Quantum spectrum measurement method and device based on Landau-Zener transition

Abstract

The invention relates to a quantum frequency spectrum measurement method and device based on Landau-Zener transition, and the method comprises the steps: slowly evolving a Bloch sphere Z-axis positive half axis to an X-axis positive half axis along an XZ meridian, and slowly evolving the Bloch sphere X-axis positive half axis to a control field of a Z-axis negative half axis along the XZ meridian after the Bloch sphere oscillates for N times at a constant oscillation frequency omega ctr within a field angle of [delta] [theta] / 2 with the X-axis positive half axis, and when the oscillation frequency of the control field is adjusted, a modulation function corresponding to the control field is changed, the size of the Fourier spectrum component is controlled, and the frequency of the signal to be measured is obtained based on the population of measurement quantum bit resonance state overturning. According to the method, higher harmonics are effectively suppressed, the resolution of signals is improved, weak signals in a complex environment are measured, interference of detuning errors and electromagnetic wave amplitude errors is resisted, spurious signals generated by heterogeneous atomic nuclei in nuclear spin measurement are eliminated, the measurement result is more accurate, and the robustness is more reliable.

Description

Technical Field

[0001] The present invention relates to the field of quantum measurement technology, and in particular to a quantum spectrum measurement method and device based on Landau-Zener transition. Background Art

[0002] In the field of "quantum sensing and measurement" technology, quantum bit systems are used as measurement platforms, such as diamond color centers, superconducting quantum bits, ion traps, etc. The method of measuring physical quantities by using the quantum properties and / or quantum phenomena of quantum systems has higher resolution and measurement accuracy than traditional measurement schemes, and can make more accurate measurements of small changes in physical quantities. It has been widely used in different fields to accurately measure different physical information, including the detection of microphysical quantities such as electromagnetic fields, electric fields, temperature, and pressure.

[0003] This measurement method is applicable to information on objects ranging in size from macroscopic to microscopic to nanoscale. For example, nanodiamonds can be implanted in cells to measure various tiny-scale information such as the structure and position of molecules. This is an advantage that traditional measurement platforms such as nuclear magnetic resonance (NMR) cannot match.

[0004] The existing technology uses quantum measurement platforms to detect the signals of nuclear spins in molecules or macroscopic electromagnetic waves. It usually requires the creation of periodic dynamical decoupling pulses (DD) to act on quantum bits to drive the periodic evolution of quantum bits. When the frequency corresponding to the evolution is the same as the signal frequency, the quantum bits undergo an ecological flip, which is manifested as the generation of resonance signals on the spectrum diagram. However, the use of DD pulses will cause quantum bits to resonate when encountering high-frequency signals, which is manifested in the spectrum diagram as multiple signal peaks or overlapping signal peaks near the frequency to be measured, making it difficult to identify the real signal. This is determined by the fixed complex components in the Fourier spectrum of the modulation function corresponding to the DD pulse. In addition, when detecting the structure of organic compounds, the pseudo-resonance signals generated by carbon atoms will also interfere with the identification of hydrogen atom signals. Summary of the invention

[0005] Based on this, the present invention provides a quantum spectrum measurement method based on Landau-Zener transition, which can avoid the interference of high-frequency signals and pseudo-resonance signals, distinguish slightly different signals, reduce the clutter peaks near the real signal, and obtain a clean and accurate spectrum of the signal to be measured.

[0006] A quantum spectrum measurement method based on Landau-Zener transition includes: initializing the quantum state of a quantum sensor placed in an environmental field of a signal to be measured to a |+> state;

[0007] The electromagnetic wave control field is loaded to the quantum bit initialized to the |+> state. The direction of the control field is to slowly evolve from the positive half axis of the Z axis of the Bloch sphere along the XZ meridian to the positive half axis of the X axis, and at a constant oscillation frequency ω at an angle of Δθ / 2 with the positive half axis of the X axis. ctr Oscillate N times, then slowly evolve from the positive half axis of the X axis along the XZ meridian to the negative half axis of the Z axis;

[0008] Change the oscillation frequency ω of the control field ctr , so that the quantum bit resonates in the environment field of the signal to be measured, and then the frequency ω of the signal to be measured is obtained signal .

[0009] Furthermore, the frequency ω of the electromagnetic wave c satisfy:

[0010] ω c =ω0-Ω / tan{arccos[F(t)]}

[0011] Where ω0 is the eigenfrequency of the two-level system of the quantum sensor, Ω is the amplitude of the electromagnetic wave, and F(t) is the modulation function.

[0012] Furthermore, the modulation function F(t) satisfies:

[0013] F(t)=fcos(ω ctr t)

[0014] Where f is the amplitude of the modulation function, ω ctr is the oscillation frequency of the control field.

[0015] Furthermore, the Δθ in the opening angle of Δθ / 2 satisfies:

[0016] Δθ=arccos(f)-arccos(-f)

[0017] Where f is the amplitude of the modulation function.

[0018] Furthermore, the oscillation number N is greater than or equal to 100.

[0019] Furthermore, the evolution time from the positive half axis of the Z axis of the Bloch sphere to the positive half axis of the X axis along the XZ meridian is t i , the evolution rate satisfies:

[0020] dθ / dt<<Ω,

[0021] Where θ = arctan(Ω / Δ)

[0022] Δ=ω0-ω c

[0023] Where Ω is the amplitude of the electromagnetic wave, Δ is the detuning amount, ω0 is the eigenfrequency of the two-level system of the quantum sensor, and ω c is the frequency of the electromagnetic wave.

[0024] Furthermore, the evolution time from the positive half axis of the Bloch sphere X-axis to the negative half axis of the Z-axis along the XZ meridian is t i , the evolution rate satisfies:

[0025] dθ / dt<<Ω,

[0026] Where θ = arctan(Ω / Δ)

[0027] Δ=ω0-ω c

[0028] Where Ω is the amplitude of the electromagnetic wave, Δ is the detuning amount, ω0 is the eigenfrequency of the two-level system of the quantum sensor, and ω c is the frequency of the electromagnetic wave.

[0029] Furthermore, before applying the control field to the quantum bit, the state of the quantum bit is prepared to The |+> state of this quantum bit is located on the positive x-axis of the Bloch sphere.

[0030] Compared with the prior art, a Bloch sphere is designed to slowly evolve from the positive half axis of the Z axis along the XZ meridian to the positive half axis of the X axis and to oscillate at a constant frequency ω within an opening angle of Δθ / 2 with the positive half axis of the X axis. ctr After oscillating N times, the control field slowly evolves from the positive half axis of the X-axis along the XZ meridian to the negative half axis of the Z-axis. When adjusting the oscillation frequency of the control field, the modulation function corresponding to the control field is changed to control the size of the Fourier spectrum component, and based on this, the population number of the quantum bit resonant state flip is measured to obtain the frequency of the signal to be measured. This method effectively suppresses high-order harmonics, improves the resolution of signals, measures weak signals in complex environments, resists interference from detuning errors and electromagnetic wave amplitude errors, and eliminates stray signals generated by heterogeneous nuclei in nuclear spin measurements, making the measurement results more accurate and more robust.

[0031] At the same time, the present invention also provides a quantum spectrum measurement device based on Landau-Zener transition, comprising: a controller, an electromagnetic wave generator, a quantum sensor, a signal analyzer, and a control field loader program stored on the controller and executable on the controller:

[0032] The controller is used to execute the control field loading program stored thereon, and output an electromagnetic wave loading control signal to the electromagnetic wave generator, and the output control parameters include: electromagnetic wave amplitude, electromagnetic wave frequency, number of oscillation cycles, oscillation frequency, and loading time;

[0033] The electromagnetic wave generator is used to receive the electromagnetic wave loading control signal output by the controller, and load the electromagnetic wave to the quantum sensor according to the loading control signal to drive the quantum bit to evolve on the XZ meridian;

[0034] The quantum sensor is placed in the environmental field to initialize the state of the quantum bit to the |+> state, and to perform state evolution of the quantum bit under the action of the loaded electromagnetic wave;

[0035] The signal analyzer is used to receive the population signal of the quantum bit state output by the quantum sensor under the driving of electromagnetic waves of different oscillation frequencies, and analyze the frequency of the signal to be measured in the environment according to the spectrum diagram of the population signal-oscillation frequency;

[0036] When the control field loading program is executed by the controller, the steps of any of the above-mentioned quantum spectrum measurement methods based on Landau-Zener transition are implemented.

[0037] Compared with the prior art, the beneficial effects of the quantum spectrum measurement device based on Landau-Zener transition of the present invention are the same as those of the quantum spectrum measurement method based on Landau-Zener transition, which will not be described in detail here.

[0038] In order to better understand and implement the present invention, the present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a relationship diagram of the energy level difference of the quantum bit in the present invention as the detuning amount Δ changes. When the detuning amount Δ is 0, the energy level difference is the electromagnetic wave amplitude Ω;

[0040] Figure 2 is a geometric relationship diagram between the detuning amount Δ and the electromagnetic wave amplitude Ω represented by the Bloch sphere in the present invention;

[0041] Figure 3 Schematic diagram of the change of the control field direction in different time periods on the Bloch sphere in the present invention, where τ is the control field oscillation period, N is the number of control field oscillations, τ = 2π / ω ctr ;

[0042] Figure 4 For Figure 3 Schematic diagram of the modulation function F(t) corresponding to the relative control field, t i is the time required for the control field direction to change from the positive half axis of the Z axis to the positive half axis of the X axis and the time required for the control field direction to change from the positive half axis of the X axis to the negative half axis of the Z axis, and f is the amplitude of the modulation function F(t);

[0043] Figure 5When f=1 and N=100, the spectrum comparison diagram of a single nuclear spin is measured under the conditions of no error, detuning error and control field amplitude error according to the present invention;

[0044] Figure 6 The spectrum comparison diagram of a single nuclear spin is measured under the conditions of no error, detuning error and control field amplitude error when f=0.1 and N=100 according to the present invention;

[0045] Figure 7 The spectrum comparison diagram of a single nuclear spin is measured under the conditions of no error, detuning error and control field amplitude error when f=0.1 and N=700 according to the present invention;

[0046] Figure 8 When f=1 and N=120, the spectrum comparison diagram of the electromagnetic wave signal in the composite frequency signal field is measured under the conditions of no error, detuning error and control field amplitude error;

[0047] Fig. 9 When f=1 and N=240, the measurement is performed under the conditions of no error, detuning error and control field amplitude error. 13 In the environment of C nuclei, 1 Spectral comparison of H nuclear spins. DETAILED DESCRIPTION

[0048] The inventor of the present invention has found through research that if false signals are to be eliminated, it is necessary to adaptively design the loading method of the control field to control the quantum state to evolve according to the set evolution path. By placing the quantum system quantized by a constant magnetic field in a composite field of a control field and an environmental field that are designed and regulated according to a certain rule, the quantum state evolution of the quantum bit obeys the Hamiltonian representation of the composite field.

[0049] For specific implementation, please refer to Figure 1 , a constant external strong magnetic field is used as the excitation field to make the NV electrons in the ambient field produce Zeeman splitting, and the NV electron spin|0> state and spin|1> state are selected to form a two-level system, and the energy level difference is Then a wave function of Ωcos(ω ctr t) electromagnetic wave as the control field. Under the joint action of the excitation field, the environmental field and the control field, The effective Hamiltonian H of the two-level system in the subspace formed by these two states is:

[0050]

[0051] In formula (1), the first term is the intrinsic Hamiltonian of the excitation field NV electron, ω0 is the eigenfrequency of the quantum bit; the second term Ωcos(ω ctr t)σ x is the Hamiltonian of the control field, Ω is the amplitude of the electromagnetic wave, ω c is the frequency of the electromagnetic wave loading the control field, σ x is the spin state of the quantum bit along the X-axis; the third term b s cos(ω signal t)σ z is the energy of the environmental field, b s is the amplitude of the signal to be measured in the environmental field, ω signal is the frequency of the signal to be measured in the environmental field, σ z is the spin state of the quantum bit along the Z axis.

[0052] exist In the rotating coordinates, the effective Hamiltonian H′ is:

[0053]

[0054] (2) In the formula, is the control field of the Landau-Zener transition form, where the detuning amount Δ=ω0-ω c , Ω is the amplitude of the electromagnetic wave.

[0055] See also Figure 2 , the direction of the control field is determined by the detuning amount Δ and the amplitude Ω of the electromagnetic wave loaded by the control field:

[0056] tan(θ)=Ω / Δ;

[0057] That is, θ=arctan(Ω / Δ).

[0058] When the direction of the control field changes slowly, that is, dθ / dt<<Ω, the quantum state evolves adiabatically. The second term of equation (2) is transformed into a rotating coordinate system and based on the rotating wave approximation, a Hamiltonian H″ describing the interaction between the quantum bit and the signal field is obtained:

[0059]

[0060] (3)In the formula, F(t) is the modulation function.

[0061] Based on the above analysis, please refer to Figure 3 The present invention designs a control field whose direction is to slowly evolve from the positive half axis of the Z axis of the Bloch sphere along the XZ meridian to the positive half axis of the X axis, and to oscillate at an angle of Δθ / 2 with the positive half axis of the X axis at an oscillation frequency ω ctrThe control field oscillates N times, and then slowly evolves from the positive half axis of the X-axis along the XZ meridian to the negative half axis of the Z-axis. The control field is used to drive the quantum bits in the environment field to evolve along the XZ meridian of the Bloch sphere. By adjusting the oscillation frequency ω of the control field ctr The qubit resonates. When the qubit resonates, the population signal changes strongly, which is reflected as a strong resonance signal peak in the spectrum. The population signal can be measured by changing the oscillation frequency ω ctr The frequency ω of the environmental field signal to be measured is obtained signal .

[0062] Based on the above design, when the number of oscillation cycles N is large enough, the time t required for the slow evolution from the positive half axis of the Z axis along the XZ meridian to the positive half axis of the X axis can be ignored. i , and the time t required to slowly evolve from the positive half axis of the X axis along the XZ meridian to the negative half axis of the Z axis i The influence on the modulation function F(t), then the modulation function F(t) corresponding to the control field satisfies:

[0063] F(t)=fcos(ω ctr t)

[0064] Where: f represents the amplitude of the control field modulation function.

[0065] At this point, the Fourier transform of the modulation function F(t) has only a single component - the oscillation frequency ω ctr , thereby suppressing higher harmonics in the measured spectrum.

[0066] At the same time, the relationship between the control angle Δθ and the amplitude f of the modulation function F(t) satisfies:

[0067] Δθ=arccos(f)-arccos(-f).

[0068] The quantum spectrum measurement method based on Landau-Zener transition of the present invention is specifically introduced below, which includes the following steps.

[0069] S10 initializes the quantum state of the quantum sensor placed in the signal environment field to be measured to the |+> state.

[0070] In a specific embodiment, the quantum bit initialized to the |+> state is prepared by a constant external strong magnetic field, and the |+> state is The |+> state of this quantum bit is located on the positive x-axis of the Bloch sphere.

[0071] S20 loads an electromagnetic wave control field to the quantum bit initialized to the |+> state. The direction of the control field is to slowly evolve from the positive half axis of the Z axis of the Bloch sphere along the XZ meridian to the positive half axis of the X axis, and at an angle of Δθ / 2 with the positive half axis of the X axis at a constant oscillation frequency ω ctrOscillate N times, and then slowly evolve from the positive half axis of the X axis along the XZ meridian to the negative half axis of the Z axis, where the frequency of the loaded electromagnetic wave ω c With the oscillation frequency ω ctr satisfy:

[0072] Where F(t) = fcos(ω ctr t)

[0073] Where: ω0 represents the eigenfrequency of the two-level system of the quantum sensor, Ω is the amplitude of the electromagnetic wave, F(t) is the modulation function, and f represents the amplitude of the modulation function.

[0074] See also Figure 3 and Figure 4 , specifically including the following sub-steps.

[0075] S21 applies a continuous wave electromagnetic wave control field to the quantum bit initialized to the |+> state, with an electromagnetic wave amplitude of Ω and an electromagnetic wave frequency of ω c , frequency ω c satisfy:

[0076] ω c =ω0-Ω / tan{arccos[F(t)]},

[0077] Where F(t) = fcos(ω ctr t)

[0078] Where: ω0 represents the eigenfrequency of the two-level system of the quantum sensor, Ω is the amplitude of the electromagnetic wave, F(t) is the modulation function, and f represents the amplitude of the modulation function.

[0079] S22 slowly evolves the direction of the control field from the positive half-axis of the Z axis of the Bloch sphere along the XZ meridian to the positive half-axis of the X axis, and the evolution time is t i , the evolution rate satisfies dθ / dt<<Ω, where:

[0080] θ satisfies: θ=arctan(Ω / Δ)

[0081] The detuning amount Δ satisfies: Δ=ω0-ω c =Ω / tan{arccos[F(t)]}.

[0082] S23 controls the field to oscillate at a constant frequency ω at an angle of Δθ / 2 with the positive half axis of the X-axis on the XZ meridian. ctr Oscillate N times, where N is greater than or equal to 100, and Δθ satisfies:

[0083] Δθ=arccos(f)-arccos(-f),

[0084] Where f is the amplitude of the modulation function.

[0085] S24 slowly evolves the direction of the control field from the positive half axis of the X axis of the Bloch sphere along the XZ meridian to the negative half axis of the Z axis, and the evolution time is t i , the evolution rate satisfies dθ / dt<<Ω, where:

[0086] θ satisfies: θ = arctan(Ω / Δ)

[0087] The detuning amount Δ satisfies: Δ=ω0-ω c =Ω / tan{arccos[F(t)]}.

[0088] S30 measures the total time T of quantum bit evolution and the population of the quantum bit state in the initial state |+>, and obtains the population and oscillation frequency ω ctr The corresponding relationship.

[0089] S40 changes the oscillation frequency of the control field ω ctr , repeat steps S20 and S30 to obtain a population-oscillation frequency spectrum, and obtain the frequency ω of the signal to be measured according to the resonance signal peak signal .

[0090] At an oscillation frequency ω ctr Driven by the control field of , if the total time of quantum bit evolution is T, then the population of quantum bit satisfies:

[0091]

[0092] When a certain oscillation frequency ω ctr and the measured signal frequency ω signal When they are equal, ω ctr =ω signal , the measured signal resonates with the quantum bit, and the population of the quantum bit satisfies:

[0093]

[0094] On the spectrum diagram ω ctr =ω signal A signal peak can be seen near the position of

[0095] When a certain oscillation frequency ω ctr and the measured signal frequency ω signal When they are not equal, ω ctr ≠ω signal When , the population number of quantum bits P≈1, that is, there is no signal peak on the spectrum diagram, which can avoid the generation of pseudo-resonance signals, such as high-order harmonics and stray signals, thereby obtaining a clean and single signal.

[0096] In nuclear spin signal measurement, the signal field is:

[0097]

[0098] Among them, the jth nuclear spin and is the fine coupling constant, ω j is the effective Larmor frequency, are the components of the nuclear spin operator in the x, y, and z directions,

[0099] Furthermore, by reducing the amplitude f of the modulation function F(t) and increasing the evolution time T or the number of oscillation cycles N, the resolution of the signal can be improved and accurate measurement of the signal can be achieved.

[0100] Experimental analysis

[0101] Experiment 1

[0102] See also Figure 5 , adjust an electromagnetic wave as the control field, where the electromagnetic wave amplitude Ω = 20 × 2πMHz, the amplitude of the modulation function f = 1, and the number of oscillation cycles N = 100; modulate a signal field to be measured, the effective Larmor frequency of the hydrogen nucleus ν H =218.22kHz fine coupling strength The experiment was carried out according to steps S10 to S40 of the present invention. Figure 5 As shown, the solid line is the spectrum diagram of measuring a single nuclear spin in the case of no detuning error and electromagnetic wave amplitude error; the dotted line is the spectrum diagram of measuring a single nuclear spin in the case of detuning error δ=1MHz and electromagnetic wave amplitude error of -0.5%; it can be seen from the figure that the solid line and the dotted line overlap, indicating that the present invention can generate a clean signal peak and can effectively resist the influence of errors, and the error resistance ability of spectrum measurement using the control field is very good.

[0103] Experiment 2

[0104] See also Figure 6 , adjust an electromagnetic wave as a control field, where the electromagnetic wave amplitude Ω = 20 × 2πMHz, the amplitude of the modulation function f = 0.1, and the number of oscillation cycles N = 100; modulate a signal field to be measured, the effective Larmor frequency of the hydrogen nucleus ν H =218.22kHz fine coupling strength The experiment was carried out according to steps S10 to S40 of the present invention. Figure 6As shown, the solid line is the spectrum diagram of measuring a single nuclear spin in the case of no detuning error and electromagnetic wave amplitude error; the dotted line is the spectrum diagram of measuring a single nuclear spin in the case of detuning error δ=1MHz and electromagnetic wave amplitude error of -0.5%; it can be seen from the figure that the changing trends of the solid line and the dotted line are basically consistent, indicating that the present invention can generate clean signal peaks and can effectively resist the influence of errors, and the control field spectrum measurement has good error resistance.

[0105] Experiment 3

[0106] See also Figure 7 , adjust an electromagnetic wave as the control field, where the electromagnetic wave amplitude Ω = 20 × 2πMHz, the amplitude of the modulation function f = 0.1, and the number of oscillation cycles N = 700; modulate a signal field to be measured, the effective Larmor frequency of the hydrogen nucleus ν H =218.22kHz fine coupling strength The experiment was carried out according to steps S10 to S40 of the present invention. Figure 6 As shown, the solid line is the spectrum diagram of measuring a single nuclear spin in the case of no detuning error and electromagnetic wave amplitude error; the dotted line is the spectrum diagram of measuring a single nuclear spin in the case of detuning error δ=1MHz and electromagnetic wave amplitude error of -0.5%; it can be seen from the figure that the changing trends of the solid line and the dotted line are basically consistent and the signal peak is sharper, indicating that the present invention can generate clean signal peaks, can effectively resist the influence of errors and has high resolution, and the error resistance ability of spectrum measurement using the control field is good.

[0107] Figure 5 and Figure 6 The effect of adjusting the amplitude f of different modulation functions on the spectrum measurement is shown, indicating that the resolution of the spectrum measurement can be effectively improved by reducing the amplitude f of the modulation function; Figure 6 and Figure 7 It is demonstrated that adjusting different evolution times or increasing the number of control field oscillation periods N can effectively improve the resolution of spectrum measurement.

[0108] Experiment 4

[0109] See also Figure 8 , adjust an electromagnetic wave as the control field, where the electromagnetic wave amplitude Ω = 20 × 2πMHz, the amplitude of the modulation function f = 1, and the number of oscillation cycles N = 120; modulate the composite frequency to measure the signal field, the signal frequency ν s ={200.0,594.05,1010.11}, signal field amplitude b s =5kHz; perform the experiment according to steps S10 to S40 of the present invention. Figure 8As shown, the solid line is the spectrum diagram of the composite frequency signal field measured without detuning error and electromagnetic wave amplitude error; the dotted line is the spectrum diagram of the composite frequency signal field measured when the detuning error δ=1MHz and the electromagnetic wave amplitude error is -1%; it can be seen from the figure that the high-order harmonics generated when the control field is applied are eliminated in the spectrum diagram applying the present invention, and a clear and single signal peak can still be obtained in the presence of detuning error and control field amplitude error.

[0110] Experiment 5

[0111] See also Fig. 9 , adjust an electromagnetic wave as a control field, where the electromagnetic wave amplitude Ω = 20 × 2πMHz, the amplitude of the modulation function f = 1, and the number of oscillation cycles N = 240; modulate a signal field to be measured, 1 The effective Larmor frequency of H nuclei ν H =425.76kHz, fine coupling strength 13 The effective Larmor frequency of C nuclei ν C =105.55kHz, fine coupling strength The experiment was carried out according to steps S10 to S40 of the present invention. Fig. 9 As shown, the solid line is the measurement without detuning error and electromagnetic wave amplitude error. 1 The spectrum of the signal of the H atomic nucleus spin; the dotted line is the measurement when the detuning error δ = 1MHz and the electromagnetic wave amplitude error is -1% 1 The spectrum of the signal of H nuclear spin; from the figure, we can see that when measuring the signal containing 13 C nucleus 1 The H nuclear spin signal spectrum exists from 13 The stray signal of C nuclei is eliminated, and a single high-resolution image is obtained. 1 H nucleus signal peak, and can effectively resist the interference of detuning error and control field amplitude error on spectrum measurement.

[0112] Detuning error and amplitude error in the control field Hamiltonian are common error forms in the field of quantum sensing. These two errors will cause the deviation of the real signal peak in the spectrum, that is, the misidentification of the signal frequency, the increase of the background noise in the spectrum, that is, the background noise is too large to cover the real signal, and the increase of the side peak, which affects the accuracy and reliability of measuring the frequency of the signal to be measured. Through the above experimental analysis, it can be seen that the present invention can effectively suppress high-order harmonics, improve the resolution of signals, measure weak signals in complex environments, resist the interference of detuning errors and electromagnetic wave amplitude errors, and eliminate the stray signals generated by heterogeneous nuclei in nuclear spin measurements, so that the measurement results are more accurate and the robustness is more reliable.

[0113] At the same time, the present invention also provides a quantum spectrum measurement device based on Landau-Zener transition, including a controller, an electromagnetic wave generator, a quantum sensor, a signal analyzer, and a control field loader program stored on the controller and executable on the controller:

[0114] The controller is used to execute the control field loading program stored thereon, and output an electromagnetic wave loading control signal to the electromagnetic wave generator, and the output control parameters include: electromagnetic wave amplitude, electromagnetic wave frequency, oscillation cycle number, oscillation frequency, and time;

[0115] The electromagnetic wave generator is used to receive the electromagnetic wave loading control signal output by the controller, and load the electromagnetic wave to the quantum sensor according to the loading control signal to drive the quantum bit to evolve on the XZ meridian;

[0116] The quantum sensor is placed in the environmental field to initialize the state of the quantum bit to the |+> state, and to perform state evolution of the quantum bit under the action of the loaded electromagnetic wave;

[0117] The signal analyzer is used to receive the population signal of the quantum bit state output by the quantum sensor under the driving of electromagnetic waves of different oscillation frequencies, and analyze the frequency of the signal to be measured in the environment according to the spectrum diagram of the population signal-oscillation frequency;

[0118] The control field loading program, when executed by the controller, implements the steps of the quantum spectrum measurement method based on Landau-Zener transition.

[0119] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the embodiments of the present application. The singular forms of "a", "said" and "the" used in the embodiments of the present application and the claims are also intended to include plural forms, unless the context clearly indicates other meanings. It should also be understood that, unless otherwise specified, "multiple" and "several" refer to two or more; "and / or" refers to and includes any or all possible combinations of one or more associated listed items; "first", "second", "third", etc. are only used to distinguish, rather than to describe a specific order or sequence, and cannot be understood as indicating or implying relative importance. When the above description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. In the description of the present application, for those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0120] The above-described embodiments only express some implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which are all within the scope of the present invention.

Claims

1. A quantum spectrum measurement method based on Landau-Zener transition, characterized in that: include: Initialize the quantum state of the quantum sensor placed in the signal environment field to be measured to the |+> state; The electromagnetic wave control field is loaded to the quantum bit initialized to the |+> state. The direction of the control field is to slowly evolve from the positive half axis of the Z axis of the Bloch sphere along the XZ meridian to the positive half axis of the X axis, and at a constant oscillation frequency ω at an angle of Δθ / 2 with the positive half axis of the X axis. ctr Oscillate N times, then slowly evolve from the positive half axis of the X axis along the XZ meridian to the negative half axis of the Z axis; Change the oscillation frequency ω of the control field ctr , so that the quantum bit resonates in the environment field of the signal to be measured, and then the frequency ω of the signal to be measured is obtained signal .

2. The quantum spectrum measurement method according to claim 1, characterized in that: The frequency ω of the electromagnetic wave c satisfy: oh c =ω0-Ω / tan{arccos[F(t)]} Where ω0 is the eigenfrequency of the two-level system of the quantum sensor, Ω is the amplitude of the electromagnetic wave, and F(t) is the modulation function.

3. The quantum spectrum measurement method according to claim 2, characterized in that: The modulation function F(t) satisfies: F(t)=fcos(ω ctr t) Where f is the amplitude of the modulation function, ω ctr is the oscillation frequency of the control field.

4. The quantum spectrum measurement method according to claim 3, characterized in that: The Δθ in the opening angle of Δθ / 2 satisfies: Δθ=arccos(f)-arccos(-f) Where f is the amplitude of the modulation function.

5. The quantum spectrum measurement method according to claim 3, characterized in that: The number of oscillations N is greater than or equal to 100.

6. The quantum spectrum measurement method according to any one of claims 2 to 5, characterized in that: The evolution time from the positive half axis of the Z axis of the Bloch sphere to the positive half axis of the X axis along the XZ meridian is t i , the evolution rate satisfies: dθ / dt<<Ω, Where θ = arctan(Ω / Δ) Δ=ω0-ω c Where Ω is the amplitude of the electromagnetic wave, Δ is the detuning amount, ω0 is the eigenfrequency of the two-level system of the quantum sensor, and ω c is the frequency of the electromagnetic wave.

7. The quantum spectrum measurement method according to claim 6, characterized in that: The evolution time from the positive half axis of the X axis of the Bloch sphere to the negative half axis of the Z axis along the XZ meridian is t i , the evolution rate satisfies: dθ / dt<<Ω, Where θ = arctan(Ω / Δ) Δ=ω0-ω c Where Ω is the amplitude of the electromagnetic wave, Δ is the detuning amount, ω0 is the eigenfrequency of the two-level system of the quantum sensor, and ω c is the frequency of the electromagnetic wave.

8. The quantum spectrum measurement method according to claim 1, characterized in that: Before applying the control field to the quantum bit, the state of the quantum bit is prepared to The |+> state of this quantum bit is located on the positive x-axis of the Bloch sphere.

9. A quantum spectrum measurement device based on Landau-Zener transition, comprising a controller, an electromagnetic wave generator, a quantum sensor, a signal analyzer, and a control field loader program stored on and executable on the controller: The controller is used to execute the control field loading program stored thereon, and output an electromagnetic wave loading control signal to the electromagnetic wave generator. The output control parameters include: Electromagnetic wave amplitude, electromagnetic wave frequency, number of oscillation cycles, oscillation frequency, loading time; The electromagnetic wave generator is used to receive the electromagnetic wave loading control signal output by the controller, and load the electromagnetic wave to the quantum sensor according to the loading control signal to drive the quantum bit to evolve on the XZ meridian; The quantum sensor is placed in the environmental field to initialize the state of the quantum bit to the |+> state, and to perform state evolution of the quantum bit under the action of the loaded electromagnetic wave; The signal analyzer is used to receive the population signal of the quantum bit state output by the quantum sensor under the driving of electromagnetic waves of different oscillation frequencies, and analyze the frequency of the signal to be measured in the environment according to the spectrum diagram of the population signal-oscillation frequency; When the control field loading program is executed by the controller, the steps of the quantum spectrum measurement method based on Landau-Zener transition as claimed in any one of claims 1 to 7 are implemented.

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