

[0127] An acquisition module 510 is used to acquire multiple quantum bit combinations in each error detection, wherein the quantum bit combination includes two quantum bits with an initial quantum state, and the number of error detections is n times;

[0128] An excitation module 520, configured to perform quantum state excitation processing on a quantum bit having an initial quantum state in at least one quantum bit combination to obtain a quantum bit having an intermediate quantum state, wherein the quantum bit having the intermediate quantum state has a target excited state;

[0129] An obtaining module 530 is used to perform multiple target gate operations on each qubit having an initial quantum state and each qubit having an intermediate quantum state to obtain a qubit having a target quantum state;

[0130] A measurement module 540 is used to measure the multiple qubits with target quantum states obtained after each error detection to obtain a measurement data set, wherein the measurement data set includes multiple measured combination probabilities of at least two qubits with target quantum states being in different first target states and a state probability of each qubit with the target quantum state being in a second target state, wherein the at least two qubits with the target quantum states belong to different qubit combinations respectively;

[0131] The determination module 550 is used to determine whether there is a correlation error between different quantum bit combinations based on multiple measured combination probabilities and multiple state probabilities.

[0132] According to the embodiments of the present application, any one or more of the modules, submodules, units, and subunits, or at least part of the functions of any one of them can be implemented in one module. According to the embodiments of the present application, any one or more of the modules, submodules, units, and subunits can be split into multiple modules for implementation. According to the embodiments of the present application, any one or more of the modules, submodules, units, and subunits can be at least partially implemented as hardware circuits, such as field programmable gate arrays (FPGAs), programmable logic arrays (PLAs), systems on chips, systems on substrates, systems on packages, application specific integrated circuits (ASICs), or can be implemented by hardware or firmware in any other reasonable way of integrating or packaging the circuit, or in any one of the three implementation methods of software, hardware, and firmware, or in any appropriate combination of any of them. Alternatively, according to the embodiments of the present application, one or more of the modules, submodules, units, and subunits can be at least partially implemented as computer program modules, and when the computer program modules are run, the corresponding functions can be executed.

[0133] For example, any multiple of the acquisition module 510, the excitation module 520, the obtaining module 530, the measuring module 540, and the determination module 550 can be combined in one module / unit / sub-unit for implementation, or any one of the modules / units / sub-units can be split into multiple modules / units / sub-units. Alternatively, at least part of the functions of one or more of these modules / units / sub-units can be combined with at least part of the functions of other modules / units / sub-units and implemented in one module / unit / sub-unit. According to an embodiment of the present application, at least one of the acquisition module 510, the excitation module 520, the obtaining module 530, the measuring module 540, and the determination module 550 can be at least partially implemented as a hardware circuit, such as a field programmable gate array (FPGA), a programmable logic array (PLA), a system on a chip, a system on a substrate, a system on a package, an application specific integrated circuit (ASIC), or can be implemented by hardware or firmware such as any other reasonable way of integrating or packaging the circuit, or implemented in any one of the three implementation methods of software, hardware, and firmware, or in any appropriate combination of any of them. Alternatively, at least one of the acquisition module 510, the excitation module 520, the obtaining module 530, the measurement module 540, and the determination module 550 may be at least partially implemented as a computer program module, and when the computer program module is executed, the corresponding function may be executed.

[0134] It should be noted that the detection device part of the parallel quantum gate correlation error in the embodiment of the present application corresponds to the detection method part of the parallel quantum gate correlation error in the embodiment of the present application. The description of the detection device part of the parallel quantum gate correlation error specifically refers to the detection method part of the parallel quantum gate correlation error, which will not be repeated here.

[0135] The embodiments of the present application are described above. However, these embodiments are only for the purpose of illustration, and are not intended to limit the scope of the present application. Although each embodiment is described above, this does not mean that the measures in each embodiment cannot be used in combination advantageously. The present application does not depart from the scope of the present application, and those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present application.

Claims

1. A method for detecting correlation errors of parallel quantum gates, characterized in that: include: In each error detection case, a plurality of quantum bit combinations are obtained, wherein the quantum bit combination includes two quantum bits having an initial quantum state, and the number of error detections is n times; Performing quantum state excitation processing on a quantum bit having an initial quantum state in at least one of the quantum bit combinations to obtain a quantum bit having an intermediate quantum state, wherein the quantum bit having the intermediate quantum state has a target excited state; Performing multiple target gate operations on each of the qubits having the initial quantum state and each of the qubits having the intermediate quantum state to obtain qubits having the target quantum state; Measuring the plurality of qubits with the target quantum state obtained after each error detection to obtain a measurement data set, wherein the measurement data set includes a plurality of measured combination probabilities of at least two qubits with the target quantum state being in different first target states and a state probability of each qubit with the target quantum state being in a second target state, wherein the at least two qubits with the target quantum state belong to different qubit combinations respectively; Based on the multiple measured combination probabilities and the multiple state probabilities, determine whether there is a correlation error between different quantum bit combinations.

2. The method according to claim 1, characterized in that In the case where the target gate operation is to control a Z gate, a quantum state excitation process is performed on a quantum bit having an initial quantum state in a quantum bit combination.

3. The method according to claim 2, characterized in that Determining whether there is a correlation error between different quantum bit combinations according to the plurality of measured combination probabilities and the plurality of state probabilities includes: When the number of the quantum bit combinations is two, determining a first combination probability threshold and a second combination probability threshold according to the two state probabilities respectively belonging to different quantum bit combinations; A correlation degree characterizing whether there is a correlation error between different quantum bit combinations is determined based on the measured combination probability, the first combination probability threshold, and the second combination probability threshold.

4. The method according to claim 3, characterized in that Determining, according to the measured combination probability, the first combination probability threshold, and the second combination probability threshold, a correlation degree characterizing whether there is a correlation error between different quantum bit combinations, including: Calculating a first absolute difference between the measured combined probability and the first combined probability threshold; Calculating a second absolute difference between the measured combined probability and the second combined probability threshold; A value indicating whether there is a correlation degree of correlation error between different quantum bit combinations is determined according to the first absolute difference and the second absolute difference.

5. The method according to claim 4, characterized in that Determining, according to the first absolute difference and the second absolute difference, whether there is a correlation error correlation degree between different quantum bit combinations, comprises: When the first absolute difference is less than the second absolute difference, determining a first correlation probability characterizing that there is a correlation error between different quantum bit combinations; When the first absolute difference is greater than the second absolute difference, a second correlation probability is determined, which indicates that there is a correlation error between different quantum bit combinations.

6. The method according to claim 1, characterized in that In the case where the target gate operation is an Iswap-like gate, a quantum state excitation process is performed on a quantum bit having an initial quantum state in each of the quantum bit combinations.

7. The method according to claim 6, characterized in that Determining whether there is a correlation error between different quantum bit combinations according to the plurality of measured combination probabilities and the plurality of state probabilities includes: When the number of the quantum bit combinations is two, determining a third combination probability threshold and a fourth combination probability threshold according to the four state probabilities respectively belonging to different quantum bit combinations; The degree of correlation that characterizes whether there is correlation error between different quantum bit combinations is determined according to the measured combination probability, the third combination probability threshold and the fourth combination probability threshold.

8. The method according to claim 7, characterized in that Determining, according to the measured combination probability, the third combination probability threshold, and the fourth combination probability threshold, a correlation degree characterizing whether there is a correlation error between different quantum bit combinations, including: Calculating a third absolute difference between the measured combined probability and the third combined probability threshold; Calculating a fourth absolute difference between the measured combined probability and the fourth combined probability threshold; A correlation degree characterizing whether correlation errors exist between different quantum bit combinations is determined according to the third absolute difference and the fourth absolute difference.

9. The method according to claim 8, characterized in that Determining, according to the third absolute difference and the fourth absolute difference, a correlation degree characterizing whether there is a correlation error between different quantum bit combinations, comprises: When the third absolute difference is less than the fourth absolute difference, determining a third correlation probability characterizing that there is a correlation error between different quantum bit combinations; When the third absolute difference is greater than the fourth absolute difference, a fourth correlation probability is determined, which characterizes the existence of correlation errors between different quantum bit combinations.

10. A parallel quantum gate correlation error detection device, comprising: An acquisition module, used for acquiring a plurality of quantum bit combinations in each error detection, wherein the quantum bit combination includes two quantum bits in an initial quantum state, and the number of error detections is n times; an excitation module, configured to perform quantum state excitation processing on a quantum bit having an initial quantum state in at least one of the quantum bit combinations to obtain a quantum bit having an intermediate quantum state, wherein the quantum bit having the intermediate quantum state has a target excited state; An obtaining module, used for performing multiple target gate operations on each of the qubits having the initial quantum state and each of the qubits having the intermediate quantum state, to obtain a qubit having a target quantum state; A measurement module, configured to measure the plurality of qubits with the target quantum state obtained after each error detection to obtain a measurement data set, wherein the measurement data set includes a plurality of measured combination probabilities of at least two qubits with the target quantum state being in different first target states and a state probability of each qubit with the target quantum state being in a second target state, wherein the at least two qubits with the target quantum state belong to different qubit combinations respectively; A determination module is used to determine whether there is a correlation error between different quantum bit combinations based on the multiple measured combination probabilities and the multiple state probabilities.

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