RU2684669C1 - Precision solid-state quantum gyroscope of continuous action on basis of spin ensemble in diamond - Google Patents

Abstract

FIELD: physics.SUBSTANCE: use: for measurements using a quantum gyroscope. Summary of invention consists in the fact that measurement of rotation in space using a rotation sensor comprising a diamond plate with colour centres, including the following steps, calibrating the sensor by translating the colour centres of the electron spins into a state with m= 0with projection of electron spins on centre axis NV equal to zero, due to constant exposure of diamond plate to incoherent optical field, as well as transfer of part of electronic spins system corresponding to nuclear spin projection m= 1, m= -1, colour centres from state m= 0 to state m= (+/-)1 and m= (-/+)1 with the projection of said spins on the NV axis of the centre, which is equal to plus one unit |0, 1} → |-1, 1} and minus the unit |0, -1} → |1, -1}, due to constant and simultaneous action on diamond plate of optical incoherent radiation, two-frequency microwave radiation and magnetic field, after which systems of nuclear spins are transferred into state m= 0 due to constant action on the diamond plate of radio-frequency radiation (RF), which realizes transitions |1, -1} ↔ |1, 0}, |-1, 1} ↔ |-1, 0}, bringing the sensor into a state which is sensitive to rotation by applying a nuclear spin in the state m to the system= 0, m= 0 of resonance radio-frequency radiation, minimizing rotation measurement error by modulation of microwave radiation frequencies in the vicinity of two resonance frequencies corresponding to different values of electron spin, recording the electron spin response from the diamond plate fluorescence signal at modulation frequencies and generating the microwave signal correcting frequency based on the measured error signal, returning the radiation frequencies to resonance circuit maximums, calculating at specified periodicity angular rotation speed of sensor as difference of continuously controlled frequency of radio-frequency radiation and known value of quadrupole splitting of nuclear spin, wherein frequency adjustment of radio-frequency radiation is carried out by modulating the frequency of radio-frequency radiation in the vicinity of the resonance frequency of the nuclear spin, Note here that nuclear spin response is detected from fluorescence signal of diamond plate at modulation frequency and corrective signal frequency is generated on the basis of measured error signal returning radiation frequency to maximum of resonance circuit.EFFECT: technical result is possibility of measuring absolute rotation of sensitive sensor element.13 cl, 10 dwg

Description

The invention relates to the field of gyroscopes, namely, to quantum gyroscopes.

The prior art patent RF №2522596, published 02.02.2014, "A method for determining the angle of disorientation of diamond crystallites in a diamond composite", which describes a method for determining the angle of disorientation of diamond crystallites in a diamond composite. The method involves placing a diamond composite into an electron paramagnetic resonance (EPR) spectrometer resonator, measuring the EPR spectra of a nitrogen-vacancy NV defect in a diamond composite with different orientations of the diamond composite relative external magnetic field, comparing the obtained dependences of the EPR lines with the calculated positions of the NV defect EPR lines in a single crystal diamond in a magnetic field, determined by calculation. Then, by increasing the width of the EPR line in the diamond composite as compared to the width of the EPR line in a diamond single crystal, the angle of disorientation of the diamond crystallites is determined. The invention allows to determine the misorientation angle of diamond crystallites in a diamond composite, provides high accuracy of measurements, as well as the possibility of optical magnetic resonance detection (ODMR), which increases the sensitivity of measurements.

The prior art patent of the Russian Federation No. 2570471, published 12/15/2014, "Method for determining the orientation of NV defects in a chip." The document describes a method for determining the orientation of NV defects in a diamond crystal. The method involves placing a sample of a diamond crystal in an external magnetic field, exposing the sample to microwave radiation, irradiating the working volume of the sample with focused laser radiation exciting photoluminescence in the working volume of the sample, which records the signal of optically detected magnetic resonance (ODMR), which is created by scanning the frequency of the microwave radiation and modulation of the external magnetic field. The spectra of the ODMR of the NV defect in a diamond crystal are measured for different orientations of a diamond crystal with respect to an external magnetic field. The obtained dependences of the ODMR lines are compared with the calculated positions of the NV defect lines in a diamond crystal in a magnetic field. Then, the orientation of the NV defect is determined by the magnitude of the deviation of the position of the NV lines of the defect from the calculated line positions. The invention solves the problem of determining the orientation of NV-defects in the crystal.

The prior art US patent No. 9541610, published 04.08.2016, "Device and method for restoring a three-dimensional magnetic field using a magnetic detection system." The document discloses a system for magnetic detection of an external magnetic field. The system includes diamond material with nitrogen vacancies (NV), containing many NV centers, a magnetic field generator that generates a magnetic field, a radio frequency (RF) excitation source that provides radio frequency excitation, an optical excitation source that provides optical excitation, optical a detector that receives the optical signal emitted by the NV diamond material; and a controller. The controller is designed to calculate a control magnetic field, control a magnetic field generator to generate a control magnetic field, receive a light detection signal from an optical detector based on an optical signal in accordance with the sum of the generated control magnetic field and external magnetic field, store measurement data based on the received detection signal light and to calculate the vector of the external magnetic field based on the measurement data.

From the prior art known US patent No. 8947080, published 12/09/2010, "Highly sensitive solid-state magnetometer." The patent describes a magnetometer for measuring the magnetic field, which may include a solid-state spin electronic system and a detector. The electron spin system can contain one or more electron spins that are located in the lattice, for example, NV centers in a diamond. The electron spins can be configured to receive optical excitation radiation and align with the magnetic field. The electron spins can be additionally induced to precess around the perceived magnetic field in response to external control, such as a radio frequency field, the spin precession frequency is linearly related to the magnetic field using the Zeeman shift of the electron spin energy levels. The detector can be configured to detect the output optical radiation from the electron spin to determine the Zeeman shift and, therefore, the magnetic field.

A disadvantage of the known solutions is the instability with respect to fluctuations of the radiation intensity, the inertia of the systems, the need for a "dark time" during which the spin system is prepared for measurement and is therefore not sensitive to rotation.

Technical task

The technical problem solved by the invention is the measurement of the absolute rotation of the sensitive element of the sensor. The technical result is the same as the technical problem.

Decision

To solve this problem, a method is proposed for measuring rotation in space using a rotation sensor containing a diamond plate with color centers, including the following steps,

- calibrate the sensor by transferring the electron spins of the color centers to the state with m _s = 0 with the projection of the electronic spins on the NV axis of the center equal to zero due to the constant impact on the diamond plate of the incoherent optical field, as well as the translation of a part of the electron spin system corresponding to the nuclear spin m projection _i = 1 m _i = -1, color centers from the state m _s = 0 to the state m _s = (+/-) 1 and m _i = (- / +) 1 with the projection of the indicated spins on the axis NV of the center equal to plus one | 0,1} → | 1,1} and minus one | 0, -1} → | 1, -1} due to constant and simultaneous influence i on the diamond plate of optical incoherent radiation, two-frequency microwave radiation (microwave) and magnetic field, then transfer the system of nuclear spins to the state m _i = 0 due to constant exposure of the diamond plate to radio frequency radiation (RF), which realizes the transitions | 1, - 1} ↔ | 1,0}, | -1,1} ↔ | -1,0},

- bring the sensor into a state sensitive to rotation due to the application to the system of a nuclear spin, which is in the state m _s = 0, m _i = 0, of resonant radio frequency radiation,

- minimize the measurement error of rotation of the modulated microwave frequencies in the vicinity of two resonant frequencies corresponding to different values of the electronic spin, while registering the response of the electronic spin on the fluorescence signal of the diamond plate at modulation frequencies and produce a correction frequency of the microwave signal based on the measured error signal returning the radiation frequency to the maxima of the resonant circuits,

- calculate with a given periodicity the angular velocity of rotation of the sensor as the difference is constantly monitored frequency of radio frequency radiation, and the known value of quadrupole splitting of the nuclear spin, while continuously adjusting the frequency of radio frequency radiation due to modulation of the frequency of radio frequency radiation in the vicinity of the resonant frequency of the nuclear spin, while registering the response nuclear spin on the fluorescence signal of the diamond plate at the modulation frequency and produce a corrective part from the signal based on the measured error signal that returns the frequency of the radiation to the maximum of the resonant circuit.

The method can be implemented with the following numerical characteristics. Using an optical system to direct radiation to a diamond plate, the pump power density on a diamond plate is not less than 10 W / mm ² , while creating a magnetic field on a diamond plate up to 20 Gauss, while providing an electromagnetic field on a diamond plate with a microwave antenna more than 90% uniformity, while using the optical system to ensure the efficiency of collecting fluorescence radiation of at least 10%.

To solve this problem, a rotation sensor on color centers is proposed, containing

- diamond plate with color centers,

- a source of incoherent light with an optical system for directing radiation onto a diamond plate, providing a pump power density sufficient to convert the system of electron spins of color centers to the state | 0.1} with the projection of said spins on the axis NV of the center equal to zero due to constant impact on the diamond plate incoherent optical field

- two sources of microwave radiation (microwave), modulated in amplitude and frequency, and a source of constant magnetic field to convert part of the system of electronic spins of color centers to the state with the projection of these spins on the axis of the NV center equal to one | 0.1} ↔ | -1 , 1} and minus unit | 0, -1} ↔ | 1, -1} due to the constant and simultaneous impact on the diamond plate of the dual-frequency microwave and magnetic field, while the source of the magnetic field is part of the antenna to create a microwave and is located in such a way which creates a magnetic field in the direction the maximum orthogonal orientation of the crystallographic axis, or in the case of the three-axis variant, creates a magnetic field in a direction not collinear to 3 m,

- two sources of radiofrequency radiation to align the system of nuclear spins into a state sensitive to rotation in sensor space due to the constant effect of RF radiation on the diamond plate, which realizes the | 1, -1} ↔ | 1,0}, | -1,1} transitions ↔ | -1,0}

- a photodetector for detecting the fluorescence of color centers in the diamond plate, as well as an optical system that allows you to direct the fluorescence from the diamond plate to the photodetector,

- a controller that, through control signals, generates feedback through constant microwave modulation in the vicinity of 2 resonant frequencies based on the magnitude of the electron spin response through fluorescence recording at the modulation frequency, as well as constant RF modulation in the vicinity of the nuclear spin resonance frequency through the registration of fluorescence at the modulation frequency, and calculates the angular velocity of rotation as the difference of the constantly controlled frequency of radio frequency radiation and the known value of the quadrupole splitting of the nuclear spin.

The sensor can be performed with the following numerical characteristics of the constituent elements.

An incoherent radiation source with a spectrum in the range from 500 nm to 580 nm, optical power at the source output of at least 0.1 W, an antenna for the microwave with a frequency range from 2.6 to 3 GHz, a source of a constant magnetic field that allows you to create a field on a diamond plate to 20 Gauss and having a temperature stability of more than 1 Gauss per hour, RF radiation sources operating in the range up to 10 MHz, a photo detector operating in the spectral range from 600 to 800 nm, having a frequency band of more than 1 MHz and providing a signal-to-signal ratio the output noise is not less than 50 dB, while the magnitude of the projection of the magnetic field on the perpendicular to the selected crystal axes is not less than 0.3 G, and the quadrupole splitting of the nuclear spin is 4.95 MHz.

List of figures

The invention is illustrated by drawings.

FIG. 1 shows a block diagram of the device.

FIG. 2 shows three-dimensional structures for implementing the invention.

FIG. 3 shows a block diagram of a device for generating, recording and processing signals.

FIG. 4 shows the crystal structure of the NV defect in diamond.

FIG. 5 a) and b) respectively the layout of the energy levels inside the forbidden zone and a detailed image of the energy levels of the ground orbital state are shown.

FIG. 6 shows an example of the hyperfine splitting observed in the optically detectable electron paramagnetic resonance.

FIG. 7 shows a diagram of the application of effects and the corresponding transitions in the work of a continuous gyroscope.

FIG. 8 shows the initialization of the nuclear spin.

FIG. 9 shows the evolution of the thermal state of the nuclear spin into a polarized state.

FIG. 10 depicts single-frequency synchronous detection. The black solid line in the center of the figure indicates the resonance circuit, the dotted one is the lock-in output of the amplifier. The figure also shows the forms of the modulating (above average graph) and modulated signal (to the right of the average graph).

In the figures introduced the following notation.

1. The source of a constant magnetic field along the axis NV.

2. Optical pumping radiation.

3. Diamond plate with NV-centers.

4. Optical pumping radiation + fluorescence emission from NV centers.

5. Optical filter to cut off the pumping radiation.

6. Fluorescence NV-centers.

7. Photo Detector.

8. RF antenna.

9. RF amplifier.

10. The adder signals from two RF generators.

11. RF amplitude modulator generator 13.

12. RF amplitude modulator generator 14.

13. A controlled sinusoidal signal generator operating in the range of 1 ... 10 MHz (RF) used in the cycle of polarization of the nuclear spin.

14. Managed sinusoidal signal generator operating in the range of 1 ... 10 MHz (RF) used in the measurement cycle.

15. Device for generating, recording and processing signals.

16. A controlled oscillator of a microwave sinusoidal signal used in the cycle of polarization of the nuclear spin, adjusted to transitions | 0> - | +1> electronic spin.

17. The controlled oscillator of the microwave sinusoidal signal used in the cycle of polarization of the nuclear spin, adjusted to transitions | 0> - | -1> of the electronic spin.

18. Amplitude generator modulator 17.

19. Amplitude modulator of the generator 16.

20. The adder signals from two microwave generators.

21. Microwave amplifier.

22. Microwave antenna.

23. The source of radiation of optical pumping.

24. Waveguide to collect radiation from diamond.

25. Printed circuit board.

26. A capacitor on the board that forms together with the coils a resonant antenna.

27. Waveguide for the excitation of the microwave antenna.

28. Strip RF antenna.

29. Bandpass filter synchronous detector MW0.

30. Signal demodulator MW0.

31. Delay line for adjusting the MW0 synchronous detector.

32. The source of the modulation signal MW0.

33. Proportional-integral-differential controller MW0.

34. The adder signal modulation and compensation MW0.

35. The adder signal modulation and compensation Δ _MW .

36. Adder for the formation of the control signal of the microwave generator 1.

37. Adder for the formation of the control signal of the microwave generator 2.

38. The control signal of the microwave generator 1.

39. The control signal of the microwave generator 2.

40. Subtractor for generating the control signal of the RF2 generator.

41. The control signal RF2.

42. The control signal RF1.

43. The source of the modulation signal Δ _MW .

44. Proportional-integral-differential controller Δ _MW .

45. The adder signal modulation and compensation δ _RF .

46. Proportionally-integrated differential controller δ _RF .

47. The source of the modulation signal δ _RF .

48. Demodulator δ _RF .

49. Band-pass filter of the synchronous detector δ _RF .

50. Delay line to adjust the synchronous detector δ _RF .

51. The input signal fluorescence.

52. Band-pass filter of the synchronous detector Δ _MW .

53. Band-pass filter of a synchronous detector Δ _MW .

54. Delay line for adjusting the synchronous detector Δ _MW .

Detailed solution description

The created technical solution includes a method of continuous measurement of the absolute speed of rotation of an object, as well as a device that allows continuous measurement of the absolute speed of rotation of an object in space based on an ensemble of NV centers in a diamond. NV-center in diamond - a defect in the crystal lattice of diamond, consisting of impurity nitrogen, and vacancy.

The advantages of such a system are high reliability, relatively small dimensions of the sensing element with a relatively higher performance in terms of accuracy compared with the known analogues. Moreover, due to natural features, this method allows for the detection of rotation with respect to three axes in one sensitive element using 4 selected crystallographic axes. Also, NV centers are stable color centers at temperatures of 0-600 K.

The method of continuous measurement of the absolute rotational speed is based on the determination of the projection of the total magnetization vector of nuclear spins of ¹⁴ N nitrogen defects or ¹³ C carbon isotope in a diamond crystal lattice containing NV (-) color defects. In the proposed method, the total magnetization vector is brought into equilibrium stationary state by two opposite effects - “initialization” and “drive”. Bringing the system into rotation leads to a deviation of the magnetization vector from the equilibrium state — the balanced state of the nuclear spin changes the projection onto the quantization axis.

Град/час, опережая похожие по компактности методы определения вращения на 1-2 порядка.Estimates of measurement errors for such a device are at the level of

Hail / hour, ahead of similarly compact methods for determining rotation by 1-2 orders of magnitude.

The measurement method has the following simultaneous processes.

1. Initialization

2. Drive - flipping of the magnetization vector from state 0 to state 1.

3. Measurement of fluorescence

4. Feedback on the level of fluorescence on drive parameters

5. Binding initialization parameters to the transition frequencies of the spin system to eliminate interference from external magnetic fields and temperature, as well as the simultaneous use of a degenerate triplet system of +1, 0, -1 nuclear spin to filter the contribution of the magnetic field.

The design of the gyroscope on the NV centers in diamond consists of a diamond plate (3, Fig. 1). Diamond plate must have certain qualities on the content of color centers in it. In the case of using C13 spins - it should have a high content of C13. In the case of using N14 - a high content of NV-color centers, and a reduced content of C13. The structure includes a source of green light (23) (500-580 nm), laser or photo diode type, and an optical system for directing green radiation to the diamond plate; an optical filter (5) for filtering radiation (4) falling from diamond (3) into a waveguide (24) from pump radiation; a photodetector (7) for detecting fluorescence (6) of color centers in a diamond plate and optical elements (24), which allow directing fluorescence from a diamond plate to a photodetector (7).

The structure of the invention also includes a (resonant) microwave (22) and RF (8) antenna, a source of microwave (16-20) and RF (10-14) signals, which are necessary for effective interaction with the electronic and nuclear spins in the composition of the defects in diamond In addition, the device must contain a source of constant magnetic field (1) and an electronic computing system to control measurements (15).

The sources of RF and microwave signals are two-channel and consist of harmonic signal generators (13, 14, 16, 17) modulated in frequency and amplitude (using modulators 11, 12, 18, 19). The signal from two channels is summed by adders (10, 20) and is amplified by amplifiers (9, 12) before being fed to the antennas.

Exercise

A rotation sensor based on the use of controlled precession of an ensemble of nuclear spins in a diamond crystal with a large number of NV centers in it. The NV center in diamond can be in several charge states q = 0, q = -1, q = + 1. In the framework of this invention uses the state q = -1.

A single NV center is represented in FIG. 4. A separate NV center consists of a nitrogen atom and a vacancy located next to it.

The NV (-) defect has 6 free electrons having a total spin S = 1. The scheme of electronic energy levels for orbitals within the forbidden zone of diamond is shown in FIG. 5, on the left.

The system of sublevels of the unexcited state is presented in FIG. 5, on the right.

NV-center has optical transitions in the visible and infrared range. The main optical transition is associated with the transition of an electron with e _x, orbitals to a ₁ orbital and is at a wavelength of 637 nm and also has a phonon-broadened spectral tail.

After the incoherent excitation of the NV center, it decays into an unexcited state either through an optical transition or through a metastable state that does not preserve the spin value, emitting a photon in the IR range. The probability of making the transition through the metastable state depends on the state of the electron spin of the NV center, being the maximum for the state with spin projection + -1 and minimal for the spin projection 0. The fluorescence intensity of the NV center in the visible range is thus highly dependent on the spin properties of the center (contrast reaches 30%), which is used for optical reading of the state of the spin system. The metastable state, which changes the spin, has no symmetry to the spin state; therefore, the spin is eventually polarized to the state with the projection 0, realizing the optical spin initialization protocol. The asymmetry of the transitions with respect to the state of the electron spin allows the optical initialization of the electron spin to occur — the incoherent transfer from the + -1 states of the electron spin to the state 0.

Also, the NV-center has allowed dipole transitions in the microwave range. In the unexcited electronic state (both electrons are on a ₁ sublevel) there is a nonzero spin spin interaction of electrons, which leads to a splitting of the energy level D ~ 2.87 GHz between states with different projection of the electron spin on the NV axis (m _s = 0 and m _s = + / -1), forming a thin splitting of the ground state. Degeneration by the sign of the projection can be removed by applying a constant magnetic field along the axis of the NV center.

In addition, each of the thin states experiences hyperfine splitting associated with the interaction of the electron spin with the spin of the N ₁₄ nucleus. Ultra slim

the splitting in the absence of external fields is from 2.8 to 7.2 MHz, depending on the state. The total Hamiltonian for the electronic and nuclear spin systems is written as follows [Philipp Neumann "The nitrogen-vacancy center in diamond", pp. 42, 56-58, 2012]:

- слагаемое в гамильтониане, соответствующее взаимодействию электронного спина с полем решетки алмаза

и внешним магнитным полем

- the term in the Hamiltonian, corresponding to the interaction of the electron spin with the field of the diamond lattice

and external magnetic field

D (≈2.87 GHz) is the quadrupole splitting of the electron spin-1 in the field of a diamond lattice;

Y _e (≈2.8 MHz / G) is the gyromagnetic ratio of the electron spin;

B _z - the value of the external magnetic field;

- оператор проекции электронного спина на ось Z;

- the operator of the projection of the electronic spin on the Z axis;

- слагаемое в гамильтониане, соответствующее сверхтонкому взаимодействию

, взаимодействию ядерного спина с внешним магнитным полем

квадрупольному взаимодействию ядерного спина

- the term in the Hamiltonian corresponding to the hyperfine interaction

interaction of nuclear spin with external magnetic field

quadrupole nuclear spin interaction

In turn, the components of the nuclear spin Hamiltonian are written as [Philipp Neumann "The nitrogen-vacancy center in diamond", p. 42, 56-58, 2012]:

- контактное взаимодействие Ферми;

- Fermi contact interaction;

- вероятность нахождения электрона внутри ядра;

- probability of finding an electron inside the nucleus;

- тензор взаимодействия;

- interaction tensor;

- диполь-дипольное взаимодействие электронного и ядерного спинов;

- dipole-dipole interaction of electron and nuclear spins;

μ ₀ is the magnetic permeability of vacuum;

γn = gnμn is the gyromagnetic ratio for the N14 core;

E _r is the rth vector ort of the Cartesian coordinate system;

r is the effective distance between the electron and nuclear spins;

B - external magnetic field;

Q is the quadrupole splitting constant for the nuclear spin;

- вектор-оператор ядерного спина;

- vector operator of nuclear spin;

- вектор-оператор электронного спина;

- vector operator of electronic spin;

The parameters of the Hamiltonian can be found in [Philipp Neumann, "The nitrogen-vacancy center in diamond", pp. 42,56-58, 2012], [L.I. Childress, "Coherent manipulation of single quantum systems in the solid state," pp. 25-26 no. March, 2007] [Victor Marcel Acosta "Optical Magnetometry with Nitrogen-Vacancy Centers in Diamond", p. 15, 2011].

The natural width of the microwave transition line at 2.87 GHz is about 100–200 kHz, and the distance between transitions corresponding to different spin states is about 2.1 MHz; thus, in the EPR and ODMR spectra, the triplet splitting of states with the projection of the electronic spin equal to 0 and 1 can be observed ( Fig. 6).

However, in the case of using the NV-center band, factors such as stress in the crystal, impurity C ₁₃ and an inhomogeneous magnetic field can bring to the inhomogeneous broadening of the microwave transitions for different NV-center of the ensemble, which may bring deterioration gyro characteristics.

Diamond crystals with a moderate content of NV-defects (1-100 ppm) are best suited for use in the device. Diamonds produced by HPHT without the use of catalysts, CVD with a controlled moderate content of nitrogen impurities, and the absence of other paramagnetic impurities, such as C ₁₃ , as well as natural diamond crystals can be used. To create an ensemble of NV centers in a crystal, it is necessary to conduct irradiation under an electron, proton, neutron, or helium beam, with particle energy exceeding 1 MeV. (3 MeV). After irradiation, it is necessary to hold the sample in a vacuum high-temperature furnace. Annealing mode may be different. As an example, annealing at a temperature of 800 degrees Celsius for 2 hours is used. In the process of annealing, vacancies formed during irradiation become mobile and “find” nitrogen impurity atoms in the diamond lattice.

A diamond crystal can be polished according to a different crystallographic axis. Commercially available plates have [100], [110], [111] orientation. For example, the [100] orientation means that the face of polishing is perpendicular to the edge of the cube of the diamond-faceted lattice. The [111] orientation means that the normal to the polishing plane is parallel to the covalent bond in the diamond lattice (see Fig. 4). For effective interaction of microwave radiation with electron spin, the magnetic alternating field should be directed perpendicular to the axis of the NV center. The most suitable solution would be a microwave resonator shown in FIG. 2, consisting of a printed circuit board (25) on which a capacitor (26) is formed, and two conductive rings (22). The signal to the microwave antenna is fed through the waveguide (27). Microwave resonator must have the necessary degree of adaptability, for use at different frequencies, for example at the transition Ms = -1 -> 0, or Ms = + 1 -> 0.

A microstrip antenna (28) is used as the RF antenna, the width of which provides the necessary uniformity of the magnetic field at the RF frequency in the diamond region.

Measurement technology of rotation on the nuclear back of nitrogen

The rotation measurement is carried out on the basis of the measurement of the precession parameters of the total magnetization vector of the nuclear spin of an ensemble of NV centers, namely, the declination or projection of the vector on the quantization axis, which change in the presence of rotation.

In order to carry out the measurement described above, it is necessary to simultaneously perform an incoherent relaxation initialization of the nuclear spin into states with projection 0 and simultaneous coherent inversion (“drive”) to state 1, or -1, or +1 and -1 simultaneously. The choice of these three cases is due to the type of polarization of the “drive” of the RF. The right circular gives +1, the left circular gives -1, the linear gives both projections. In the process of these effects, it is necessary to measure the projection of the nuclear spin by projecting it onto the state of the electronic spin. This projection is successfully performed during the initialization process, which will be discussed in more detail below. By fluorescence contrast depending on the state of the electronic spin, the detuning of the “drive” parameters is determined, namely the frequency, and the system is controlled by the feedback method to close the work cycle into a closed loop (close-loop).

Process 1: Relaxation Polarization of Nuclear Spin

Subprocess 1.1

The initialization of the nuclear spin ensemble of NV centers is carried out in accordance with FIG. 7, FIG. 8. To do this, radiation of an incoherent pumping optical (500-600 nm), coherent resonant UHF1 field at the frequencies of the corresponding transitions | 0.1} → | -1.1} (UHF), | 0, -1} → | 1 , -1} (UHF1) (Fig. 8), radio frequencies at the transitions | 1, -1} → | 1,0}, | -1,1} → | -1,0} (RF) - the frequencies of these transitions are the same .

The combination of the application of the three types of radiation brings the system into a state with projections of the electron and nuclear spin equal to 0, because optical pumping, transferring populations from the level Ms = + - 1 to Ms = 0, transfers the populations of nuclear sublevels without changes. And as it follows from Fig. 8 ,, the level | 0,0}, the only “dark” level from which microwaves do not transfer, therefore, it accumulates the population. This method has been studied numerically. FIG. 9

The time dependence of the states that started from equally populated thermal populations is given.

As a result, we have an analog of incoherent pumping for a three-level system — a nuclear spin — a pumping state from nonzero projections into a zero projection over the characteristic time T _init with speed G _init = 1 / T _init .

Subprocess 1.2

In reality, for a stable initialization operation, it is necessary that shifts in energy levels due to the Zeeman effect (3 MHz / G), or temperature (70 kHz / deg) do not lead to a change in the total spin polarization velocity. For this purpose, a feedback method is implemented using the synchronous detection method. By modulating the frequency of the microwave field in the vicinity of the resonant frequency, it is possible to realize a dispersed circuit, with the linear dependence of the signal necessary for the implementation of the feedback on the distance to the desired frequency, using the synchronous detection circuit shown in FIG. ten.

Process 2. Drive the nuclear spin in the ground state of the electron spin.

By virtue of the implementation of the process 1 - “initialization”, the nuclear spin relaxes to the state m _i = 0 - i.e. to the "Equator" sphere of possible positions of the back (not the sphere of the Bloch). As a result of this relaxation, the nuclear spin gradually loses the phase and projection that it had.

In contrast to initialization, “drive” is necessary for a flip from the zero projection to 1 (-1, or both). This process, together with decoherence, leads to the fact that the populations of nuclear states come to equilibrium, which can be determined from a system of kinetic equations:

Where G is the initialization speed, Ω is the frequency of the Rabi drive field.

Whence for the case when pumping is carried out immediately on +1 and -1 projections

Where α = Ω / G

As can be seen, with a constant initialization rate G, population, and therefore, the level of fluorescence depends on the detuning of the RF drive frequency.

Rotation triggers extra fluorescence level drift (see below). Leaving the level of fluorescence due to rotation can be compensated by RF detuning. The detuning required to compensate will unambiguously characterize the amount of rotation. In this case, since the effect of rotation will be compensated, the operating point will remain unchanged. To do this, however, the system must be deduced from the maximum or minimum of fluorescence, in which the response of the system is quadratic in deflecting effects.

To bring the system into a sensitive state, it is necessary to set the system on the slope of the resonant circuit in the absence of rotation. The choice of the working point of the gyroscope according to the parameters G, Δ, α - determines the sensitivity of the signal to rotation. The optimal sensitivity position corresponds to Δ = ± Ω / √3. Then the frequency changes of Rabi with resonance detuning will be equal

Leading to sensitivity in the population

Process 3. Measuring the state of the nuclear spin by projecting it onto the electron spin and measuring rotation

When making a spin, the spin system continues to precess in space, while the antenna, and with it the radio frequency field, begins to rotate, gaining phase with respect to the rotating spin. A linear change in phase with time is a change in frequency. The appearance of this additional frequency will change the precession frequency, which will lead to a change in the level of the fluorescence signal as described above. A feedback loop (45-50 of Fig. 3), in which the control action is the detuning of the RF generator, and the controlled value — the fluorescence value of the NV-center ensemble compensates for this change. In this case, the compensation feedback signal will be a measure of the change in the precession frequency. Thus, due to feedback compensation, the instrument's operating point is almost not shifted until changes in the rotational speed are slower than the speed of the feedback loop, and the detuning of the RF generator frequency is linearly proportional to the angular velocity of rotation.

In the scheme of continuous measurement, three simultaneous modulations of frequencies occur (RF1 ~ 5 MHz). The frequencies of the microwave, for which there is a minimum of fluorescence, and RF, for which there is a maximum of fluorescence, represent a linear combination of external parameters: magnetic field, temperature and angular velocity of rotation. The position of the extremes is determined by sinusoidal or meandering modulation of the parameters, followed by synchronous demodulation of 1 harmonic of the received signal and adjustment of the parameter bias in the feedback loop. Details of the work of this method can be, for example, found in [Arie et al., Opt. Lett. 17, 1204, 1992].

However, to bind simultaneously in 3 parameters, it is necessary to spread the modulation frequencies, on the one hand, so that the beats between the individual modulation frequencies do not fall into the frequency domain of demodulation, on the other hand, do not exceed the system response speed. To increase the accuracy due to the inertia of temperature, the microwave frequencies are represented as F _MW1 = F _MW0 -Δ _MW , F _MW2 = F _MW0 + Δ _MW . The frequency F _MW0 is linearly related to the temperature of the sensor, while Δ _{MW is} primarily tied to the projection of the external magnetic field. What allows to make slow modulation F _MW0 and fast modulation Δ _MW . The error signal of slow modulation is not of interest to calculate the angular velocity.

The third RF modulation occurs at an intermediate frequency (between the modulation frequencies Δ _MW and F _MW0 ). The RF1 δ _RF error signal contains the angular velocity of rotation, from which the angular velocity of rotation is obtained by subtracting the nuclear quadrupole splitting.

As mentioned above, with constant operation, the frequencies of RF1, RF2, UHF1, UHF2 are modulated. Sources of modulations are the generators of a sinusoidal signal (32, 43, 47, Fig. 3). The modulation signals are summed with the feedback signals from the proportional-integral differential controllers (33, 44, 46) on the adders (34, 35, 45). The resulting control signals using the adder (36) and subtractors (37, 40) form the control signals for the microwave generators (38), microwave frequencies (39), RF1 (42), RF2 (41). These signals change the frequencies of the oscillators, allowing you to scan the resonant lines at the frequencies described in the “Process 1” section.

When modulating frequencies, the fluorescence signal (51) contains all the components of the signal offset from the resonant frequencies, spectrally transferred to the modulation frequency. Demodulation of the component data is carried out by spectral filtering at the modulation frequency using band-pass filters (29, 49, 52) and then multiplying (30, 48, 53) the signal by the modulation signal from the oscillators (32, 43, 47), the phase of which is compensated to take into account the inevitable response delay of the system subject to modulation, delay lines (31, 50, 54). The demodulated frequency offset signals are fed to proportional-integral-differential controllers (33, 44, 46), which close the feedback loop of the reference to the resonant lines.

The application of the developed technical solution allows to obtain the following technical indicators.

Reducing the volume of the sensitive element of the sensor: less than 1 cu. cm.

High specific spectral sensitivity of the element: 0.3 × 10-3 UAH / hour

Low sensitivity drift: ~ 10-3 UAH / hour

The ability to create a hybrid device that includes a sensor measuring three physical parameters (3-axis gyroscope, magnetometer, temperature sensor).

Claims (23)

1. The method of measuring rotation in space using a rotation sensor containing a diamond plate with color centers, including the following steps: - calibrate the sensor by transferring the system of electronic spins of color centers to the state with m _s = 0 with the projection of electronic spins on the axis of the NV center zero, due to the constant impact on the diamond plate of the incoherent optical field, as well as the transfer of a part of the system of electronic spins corresponding to the projection of the nuclear spin m _i = 1, m _i = -1, color centers from the state m _s = 0 to the state m _s = (+/-) 1 and m _i = (- / +) 1 with the projection of the indicated spins on the axis of the NV center, equal to the unit | 0,1} → | -1,1} and minus the unit | 0, -1} → | 1, -1}, due to constant and simultaneous air Optical incoherent radiation, dual-frequency microwave radiation (UHF) and magnetic field are applied to the diamond plate, and then the systems of nuclear spins are transferred to the state m _i = 0 due to the constant exposure of the diamond plate to radio frequency radiation (RF), which realizes the transitions | 1, - 1} ↔ | 1,0}, | -1,1} ↔ | -1,0}, - bring the sensor into a state sensitive to rotation due to the application to the system of a nuclear spin, which is in the state m _s = 0, m _i = 0, of resonant radio frequency radiation, - minimize the measurement error of rotation of the modulated microwave frequencies in the vicinity of two resonant frequencies corresponding to different values of the electronic spin, while registering the response of the electronic spin on the fluorescence signal of the diamond plate at modulation frequencies and produce a correction frequency of the microwave signal based on the measured error signal returning the radiation frequency to the maxima of the resonant circuits, - calculate with a given periodicity the angular velocity of rotation of the sensor as the difference of the continuously monitored frequency of radio frequency radiation and the known value of quadrupole splitting of the nuclear spin, while constantly adjusting the frequency of radio frequency radiation by modulating the frequency of radio frequency radiation in the vicinity of the resonant frequency of nuclear spin, while registering the response of nuclear back on the fluorescence signal of the diamond plate at the modulation frequency and often produce corrective y signal based on the measured error signal returns to the high frequency radiation the resonance circuit. 2. The method according to p. 1, characterized in that they provide with the help of an optical system for directing radiation to a diamond plate the pump power density on the diamond plate is not less than 10 W / mm ² . 3. The method according to p. 2, characterized in that they create a magnetic field on the diamond plate up to 20 Gs. 4. The method according to p. 3, characterized in that they provide with a microwave antenna electromagnetic field on a diamond plate with a uniformity of more than 90%. 5. The method according to p. 4, characterized in that with the help of the optical system provide the efficiency of collecting fluorescence emission of at least 10%. 6. The rotation sensor on the color centers, containing - diamond plate with color centers, - a source of incoherent light with an optical system for directing radiation onto a diamond plate, providing a pump power density sufficient to convert the system of electron spins of color centers to the state | 0.1} with the projection of the indicated spins on the axis of the NV center equal to zero due to constant exposure on a diamond plate incoherent optical field, - two sources of microwave radiation (microwave), modulated in amplitude and frequency, and a source of constant magnetic field to convert part of the system of electronic spins of color centers to the state with the projection of these spins on the axis of the NV center, equal to one | 0.1} ↔ | - 1.1} and minus unit | 0, -1} ↔ | 1, -1}, due to the constant and simultaneous effects on the diamond plate of the dual-frequency microwave and magnetic field, the source of the magnetic field is part of the antenna to create a microwave and is located the way that creates a magnetic field in nap the maximum orthogonal orientation of the crystallographic axis, or in the case of the three-axis version, creates a magnetic field in a direction that is not collinear with the three axes, - two sources of radiofrequency radiation to align the system of nuclear spins into a state sensitive to rotation in sensor space due to the constant effect of RF radiation on the diamond plate, which realizes the | 1, -1} ↔ | 1,0}, | -1,1} transitions ↔ | -1,0} - a photodetector for detecting the fluorescence of color centers in the diamond plate, as well as an optical system that allows you to direct the fluorescence from the diamond plate to the photodetector, - a controller that, through control signals, generates feedback through constant microwave modulation in the vicinity of two resonant frequencies based on the magnitude of the electron spin response through fluorescence recording at the modulation frequency, as well as constant RF modulation in the vicinity of the nuclear spin resonance frequency through the registration of fluorescence at the modulation frequency and calculates the angular velocity of rotation as the difference of the constantly monitored frequency of the radio frequency emitted and the known value of the quadrupole splitting of the nuclear spin. 7. The sensor according to claim 6, characterized in that the source of incoherent radiation with a spectrum in the range from 500 to 580 nm is used, the optical power at the source output is at least 0.1 W. 8. Sensor according to claim 7, characterized in that an antenna is used for a microwave with a frequency range of 2.6 to 3 GHz. 9. The sensor according to claim. 8, characterized in that a source of a constant magnetic field is used, which allows creating a field on a diamond plate up to 20 Gs and having a temperature stability of more than 1 Gs per hour. 10. The sensor according to claim 9, characterized in that it includes RF radiation sources operating in the range up to 10 MHz. 11. The sensor according to claim 10, characterized in that a photodetector is used operating in the spectral range from 600 to 800 nm, having a frequency band of more than 1 MHz and providing a signal-to-noise ratio at the output of at least 50 dB. 12. The sensor according to claim 11, characterized in that the magnitude of the projection of the magnetic field on the perpendicular to the selected axes of the crystal is at least 0.3 Gs. 13. The sensor according to claim 12, characterized in that the quadrupole splitting of the nuclear spin, equal to 4.95 MHz, is used.

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