Phase difference measuring device and electrical equipment equipped therewith

Abstract

To measure a phase difference between a plurality of physical fields with high sensitivity.SOLUTION: A phase difference measurement device (10) comprises: an electric magnetic wave irradiation part (2) which repeatedly irradiates a quantum sensor element (1) with an electromagnetic wave for operating an electron spin state of the quantum sensor element (1) changing with an interaction with a first physical field or second physical field generated with an AC signal; and a phase difference measurement part (3) which acquires a plurality of electron spin states after the interaction with the first physical field or second physical field, and measures the phase difference between a plurality of physical fields based upon the plurality of acquired electron spin states.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a technology using quantum sensors, and more particularly to a device, method, and electrical equipment equipped with a phase difference measuring device for magnetic and electric fields using quantum sensors. [Background technology]

[0002] When alternating current is supplied through power lines in a power system, reactive power flows through the lines. As reactive power increases, power loss increases, so power systems are connected to devices that adjust the power factor, which are highly effective in improving the stability of the power system and suppressing power fluctuations. For example, Patent Document 1 discloses a system for adjusting the reactive power of distribution lines.

[0003] Devices that adjust the power factor are called phase-shifting equipment. Phase-shifting equipment includes power capacitors, shunt reactors, synchronous phase-shifting machines, and static VAR compensators (SVCs). When adjusting and improving the power factor of a power system using phase-shifting equipment, the reactive power flowing through the power system is measured. Reactive power is expressed using the RMS value of the voltage, the RMS value of the current, and the phase difference between the voltage and current.

[0004] High currents and high voltages flow through power lines. For example, in ultra-high voltage substations, voltages of tens of thousands of volts flow through transmission lines, and in distribution substations, voltages ranging from several thousand to tens of thousands of volts flow through distribution lines. To measure the high currents and voltages flowing through power lines, substations are equipped with transformers such as current transformers and voltage transformers in addition to phase-shifting equipment. Until now, for alternating current flowing through power lines, the phase difference between the phase of voltage and the phase of current has been measured by measuring the phase of voltage and the phase of current, respectively, in non-insulated transformers connected to transmission lines and distribution lines (or in the circuits surrounding the transformers). Phase-shifting equipment adjusts the power factor of the power system based on the measured phase difference.

[0005] In recent years, diamond has attracted attention as a material for sensor elements that measure magnetic fields. In the crystal structure of diamond, a complex defect called a nitrogen-vacancy center is sometimes observed. This nitrogen-vacancy center consists of a pair of a nitrogen atom that substitutes for a carbon atom at a position in the crystal lattice, and a vacancy (missing carbon atom) located adjacent to the nitrogen atom, and is also called an NV center (Nitrogen Vacancy center). In addition to NV centers, complex defects called silicon-vacancy centers and complex defects called germanium-vacancy centers are sometimes observed in the crystal structure of diamond, and these complex defects including NV centers are collectively called color centers.

[0006] An NV center exhibits magnetic properties called electron spin when electrons are trapped in the vacancy (negatively charged state, hereinafter referred to as NV - -). This NV - - exhibits a longer transverse relaxation time (decoherence time, hereinafter referred to as T2) compared to a state where no electrons are trapped (neutral state, hereinafter referred to as NV 0 0). In other words, for the electron spin state of NV - -, after the magnetization of electron spins aligned along the longitudinal direction of an external magnetic field (hereinafter referred to as the "quantization axis") is tilted to the transverse direction, it takes a long time for the transverse magnetization as a whole to disappear due to the misalignment of individual spin directions caused by precession of individual spins. Furthermore, NV - - exhibits a long T2 value even at room temperature (approximately 300K).

[0007] NV - -'s electron spin state changes in response to an external magnetic field, and measurement of this electron spin state can also be performed at room temperature, so diamond containing NV centers can be used as a material for magnetic field sensor elements.

[0008] For example, Patent Document 2 discloses a method for measuring an alternating current magnetic field through magnetic resonance induced by electron spins in diamond. A pulse sequence based on the spin echo method is applied to the spins.

[0009] For example, Patent Document 3 discloses a method for measuring an alternating-current magnetic field by an Optically Detected Magnetic Resonance (ODMR) method for electron spins in diamond. An NV center is excited by laser light, and a magnetic resonance signal (phase information) relating to the spin state is detected by measuring a change in fluorescence intensity emitted from the NV center.

[0010] In addition to sensors using a color center of diamond, there are various types of sensors used as magnetic field sensor elements, for example, sensors using a color center in silicon carbide (SiC), an optically pumped atomic magnetometer (OPM), a superconducting quantum interference device (SQUID), and the like. These diamond color centers, silicon carbide color centers, optically pumped atomic magnetometers, and superconducting quantum interference devices are called quantum sensors because they measure physical quantities using quantum effects.

Prior Art Literature

Patent Literature

[0011]

Patent Literature 1

Patent Literature 2

Patent Literature 3

Summary of the Invention

Problem to be Solved by the Invention

[0012] When measuring the phase difference between voltage and current in alternating current (AC) lines carrying high currents and voltages at a non-insulated transformer (or in the circuit surrounding the transformer), the transformer requires a protective circuit to shield the circuit from the high current and voltage. As a result, the scale and cost of electrical equipment, including transformers, switches, and other power transmission and distribution equipment, as well as power lines, increase. In recent years, various facilities have been installed, for example, to connect DC power from solar power generation facilities to the power grid, further increasing the scale of electrical equipment. There is a need to measure the phase difference between voltage and current in AC lines flowing through electrical equipment without requiring protective circuits.

[0013] Furthermore, as electrical equipment deteriorates over time, signs of failure may appear, creating a phase difference between the minute electric field and the minute magnetic field generated by fluctuations in the alternating current flowing through the equipment. To quickly detect signs of electrical equipment failure, it is necessary to measure the phase difference between the magnetic and electric fields with high sensitivity.

[0014] The present invention aims to measure the phase difference between multiple physical fields with high sensitivity. [Means for solving the problem]

[0015] The present invention, which solves the above problems, includes, for example, the following embodiments.

[0016] (Section 1) An electromagnetic wave irradiation unit repeatedly irradiates a quantum sensor element with electromagnetic waves to manipulate the electron spin state of the quantum sensor element, which changes due to interaction with a first or second physical field generated by an AC signal, A phase difference measuring unit that acquires a plurality of electron spin states after interaction with the first physical field or the second physical field, and measures the phase difference between the plurality of physical fields based on the acquired plurality of electron spin states, A phase difference measuring device equipped with the following features. (Section 2) The phase difference measuring unit is A first physical field phase calculation unit calculates the phase of the first physical field based on a plurality of electron spin states after interaction with the first physical field, A second physical field phase calculation unit calculates the phase of the second physical field based on a plurality of electron spin states after interaction with the second physical field, Includes, A phase difference measuring device according to item 1, which measures the phase difference based on the calculated phase of the first physical field and the phase of the second physical field. (Section 3) The first physical field phase calculation unit calculates the phase of the first physical field by fitting multiple time-series data corresponding to multiple electron spin states after interaction with the first physical field. The phase difference measuring apparatus according to item 2, wherein the second physical field phase calculation unit calculates the phase of the second physical field by fitting a plurality of time-series data corresponding to a plurality of electron spin states after interaction with the second physical field. (Section 4) The phase difference measuring apparatus according to any one of items 1 to 3, wherein the electromagnetic wave irradiation unit is a pulse sequence for observing the free induction decay (FID) signal of the electron spin state, and the electromagnetic wave is repeatedly irradiated onto the quantum sensor element with a pulse sequence including a plurality of π / 2 pulses. (Section 5) The electromagnetic wave irradiation unit is a pulse sequence for observing the spin echo signal of the electron spin state, and repeatedly irradiates the quantum sensor element with the electromagnetic wave in a pulse sequence including a plurality of π / 2 pulses and π pulses between the plurality of π / 2 pulses. The phase difference measuring apparatus according to item 3, wherein each of the first physical field phase calculation unit and the second physical field phase calculation unit fits a plurality of time-series data corresponding to the curvature of the AC signal. (Section 6) The phase difference measuring unit is A light irradiation unit that irradiates the quantum sensor element with light for reading the phase information of the electron spin state after interaction with the first physical field or the second physical field, A change detection unit for detecting changes occurring in the quantum sensor element due to the irradiation of the aforementioned light, A data processing unit reads the phase information of the electron spin state from the detected change, and measures the phase difference between the phase of the first physical field and the phase of the second physical field based on the read-out phase information of the electron spin state, A phase difference measuring apparatus according to any one of items 1 to 5, further comprising: (Section 7) The phase difference measuring apparatus according to item 6, further comprising a pulse pattern generator that uses the fluorescence intensity when the electron spin state is initialized as a trigger to output a pulse signal for operation timing to the electromagnetic wave irradiation unit and the light irradiation unit, and corrects the deviation of the measurement period. (Section 8) The phase difference measuring device according to item 7, wherein the pulse signal for operation timing is connected in series between a plurality of the phase difference measuring devices. (Section 9) The phase difference measuring device according to any one of items 1 to 8, wherein the AC signal is an AC signal transmitted through electrical equipment. (Section 10) The steps include repeatedly irradiating a quantum sensor element with electromagnetic waves to manipulate the electron spin state of the quantum sensor element, which changes due to interaction with a first or second physical field generated by an AC signal, A step of obtaining a plurality of electron spin states after interaction with the first physical field or the second physical field, and measuring the phase difference between the phase of the first physical field and the phase of the second physical field based on the obtained plurality of electron spin states, A phase difference measurement method, including the above. (Section 11) The step of measuring the phase difference is, A step of calculating the phase of the first physical field based on a plurality of electron spin states after interaction with the first physical field, A step of calculating the phase of the second physical field based on a plurality of electron spin states after interaction with the second physical field, Includes, The phase difference measurement method according to item 10, wherein the phase difference is measured based on the calculated phase of the first physical field and the phase of the second physical field. (Section 12) The step of calculating the phase of the first physical field involves fitting multiple time-series data corresponding to multiple electron spin states after interaction with the first physical field to calculate the phase of the first physical field, The phase difference measurement method according to item 11, wherein the step of calculating the phase of the second physical field is to calculate the phase of the second physical field by fitting a plurality of time series data corresponding to a plurality of electron spin states after interaction with the second physical field. (Section 13) An electrical installation equipped with a phase difference measuring device as described in any one of items 1 to 9. [Effects of the Invention]

[0017] According to the present invention, it is possible to measure with high sensitivity the phase difference between multiple physical fields, such as magnetic and electric fields, generated around electrical equipment through which alternating current flows. [Brief explanation of the drawing]

[0018] [Figure 1] This figure schematically shows the general configuration of a phase difference measuring device 10 according to one embodiment of the present invention. [Figure 2] Figure 1 is a schematic diagram illustrating a specific example of the configuration of the phase difference measuring device 10 shown in Figure 1. [Figure 3] This is a schematic diagram of an electrical installation 9 equipped with a phase difference measuring device 10 according to one embodiment of the present invention. [Figure 4] This is a schematic diagram of an electrical installation 9 equipped with a phase difference measuring device 10 according to one embodiment of the present invention. [Figure 5] This diagram schematically shows the energy levels of electrons at the NV-center of diamond. [Figure 6] This is an example pulse sequence used to sense a magnetic field using the optical detection magnetic resonance (ODMR) method, and it is a pulse sequence used to observe a free induction decay (FID) signal. [Figure 7] This figure illustrates one aspect of the phase difference measurement concept of the present invention. [Figure 8] This figure illustrates one aspect of the phase difference measurement concept of the present invention. [Figure 9] This flowchart shows the procedure for a phase difference measurement method according to one embodiment of the present invention. [Figure 10] This figure illustrates another aspect of the phase difference measurement concept of the present invention. [Figure 11] This figure illustrates another aspect of the phase difference measurement concept of the present invention. [Figure 12] This is another example of a pulse sequence used to sense a magnetic field using the optically detected magnetic resonance (ODMR) method, specifically a pulse sequence for observing spin echo signals. [Figure 13] This shows the results of a numerical simulation regarding the phase measurement of magnetic and electric fields in Example 1. [Figure 14] This is the result of a numerical simulation regarding the phase measurement of magnetic and electric fields in Example 2. [Figure 15] This is the result of a numerical simulation regarding the phase measurement of magnetic and electric fields according to Example 3. [Figure 16] This is a diagram illustrating the concept of the first improvement relating to Example 4. [Figure 17] This figure schematically shows the general configuration of the phase difference measuring device 10 with the first improvement according to Example 4. [Figure 18] These are the magnetic resonance signals before and after the first improvement according to Example 4. [Figure 19] This figure illustrates the concept of the second improvement according to Example 4, and shows a first connection configuration when applying a trigger signal to multiple phase difference measuring devices. [Figure 20] This figure illustrates the concept of the second improvement according to Example 4, and shows a second connection configuration when applying a trigger signal to multiple phase difference measuring devices. [Figure 21]This is the magnetic resonance signal obtained by the first connection configuration shown in Figure 19. [Figure 22] This is the magnetic resonance signal obtained by the second connection configuration shown in Figure 20. [Modes for carrying out the invention]

[0019] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the following description and drawings, the same reference numerals indicate the same or similar components, and therefore, redundant explanations of the same or similar components will be omitted.

[0020] In this specification, a physical quantity refers to a quantity whose dimensions are determined under a certain system in physics and which can be expressed as a multiple of a defined physical unit. Examples of physical quantities include magnetic fields, electric fields, temperature, and mechanical quantities (such as mechanical stress and pressure). Magnetic fields, electric fields, and mechanical quantities include physical quantities that do not change over time and physical quantities whose direction changes over time. That is, magnetic fields include static magnetic fields and alternating magnetic fields, electric fields include electrostatic fields and alternating electric fields, and mechanical quantities include static mechanical quantities and alternating mechanical quantities.

[0021] In the embodiment described below, the magnetic field and electric field are defined as the first physical field and the second physical field, respectively, and the phase difference between the voltage phase and the current phase of an alternating current flowing through an electrical installation is measured. For example, the frequency of the alternating current is approximately 50 Hz to 60 Hz.

[0022] <Relationship between the phases of magnetic and electric fields and the phases of voltage and current> This section explains the relationship between the phase of the magnetic field and electric field generated around the electrical equipment 9, and the phase of the voltage and current related to the alternating current flowing through the electrical equipment 9. Regarding the magnetic and electric fields generated around the electrical equipment 9 through which alternating current flows, the phase of the magnetic field correlates with the phase of the alternating current, and the phase of the electric field correlates with the phase of the alternating voltage.

[0023] The phase of the electric current is measured by measuring the phase of the magnetic field generated by the flow of the current. The phase of the magnetic field is calculated from the first term of the electron spin Hamiltonian, which is determined by the Zeeman effect and functions as a magnetic field sensor. The magnetic field strength is calculated from the first term, and the phase of the magnetic field is calculated from the temporal variation of the multiple calculated magnetic field strengths.

[0024] The voltage phase is measured by measuring the magnetic resonance signal at zero magnetic field splitting, where the magnetic field does not contribute to the signal strength but the electric field does. The electric field phase is calculated from the third term of the electron spin Hamiltonian, which functions as an electric field sensor, as described later. The electric field strength is calculated from the third term, and the electric field phase is calculated from the temporal variation of the multiple calculated electric field strengths. When measuring the voltage phase (electric field phase), zero-point adjustment of the phase should be performed in advance. For example, the rate of change of voltage over time is maximum at the zero-crossing point of the voltage strength, so this point is used as the zero-point reference.

[0025] As will be described later with reference to Figure 5, when a magnetic field is applied to the sensor element 1, the quantum state of the sensor element 1 is separated in proportion to the strength of the applied magnetic field due to the Zeeman effect. In contrast, when no magnetic field is applied to the sensor element 1, the first term due to the Zeeman effect of the electron spin Hamiltonian, which will be described later, does not contribute to the magnetic resonance signal. The magnetic resonance signal when the sensor element 1 is split at zero magnetic field is contributed by the third term (and the second term), which functions as an electric field sensor.

[0026] [Device configuration] Figure 1 is a schematic diagram showing the general configuration of a phase difference measuring device 10 according to one embodiment of the present invention. Figure 2 is a schematic diagram showing a specific example of the configuration of the phase difference measuring device 10 shown in Figure 1.

[0027] The phase difference measuring device 10 (hereinafter simply referred to as the measuring device 10) comprises a sensor element 1, an electromagnetic wave irradiation unit 2, and a phase difference measuring unit 3. In this embodiment, the sensor element 1 is attached to the tip of the probe 11 of the measuring device 10.

[0028] Sensor element 1 is a quantum sensor element. In this embodiment, sensor element 1 is a diamond crystal having color centers, and NV centers are used as color centers. An NV center is a composite (composite defect) of nitrogen (N) substituted for a carbon atom and a vacancy (V) adjacent to the nitrogen. In this embodiment, sensor element 1 is pre-generated in a predetermined region on the diamond crystal 12 by a known method. Exemplarily, the region contains approximately several thousand (concentration: ~1 × 10⁻¹⁶) 12 / cm -3 Multiple sensor elements 1 are generated. In this embodiment, sensor element 1 is an ensemble NV center.

[0029] The electron spin state of the sensor element 1 is changed by the interaction 8 with the object 9. In this embodiment, the object 9 is electrical equipment, and the interaction 8 is the interaction due to the magnetic field and electric field. Due to the interaction 8 with the object 9, the electron spin state of the color center of the sensor element 1 becomes a state corresponding to the strength of the magnetic field and electric field generated around the electrical equipment, which is the object 9.

[0030] The electromagnetic wave irradiation unit 2 irradiates the sensor element 1 with electromagnetic waves to manipulate the electron spin state of the sensor element 1 by magnetic resonance. As an example, in this embodiment, the electromagnetic wave irradiation unit 2 includes a known microwave (MW) oscillator 21, a switch 22 that irradiates the electromagnetic waves in a pulsed form, and an amplifier 23. The switch 22 and amplifier 23 can be configured in any way. In this embodiment, the electromagnetic wave irradiation unit 2 irradiates the sensor element 1 with electromagnetic waves in a pulsed form to manipulate the electron spin state of the sensor element 1.

[0031] Various pulse sequences can be used in the electromagnetic wave pulse sequence that the electromagnetic wave irradiation unit 2 irradiates onto the sensor element 1 to generate magnetic resonance.

[0032] Exemplary, in this embodiment, a pulse sequence is used to observe a free induction decay (FID) signal as the magnetic resonance signal. Such a pulse sequence observing a free induction decay (FID) signal is even simpler than the pulse sequences based on the Hahn echo method or the Ramsey method, which are exemplified as examples of pulse sequences used when detecting magnetic resonance signals. Exemplary, in other embodiments, a pulse sequence observing a spin echo signal can be used as the magnetic resonance signal.

[0033] The electromagnetic wave irradiation unit 2 irradiates the sensor element 1 with electromagnetic waves through an electromagnetic wave irradiation antenna 14 positioned near the sensor element 1. The antenna 14 is formed on a diamond crystal 12 using a conductive metal, for example, by lithography.

[0034] The phase difference measurement unit 3 calculates the phase of the magnetic field and the phase of the electric field individually based on the changes in the multiple electron spin states of the sensor element 1 after they have changed due to interaction 8 with the object 9, and measures the phase difference between the phase of the magnetic field and the phase of the electric field. Both the phase of the magnetic field and the phase of the electric field are calculated by fitting time-series data of the magnetic resonance signal. In this embodiment, the phase of the magnetic field and the phase of the electric field are calculated by fitting time-series data of multiple free induction decay (FID) signals. The phase difference measurement unit 3 comprises a light irradiation unit 31, a change detection unit 32, and a data processing unit 33.

[0035] The light irradiation unit 31 irradiates the sensor element 1 with light to read the phase information of the electron spin state of the sensor element 1 after it has interacted with the object 9. The light irradiation unit 31 also irradiates the sensor element 1 with light to initialize the electron spin state of the sensor element 1. As an example, in this embodiment, the light irradiation unit 31 comprises a light source 311, an acoustic optical modulator (AOM) 312, and an objective lens 313. The acoustic optical modulator 312 and the objective lens 313 can be configured in any configuration.

[0036] The light source 311 emits light to read the phase information of the electron spin state of the sensor element 1 after it has interacted with the object 9. The light source 311 also emits light to excite and initialize the electron spin state of the sensor element 1. The wavelength of the light emitted by the light source 311 is determined according to the type of sensor element 1. In this embodiment, the light source 311 emits laser light with a wavelength of 532 nm (green). Various known laser generators can be used as the light source 311. In this embodiment, the light source 311 is a semiconductor laser that emits green laser light.

[0037] The objective lens 313 focuses the light emitted from the light source 311 and irradiates the region on the diamond crystal 12 where the sensor element 1 is generated. For example, the spot size of the laser beam focused on the diamond crystal 12 is approximately 2 μm in diameter. As the spot size of the laser beam decreases, the intensity of the laser beam per unit area increases, and the efficiency of the photocurrent generated in the conductive band of the diamond also increases.

[0038] In the configuration illustrated in Figure 2, the laser beam spot is positioned to cover the region on the diamond crystal 12 where the sensor element 1 is generated. Preferably, the laser beam spot can be positioned at an offset location from approximately the center of the region where the sensor element 1 is generated.

[0039] The change detection unit 32 detects changes occurring in the sensor element 1. In this embodiment, the change detection unit 32 detects the light emitted from the sensor element 1 and detects the magnetic resonance signal as a change in emission intensity using a known photodetection magnetic resonance (ODMR) method. In this case, the change detection unit 32 can be, for example, a known photodiode. For example, an avalanche photodiode can be used as the photodiode.

[0040] In this embodiment, the electromagnetic wave irradiation unit 2 irradiates the operating electromagnetic waves in a pulsed form. Therefore, in this embodiment, detection is specifically performed using the Pulsed Optically Detected Magnetic Resonance (pODMR) method.

[0041] The data processing unit 33 is connected to the change detection unit 32 and reads the phase information of the electron spin state of the sensor element 1 after it has interacted with the object 9 from the change detected by the change detection unit 32. Based on the read phase information, it measures the phase difference between the phase of the magnetic field and the phase of the electric field. The data processing unit 33 includes a magnetic field phase calculation unit 331, an electric field phase calculation unit 332, and a phase difference signal output unit 333.

[0042] The data processing unit 33 can be, for example, a well-known general-purpose computer or various information terminal devices such as a smartphone. The data processing unit 33 may be integrated with the measuring device 10, or, as shown in the figure, it may be provided outside the measuring device 10 and connected to the measuring device 10 via a wired or wireless network 99.

[0043] The magnetic field phase calculation unit 331 calculates the phase of the magnetic field based on the multiple electron spin states after interaction with the magnetic field. The observed magnetic resonance signal reflects the electron spin state, and the phase of the magnetic field is calculated by fitting time-series data of the multiple magnetic resonance signals after interaction with the magnetic field.

[0044] The electric field phase calculation unit 332 calculates the phase of the electric field based on the multiple electron spin states after interaction with the electric field. The observed magnetic resonance signal reflects the electron spin state, and the phase of the electric field is calculated by fitting time-series data of the multiple magnetic resonance signals after interaction with the electric field.

[0045] In this embodiment, the magnetic field phase calculation unit 331 and the electric field phase calculation unit 332 calculate the magnetic field phase and the electric field phase, respectively, by fitting time-series data of multiple free induction decay (FID) signals.

[0046] The phase difference signal output unit 333 outputs a signal containing information about the phase difference between the phase of the magnetic field and the phase of the electric field. The phase difference signal is transmitted, for example, via a network 99 to a computer device (not shown) that centrally manages the operating status of other electrical equipment. Subsequently, the centralized management computer device determines whether power factor adjustment is necessary based on the received phase difference signal and transmits information about power factor adjustment along with the phase difference signal to a phase regulating device (not shown). The phase regulating device adjusts the power factor of the power system based on the received phase difference signal and the information about power factor adjustment. Alternatively, the phase difference signal is transmitted directly to a phase regulating device (not shown) via a network 99, for example, and the phase regulating device adjusts the power factor of the power system based on the received phase difference signal.

[0047] Figures 3 and 4 are schematic diagrams of electrical equipment 9 equipped with a phase difference measuring device 10 according to one embodiment of the present invention. As an example of electrical equipment 9, Figure 3 shows a current transformer 9a and Figure 4 shows a transformer 9b. The placement of the measuring device 10 shown in these figures is just one example.

[0048] The measuring device 10 is positioned to detect the magnetic and electric fields generated around the electrical equipment 9 (9a, 9b). Preferably, the measuring device 10 is positioned such that the direction of the axis in which the sensor element 1 detects the magnetic or electric field is aligned with the direction of the magnetic or electric field generated around the electrical equipment 9.

[0049] In other embodiments, multiple measuring devices 10,10 can be placed in a single electrical installation 9. For example, the first measuring device 10 for measuring the voltage phase can be placed at the location with the highest electric field strength in the current transformer 9a, and the second measuring device 10 for measuring the current phase can be placed at the location with the highest magnetic field strength in the current transformer 9a. The same applies when the electrical installation 9 is a transformer 9b.

[0050] [Measurement principle] In the present invention, the phase difference between the magnetic field and the electric field generated around the electrical equipment 9 is measured using the sensor element 1. The sensor element 1 is a quantum sensor element, whereby the phase difference between the voltage and current relating to the alternating current flowing through the electrical equipment 9 is measured with high sensitivity. The magnetic resonance signal used for calculating the phase of the magnetic field and the phase of the electric field is detected by the optically detected magnetic resonance (ODMR) method. This enables non-contact measurement of the phase difference between the voltage and current relating to the alternating current without directly electrically connecting to the electrical equipment 9.

[0051] Hereinafter, the principle and procedure for detecting a magnetic resonance signal by the optically detected magnetic resonance (ODMR) method will first be described. Next, a method for calculating the intensity of the magnetic field and the electric field from the detected magnetic resonance signal will be described. Finally, the phase difference measurement concept of the present invention for measuring the phase difference between the phase of the voltage and the phase of the current relating to alternating current will be described.

[0052] <Detection of Magnetic Resonance Signal by Optically Detected Magnetic Resonance (ODMR) Method> FIG. 5 shows NV of diamond - is a diagram schematically showing the energy levels of electrons at the center.

[0053] In the present embodiment, nitrogen-vacancy (NV) centers in diamond are used as the sensor element 1. The ground state of the NV center is a spin triplet state with magnetic quantum number m s = -1, 0, +1, and in the steady state at room temperature, all levels are equally distributed in the ground state.

[0054] Electrons with magnetic quantum number m s = 0 in the ground state transition to an excited state when irradiated with laser light having a wavelength of 532 nm (green), emit red fluorescence, and relax to the ground state with magnetic quantum number m s = 0.

[0055] On the other hand, when electrons with magnetic quantum number m s = 0 in the ground state are irradiated with microwaves having a resonance frequency of 2.87 GHz, electron spin resonance (ESR) occurs, resulting in magnetic quantum number m sIt transitions to a doubly degenerate ground state with a magnetic quantum number m = ±1. s Electrons with a magnetic quantum number of m = ±1 transition to an excited state when irradiated with laser light of wavelength 532 nm (green), and then, with a certain probability, s It returns to the ground state of =0. This series of processes is a non-radiative transition that does not emit fluorescence.

[0056] Thus, the process of emitting red fluorescence involves magnetic resonance, where electrons reach a magnetic quantum number m. s This becomes less likely when the ground state is ±1. Also, the magnetic quantum number m s The double degenerate ground state of =±1 is separated by Zeeman splitting in proportion to the strength of the external magnetic field, and therefore the fluorescence intensity also changes depending on the magnetic quantum number m of the electrons. s It changes depending on whether the state is ±1 or not. Therefore, when the microwave frequency is swept around 2.87 GHz, the magnetic resonance signal can be detected as the point where the red fluorescence intensity decreases.

[0057] Figure 6 shows an example pulse sequence for sensing a magnetic field using the photodetector magnetic resonance (ODMR) method. The pulse sequence of the electromagnetic wave used for operation shown in Figure 6 is a pulse sequence that observes the free induction decay (FID) signal using a pulse sequence containing two π / 2 pulses.

[0058] The states I to V of the pulse sequence shown in Figure 6 will be explained. State I represents the state in which electron spins have been initialized by irradiation with laser light. In the Bloch sphere, a notation that represents quantum states on a unit sphere, electron spins are aligned along the z-axis, which is the quantization axis.

[0059] Next, in state II, a π / 2 pulse is applied to tilt the electron spin along the quantization axis to a plane perpendicular to the quantization axis. The electron spin is then tilted to the xy-plane of the Bloch sphere. Subsequently, in state III, the electron spin, tilted to the xy-plane, undergoes phase relaxation while rotating in the xy-plane of the Bloch sphere due to interaction with the magnetic field over a predetermined time τ. The strength of the interaction corresponds to the strength of the magnetic field felt by the electron spin. In state III, the electron spin undergoes phase relaxation while rotating in the xy-plane of the Bloch sphere due to interaction with the magnetic field. This process is observed as a free induction decay (FID) signal in the subsequent state V.

[0060] After a predetermined time τ has elapsed while the electron spin is phase-relaxed in state III, the π / 2 pulse is irradiated in state IV to project the phase-relaxed electron spin onto the quantization axis. The electron spin, which was located in the xy-plane of the Bloch sphere, is projected onto the z-axis, which is the quantization axis, and aligned along the z-axis.

[0061] Subsequently, in state V, the sensor element is irradiated with laser light, and the phase information of the electron spin state after the interaction is read out by detecting the light emitted from the sensor element.

[0062] In the pulse sequence containing two π / 2 pulses illustrated in Figure 6, the electron spin undergoes phase relaxation while rotating in the xy-plane of the Bloch sphere in state III. Magnetic resonance (MRT) detects the signal generated during this phase relaxation of the electron spin as a magnetic resonance signal. The time τ between π / 2 pulses corresponds to the duration of state III in which the electron spin undergoes phase relaxation, and this time τ determines the sensitivity of the measurement. This is because the degree to which the electron spin undergoes phase relaxation due to interaction with the magnetic field corresponds to the strength of the magnetic field felt by the electron spin.

[0063] Similar to magnetic fields, electric fields can also be sensed using the pulse sequence exemplified in Figure 6.

[0064] <Method for calculating magnetic field and electric field strength based on magnetic resonance signals> In optically detected magnetic resonance (ODMR) spectroscopy, the phase information (magnetic resonance signal) of the electron spin state of the sensor element 1 after interaction with the object 9 is detected as a change in emission intensity. The detected phase information corresponds to the physical quantity of the object. Therefore, by appropriately processing the detected phase information of the electron spin state after interaction, the physical quantity of the object can be calculated. The physical quantity of the object can be calculated based on the Hamiltonian of the electron spin.

[0065] Hamiltonian H of electron spin gs It can be expressed by the following formula.

number

[0066] First item

number

[0067] The second and third terms are terms resulting from dipole interactions (i.e., spin-to-spin interactions). Second term

number

number

[0068] Therefore, the magnetic field strength can be calculated based on the first term. The temperatures and mechanical quantities can be calculated based on the second term. The electric field strength can be calculated based on the third term.

[0069] In this invention, although the absolute values ​​of the magnetic and electric field strengths are not required, the magnitude of the magnetic resonance signal after interaction with the magnetic field is the Hamiltonian H of the electron spin. gs The first term of the equation can be used to calculate the magnitude of the magnetic resonance signal after interaction with the electric field, and the third term can be used to calculate the magnitude of the magnetic resonance signal after interaction with the electric field. This allows the magnetic resonance signal after interaction with the magnetic and electric fields to be separated into a component due to interaction with the magnetic field and a component due to interaction with the electric field.

[0070] <Concept of Phase Difference Measurement> Figures 7 and 8 are diagrams illustrating the concept of phase difference measurement according to the present invention.

[0071] In Figure 7, the upper panel shows the temporal fluctuation of the alternating current flowing through the electrical equipment, which is the object 9, and the lower panel shows an example pulse sequence when sensing the magnetic and electric fields using the optically detected magnetic resonance (ODMR) method. Specifically, the frequency of the alternating current is approximately 50 Hz to 60 Hz. Figure 8 is a magnified view of the area enclosed by the dashed line in the pulse sequence shown in the lower panel of Figure 7. The symbols I to V in Figure 8 correspond to states I to V in the pulse sequence shown in Figure 6.

[0072] As mentioned above, regarding the magnetic and electric fields generated around the electrical equipment 9 through which alternating current flows, the phase of the magnetic field correlates with the phase of the alternating current, and the phase of the electric field correlates with the phase of the alternating voltage. In this invention, the phase difference between the magnetic and electric fields generated around the electrical equipment 9 through which alternating current flows is measured using a sensor element 1. This allows for highly sensitive measurement of the phase difference between the voltage and current related to the alternating current flowing through the electrical equipment 9.

[0073] The phase difference between the magnetic field phase and the electric field phase is calculated based on multiple electron spin states after interaction with the magnetic and electric fields. The electron spin states are acquired by measuring the magnetic resonance signal using a pulse sequence exemplified in Figures 7 and 8 (more specifically, Figure 6). As illustrated in Figures 7 and 8, the pulse sequence shown in Figure 6 is repeated multiple times during one cycle of the AC current, thereby acquiring multiple data points of the magnetic resonance signal.

[0074] If the frequency of the alternating current flowing through the electrical equipment 9 is, for example, approximately 60 Hz, the measurement using the pulse sequence exemplified in Figure 8 is repeated approximately 512 times during one cycle of the alternating current, and approximately 512 magnetic resonance signals can be obtained as multiple electron spin states after interaction with the magnetic and electric fields. These approximately 512 magnetic resonance signal data are time-series data corresponding to multiple electron spin states after interaction with the magnetic field. The phase of the magnetic field is calculated by curve fitting these approximately 512 magnetic resonance signal data. When fitting the data, trigonometric functions such as the sine function and cosine function are used as functions, and four parameters such as signal offset, amplitude, frequency, and phase are used as parameters. Similarly to the magnetic field, the phase of the electric field is calculated by curve fitting the data of multiple magnetic resonance signals after interaction with the electric field.

[0075] Furthermore, if the frequency of the alternating current flowing through the electrical equipment 9 is, for example, approximately 50 Hz, the measurement using the pulse sequence exemplified in Figure 8 will be repeated approximately 614 times during one cycle of the alternating current, and approximately 614 magnetic resonance signals can be obtained as multiple electron spin states after interaction with the magnetic and electric fields.

[0076] [Measurement Procedure] Figure 9 is a flowchart showing the procedure for a phase difference measurement method according to one embodiment of the present invention. Steps S1 to S5 are procedures for calculating the phase of the magnetic field, and steps S6 to S10 are procedures for calculating the phase of the electric field. In step S11, the phase difference between the magnetic field and the electric field is calculated, and information regarding the calculated phase difference is output in step S12.

[0077] In step S1, the electron spin of the color center (NV center) of the sensor element 1 is initialized by irradiating the sensor element 1 with laser light. Then, the initialized electron spin of the NV center is made to interact with the magnetic and electric fields generated around the object 9. After sufficient time has passed for the interaction to occur, the electron spin state of the NV center will be in a state corresponding to the strength of the magnetic field. The state in step S1 corresponds to state I of the pulse sequence shown in Figure 6.

[0078] In step S2, magnetic field sensing is performed by irradiating the sensor element 1 with electromagnetic waves for spin manipulation. In this embodiment, magnetic field sensing is performed by irradiating with two π / 2 pulses according to the pulse sequence shown in Figure 6. That is, in this embodiment, the electron spin state of the NV center is manipulated to correspond to states II to IV of the pulse sequence shown in Figure 6.

[0079] In step S3, laser light is irradiated onto the sensor element 1, and the phase information of the electron spin state after interaction is read out by detecting the change occurring in the sensor element 1. In this embodiment, the phase information of the electron spin state after interaction is read out by detecting the light emitted from the sensor element 1. The phase information of the electron spin state after interaction is detected as a change in emission intensity using the change detection unit 32 by the photodetector magnetic resonance (ODMR) method. The magnetic resonance signal detected as a change in emission intensity represents the phase information of the electron spin state after interaction. The state in step S3 corresponds to state V of the pulse sequence shown in Figure 6.

[0080] In step S4, it is determined whether the series of measurement processes in steps S1 to S3 have been repeated a predetermined number of times. If the series of measurement processes have been repeated a predetermined number of times (Yes in step S4), the process in step S5 is performed. If the process has not been repeated a predetermined number of times (No in step S4), the process starts again from step S1.

[0081] As mentioned above, if the frequency of the alternating current flowing through the electrical equipment 9 is, for example, approximately 50 Hz to approximately 60 Hz, it is possible to perform the pulse sequence measurement exemplified in Figure 8 approximately 512 times during one cycle of the alternating current. For example, the series of measurement processes from steps S1 to S3 can be repeated approximately 512 times.

[0082] In step S5, the phase of the magnetic field is calculated based on a predetermined number of electron spin states after interaction with the magnetic and electric fields, which are obtained through a series of measurement processes in steps S1 to S4.

[0083] The magnetic field strength is calculated from the phase information of the electron spin state after interaction, which is read out in step S3. The phase information of the electron spin state after interaction detected by the change detection unit 32 is in a state corresponding to the magnetic and electric fields of the object 9. Therefore, the magnetic field strength can be calculated by appropriately processing the magnetic resonance signal representing the detected phase information of the electron spin state after interaction. For example, the magnetic field strength is calculated from the measurement results of the electron spin state in the ground state after interaction, using the Hamiltonian H of the electron spin mentioned above. gs It can be calculated based on the first term due to the Zeeman effect.

[0084] By calculating the magnetic field strength for each of the multiple electron spin state phase information obtained through the series of measurement processes in steps S1 to S4, data on the temporal variation of the magnetic field strength can be obtained. The phase of the magnetic field is calculated by curve fitting this obtained data on the temporal variation of the magnetic field strength.

[0085] Steps S6 to S9 perform the same processing as in steps S1 to S4. In step S6, the electron spin of the color center (NV center) of the sensor element 1 is initialized by irradiating the sensor element 1 with laser light. Then, the initialized electron spin of the NV center is made to interact with the magnetic and electric fields generated around the object 9. In step S7, electric field sensing is performed by irradiating the sensor element 1 with electromagnetic waves for spin manipulation. In step S8, the phase information of the electron spin state after interaction is read out by irradiating the sensor element 1 with laser light and detecting the change occurring in the sensor element 1. In step S9, it is determined whether the series of measurement processes in steps S6 to S8 have been repeated a predetermined number of times. If the series of measurement processes have been repeated a predetermined number of times (Yes in step S9), the process in step S10 is performed; if it has not been repeated a predetermined number of times (No in step S9), the process starts again from step S6.

[0086] In step S10, the phase of the electric field is calculated based on a predetermined number of electron spin states after interaction with the magnetic and electric fields, which are obtained through a series of measurement processes in steps S6 to S9.

[0087] The electric field strength is calculated from the phase information of the electron spin state after interaction, which is read out in step S8. The phase information of the electron spin state after interaction detected by the change detection unit 32 is in a state corresponding to the magnetic field and electric field of the object 9. Therefore, the electric field strength can be calculated by appropriately processing the magnetic resonance signal representing the detected phase information of the electron spin state after interaction. For example, the electric field strength is calculated from the measurement results of the electron spin state in the ground state after interaction, using the Hamiltonian H of the electron spin mentioned above. gs It can be calculated based on the third term, which functions as an electric field sensor.

[0088] By calculating the electric field intensity for each of the multiple electron spin state phase information obtained through the series of measurement processes in steps S6 to S9, data on the temporal variation of the electric field intensity can be obtained. The phase of the electric field is calculated by curve fitting this obtained data on the temporal variation of the electric field intensity.

[0089] In step S11, the phase difference between the phase of the magnetic field and the phase of the electric field is calculated from the difference between the phase of the magnetic field calculated in step S5 and the phase of the electric field calculated in step S10.

[0090] In step S12, a signal containing information about the phase difference between the phase of the magnetic field and the phase of the electric field, calculated in step S11, is output. The signal containing information about the phase difference is transmitted, for example, via network 99 and used for power factor adjustment by phase regulating equipment.

[0091] [effect] As described above, according to the present invention, the phase difference between the magnetic and electric fields generated around electrical equipment through which alternating current flows can be measured with high sensitivity. This makes it possible to measure the phase difference between voltage and current related to alternating current even in electrical equipment through which large currents and high voltages flow, without requiring protective circuits to protect the circuit from large currents and high voltages. Since protective circuits are not required, the scale of the electrical equipment can be made smaller and less expensive.

[0092] In this invention, the phase difference between the magnetic and electric fields generated around an electrical facility carrying alternating current is measured using a quantum sensor element. This makes it possible to measure the phase difference between the voltage and current related to the alternating current flowing through the electrical facility with high sensitivity. The magnetic resonance signal used to calculate the phase of the magnetic field and the phase of the electric field is detected by the photodetector magnetic resonance (ODMR) method. This makes it possible to measure the phase difference between the voltage and current related to the alternating current flowing through the electrical facility non-contactually, without directly connecting to the electrical facility.

[0093] [Other forms] Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to the embodiments described above.

[0094] In the embodiment described above, the pulse sequence of electromagnetic waves irradiated by the electromagnetic wave irradiation unit 2 onto the sensor element 1 is a pulse sequence used to observe the free induction decay (FID) signal, as illustrated in Figure 6. However, the pulse sequence used to detect the magnetic resonance signal is not limited to this. As will be explained with reference to Figures 10 to 12, instead of observing the free induction decay (FID) signal, a pulse sequence based on the Hahn echo method may be used to observe the spin echo signal as the magnetic resonance signal.

[0095] <Pulse sequence for measuring the curvature of AC signals> Figures 10 and 11 illustrate another aspect of the phase difference measurement concept of the present invention.

[0096] In Figure 10, the upper panel shows the temporal fluctuation of the alternating current flowing through the electrical equipment, which is object 9, and the lower panel shows another exemplary pulse sequence when sensing the magnetic and electric fields using the optically detected magnetic resonance (ODMR) method. Exemplarily, the frequency of the alternating current is approximately 50 Hz to 60 Hz. Figure 11 is a magnified view of the area enclosed by the dashed line in the pulse sequence shown in the lower panel of Figure 10. The symbols I to VII in Figure 11 correspond to states I to VII in the pulse sequence shown in Figure 12.

[0097] In another aspect of the phase difference measurement concept of the present invention, the electron spin state is acquired by measuring the magnetic resonance signal in a pulse sequence illustrated, for example, in Figures 10 and 11 (more specifically, in Figure 12). Similar to the phase difference measurement concept of the present invention described with reference to Figures 6 to 8, the pulse sequence shown in Figure 12 is repeated multiple times during one cycle of AC, as illustrated in Figures 10 and 11, thereby acquiring multiple data points of the magnetic resonance signal.

[0098] Figure 12 shows another exemplary pulse sequence for sensing a magnetic field using the photodetector magnetic resonance (ODMR) method. The pulse sequence of the operating electromagnetic wave shown in Figure 12 is a pulse sequence based on the spin echo method (Hahn echo method), which observes the spin echo signal with a pulse sequence containing two π / 2 pulses and a π pulse in between.

[0099] The pulse sequence shown in Figure 12, from state I to state VII, will be explained. State I represents the state in which electron spins are initialized by laser irradiation. In the Bloch sphere, a notation that represents quantum states on a unit sphere, electron spins are aligned along the z-axis, which is the quantization axis.

[0100] Next, in state II, the electron spin along the quantization axis is tilted to a plane perpendicular to the quantization axis by irradiating it with a π / 2 pulse. The electron spin is then tilted to the xy plane. Subsequently, in state III, the electron spin tilted to the xy plane undergoes phase relaxation during a predetermined time τ0 due to interaction with the alternating magnetic field and the static magnetic field. The strength of the interaction corresponds to the strength of the magnetic field felt by the electron spin and corresponds to region B shown in Figure 11.

[0101] After a predetermined time τ0 has elapsed in state III, a π pulse is irradiated in state IV to reverse the electron spin, which has been phase-relaxed by interaction with the object being measured, in the plane. From state III to state IV, the electron spin rotates in the xy plane. In this process, in the reversed state V, the static magnetic field component is canceled out as the electron spin re-converges, but the AC magnetic field component is not canceled out because its intensity is reversed compared to state III.

[0102] Subsequently, during a predetermined time τ0 in state V, the electron spin undergoes phase relaxation through interaction with the alternating and static magnetic fields, similar to state III. The strength of the interaction corresponds to the strength of the magnetic field felt by the electron spin and corresponds to region A shown in Figure 11.

[0103] After a predetermined time τ0 has elapsed in state V, a π / 2 pulse is irradiated in state VI to project the phase-relaxed electron spin onto the quantization axis. The electron spin, which was located in the xy plane, is projected onto the z axis, which is the quantization axis, and aligned along the z axis.

[0104] Subsequently, in state VII, the sensor element is irradiated with laser light, and the phase information of the electron spin state after the interaction is read out by detecting the light emitted from the sensor element.

[0105] Similar to magnetic fields, electric fields can also be sensed using the pulse sequence exemplified in Figure 12.

[0106] As explained with reference to Figure 12, the pulse sequence based on the spin echo method includes a π pulse between two π / 2 pulses. As shown in state IV, the irradiation of the π pulse inverts the electron spin along the z axis in the Bloch sphere. As a result, the observed spin echo signal reflects the curvature of the magnetic and electric fields being sensed, as shown in Figure 11. As shown in Figure 11, the inversion of the electron spin in state IV means that the phase information (magnetic resonance signal) of the interacted electron spin state read out in state VII reflects the difference (AB) between region A shown in Figure 11 and region B shown in Figure 12.

[0107] As shown in Figure 11, the alternating current (AC) periodically increases and decreases. This periodic fluctuation of the AC causes the periods of the magnetic and electric fields being sensed to also fluctuate. In a periodically fluctuating AC, when the AC signal increases, the difference (AB) represented by the magnetic resonance signal read out in state VII is a positive value. At the peak of the signal where the AC signal takes its extremum, the difference (AB) becomes 0 (zero), and when the AC signal decreases, the difference (AB) becomes a negative value.

[0108] In the embodiments described above, the magnetic resonance signals used to calculate the strength of the magnetic and electric fields are detected by the optically detected magnetic resonance (ODMR) method. However, the method used to detect the magnetic resonance signals is not limited to the optically detected magnetic resonance (ODMR) method. Instead of the optically detected magnetic resonance (ODMR) method, the magnetic resonance signals can also be detected by, for example, the electrodetected magnetic resonance (EDMR) method. In this case, a pair of measuring electrodes for detecting the magnetic resonance signals are electrically connected to the sensor element 1. A bias voltage is applied between the pair of measuring electrodes to apply an electric field to the sensor element 1 through the measuring electrodes.

[0109] In the embodiment described above, the phase difference measuring device 10 measures the phase difference between the magnetic field and electric field generated around the electrical equipment 9. Examples of electrical equipment 9 include transformers such as current transformers 9a and voltage transformers 9b, but the electrical equipment 9 is not limited to these. The electrical equipment 9 can be, for example, power transmission and distribution equipment such as transformers and switches, or power lines such as transmission lines and distribution lines. The phase difference measuring device 10 can be attached to such electrical equipment 9 to measure the phase difference between the magnetic field and electric field generated around the electrical equipment 9.

[0110] In the embodiment described above, one measuring device 10 is placed in one electrical installation 9, and one measuring device measures the phase of the magnetic field and the phase of the electric field. However, multiple measuring devices 10,10 may be placed in one electrical installation 9, and each measuring device 10 may measure the phase of the magnetic field and the phase of the electric field, respectively. In this case, the multiple measuring devices 10,10 can coordinate their operations and data and share the processing of steps S1 to S12.

[0111] For example, the first measuring device 10 can perform steps S1 to S5 to calculate the phase of the magnetic field, the second measuring device 10 can perform steps S6 to S10 to calculate the phase of the electric field, and either the first or second measuring device 10 can perform steps S11 to S12 to calculate the phase difference between the magnetic field and the electric field. By coordinating the operation and data of multiple measuring devices 10, the processes of steps S1 to S5 for calculating the phase of the magnetic field and steps S6 to S10 for calculating the phase of the electric field can be processed in parallel.

[0112] In the embodiment described above, the phase difference between the phase of the magnetic field and the phase of the electric field is measured for the magnetic and electric fields generated around the electrical equipment 9. However, the type of physical quantity to be measured is not limited to magnetic and electric fields. The type of physical quantity to be measured by the phase difference measuring device 10 is the spin Hamiltonian H of the electron spin mentioned above. gsThe physical fields described therein can be magnetic fields, electric fields, temperature, and mechanical quantities, and the phase difference measuring device 10 can measure the phase difference between these multiple physical fields, that is, it can measure the phase difference between two physical fields selected from multiple types of physical fields (magnetic fields, electric fields, temperature, and mechanical quantities).

[0113] The combination of two physical fields may be of different types, such as a magnetic field and an electric field, or it may be of the same type, such as two different magnetic fields. In the former case, for example, as illustrated in the embodiment described above, the phase difference measuring device 10 can measure the phase difference between the phase of the magnetic field and the phase of the electric field generated around a certain electrical installation 9. In the latter case, for example, the phase difference measuring device 10 can measure the phase difference between the phase of the magnetic field generated around one electrical installation 9 and the phase of the magnetic field generated around the other electrical installation 9.

[0114] The phase difference measuring device 10 is not limited to measuring the physical field generated around the electrical equipment 9; it can measure the phase difference between multiple physical fields generated around various devices through which alternating current flows.

[0115] [Examples] The following examples illustrate the features of the present invention. [Examples]

[0116] In Example 1, numerical simulations were performed using a free induction attenuation (FID) signal.

[0117] <Conditions for numerical simulation> The pulse sequence was a simple FID sequence. Since each measurement relies on a single sequence, magnetic resonance signal accumulation was not performed. The AC frequency was set to 60 Hz, and the pulse sequence was assumed to repeat approximately 512 times.

[0118] The assumed conditions (a) to (f) for the sensor element sampling and pulse sequence are as follows:

[0119] (a) Coherence time T2 * This is 1 μs. T2 * If the value is 1 μS, the total concentration of NV centers is approximately 10 ppm. (b) The diameter of the laser spot is 10 μm, and the NV central density "NV" is 0.5 ppm (= 8.8 × 3 × 10 16 cm -3 Therefore, the number of NV centers in the spherical volume is approximately 4.6 × 10⁻⁶. 7 . (c) 1% contrast. Note that this can increase to approximately 10% between spin states. (d) 0.1 photons on average per readout for each NV center. (e) The pulse sequence used to measure the FID signal is a pulse sequence that includes two π / 2 pulses as illustrated in Figure 6. (f) The laser pulse length is 30 μs, the waiting time between the laser pulse and the first π / 2 pulse is 1 μs, the π / 2 pulse length is 40 ns, and the delay between these pulses is 0.5 μs.

[0120] In Example 1, the magnetic field strength was assumed to have an amplitude of 40 μT, and the electric field strength was assumed to have an amplitude of 20 kV / cm.

[0121] <Results of numerical simulation> Figure 13 shows the results of numerical simulations related to the phase measurement of magnetic and electric fields according to Example 1. (A) is the result of the simulation related to the phase measurement of the magnetic field, and (B) is the result of the simulation related to the phase measurement of the electric field.

[0122] The amplitude of the magnetic field strength depends on the distance r from the current line (wire). When the distance r is 0.1m, the amplitude of the magnetic field strength is approximately 2mT and attenuates by 1 / r. The assumed magnetic field strength amplitude of 40μT in the numerical simulation of Example 1 corresponds to a distance of approximately 5m from the current line. For simple reference, the effect of the magnetic field on the spin Hamiltonian is approximately 28GHz·T. -1 It is known that this is the case. The results are shown in Figure 13(A).

[0123] In Figure 13(A), the points plotted with the cross symbol "×" represent the simulated signal strengths of the free induction decay (FID) signal, corresponding to the magnetic field strength. By curve fitting these points plotted with the cross symbol "×", the phase φ of the magnetic field is obtained. B = 101.3 ± 5.6 mrad was obtained.

[0124] The amplitude of the electric field strength depends on the distance d between the current wire and the ground plane on which the diamond NV center sample is located. When the distance d is 1m, the amplitude of the electric field strength is approximately 0.2kV / cm and attenuates by 1 / d. The assumed electric field strength amplitude of 20kV / cm in the numerical simulation of Example 1 corresponds to a distance of approximately 1cm from the current wire. For simple reference, the effect of the perpendicular electric field on the spin Hamiltonian is approximately 17HzcmV. -1 It is known that the direction of the electric field does not have an effect, and in the simulation, this effect was modeled in the same way as the magnetic field. The results are shown in Figure 13(B).

[0125] In Figure 13(B), the multiple points plotted with the cross symbol "×" represent the simulated signal strengths of the freely induced decay (FID) signal, corresponding to the electric field strength. By curve fitting these multiple points plotted with the cross symbol "×", the phase φ of the electric field is obtained. E = 86.2 mrad, with an error of +16.4 mrad to -15.74 mrad. [Examples]

[0126] In Example 2, numerical simulations were performed by changing the distance from the current line (wire) compared to Example 1. Unless otherwise specified, the conditions for the numerical simulations in Example 2 were the same as those in Example 1.

[0127] In Example 2, the magnetic field strength was assumed to have an amplitude of 200 μT, and the electric field strength was assumed to have an amplitude of 200 kV / cm.

[0128] <Results of numerical simulation> Figure 14 shows the results of numerical simulations related to the phase measurement of magnetic and electric fields according to Example 2. (A) is the result of the simulation related to the phase measurement of the magnetic field, and (B) is the result of the simulation related to the phase measurement of the electric field.

[0129] The assumed magnetic field strength amplitude of 200 μT in the numerical simulation of Example 2 corresponds to a distance of approximately 1 m from the current line. The results are shown in Figure 14(A). By curve fitting these multiple points plotted with the cross symbol "×" in Figure 14(A), the phase φ of the magnetic field is obtained. B = 100.2 ± 1.1 mrad was obtained.

[0130] The assumed electric field intensity amplitude of 200 kV / cm in the numerical simulation of Example 2 corresponds to a distance of approximately 1 mm from the current line. The results are shown in Figure 14(B). By curve fitting these multiple points plotted with the cross symbol "×" in Figure 14(B), the phase φ of the electric field is obtained. E =100.2±1.9 mrad was obtained.

[0131] <Consideration> Assuming the magnitudes of the large currents and high voltages actually flowing through power grid lines, and assuming the following numerical values ​​for measurement conditions, the measurement accuracy required to measure the phase difference between the magnetic and electric fields during one cycle of AC supplied via current lines (wires) is approximately 5.82 mrad.

[0132] [Measurement conditions] ·Frequency f: 50 / 60Hz Voltage V amplitude : Approximately 2×10 4 V ·Current I amplitude : about 10 3 A In Example 1, at the assumed distance from the current line, i.e., the distance between the current line and the diamond NV center sample, the phase φ of the magnetic field obtained by numerical simulation B The error is ±5.6 mrad, and the phase of the electric field is φ E The error was +16.4 mrad or -15.74 mrad. These φ B and φ E Of the errors, the phase φ of the electric field is particularly important. E This value significantly exceeds the required measurement accuracy of approximately 5.82 mrad mentioned above, and it was considered that achieving this would be difficult at the distance from the current line assumed in Example 1.

[0133] In contrast, in Example 2, where the distance from the current line was assumed to be shorter than in Example 1, the phase φ of the magnetic field obtained by numerical simulation was B The error is ±1.1 mrad, and the phase of the electric field is φ E The error was ±1.9 mrad.

[0134] Therefore, numerical simulations have shown that by placing the diamond NV center sample at a distance of approximately 1 m for magnetic field measurement and approximately 1 mm for electric field measurement, which are the distances assumed in Example 2 from the current line, it is possible to actually measure the phase difference of voltage and current for large currents and high voltage ACs that actually flow through power lines in a power system with sufficient measurement accuracy. [Examples]

[0135] In Example 3, numerical simulations were performed using spin echo signals.

[0136] <Conditions for numerical simulation> The pulse sequence was based on the spin echo method (Hahn echo method). Since each measurement relies on a single sequence, magnetic resonance signal accumulation was not performed. The AC frequency was set to 60 Hz, and the pulse sequence was assumed to repeat approximately 204 times.

[0137] The assumed conditions (a) to (f) for the sensor element sampling and pulse sequence are as follows:

[0138] (a) The coherence time T2 is 100 μs. (b) Sensor volume is 8.5 × 10 -4 mm 3 The number of NV centers is 10 11 . (c) 0.5% contrast. Note that the contrast may be 7.5% if the NV centers are not aligned between spin states, and 30% if they are aligned. (d) 0.1 photons on average per readout for each NV center. (e) The pulse sequence for measuring the spin echo signal is a pulse sequence that includes a π pulse between two π / 2 pulses, as illustrated in Figure 12. (f) The laser pulse length is 30 μs, the waiting time between the laser pulse and the first π / 2 pulse is 1 μs, the π / 2 pulse length is 40 ns, and the delay between π / 2 pulses is 50 μs.

[0139] In Example 3, it was assumed that the diamond NV center sample was placed at the same distance as in Example 1. That is, as in Example 1, the magnetic field strength was assumed to have an amplitude of 40 μT, and the electric field strength was assumed to have an amplitude of 20 kV / cm.

[0140] <Results of numerical simulation> Figure 15 shows the results of numerical simulations related to the phase measurement of magnetic and electric fields according to Example 3. (A) is the result of the simulation related to the phase measurement of the magnetic field, and (B) is the result of the simulation related to the phase measurement of the electric field.

[0141] In the pulse sequence based on the spin echo method, the electron spin is inverted along the z-axis in the Bloch sphere by irradiation with a π pulse. As a result, the observed spin echo signal contains information corresponding to the curvature of the AC current. Since the curvature is measured using the derivative, the curve shown in Figure 15 appears to be a cosine wave rather than a sinusoidal wave.

[0142] In Figure 15(A), the multiple points plotted with the cross symbol "×" represent the simulated signal intensity of the spin echo signal corresponding to the magnetic field strength. By curve fitting these multiple points plotted with the cross symbol "×", the phase φ of the magnetic field is obtained. B = 100.3 mrad, with an error of +0.8 mrad to -0.9 mrad was obtained.

[0143] In Figure 15(B), the multiple points plotted with the cross symbol "×" represent the simulated signal strengths of the spin echo signal corresponding to the electric field strength. By curve fitting these multiple points plotted with the cross symbol "×", the phase φ of the electric field is obtained. E = 101.5 ± 2.2 mrad was obtained.

[0144] The results from Example 3 show that the phase φ of the magnetic field B Error and phase φ of the electric field E Both errors were found to be significantly below the required measurement accuracy of approximately 5.82 mrad mentioned above.

[0145] <Consideration> The measurement accuracy of the phase obtained by numerical simulation was compared between Example 1 and Example 3. The phase φ of the magnetic field. B Error and phase φ of the electric field EBoth errors were better in the numerical simulation results of Example 3 than in the numerical simulation results of Example 1. The assumed distance from the current line, i.e., the distance between the current line and the diamond NV center sample, was the same in Example 1 and Example 3. For the detection of the magnetic resonance signal, the simulation was performed assuming a pulse sequence that observes the free induction decay (FID) signal in Example 1, and a pulse sequence based on the spin echo method that observes the spin echo signal in Example 3.

[0146] Therefore, numerical simulations have shown that when diamond NV-centered samples are placed at the same distance from the current lines, it is preferable to observe the magnetic resonance signal using a pulse sequence based on the spin echo method, which observes the spin echo signal, rather than a pulse sequence that observes the free induction decay (FID) signal. [Examples]

[0147] In Example 4, improvements were made to the phase difference measuring device, and the presence or absence of performance improvement due to the improvements was verified. Two improvements were made in Example 4. The first improvement involved correcting the pulse period deviation in the phase difference measuring device. The second improvement involved correcting the phase deviation in multiple phase difference measuring devices.

[0148] Figure 16 is a diagram illustrating the concept of the first improvement according to Embodiment 4. The pulse sequence shown in Figure 16 corresponds to the pulse sequence shown in Figure 6, or the portion enclosed by the dashed line in the pulse sequence shown in Figure 8. The symbols I to IV in the figure correspond to states I to IV shown in Figure 6 or Figure 8, etc. Figure 16 illustrates the relationship between the pulse sequence and the timing of data (phase information of electron spin states) read out by laser light irradiation. In the figure, the symbol Rd indicates the range of data read out by laser light.

[0149] The ideal pulse sequence and data readout timing to be set in the device is shown in (A). In contrast, the pulse sequence and data readout timing during actual measurement were as shown in (B). As shown in (B), in actual measurement, the pulse period may be shifted due to the limit of the clock frequency generated by the pulse pattern generator. As a result, the range Rd of the laser light readout data may also be shifted by the time indicated by the symbol Td from the laser light irradiation timing (fluorescence emission timing) corresponding to state V. A pulse pattern generator refers to a waveform signal generator such as a pattern generator, function generator, or pulse streamer.

[0150] In the first improvement, as shown in (C), a predetermined fluorescence intensity was set as the trigger Trg and applied to the timing adjustment to correct the deviation in the pulse period. In this embodiment, the magnitude of the fluorescence intensity set as the trigger (trigger level of the pulse pattern generator) was set to approximately 5% to approximately 90% of the rising portion fluorescence intensity emitted from the sensor element when electron spin initialization is performed by irradiation with laser light as shown in state I. If the trigger level is set higher than 90%, the trigger will not be read when a large magnetic resonance of about 10% occurs. Also, if it is set lower than 5%, there is a risk of misinterpreting shot noise as the trigger. The set trigger was applied to adjust the data readout timing by irradiation with laser light as shown in state V. Timing correction by applying the trigger was performed for each pulse. The setting of the fluorescence intensity to be used as the trigger was performed by the data processing unit 33 (PC). The lower limit of the trigger level can be set based on quantum noise or shot noise, the upper limit can be set based on the maximum value of the spin contrast ratio, and the range of the trigger level can be set within those ranges.

[0151] Figure 17 is a schematic diagram showing the general configuration of the phase difference measuring device 10 with the first improvement. As shown in Figure 17, the phase difference measuring device 10 with the first improvement further includes a pulse pattern generator 4 with a trigger set to correct the deviation of the pulse period. The pulse pattern generator 4 uses the fluorescence intensity when the electron spin state is initialized as a trigger to output a pulse signal for operation timing to the electromagnetic wave irradiation unit 2 and the light irradiation unit 31, thereby correcting the deviation of the measurement period.

[0152] The performance improvement was verified before and after the first improvement was implemented. Figure 18 shows the magnetic resonance signals before and after the first improvement. (A) is the magnetic resonance signal before the first improvement, and (B) is the magnetic resonance signal after the first improvement. From the comparison of the magnetic resonance signals shown in Figure 18, it was confirmed that the physical field signal was accurately read without any shift in the pulse sequence period.

[0153] Figures 19 and 20 are diagrams illustrating the concept of the second improvement according to Embodiment 4, and show the connection configuration when applying a trigger signal to multiple phase difference measuring devices. Figure 19 shows the first connection configuration, and Figure 20 shows the second connection configuration.

[0154] As shown in Figures 19 and 20, a pulse pattern generator 4 was connected to realize the pulse sequence exemplified in Figures 6 and 8, etc., across multiple phase difference measuring devices 10a and 10b. The pulse pattern generator 4 outputs pulse signals for operation timing to each part of the multiple phase difference measuring devices (switch 22, acousto-optic modulation element 312), causing the multiple phase difference measuring devices 10a and 10b to operate synchronously. The pulse pattern generator 4 receives a trigger signal set in the data processing unit 33 (PC), and time information is fed back from the data processing unit 33 to the pulse pattern generator 4. In this embodiment, the magnetic field (first physical field) was measured using the phase difference measuring device 10a shown on the left side of the figure, and the electric field (second physical field) was measured using the phase difference measuring device 10b shown on the right side of the figure, for the same object 9 (electrical equipment 9 in the example shown in the embodiment).

[0155] In the first connection configuration shown in Figure 19, pulse signals for operation timing were input in parallel from the pulse pattern generator 4 to each part of the multiple measuring devices 10a and 10b via signal lines 41, 42, 43, and 44. Similarly, trigger signals were input in parallel from the data processing units 33 of each measuring device 10a and 10b to the pulse pattern generator 4 via signal lines 51 and 52.

[0156] In the second connection configuration shown in Figure 20, pulse signals for operation timing were input in series from the pulse pattern generator 4 to each part of the multiple measuring devices 10a and 10b via the series-connected signal lines 41A and 41B and the series-connected signal lines 42A and 42B. Similarly, for the trigger signal, the trigger signal was input in series from the data processing unit 33 of each measuring device 10a and 10b to the pulse pattern generator 4 via the series-connected signal lines 51A and 51B.

[0157] The performance improvement resulting from the second modification was compared between the first and second connection configurations. Figure 21 shows the magnetic resonance signal obtained using the first connection configuration shown in Figure 19. (A) is the magnetic resonance signal obtained by the phase difference measuring device 10a shown on the left side of Figure 19, and (B) is the magnetic resonance signal obtained by the phase difference measuring device 10b shown on the right side of Figure 19. Figure 22 shows the magnetic resonance signal obtained using the second connection configuration shown in Figure 20. (A) is the magnetic resonance signal obtained by the phase difference measuring device 10a shown on the left side of Figure 20, and (B) is the magnetic resonance signal obtained by the phase difference measuring device 10b shown on the right side of Figure 20. To facilitate comparison, the horizontal axis scales of the graphs in (A) and (B) have been aligned.

[0158] As shown in Figures 21(A) and 21(B), with the first connection configuration, a phase shift (peak position) of the magnetic resonance signal occurred between the multiple phase difference measuring devices 10a and 10b each time a measurement was performed. In contrast, as shown in Figures 22(A) and 22(B), with the second connection configuration, the phase shift of the magnetic resonance signal was reduced and almost eliminated compared to the first connection configuration, and the magnetic resonance signal was always acquired with a consistent phase between the multiple phase difference measuring devices 10a and 10b. Thus, the second connection configuration shown in Figure 20, in which the pulse signal for operation timing is input in series to each part of the multiple phase difference measuring devices 10a and 10b, reduces the phase shift of the magnetic resonance signal obtained by measurement compared to the first connection configuration shown in Figure 19, in which the pulse signal for operation timing is input in parallel to each part of the multiple phase difference measuring devices 10a and 10b, confirming that the second connection configuration has improved performance compared to the first connection configuration.

[0159] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The technical scope of the present invention is not limited to the embodiments described above, but also includes cases where phase is measured by a combination such as measuring the magnetic field (current) as a continuous wave (CW) and measuring the electric field (voltage) as a pulse sequence. [Explanation of symbols]

[0160] 1. Sensor element (NV center of diamond) 2 Electromagnetic wave irradiation section 3 Phase difference measurement section 8 Interaction 9(9a,9b) Electrical equipment (current transformers, voltage transformers) 10(10a,10b) Phase difference measuring device 11 probes 12 Diamond Crystals 14 Antennas 21 Microwave (MW) Oscillators 22 switches 23 Amplifier 31 Light-irradiating section 311 Light source 312 Acousto-optical modulation element (AOM) 313 Objective lens 32 Change detection unit 33 Data Processing Unit 331 Magnetic field phase calculation unit 332 Electric field phase calculation unit 333 Phase difference signal output section 99 Network

Claims

1. An electromagnetic wave irradiation unit repeatedly irradiates a quantum sensor element with electromagnetic waves to manipulate the electron spin state of the quantum sensor element, which changes due to interaction with a magnetic or electric field generated by an AC signal, A phase difference measuring unit that acquires a plurality of electron spin states after interaction with the magnetic field or the electric field, and measures the phase difference between the phase of the magnetic field and the phase of the electric field based on the acquired plurality of electron spin states, A light irradiation unit that irradiates the quantum sensor element with light for reading the phase information of the electron spin state after interaction with the magnetic field or electric field, A change detection unit for detecting changes occurring in the quantum sensor element due to the irradiation of the aforementioned light, A data processing unit reads the phase information of the electron spin state from the detected change, and measures the phase difference between the phase of the magnetic field and the phase of the electric field based on the read-out phase information of the electron spin state, A phase difference measurement unit including, A pulse pattern generator that uses the fluorescence intensity when the electron spin state is initialized as a trigger to output a pulse signal for operation timing to the electromagnetic wave irradiation unit and the light irradiation unit, and corrects the deviation of the measurement period, A phase difference measuring device equipped with the following features.

2. The phase difference measuring unit is A magnetic field phase calculation unit calculates the phase of the magnetic field based on a plurality of electron spin states after interaction with the magnetic field, An electric field phase calculation unit calculates the phase of the electric field based on a plurality of electron spin states after interaction with the electric field, It further includes, A phase difference measuring device according to claim 1, which measures the phase difference based on the calculated phase of the magnetic field and the phase of the electric field.

3. The magnetic field phase calculation unit calculates the phase of the magnetic field by fitting multiple time-series data corresponding to multiple electron spin states after interaction with the magnetic field, The phase difference measuring device according to claim 2, wherein the electric field phase calculation unit calculates the phase of the electric field by fitting a plurality of time-series data corresponding to a plurality of electron spin states after interaction with the electric field.

4. The phase difference measuring apparatus according to claim 1, wherein the electromagnetic wave irradiation unit is a pulse sequence for observing the free induction decay (FID) signal of the electron spin state, and the electromagnetic wave is repeatedly irradiated onto the quantum sensor element with a pulse sequence including a plurality of π / 2 pulses.

5. The electromagnetic wave irradiation unit is a pulse sequence for observing the spin echo signal of the electron spin state, and repeatedly irradiates the quantum sensor element with electromagnetic waves in a pulse sequence that includes a plurality of π / 2 pulses and π pulses between the plurality of π / 2 pulses. The phase difference measuring device according to claim 3, wherein each of the magnetic field phase calculation unit and the electric field phase calculation unit fits a plurality of time-series data corresponding to the difference in the intensity of the AC signal before and after irradiation with a π pulse.

6. The phase difference measuring device according to claim 1, wherein the AC signal is an AC signal transmitted through electrical equipment.

7. An electrical installation comprising a phase difference measuring device according to any one of claims 1 to 6.

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