Methods and related equipment for measuring electron spin of NV color centers

Abstract

This application relates to a method and related equipment for measuring the electron spin of an NV center. Based on the hyperfine interaction between the NV center and the target atomic nucleus in the diamond it resides in, the electron spin state of the NV center is mapped to the nuclear spin state of the atomic nucleus. The method includes: repeatedly performing a quantum non-destructive measurement procedure on the electron spin multiple times to obtain multiple measured values ​​of the magnetic quantum number. The quantum non-destructive measurement procedure includes: based on the hyperfine interaction, mapping the electron spin state carried by the nuclear spin state back to the optically distinguishable state to be measured, and obtaining the measured value by measuring the fluorescence intensity emitted by the NV center under laser excitation; selecting the correct result from multiple measured values. This application solves the problem that after the standard ODMR measures the spin state of the NV center, the electron spin state of the NV center is reset, making it unsuitable for Ising machine feedback control that requires multiple iterations.

Description

Technical Field

[0001] This application relates to the field of quantum information processing technology, and in particular to a method and related equipment for measuring the electron spin of NV color centers. Background Technology

[0002] The NV-center Ising machine is a dedicated quantum simulator or quantum computer that uses nitrogen-vacancy (NV) centers in diamond as the physical carriers of qubits to construct and run the Ising model. Currently, in NV-center Ising machine technology, the main technique for reading the spin states of NV centers is Optically Detected Magnetic Resonance (ODMR). The destructive problems of ODMR readout include: During the standard ODMR readout of the spin state of the NV color center, the following method is used: After laser irradiation of the NV color center, the electron spin magnetic quantum number of the NV color center... The state relaxes to the state through intersystem crossing (ISC). The baseline state. Single readout fidelity is approximately... However, after standard ODMR measures the spin state of the NV center, the electron spin state of the NV center is reset, making it unusable for Ising machine feedback control, which requires multiple iterations, leading to the breakdown of the Ising machine feedback loop. Intersystem crossing (ISC) is an important nonradiative transition process in molecular and solid-state systems. Summary of the Invention

[0003] The present application provides a method and related equipment for measuring the electron spin of the NV center, which at least solves the problem mentioned in the background art that after the standard ODMR measures the spin state of the NV center, the electron spin state of the NV center is reset and cannot be used for Ising machine feedback control that requires multiple iterations.

[0004] According to one aspect of this application, a method for measuring the electron spin of an NV color center is provided, which maps the electron spin state of the NV color center to the nuclear spin state of the atomic nucleus based on the hyperfine interaction between the NV color center and the target atomic nucleus in the diamond in which it is located, so that the magnetic quantum number characterizing the electron spin state is... The method includes taking different values ​​for the nuclear spin to correspond to different states. The electron spin is repeatedly subjected to a quantum non-destructive measurement process multiple times to obtain the magnetic quantum number. The quantum non-destructive measurement process includes: based on the hyperfine interaction, mapping the electron spin state carried by the nuclear spin state back to the optically distinguishable state to be measured, and then obtaining the measured value by measuring the fluorescence intensity emitted by the NV color center under laser excitation; Select the correct result from the multiple measured values.

[0005] Furthermore, the NV color centers are at least applied to a quantum computer, which includes multiple logical spins composed of multiple NV color centers in diamond. After selecting the correct result from multiple measurements, the method further includes: The correct result is taken as the final decision result of the logical spin.

[0006] Further, the state to be measured includes a reference state or a flipped state. After measuring the fluorescence intensity emitted by the NV color center, the electron spin is in the reference state. The step of mapping the electron spin state carried by the nuclear spin state back to the optically distinguishable state to be measured includes: A microwave pulse is applied to the electron spin to cause the electron spin to flip from the reference state to the flipped state or remain in the reference state under the action of the microwave pulse, wherein: When the nuclear spin is in the first state and the frequency of the applied microwave pulse resonates with the first transition frequency of the electron spin, under the hyperfine interaction, the microwave pulse drives the electron spin to flip from the reference state to the flipped state; When the nuclear spin is in the second state and the frequency of the microwave pulse is detuned from the first transition frequency, the electron spin remains in the reference state.

[0007] Further, the state to be tested includes a reference state or a flipped state, the quantum nondestructive measurement procedure is executed R times, where R is an odd number, the measured values ​​include the measured values ​​corresponding to the reference state and / or the flipped state, and the step of selecting the correct result from the multiple measured values ​​includes: A majority vote is conducted on the R measured values, and the measured value with the most votes is taken as the correct result.

[0008] Furthermore, the measured value , ( ),value The measured value of the reference state, the value The measured value in the flipped state, wherein the fidelity of the measured value in a single measurement is The effective fidelity of the measurement with the most votes is ,but The following relationship must be satisfied:

[0009] in, express Round up.

[0010] Furthermore, if the set time budget is The time for a single measurement is Then the optimal number of repetitions for R is... equal and The value is rounded down, and the single measurement time includes the time for a single execution of the quantum non-destructive measurement process.

[0011] Furthermore, the method also includes: If the characteristic evolution time of the dynamic system is The time required to map the electron spin state to the nuclear spin state is The total time taken to obtain multiple of the measured values + At that time, control No more than 1.25% The dynamic system is a system in which the logical spin is allowed to maintain effective evolution and correlation between two adjacent feedback updates.

[0012] Furthermore, the method also includes: In the measurement of the j-th electron spin... When the measured value is given, the ( ) The measured values ​​of the electron spins are transmitted to the calculation module for preprocessing. The preprocessing includes at least one of majority voting and feedback calculation. The feedback calculation is used to calculate the feedback field required to adjust the electron spins based on the final decision result, where j is an integer.

[0013] Furthermore, the step of mapping the electron spin state of the NV color center to the nuclear spin state of the atomic nucleus includes: A pre-set controlled NOT gate control condition is applied to the nuclear spin. The controlled NOT gate control condition is configured to: when the electron spin is in a reference state, keep the nuclear spin in a first state of no rotation; when the electron spin is in a flipped state, switch the nuclear spin from the first state to a rotation angle. The second state.

[0014] Furthermore, the controlled NOT gate control condition is configured as follows: ; In the above formula, The electron spin is in The projection operator in this reference state The electron spin is in The projection operator in this flipped state, symbol " " represents the tensor product, For the identity operator of the nuclear spin, This indicates that the nuclear spin does not rotate. This indicates that the nuclear spin revolves around the NV color center. Axis rotation angle Rotation operator.

[0015] Furthermore, the step of applying a pre-set controlled NOT gate control condition to the nuclear spin includes: A radio frequency pulse is applied to the nuclear spin, causing the nuclear spin to rotate by an angle under the action of the radio frequency pulse. Or not rotate, where: When the electron spin is in the flipped state, and the deviation between the frequency of the applied radio frequency pulse and the second transition frequency of the nuclear spin is less than a predetermined value, under the hyperfine interaction, the radio frequency pulse is in a resonant state to drive the nuclear spin rotation angle. ; When the electron spin is in the reference state and the frequency of the radio frequency pulse is detuned to the transition frequency, the nuclear spin does not rotate.

[0016] Furthermore, the step of selecting the correct result from the plurality of said measurements also includes: Under asymmetric noise conditions, when performing maximum likelihood estimation on R measurements based on the likelihood function, a predetermined statistical decision strategy is used to extract the correct result from the R measurements. This predetermined statistical decision strategy includes weighted voting or threshold decision; and / or... The atomic nucleus includes the nucleus of the target carbon element or the target nitrogen element, and the target carbon element is located in the first shell near the NV color center.

[0017] According to another aspect of this application, an apparatus for measuring the electron spin of an NV center is provided, the apparatus being used to implement the method for measuring the electron spin of an NV center.

[0018] According to another aspect of this application, an electronic device is provided, comprising: a processor, and a memory storing a program, the program including instructions that, when executed by the processor, cause the processor to perform the method for measuring the electron spin of the NV color center.

[0019] According to another aspect of this application, a non-transient machine-readable medium storing computer instructions is provided for causing a computer to perform the method for measuring the electron spin of the NV color center.

[0020] The beneficial effects of the embodiments of this application are as follows: This application's embodiments map the electron spin state of the NV color center to the nuclear spin state of the atomic nucleus, so that the magnetic quantum number characterizing the electron spin state... Different values ​​of nuclear spin correspond to different states, thus the state information of electron spin is cached in the nuclear spin. In other words, this application uses nuclear spin as a "quantum cache" to cache the electron spin state. The provided method for measuring the electron spin of the NV color center can repeatedly perform a quantum non-destructive measurement process on the electron spin to obtain the magnetic quantum number. Multiple measurements are obtained. During measurement, the electron spin state carried by the nuclear spin state is mapped back to the optically distinguishable state of the electron spin before the measurement value is obtained by optical readout. Although optical readout resets the electron spin state, since the nuclear spin is not coupled with optical transitions, each measured value (i.e., the optical readout result) actually reflects the historical state of the electron spin stored in the nuclear spin, solving the problem of iterative closed-loop breakage caused by destructive measurement in traditional ODMR readout methods. This application can also select the correct result from multiple obtained measurements (this correct result can be used as the final decision result of the logical spin), and can obtain high-fidelity repeatable measurement results of the electron spin without losing the original state information of the electron spin, improving the accuracy of the final decision result of the determined logical spin and significantly reducing the probability of misjudgment. The measured electron spin can be reinitialized according to the feedback field calculated by the quantum computer, thereby supporting the closed-loop iterative control of the quantum computer and ensuring iterative convergence.

[0021] Details of one or more embodiments of this application are set forth in the following drawings and description to make other features, objects and advantages of this application more readily apparent. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a flowchart illustrating a method for measuring the electron spin of an NV color center according to an embodiment of this application.

[0024] Figure 2 A graph showing the fidelity improvement for repeated measurements (repeated readings). Detailed Implementation

[0025] Embodiments of this application will now be described in more detail with reference to the accompanying drawings. While some embodiments of this application are shown in the drawings, it should be understood that embodiments of this application can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the embodiments of this application. It should be understood that the accompanying drawings and embodiments are for illustrative purposes only and are not intended to limit the scope of protection of this application.

[0026] As mentioned above, after the standard ODMR measures the spin state of the NV center, the electron spin state of the NV center is reset, making it unsuitable for Ising machine feedback control, which requires multiple iterations. In response, the inventors of this application, through in-depth research, discovered that diamond, in addition to the NV center, also contains carbon elements (such as...). , The nuclei of carbon atoms possess magnetic moments (i.e., spin). A hyperfine interaction exists between the NV color center and the carbon nucleus; this interaction is a magnetic dipole interaction between the NV color center and the nuclear spin of a carbon nucleus at a specific location. Based on this hyperfine interaction, quantum non-destructive measurement operators (QND) can be constructed to extract accurate information about the quantum state without destroying the quantum state of the measured electron spin.

[0027] In the process of constructing quantum non-destructive measurement QND operators, although non-destructive measurement QND for general quantum information experiments can achieve single readout of the electron spin of the NV color center, when the QND readout is specifically designed for a quantum computer oriented towards the Ising model, the fidelity of the readout result is limited and insufficient to support large-scale dynamical systems. , (The total number of logical spins participating in one iterative feedback calculation). When the size of the dynamical system exceeds 100 logical spins, if the single readout accuracy is only approximately... The overall probability of a single, accurate readout of the entire dynamical system decreases rapidly with scale. While a single readout may appear to have high fidelity, it is still insufficient for large-scale dynamical systems.

[0028] To address the aforementioned problems, the first embodiment of this application provides a method for measuring the electron spin of an NV color center. Based on the hyperfine interaction between the NV color center and the target atomic nucleus in the diamond it resides in, the electron spin state of the NV color center is mapped to the nuclear spin state of the atomic nucleus, thereby enabling the characterization of electron spin (such as electron spin...) Quantity Magnetic quantum number of the state Nuclear spin with different values ​​( ( ) correspond to different states. Thus, the electron spin is controlled. State information is cached in the nuclear spin middle.

[0029] Please see Figure 1 The measurement method provided in this application includes the following steps: Step S11: Repeatedly perform a quantum non-destructive measurement procedure on the electron spin multiple times to obtain the magnetic quantum number. The quantum non-destructive measurement process includes: based on hyperfine interaction, mapping the electron spin state carried by the nuclear spin state back to the optically distinguishable state to be measured, and then obtaining the measurement value by measuring the fluorescence intensity emitted by the NV color center under laser excitation.

[0030] Step S12: Select the correct result from multiple measurements.

[0031] Although the electron spin state of the NV color center is reset after a single measurement, While the electron spin's magnetic moment is approximately 2000 times smaller than that of the electron spin, the nuclear spin does not participate in optical transitions. The historical state of the electron spin remains cached within the nuclear spin, laying the foundation for subsequent repeated measurements. In the optical readout process of this application, the electron spin itself is reset, but the protected historical state information has already been transferred and stored in the nuclear spin. Therefore, the overall process achieves non-destructive reading of the electron spin state information. This realizes indirect quantum non-destructive reading of electron spin based on electron spin state storage using auxiliary nuclear spin.

[0032] Therefore, selecting the correct result from multiple measurements can improve the overall probability of accurate measurements in large-scale dynamic systems, thereby improving the accuracy in multi-round iterative feedback control.

[0033] Based on the above steps S11 to S12, this embodiment of the application maps the electronic spin state of the NV color center to the nuclear spin state of the atomic nucleus, so that the magnetic quantum number characterizing the electronic spin state... Different values ​​of nuclear spin correspond to different states, thus the state information of electron spin is cached in the nuclear spin. In other words, this application uses nuclear spin as a "quantum cache" to cache the electron spin state. The provided method for measuring the electron spin of the NV color center can repeatedly perform a quantum non-destructive measurement process on the electron spin to obtain the magnetic quantum number. Multiple measurements are obtained. During measurement, the electron spin state carried by the nuclear spin state (i.e., the electron spin state stored in the nuclear spin) is mapped back to the optically distinguishable state to be measured before optical readout is performed to obtain the measurement value. Although optical readout resets the electron spin state, since the nuclear spin is not coupled with optical transitions, each measured value (i.e., the optical readout result) actually reflects the historical state of the electron spin stored in the nuclear spin, solving the problem of iterative closed-loop breakage caused by destructive measurement in traditional ODMR readout methods. This application can also select the correct result from multiple measurements (this correct result can be used as the final decision result of the logical spin), and can obtain high-fidelity repeatable measurement results of the electron spin without losing the original state information of the electron spin, improving the accuracy of the final decision result of the determined logical spin and significantly reducing the probability of misjudgment. The measured electron spin can be reinitialized according to the feedback field calculated by the quantum computer, thereby supporting the closed-loop iterative control of the quantum computer (such as the NV color center Ising machine) and ensuring iterative convergence.

[0034] When measuring the fluorescence intensity emitted by the NV color center under laser excitation, the standard ODMR reading method can be used, which involves irradiating the electron spin with a 532nm laser to indirectly obtain the historical state information of the electron spin stored in the nuclear spin.

[0035] The NV color centers in this application are applied at least to quantum computers, which include multiple logical spins. Logical spins are composed of multiple NV color centers in diamond. This application selects the correct result from multiple measurements and uses that result as the final decision for the logical spin, thereby improving the fidelity of the logical spin.

[0036] The atomic nucleus includes the nucleus of the target carbon or nitrogen element, located in the first shell closest to the NV center. The first shell consists of the group of carbon elements surrounding the NV center in the diamond crystal that are directly bonded to or closest to the vacancy at the NV center. When the atomic nucleus is the nucleus of the target carbon element located in the first shell, the nuclear spin of the nucleus can be addressed. Addressability means that the nuclear spin of the target carbon element can be distinguished from and manipulated individually by utilizing hyperfine coupling differences, spectral resolution, or pulse selectivity. The type of target carbon element can include... , One of them. The target nitrogen element may include , One of them.

[0037] The state to be measured includes a reference state or a flipped state. After measuring the fluorescence intensity emitted by the NV center, the electron spin is in the reference state. The steps to map the electron spin state carried by the nuclear spin state back to the optically distinguishable state to be measured include: A microwave pulse is applied to the electron spin, causing the electron spin to flip from a reference state to a flipped state or remain in the reference state under the influence of the microwave pulse, wherein: When the nuclear spin is in the first state and the frequency of the applied microwave pulse resonates with the first transition frequency of the electron spin, the microwave pulse drives the electron spin to flip from the reference state to the flipped state under hyperfine interaction. When the nuclear spin is in the second state and the frequency of the microwave pulse is detuned from the first transition frequency, the electron spin remains in the reference state.

[0038] Therefore, when it is necessary to read the historical states of electron spins stored in the nuclear spin, this application maps the nuclear spin state back to the optically distinguishable state to be measured (i.e., the historical states of electron spins stored in the nuclear spin) using an applied microwave pulse. By reading the brightness of the fluorescence generated by the optical transition process of the electron spin under laser irradiation, the measurement value of the corresponding state to be measured is obtained. When the state to be measured includes a reference state or a flipped state, the fluorescence corresponding to the reference state is bright, and the fluorescence corresponding to the flipped state is dark, thereby accurately measuring the state to be measured.

[0039] The quantum nondestructive measurement process is executed R times, where R is an odd number. The measurements include those corresponding to the reference state and / or the flipped state. The step of selecting the correct result from multiple measurements involves: a majority vote on the R measurements, with the measurement receiving the most votes being the correct result. By using the measurement receiving the most votes as the correct result, the accuracy of the measurements and their corresponding final decisions is improved, meeting the high-fidelity requirements of measurements for large-scale dynamical systems.

[0040] Measured values , ( ),value The measured value is the reference state value. For the measured value in the flipped state, where the fidelity of a single measurement is... (i.e., the probability that a single measurement is correctly judged), the effective fidelity of the measurement with the most votes is ,but The following relationship must be satisfied:

[0041] In the above formula, express Round up.

[0042] Therefore, this application has the following effect: The measurements obtained through independent quantum non-destructive measurement processes are then subject to majority voting, which is equivalent to assigning a probability of correctness to each measurement. 、( Given a probability of error, the probability that a given measurement is correct more than half the time is calculated. This probability of more than half the time is the effective fidelity. ,because When choosing an odd number, there is no tie; majority voting always produces a correct result, and when... When >0.5, as Increase It monotonically approaches 1, thus statistically significantly improving the fidelity and reliability of the final decision result of the logical spin.

[0043] exist When the number of times reaches 11, the values ​​of each number are... The quantitative results are shown in Table 1 below. Figure 2 As shown:

[0044] Table 1 The readout fidelity of a single quantum nondestructive measurement is typically up to 95%, which is insufficient to support the overall fidelity of large-scale systems (N > 100). (demand). As can be seen from Table 1, regardless of single-shot fidelity... Whether it is 90% or 95%, the measurement method provided in this application is used, as... Increasing the value improves the effective fidelity. Gradually improve, in At the same time, two single-shot fidelity corresponding The accuracy rate is consistently above 99%, significantly improving the reliability of the final judgment. In other words, five repeated reads are sufficient to achieve a high fidelity. from Upgraded to Therefore, this application is preferred. Greater than or equal to five.

[0045] Single-step quantum nondestructive measurement also presents a contradiction between the sequence time consumption and the real-time feedback requirement. To resolve this contradiction, this application will impose corresponding constraints on the measurement time and the corresponding time and the characteristic evolution time of the dynamic system to ensure the speed of measurement and the real-time feedback.

[0046] If the set time budget is The time for a single measurement is Then the optimal number of repetitions for R is... equal and The value is rounded down, and the single measurement time includes the time for a single execution of the quantum non-destructive measurement process. The following relationship must be satisfied: .

[0047] Therefore, within a fixed time budget, the maximum number of complete measurements that can be performed under this application is [number missing]. Since increasing the number of repetitions improves the effective fidelity through majority voting, and R is an integer such that it is an odd number, therefore... Using the floor value as the optimal number of repetitions maximizes statistical gain under a fixed time budget, resulting in higher accuracy and reliability of the final decision.

[0048] In some implementations... , , =5.

[0049] To accommodate the real-time requirements of feedback control, the method provided in this application further includes the following steps: If the characteristic evolution time of the dynamic system is The time required to map electron spin states to nuclear spin states is The total time required to obtain multiple measurements + At that time, control No more than 1.25% ,Right now much smaller A dynamical system is a system in which the logical spin is allowed to maintain efficient evolution and correlation between two adjacent feedback updates. For example, if... Approximately 4ms = .

[0050] As can be seen, to ensure a balance between the real-time performance of feedback control and the measurement time, this application controls the total time of the entire measurement process to be within the characteristic evolution time of the dynamic system. Since the total time is much smaller than the characteristic evolution time, the operation of reading the measured value can be regarded as an instantaneous snapshot of the electron spin state, avoiding state aging or evolution distortion caused by measurement delay. This ensures that the feedback control can make timely decisions based on the current accurate electron spin state, maintaining the effectiveness and real-time performance of the closed-loop iteration.

[0051] The method provided in this application also includes the following steps: In measuring the spin of the j-th electron... When the measurement value is 1, the 2nd measurement value will be 3. The measured value of the electron spin is transmitted to the computing module for preprocessing. Preprocessing includes at least one of majority voting and feedback calculation. The feedback calculation is used to calculate the feedback field required for feedback adjustment of the electron spin based on the final decision result. j is an integer, and the computing module may include a field-programmable gate array (FPGA) of a quantum computer. In other words, the raw data—the measured value read from the previous stage—can be sent to the computing module for real-time preprocessing as soon as it is available, without waiting for all electron spins and all repetitions to complete before unified processing. That is, this application, by... The measured value of the electron spin is in the measurement of the j-th electron spin. Simultaneously, the measured values ​​are transmitted to the computation module for preprocessing, achieving pipelined parallelism between measurement and preprocessing. This pipelined parallel design allows for overlap between measurement and preprocessing, hiding some of the preprocessing delay, so that when the measurement of the j-th electron spin is completed, the measurement of the j-th electron spin is completed. The feedback field of each electron spin is ready, thereby shortening the overall iteration cycle and improving the efficiency of real-time feedback control.

[0052] In this application, the step of mapping the electronic spin state of the NV color center to the nuclear spin state of the atomic nucleus includes: A pre-set controlled NOT gate control condition is applied to the nuclear spin. The controlled NOT gate control condition is configured as follows: when the electron spin is in the reference state, the nuclear spin is in a first state of no rotation; when the electron spin is in a flipped state, the nuclear spin is switched from the first state to a rotation angle. The second state.

[0053] Here, this application applies a controlled NOT gate control condition to the nuclear spin, realizing a deterministic mapping from electron spin state information to nuclear spin through a nuclear spin conditional rotation operation controlled by the electron spin state. The binary state of the electron spin (reference state / flipped state) is transformed into a distinguishable state of the nuclear spin (no rotation / rotation angle). This allows the measured state (reference state / flipped state) of the electron spin to be measured to be stored in the form of nuclear spin states, providing a physical foundation for non-destructive and repeatable measurements.

[0054] The controlled NOT gate control conditions are configured as follows: ; In the above formula, For electron spin to be in The projection operator in this reference state For electron spin to be in The projection operator in this flipped state, symbol " " represents the tensor product, nuclear spin The identity operator, This indicates that the nuclear spin does not rotate. Indicates the nuclear spin around the NV color center Axis rotation angle Rotation operator.

[0055] The controlled NOT gate control conditions configured above can be applied when the electron spin is in a controlled NOT state. In this state, the nuclear spin remains unchanged (identity operator). When the electron spin is at In the flipped state, the nuclear spin rotates about the z-axis by an angle. Thus, the controlled NOT gate control condition encodes the quantum state information of the electron spin (whether it is a reference state or a flipped state) into the phase of the nuclear spin in the way that the nuclear spin has rotated, thereby realizing a deterministic mapping from the electron spin state to the nuclear spin.

[0056] The steps of applying pre-set controlled NOT gate control conditions to nuclear spins include: A radio frequency (RF) pulse is applied to the nuclear spin to cause the nuclear spin to rotate by an angle under the action of the RF pulse. Or not rotate, where: When the electron spin is in a flipped state, and the deviation between the frequency of the applied radio frequency pulse and the second transition frequency of the nuclear spin is less than a predetermined value, the radio frequency pulse is in a resonant state under hyperfine interaction to drive the nuclear spin rotation angle. When the electron spin is in the reference state and the frequency of the radio frequency pulse is detuned to the transition frequency, the nuclear spin does not rotate.

[0057] The steps described above for applying controlled NOT gate control conditions utilize the dependence of the nuclear spin resonance frequency on the electron spin state caused by hyperfine interaction to achieve conditional manipulation of the nuclear spin state by the electron spin state, thereby reliably mapping the electron spin state to the rotation state of the nuclear spin and realizing the reliable storage of the historical state of the electron spin by the nuclear spin.

[0058] To make the above-described method for measuring the electron spin of the NV color center clearer, the second embodiment of this application, based on the first embodiment, incorporates the appendix... Figure 2 An application example is provided to further illustrate the above measurement method.

[0059] I) This embodiment first introduces the technical principle of the method for measuring the electron spin of the NV color center as follows: 1.1 Physical definition of quantum nondestructive measurement (hereinafter referred to as QND measurement) involved in the quantum nondestructive measurement process: The strict definition of QND measurement is: measurement operator (This application refers to a measured value) satisfies the system Hamiltonian. commutation relations and ,in To measure the coupled Hamiltonian. This guarantees: (1) The measured physical quantity (in this application, the measured value characterizing the spin state of the NV color center) is not disturbed during the measurement process—the intrinsic value (i.e. the value mapped and stored in the nuclear spin) remains unchanged after the measurement.

[0060] (2) The back-action of the measurement does not affect the subsequent evolution of the number of measurands (NV center spin states).

[0061] For NV centers, the goal is to measure the electron spin of the NV centers using QND. Quantum numbers (i.e. magnetic quantum numbers (Measured values). Traditional direct ODMR readout operations do not meet the QND measurement conditions—the ISC channel will... The quantum number is nonunitally projected onto This is for Destructive measurements.

[0062] 1.2 Physical Mechanism of QND Measurement Using Nuclear Spin The QND measurement strategy in this embodiment is indirect measurement: the electron spin of the NV color center is not directly measured. Instead, Information mapped to auxiliary systems (nuclear spin) (state), and then measure nuclear spin. State. And in each measurement of nuclear spin... In the state, the electron spin is used as an optical readout interface to read the state information of the electron spin stored in the nuclear spin (i.e., the quantum non-destructive measurement process in step S11 of the first embodiment of this application).

[0063] (a) The physical principle of a revolving door: Hyperfine coupling Hamiltonian of hyperfine interaction between electron spin and nuclear spin (For pure vertical terms, take the effective Hamiltonian). This is the parallel hyperfine constant. The time evolution under this Hamiltonian... Conditional phase accumulation occurs when the rotation angle of the nuclear spin depends on the electron spin. The measured values ​​are shown below: Electron spin in ( ): (Nuclear spin does not rotate).

[0064] Electron spin in ( ): (Nuclear spin angle) ).

[0065] When evolution time At that time, the conditions for achieving completeness are met. Spin (CNOT gate: controlled NOT gate), the nuclear spin state faithfully reflects the electron spin. value.

[0066] Time evolution In the formula As the imaginary unit, its existence makes It becomes a unitary operator, describing the coherent evolution of quantum states.

[0067] Time evolution The formula states that the combined system of electron spin and nuclear spin, in the hyperfine interaction Hamiltonian... Under the influence of the free evolution time The corresponding unitary evolution operator.

[0068] Time evolution The formula originates from the standard time evolution relation in quantum mechanics. Its physical meaning is that different electron spins result in different effective Hamiltonians experienced by the nuclear spin, thus leading to the accumulation of different phases within the nuclear spin. Strictly speaking, This longitudinal coupling term directly produces conditional phase evolution, that is, the prespin of the nuclear spin around its quantization axis, rather than directly... Flip into If the nuclear spin is prepared in advance on a superposition substrate (e.g., through a... If a radio frequency pulse is placed on the equatorial plane of a Bloch sphere, then this phase accumulation on the Bloch sphere can be equivalently understood as a recurrence of... Rotation of the axis.

[0069] therefore, A more accurate explanation of the formula is: if an electron is in a certain spin eigenstate, the nuclear spin accumulates phase according to the corresponding angular velocity; when the electron is in different eigenstates, the nuclear spin phase accumulation is different. Combined with preceding and following basis rotation pulses, this "conditional phase difference" can be converted into a "conditional rotation" or a controlled NOT gate CNOT-type mapping, thus allowing the nuclear spin to ultimately carry the state information of the electron spin.

[0070] (b) The key to quantum nondestructive measurement—measurement acting on an auxiliary system Optical readout of nuclear spin does not affect electron spin. —Because the magnetic moment of nuclear spin is about 2000 times smaller than that of electron spin, nuclear spin does not directly participate in optical transitions. Laser irradiation only reads a "copy of the electron spin information stored in the nuclear spin," without directly perturbing the electron spin itself.

[0071] The actual object of laser irradiation and reading is still the fluorescence intensity generated by the electron spin optical transition process of the NV color center, rather than the nuclear spin itself.

[0072] Because nuclear spin does not directly participate in the optical transitions excited by the NV center at 532 nm laser light, it cannot be directly detected optically through fluorescence intensity like electron spin. The so-called "nuclear spin readout" is essentially an indirect readout, and the steps can be summarized as follows: (1) First, the electron spin state information of the NV color center is mapped to the nuclear spin through hyperfine coupling (i.e. hyperfine interaction).

[0073] (2) When it is necessary to read the nuclear spin, the state of the nuclear spin on the selected measurement substrate is mapped to the fluorescence intensity "bright / dark" readout channel that can distinguish the electron spin through selective microwave pulses.

[0074] (3) Finally, the electron fluorescence intensity is still read using a 532 nm laser to indirectly obtain the historical information (i.e., the measured value) of the electron spin state stored in the nuclear spin.

[0075] Therefore, nuclear spins serve as information storage, while electron spins serve as the interface for optically reading out the historical states (states to be measured) of electron spins stored in nuclear spins.

[0076] Strictly speaking, the electron spin is indeed reset during optical readout. However, this does not affect the properties of QND, because the information protected by QND has already been transferred to the nuclear spin during the mapping stage. Feedback manipulation can be performed based on the information stored in the nuclear spin.

[0077] 1.3 Statistical Principles for Improving Effective Fidelity Through Repeated Measures The repeatability of QND measurements allows for multiple samplings without disrupting the electron spin states stored in the nuclear spins being measured. Sub-independent sampling measurement results The majority vote determination is equivalent to the statistical inference of the binomial distribution: in a single fidelity Down, Validity of second majority vote for:

[0078] Effective fidelity The acquisition of this is essentially a trade-off between time and precision.

[0079] Here This represents the probability that a single QND measurement is correct. Let the true electron spin state be denoted as... The output of a single measurement is denoted as Then it can be written as:

[0080] If the two states occur with equal probability, it can also be written as the average discrimination fidelity:

[0081] This can be determined through calibration experiments; a typical approach is as follows: First, prepare an electron with a known spin state (e.g., and A large number of single QND measurements were performed. The probability that the measured values ​​matched the true values ​​was statistically analyzed to obtain the confusion matrix. Based on this confusion matrix, the single-sample effective discrimination fidelity was extracted. . It is actually a comprehensive indicator that includes factors such as: electron spin to nuclear spin mapping error, nuclear spin to electron spin readout interface error, optical fluorescence discrimination error, threshold error, pulse error, and decoherence noise.

[0082] II) Construction of QND Measurement Operator Utilizing NV color center electron spin ( ) and neighboring target carbon elements nuclear spin ( The hyperfine interactions between them are used to construct the QND measurement operator.

[0083] Ultra-fine Hamiltonian:

[0084] in and These are the parallel hyperfine coupling constant and the vertical hyperfine coupling constant, respectively. For the first shell... nuclear spin, , .

[0085] QND Measurement Conditions: Measurement Operator It must commutate with the system Hamiltonian Select (electron spin) (components), because China only The terms are not interchangeable, therefore this can be eliminated through pulse sequence design. The impact of the item.

[0086] QND measurement pulse sequence: Step 1 (Perform state mapping operation for conditional spin): Apply controlled NOT gate control conditions to the nuclear spin. Only when the electron spin is in Time-space rotation nuclear spin angle :

[0087] Implementation method: In A radio frequency pulse is applied at the second transition frequency of the nuclear spin.

[0088] Step 2 (Nuclear Spin Readout): Optical readout of nuclear spins—reading the state to be measured stored in the nuclear spins using an electron spin-assisted nuclear spin fluorescence protocol. Nuclear spins are unaffected by laser light during optical readout (nuclear spins are not coupled to optical transitions, enabling repeated measurements of the state to be measured).

[0089] Step 3 (Reset Pulse): The reset pulse (microwave pulse) maps the measured state stored in the nuclear spin back to the electron spin, preparing for the next QND measurement.

[0090] Key: The electron spin state to be measured throughout the entire process The quantum number remains unchanged, enabling non-destructive readout.

[0091] (iii) Enhanced fidelity for repeated reads like Figure 2 As shown, repeat The QND measurement determines the test state through majority voting: Results obtained from each QND measurement ( ), single-shot fidelity is . The final decision is obtained through majority voting after the QND measurement.

[0092] The quantitative results are shown in Table 1 of the first embodiment.

[0093] Optimal number of choices Limited by time budget and single QND measurement time :

[0094] For example: , , =5.

[0095] IV) Compatibility Design with Feedback Control Timing constraints: The entire QND measurement process (including (Number of repetitions) Total time spent + It must be much smaller than the characteristic evolution time of the dynamic system. : For the measurement feedback Ising machine: (After dynamic decoupling) It satisfies the timing constraints.

[0096] If the fast feedback condition is met, the dynamic system can still be described by the effective master equations.

[0097] For example, More preferably, The calculations are kept to the order of one percent to ensure that measurement, voting decisions, and feedback calculations can be completed before the system loses its effective relevance.

[0098] Pipeline design: When the j-th electron spin is undergoing the first spin... During the (th) repeated read, the () The measured data of each electron spin has been sent to the computing module (such as an FPGA) to begin preprocessing calculations, achieving overlap between measurement and feedback calculations. This eliminates the need to wait until all spins and all repetition cycles have been completed before processing.

[0099] For example, pipeline design can be understood in two layers: 1) Local readout processing layer: Threshold discrimination is performed on the single fluorescence intensity count results (measured values).

[0100] For the same logical spin Repeated measurement readings are accumulated, or a majority vote or maximum likelihood estimate is performed.

[0101] Output the final decision result of this logical spin.

[0102] 2) Global Feedback Computation Layer: Once the final decision result of a certain logical spin has been determined, it can be sent to the computation module (such as the matrix-vector multiplication unit of an FPGA) in advance. This process gradually forms a vector composed of all measured values. Then calculate the feedback field. . This is the coupling matrix. is the electron spin state vector.

[0103] Therefore, pipeline design serves both majority voting and subsequent feedback calculations, and the two can overlap in time.

[0104] In this regard, the step of selecting the correct result from multiple measurements may also include the following steps: Under asymmetric noise conditions, when performing maximum likelihood estimation on R measurements based on the likelihood function, a predetermined statistical decision strategy is employed to extract the correct result from the R measurements. This predetermined statistical decision strategy includes weighted voting or threshold decision. In weighted voting, measurements with different fidelities are weighted and summed, and then the summation result is compared with a set threshold to make the final decision.

[0105] The principle behind maximum likelihood estimation (MLE) for determining the correctness of repeated reads is as follows: From This application can also introduce the Maximum Likelihood Estimation (MLE) criterion to extract the optimal estimate (i.e., the correct result) from the repeated QND measurement readings. MLE degenerates into majority voting under symmetric noise conditions and provides a weighted voting threshold under asymmetric noise conditions, thus possessing statistical optimality.

[0106] 1.1) Problem Modeling Let the true state of electron spin be (correspond and Each QND measurement result is as follows: , The measurement channel is determined by conditional probability. Description. In the symmetrical case:

[0107] in For single QND measurement readout fidelity. Measurement result sequence. In the given They are independent and identically distributed.

[0108] 1.2) MLE under symmetrical noise: majority voting The likelihood function is:

[0109] in , Log-likelihood ratio:

[0110] because , The symbols are entirely composed of Therefore, the decision criterion for MLE is:

[0111] Conclusion: Under the symmetric fidelity assumption, MLE is equivalent to majority voting.

[0112] 1.3) MLE under asymmetric noise: weighted voting If read out and The fidelity is asymmetric, defined as:

[0113] Error probability , .

[0114] Likelihood function:

[0115] Log-likelihood ratio:

[0116] make , ,but The MLE decision threshold is:

[0117] This criterion is equivalent to weighted voting: each The results are assigned weights. Each The results are assigned weights. The sign of the sum determines the verdict.

[0118] 1.4) The processing steps (implemented based on FPGA) are shown in Table 2 below:

[0119] Table 2 1.5) Effective fidelity precise expression Under symmetrical noise, the effective fidelity after majority voting is:

[0120] when When the number is even and a tie occurs, it is handled according to preset rules (such as random selection), and the effective fidelity needs to be corrected as follows:

[0121] Effective fidelity under asymmetric noise can be obtained through numerical integration or lookup tables, generally in the form of:

[0122] The summation range coverage judgment is as follows: All .

[0123] 1.6) Integration advantages with the Ising machine iteration In the symmetrical case, the FPGA only requires one accumulator and one comparator, with a delay of less than one clock cycle, and is fully compatible with pipelined feedback.

[0124] because Usually, small odd numbers (3, 5, 7, 11) are chosen, and the majority vote is close to the statistical optimum, so floating-point operations are not required.

[0125] If asymmetric calibration is required, a threshold can be pre-stored. It can be implemented using an integer comparator, and the additional overhead is negligible.

[0126] The above method elevates the multiple repeated readings from "majority voting" to a decision mechanism with strict statistical optimality, significantly enhancing the feasibility of this application.

[0127] As can be seen from the above, this application achieves multiple measurement readouts without destroying the electron spin state, supporting the iterative feedback closed loop of quantum computers. Secondly, the effective fidelity of the final decision result can be increased from [previous level] through at least five repeated measurements. Upgraded to That's all. Total time spent on the measurement process. Much smaller than the characteristic evolution time of the dynamic system This method satisfies the fast feedback condition. The method provided in this application does not change the hardware measurement readout method; it is implemented solely through microwave / RF pulse sequence design, resulting in low design cost.

[0128] In some implementations, this application can use an integer comparator + addition tree to implement the statistical decision of majority voting. The decision steps are as follows: Will The measured values ​​obtained from the previous measurement are input into an addition tree to calculate the number E of '1's. Then, an integer comparator connected to the addition tree compares the number E with a set threshold. Perform integer comparisons and output the correct result. For example, ... The binary result obtained from the QND measurement Given an addition tree circuit, calculate the sum. Then, an integer comparator is used to determine: if... If the result is positive, the final state is "1"; otherwise, it is "0". This addition tree can be constructed using full adders or half adders. The integer comparator outputs a single-bit decision result. The entire circuit consisting of the addition tree and the integer comparator can be completed in a single clock cycle in a Field Programmable Gate Array (FPGA) or Application Specific Integrated Circuit (ASIC), with a delay typically less than 10 ns. For other repetition counts... Simply adjust the threshold to That's all.

[0129] In some implementations, this application may also employ a look-up table (LUT) to achieve majority voting. A look-up table is suitable for situations where the number of repetitions R is relatively small (typically...). The statistical decision circuit for ( ) has the advantages of fixed delay and simple logic. For example, the specific implementation steps are as follows: Step 1, Address Encoding: The measurement values ​​obtained from R measurements (e.g., 5 measurements) This is encoded as an R-bit binary address. The most significant bit (MSB) The least significant bit (LSB) is the address space size. (e.g., when R is 5, ).

[0130] Step 2, Truth Table Pre-calculation: For each possible binary address {e.g., the address when R=5 (00000~11111)}, calculate the number of "1"s. If the number of "1"s... Set threshold The decision output is 1 (corresponding to electron spin). (State). Otherwise, output 0 (corresponding to) (State). The following table lists some examples:

[0131] Table 3 Step 3: The storage implementation of the lookup table can be configured as follows: using a ( The lookup table is stored in a predetermined memory location of 5 bits, with the address line width set to R and the data width set. For example, the address line width is set to 5 and the data width to 1. The 32 outputs of the truth table (Table 3) are then stored in the lookup table memory location in address order. The predetermined memory may include read-only memory (ROM) or programmable logic devices.

[0132] Step 4, the majority voting decision process is configured as follows: After obtaining a set of R measurement values ​​(e.g., 5 measurements), these values ​​are concatenated into an R-bit address and directly sent to the address input of a predetermined memory [e.g., a read-only memory (ROM)]. The predetermined memory then outputs the decision value (i.e., the correct result) corresponding to that address to complete the majority voting. If the read-only memory (ROM) outputs the decision value corresponding to that address after a fixed delay (typically <5 ns), then the majority voting is complete.

[0133] When implementing majority voting using a lookup table, When the address line width of the lookup table cell is 3, the size of the read-only memory (ROM) can be ( ) bit, threshold .when At that time, the address width was 7 and the ROM size was bit, threshold Generally, the storage required for lookup table LUTs is... Entries. For , This can be easily implemented in Field Programmable Gate Arrays (FPGAs) or Application-Specific Integrated Circuits (ASICs).

[0134] Compared to certificate comparator schemes, lookup tables offer several advantages: Lookup tables have a constant latency of one read from a predetermined memory location (e.g., ROM read), making them suitable for small R values. Implementation is simple (using case statements or arrays). Integer comparators with addition trees, on the other hand, have resources that grow linearly with R, with no storage limit, making them suitable for R values ​​of any size.

[0135] Implementation examples, based on QND readout of nuclear spin: Hardware configuration: Single NV color center, with one addressable target carbon element in its nearest neighbor. nuclear spin ( 4. Kelvin runtime environment ( The system consists of a radio frequency coil (manipulating nuclear spins and providing radio frequency pulses) and a microwave antenna (manipulating electron spins and providing microwave pulses). Addressable means being able to distinguish and manipulate the nuclear spin of a target carbon element from the nuclear spins of other observers using ultra-fine coupling differences, spectral resolution, or pulse selectivity. If the nuclear spin is not addressable, the following problems will arise: 2.1) Crosstalk: The pulse applied to the target nuclear spin will also partially affect other nuclear spins.

[0136] 2.2) Spectral aliasing: Hyperfine splitting of different nuclear spins is too close together, making it impossible to clearly distinguish which nuclear spin is responding.

[0137] 2.3) Incorrect mapping: Information that should have been written to the target nuclear spin was partially written to other nuclear spins, causing the conditional spins to no longer correspond one-to-one.

[0138] 2.4) Readout ambiguity: The subsequent "nucleus-to-electron" readout interface cannot confirm which nuclear spin branch information is being read.

[0139] Therefore, if the target nucleus spin is not addressable, it will significantly increase measurement errors and even compromise the reliability of the entire QND measurement scheme. For this reason, this application uses the term "nearest neighbor, addressable" to describe the target nucleus spin. Nuclear spin is one of the preferred implementation conditions. The first layer of carbon elements closest to the NV color center vacancy can be selected as the addressable target carbon element.

[0140] QND measurement sequence parameters: Conditional rotation angle (Completely flipping nuclear spin, maximum information extraction). Nuclear spin rotation time: Nuclear spin measurement readout time: The reset time for writing nuclear spin into electron spin (i.e., the time to map back to the state under test): Total measurement time for a single QND test: .

[0141] Repeated reading: times, total time Single-shot fidelity Effective fidelity . Overall fidelity of a logic spin system:

[0142] This application provides three embodiments of an apparatus for measuring the electron spin of an NV center, which is used to implement a method for measuring the electron spin of an NV center. For details on the method for measuring the electron spin of an NV center, please refer to the first and second embodiments of this application; they will not be repeated here.

[0143] The fourth embodiment of this application provides an electronic device, including: a processor and a memory storing a program, the program including instructions, which, when executed by the processor, cause the processor to perform a method for measuring the electron spin of the NV center. For details on the method for measuring the electron spin of the NV center, please refer to the first and second embodiments of this application; further details will not be repeated here.

[0144] The fifth embodiment of this application provides a non-transitory machine-readable medium storing computer instructions for causing a computer to execute a method for measuring the electron spin of the NV center. For details on the method for measuring the electron spin of the NV center, please refer to the first and second embodiments of this application; further details will not be repeated here.

[0145] Computer programs used to implement the methods of the embodiments of this application may be written in any combination of one or more programming languages. These computer programs may be provided to a processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus, such that when executed by the processor or controller, the computer programs cause the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The computer programs may be executed entirely on a machine, partially on a machine, or as a standalone software package, partially on a machine and partially on a remote machine, or entirely on a remote machine or server.

[0146] In the context of embodiments of this application, a machine-readable medium can be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, apparatus, or device. A machine-readable medium can be a machine-readable signal medium or a machine-readable storage medium. A machine-readable signal medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, or infrared systems, apparatus, or devices, or any suitable combination of the foregoing. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, compact optical disc read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0147] It should be noted that the term "comprising" and its variations used in the embodiments of this application are open-ended, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; and the term "some embodiments" means "at least some embodiments". The modifications of "one" and "multiple" mentioned in the embodiments of this application are illustrative and not restrictive. Those skilled in the art should understand that, unless explicitly indicated otherwise in the context, they should be understood as "one or more".

[0148] The user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in the embodiments of this application are all information and data authorized by the user or fully authorized by all parties. Furthermore, the collection, use and processing of related data must comply with the relevant laws, regulations and standards of the relevant countries and regions, and corresponding operation entry points are provided for users to choose to authorize or refuse.

[0149] The steps described in the method embodiments provided in this application can be performed in different orders and / or in parallel. Furthermore, the method embodiments may include additional steps and / or omit the steps shown. The scope of protection of this application is not limited in this respect.

[0150] The term "embodiment" in this specification refers to a specific feature, structure, or characteristic described in connection with an embodiment that may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily imply the same embodiment, nor does it imply independence from or alternative to other embodiments. The various embodiments in this specification are described in a related manner, with reference to each other for similar or identical parts. In particular, for apparatus, device, and system embodiments, since they are substantially similar to method embodiments, the description is relatively simple, and relevant details are referred to in the description of the method embodiments.

[0151] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of patent protection. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. A method for measuring the electron spin of an NV color center, characterized in that, Based on the hyperfine interaction between the NV color center and the target atomic nucleus in the diamond it resides in, the electronic spin state of the NV color center is mapped to the nuclear spin state of the atomic nucleus, so that the magnetic quantum number characterizing the electronic spin state... The method includes taking different values ​​for the nuclear spin to correspond to different states. The electron spin is repeatedly subjected to a quantum non-destructive measurement process multiple times to obtain the magnetic quantum number. The quantum non-destructive measurement process includes: based on the hyperfine interaction, mapping the electron spin state carried by the nuclear spin state back to the optically distinguishable state to be measured, and then obtaining the measured value by measuring the fluorescence intensity emitted by the NV color center under laser excitation; Select the correct result from the multiple measured values.

2. The method for measuring electron spin at NV color centers according to claim 1, characterized in that, The NV color center is applied at least to a quantum computer, which includes multiple logical spins composed of multiple NV color centers. After selecting the correct result from multiple measurements, the method further includes: The correct result is taken as the final decision result of the logical spin.

3. The method for measuring electron spin at NV color centers according to claim 1, characterized in that, The state to be measured includes a reference state or a flipped state. After measuring the fluorescence intensity emitted by the NV color center, the electron spin is in the reference state. The step of mapping the electron spin state carried by the nuclear spin state back to the optically distinguishable state to be measured includes: A microwave pulse is applied to the electron spin to cause the electron spin to flip from the reference state to the flipped state or remain in the reference state under the action of the microwave pulse, wherein: When the nuclear spin is in the first state and the frequency of the applied microwave pulse resonates with the first transition frequency of the electron spin, under the hyperfine interaction, the microwave pulse drives the electron spin to flip from the reference state to the flipped state; When the nuclear spin is in the second state and the frequency of the microwave pulse is detuned from the first transition frequency, the electron spin remains in the reference state.

4. The method for measuring electron spin at NV color centers according to claim 2, characterized in that, The state to be tested includes a reference state or a flipped state; the quantum non-destructive measurement procedure is executed R times, where R is an odd number; the measured values ​​include those corresponding to the reference state and / or the flipped state; and the step of selecting the correct result from the multiple measured values ​​includes: A majority vote is conducted on the R measured values, and the measured value with the most votes is taken as the correct result.

5. The method for measuring electron spin at NV color centers according to claim 4, characterized in that, The measured value , ( ),value The measured value of the reference state, the value The measured value in the flipped state, wherein the fidelity of the measured value in a single measurement is The effective fidelity of the measurement with the most votes is ,but The following relationship must be satisfied: in, express Round up.

6. The method for measuring electron spin at NV color centers according to claim 4 or 5, characterized in that, If the set time budget is The time for a single measurement is Then the optimal number of repetitions for R is... equal and The value is rounded down, and the single measurement time includes the time for a single execution of the quantum non-destructive measurement process.

7. The method for measuring electron spin at NV color centers according to claim 6, characterized in that, The method further includes: If the characteristic evolution time of the dynamic system is The time required to map the electron spin state to the nuclear spin state is The total time taken to obtain multiple of the measured values + At that time, control No more than 1.25% The dynamic system is a system in which the logical spin is allowed to maintain effective evolution and correlation between two adjacent feedback updates.

8. The method for measuring electron spin at NV color centers according to claim 4 or 5, characterized in that, The method further includes: In the measurement of the j-th electron spin... When the measured value is given, the ( ) The measured values ​​of the electron spins are transmitted to the calculation module for preprocessing. The preprocessing includes at least one of majority voting and feedback calculation. The feedback calculation is used to calculate the feedback field required to adjust the electron spins based on the final decision result, where j is an integer.

9. The method for measuring the electron spin of the NV color center according to any one of claims 1 to 5, characterized in that, The steps of mapping the electron spin state of the NV color center to the nuclear spin state of the atomic nucleus include: A pre-set controlled NOT gate control condition is applied to the nuclear spin. The controlled NOT gate control condition is configured to: when the electron spin is in a reference state, keep the nuclear spin in a first state of no rotation; when the electron spin is in a flipped state, switch the nuclear spin from the first state to a rotation angle. The second state.

10. The method for measuring electron spin at NV color centers according to claim 9, characterized in that, The controlled NOT gate control condition is configured as follows: ； In the above formula, The electron spin is in The projection operator in this reference state The electron spin is in The projection operator in this flipped state, symbol " " represents the tensor product, For the identity operator of the nuclear spin, This indicates that the nuclear spin does not rotate. This indicates that the nuclear spin revolves around the NV color center. Axis rotation angle Rotation operator.

11. The method for measuring the electron spin of the NV color center according to claim 10, characterized in that, The steps of applying a pre-set controlled NOT gate control condition to the nuclear spin include: A radio frequency pulse is applied to the nuclear spin, causing the nuclear spin to rotate by an angle under the action of the radio frequency pulse. Or not rotate, where: When the electron spin is in the flipped state, and the deviation between the frequency of the applied radio frequency pulse and the second transition frequency of the nuclear spin is less than a predetermined value, under the hyperfine interaction, the radio frequency pulse is in a resonant state to drive the nuclear spin rotation angle. ; When the electron spin is in the reference state and the frequency of the radio frequency pulse is detuned to the transition frequency, the nuclear spin does not rotate.

12. The method for measuring the electron spin of the NV color center according to any one of claims 1 to 5, characterized in that, The step of selecting the correct result from the plurality of said measurements further includes: Under asymmetric noise conditions, when performing maximum likelihood estimation on R measurements based on the likelihood function, a predetermined statistical decision strategy is used to extract the correct result from the R measurements. This predetermined statistical decision strategy includes weighted voting or threshold decision; and / or... The atomic nucleus includes the nucleus of the target carbon element, which is located in the first shell near the NV color center.

13. A device for measuring the electron spin of an NV color center, characterized in that, The apparatus for measuring the electron spin of the NV center is used to implement the method for measuring the electron spin of the NV center according to any one of claims 1 to 12.

14. An electronic device comprising: A processor, and a memory storing a program, characterized in that the program includes instructions that, when executed by the processor, cause the processor to perform the method for measuring the electron spin of the NV color center according to any one of claims 1 to 12.

15. A non-transitory machine-readable medium storing computer instructions, characterized in that, The computer instructions are used to cause the computer to perform the method for measuring the electron spin of the NV color center as described in any one of claims 1 to 12.

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