magnetic field detection device

Abstract

This magnetic field detection device (1) comprises: a diamond substrate (10) which has an NV center (11); a light-emitting element (12) which irradiates the diamond substrate (10) with green light; a light reception element (13) which receives red light generated by inputting the green light to the diamond substrate (10); a first radiation body (22) which applies a microwave to a circuit-to-be-measured (100); and a second radiation body (24) which applies the microwave to the NV center (11) of the diamond substrate (10), wherein a current is excited in the circuit-to-be-measured (100) by applying the microwave to the circuit-to-be-measured (100) by means of the first radiation body (22), and a magnetic field generated from the circuit-to-be-measured (100) is measured by applying the microwave to the NV center (11) by means of the second radiation body (24).

Description

[Technical Field]

[0001] The present disclosure relates to a magnetic field detection device. [Background technology]

[0002] Patent Document 1 discloses a magnetic field detection device using diamond with NV centers. In the technology described in Patent Document 1, an alternating current is passed through the object to be measured, and an AC magnetic field is applied to the diamond NV center sensor. An electric field is applied to the diamond NV center sensor by electrodes. In the control by the electric field, the energy difference between the first state |Br〉 and the second state |Da〉 in the electron spin is made equal to the frequency of the AC magnetic field in the object to be measured. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-023965 Summary of the Invention

[0004] A magnetic field detection device according to one embodiment comprises a diamond substrate having an NV center, a light-emitting element that irradiates green light onto the diamond substrate, a light-receiving element that receives red light generated by inputting the green light into the diamond substrate, a first radiator that applies microwaves to a circuit under measurement, and a second radiator that applies microwaves to the NV center of the diamond substrate. By applying microwaves to the circuit under measurement using the first radiator, a current is excited in the circuit under measurement, and by applying microwaves to the NV center using the second radiator, the magnetic field emitted from the circuit under measurement is measured.

[0005] One embodiment of the magnetic field detection device comprises a diamond substrate having an NV center, a light-emitting element that irradiates the diamond substrate with green light, a radiator that applies microwaves of a specific frequency to the NV center of the diamond substrate, a light-receiving element that receives red light generated by inputting green light to the diamond substrate, an AC circuit that applies an AC current of a frequency that causes electron spin double resonance to the circuit under test, and a static magnetic field generator that applies a static magnetic field to the NV center of the diamond substrate.The magnetic field detection device measures the magnetic field emitted from the circuit under test by applying an AC current to the circuit under test using the AC circuit and applying microwaves to the NV center using the radiator. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a block diagram illustrating an example of a magnetic field detection device according to the first embodiment. [Figure 2] FIG. 2 is a graph showing an example of the relationship between the frequency of microwaves and the luminance of red light. [Figure 3] FIG. 3 is a schematic diagram illustrating an example of control in the magnetic field detection device. [Figure 4] FIG. 4 is a schematic diagram illustrating another example of control in the magnetic field detection device. [Figure 5] FIG. 5 is a block diagram illustrating an example of a magnetic field detection device according to the second embodiment. [Figure 6] FIG. 6 is a block diagram illustrating an example of a magnetic field detection device according to the third embodiment. [Figure 7] FIG. 7 is a graph showing another example of the relationship between the microwave frequency and the luminance of red light. [Figure 8] FIG. 8 is a schematic diagram illustrating another example of control in the magnetic field detection device. [Figure 9] FIG. 9 is a graph showing another example of the relationship between the microwave frequency and the luminance of red light. [Figure 10] FIG. 10 is a graph showing the relationship between microwave frequency and red light brightness. DETAILED DESCRIPTION OF THE INVENTION

[0007] A magnetic field detection device according to an embodiment will be described below. The magnetic field detection device 1 is for detecting a magnetic field generated in a measurement target circuit 100. Fig. 1 is a block diagram illustrating an example of a magnetic field detection device according to a first embodiment.

[0008] [First embodiment] (Circuit to be measured) The circuit under measurement 100 is an object to be detected by the magnetic field detection device 1, in other words, a sample. The circuit under measurement 100 generates a magnetic field when a current flows through the circuit.

[0009] (magnetic field detection device) The magnetic field detecting device 1 includes a diamond substrate 10, a light emitting element 12, a light receiving element 13, a first radiator 22, and a second radiator 24. The magnetic field detecting device 1 further includes a first microwave source 21 and a second microwave source 23. The magnetic field detecting device 1 further includes a signal control unit 30.

[0010] The diamond substrate 10 is a so-called diamond sensor. The diamond substrate 10 has an NV center 11 formed in a diamond crystal. The diamond substrate 10 further has a first microwave source 21, a first radiator 22, a second microwave source 23, and a second radiator 24 arranged thereon.

[0011] The diamond crystal has an NV center 11. The diamond crystal has a side length of, for example, 2 mm. The diamond crystal has a thickness of, for example, 300 μm.

[0012] The NV center 11 may be arranged singly or in plural on one surface of the diamond crystal. The NV center 11 may be oriented in one direction. The NV center 11 may also be a crystal with a plurality of different orientations.

[0013] NV centers 11 are complex defects in diamond crystals where carbon would normally be present, replaced by nitrogen, with a vacancy at the adjacent position. NV centers 11 are missing some of the degenerate shared electron pairs. In zero magnetic field, NV centers 11 have electrons with spin angular momentum at two levels, m=0 and m=±1. Because the m=±1 electrons have a magnetic moment, they are affected by an external magnetic field, and the degeneracy of m=±1 is broken, resulting in two more energy levels. The strength of an external magnetic field can be detected by detecting the electron spin resonance caused by these using light waves and microwaves.

[0014] The electrons in the NV center 11 are excited by light with a wavelength of 532 nm and emit fluorescence with a wavelength of 638 nm during the relaxation process. This fluorescence process is unlikely to occur at the electron spin resonance frequency. Therefore, by utilizing this property, the state of the m = ±1 electrons can be observed. The electron spin resonance frequency of the NV center 11 in a diamond crystal is known to be approximately 2.87 GHz in zero magnetic field. When microwaves with the frequency of this resonance point (resonance frequency) are irradiated, the fluorescence with a wavelength of 638 nm is quenched. Furthermore, the resonant frequency of the microwave changes due to changes in the state of the m = ±1 electrons depending on the strength of the external magnetic field, etc. Then, by capturing this change as a frequency change in the fluorescence intensity, magnetic fields and currents can be detected.

[0015] The light-emitting element 12 and the light-receiving element 13 detect the magnetism of the circuit 100 under test. In this embodiment, the light-emitting element 12 and the light-receiving element 13 detect the magnetism while scanning the circuit 100 under test. The light-emitting element 12 and the light-receiving element 13 are arranged facing each other on the diamond substrate 10. The light-emitting element 12 and the light-receiving element 13 input and output light to the NV center 11 of the diamond crystal. The light-emitting element 12 is a light source, and the light-receiving element 13 is a light receiver. The light-emitting element 12 and the light-receiving element 13 are controlled by a signal control unit 30. The signal control unit 30 controls the light emission of the light-emitting element 12. The signal control unit 30 controls the light reception of the light-receiving element 13. The signal control unit 30 processes the red fluorescent light signal received by the light-receiving element 13. The signal control unit 30 outputs the magnetic field strength as a result.

[0016] The light-emitting element 12 irradiates the diamond substrate 10 with green light. The light-emitting element 12 emits excitation light that irradiates the diamond crystal. The light-emitting element 12 irradiates the excitation light to the NV center 11. The light-emitting element 12 is a laser diode. The light-emitting element 12 emits laser light with a wavelength of, for example, 527 nm under the control of the signal control unit 30. The light-emitting element 12 emits green excitation light. For example, a green light-emitting diode (LED: Light Emitting Diode), a green surface-emitting laser diode (VCSEL: Vertical Cavity Surface Emitting Laser), a green edge-emitting laser diode (LD: Laser Diode), etc. can be used as the light-emitting element 12.

[0017] The light receiving element 13 receives red light generated by inputting green light into the diamond substrate 10. The light receiving element 13 detects fluorescence from the diamond substrate 10. The light receiving element 13 is a photodiode. The light receiving element 13 receives fluorescence from the NV centers 11 of the diamond crystal based on the control of the signal control unit 30. The light receiving element 13 receives fluorescence emitted by the excitation light from the diamond crystal. For example, a Si-PIN photodiode (PD: Photo Diode) and a Si-avalanche photodiode (Si-APD) can be used as the light receiving element 13.

[0018] The first microwave source 21 generates microwaves to be irradiated onto the circuit 100 under test. The first microwave source 21 is, for example, a voltage controlled oscillator (VCO). The first microwave source 21 is electrically connected to the first radiator 22 via a high-frequency transmission line. The operation of the first microwave source 21 is controlled by the signal control unit 30. The first microwave source 21 turns on and off the microwaves based on an operation control command from the signal control unit 30.

[0019] The first radiator 22 applies microwaves to the circuit under test 100. The first radiator 22 transmits the microwaves to be irradiated to the circuit under test 100. The first radiator 22 transmits microwaves from the first microwave source 21. The first radiator 22 is, for example, a minute loop antenna. The first radiator 22 has a frequency of, for example, 2.8 GHz or more and 2.9 GHz or less. The first radiator 22 has an input power of, for example, -20 dBm or more and +20 dBm or less.

[0020] The second microwave source 23 generates microwaves to be irradiated onto the NV centers 11 of the diamond crystal. The second microwave source 23 is, for example, a voltage-controlled oscillator. The second microwave source 23 is electrically connected to the second radiator 24 via a high-frequency transmission line. The operation of the second microwave source 23 is controlled by the signal control unit 30. The second microwave source 23 turns the microwaves on and off based on operation control commands from the signal control unit 30.

[0021] The second radiator 24 applies microwaves to the NV centers 14 of the diamond substrate 10. The second radiator 24 transmits microwaves to be irradiated to the NV centers 11 of the diamond substrate 10. The second radiator 24 transmits microwaves from the second microwave source 23. The second radiator 24 is, for example, a minute loop antenna. The second radiator 24 has, for example, a frequency of 2.8 GHz or more and 2.9 GHz or less. The second radiator 24 has, for example, an input power of -20 dBm or more and +20 dBm or less.

[0022] (Signal control unit) The signal control unit 30 is a controller of the magnetic field detection device 1. The signal control unit 30 includes a numerical calculation device (processor) such as a CPU (Central Processing Unit). In the embodiment, the signal control unit 30 includes a control unit 31 and an image processing unit 32.

[0023] The control unit 31 controls the magnetic field detection device 1. The control unit 31 controls the generation of microwaves from the first microwave source 21. The control unit 31 outputs an operation control command that controls the on / off switching operation of the microwaves from the first microwave source 21. The control unit 31 controls the generation of microwaves from the second microwave source 23. The control unit 31 outputs an operation control command that controls the on / off switching operation of the microwaves from the second microwave source 23. The control unit 31 controls the emission of green light from the light-emitting element 12. The control unit 31 outputs an operation control command that controls the on / off switching operation of the emission of green light from the light-emitting element 12. The control unit 31 controls the reception of light by the light-receiving element 13. The control unit 31 outputs an operation control command that controls the on / off switching operation of the reception of red light by the light-receiving element 13.

[0024] The control unit 31 detects the magnetic field of the circuit under test 100. More specifically, the control unit 31 applies microwaves to the circuit under test 100 via the first radiator 22, thereby exciting a current in the circuit under test 100. The control unit 31 measures the magnetic field by applying microwaves to the NV center 11 via the second radiator 24. A method for detecting the magnetic field will be described later.

[0025] The image processing unit 32 creates an image based on the magnetic field detected by the control unit 31. The image processing unit 32 creates an image that allows the strength of the detected magnetic field to be confirmed. For example, the image processing unit 32 creates an image in which the color is changed between positions where the magnetic field is strong and positions where the magnetic field is weak.

[0026] (Magnetic field detection method) A method for detecting the magnetic field of the circuit 100 to be measured in the magnetic field detecting device 1 will be described. When detecting a magnetic field, the circuit 100 to be measured is brought close to or in close contact with the magnetic field acting surface of the diamond substrate 10 of the magnetic field detecting device 1.

[0027] The microwaves generated by the first microwave source 21 under the control of the control unit 31 propagate through the high-frequency transmission line to the first radiator 22. Then, the microwaves are radiated from the first radiator 22 toward the circuit 100 under test. Then, the radiated microwaves generate a magnetic field in the circuit 100 under test.

[0028] The microwaves generated by the second microwave source 23 under the control of the control unit 31 propagate to the second radiator 24 through the high-frequency transmission line. Then, the microwaves are radiated from the second radiator 24. Then, the microwaves radiated from the second radiator 24 act on the NV centers 11 of the diamond substrate 10, causing electron spin resonance. A spatial change in the direction or magnitude of the magnetic field generated in the circuit 100 to be measured acts on the NV centers 11 of the diamond crystals of the diamond substrate 10 of the magnetic field detection device 1.

[0029] Then, under the control of the control unit 31, the fluorescent and excitation light is scanned across the diamond substrate 10 by the light-emitting element 12 and the light-receiving element 13. More specifically, the green excitation light from the light-emitting element 12 is incident on the diamond crystal. The green excitation light incident on the diamond crystal then diffuses widely within the diamond crystal, irradiating and exciting the NV centers 11.

[0030] The excited NV centers 11 then emit red fluorescence, which enters the diamond crystal. The red fluorescence then diffuses widely within the diamond crystal and enters the light-receiving surface of the light-receiving element 13.

[0031] Then, under the control of the control unit 31, the light receiving element 13 receives, from the diamond crystal, an electron spin resonance signal of the NV center 11 excited by the excitation light as fluorescence. Under the control of the control unit 31, the light receiving element 13 receives a fluorescence signal corresponding to a change in the direction or magnitude of the magnetic field.

[0032] The magnetic field of the circuit under test 100 acts on the NV center 11, changing the electron spin resonance frequency. The intensity of the red fluorescence changes in response to the change in the electron spin resonance frequency. The magnetic field detection device 1 detects the magnitude of the magnetic field by reading this. The magnetic field detection device 1 also functions as a current sensor by measuring the magnetic field caused by a current.

[0033] The method for detecting a magnetic field in the signal control unit 30 will be described in more detail with reference to FIG. 2. FIG. 2 is a graph showing an example of the relationship between microwave frequency and luminance of red light. First, the control unit 31 turns off the microwaves from the second radiator 24 to the circuit under test 100. The control unit 31 acquires the luminance of red light when the microwaves from the second radiator 24 to the circuit under test 100 are turned off as a reference value A. Then, the control unit 31 turns on the microwaves from the second radiator 24 to the circuit under test 100. The control unit 31 acquires the luminance B of red light when the microwaves from the second radiator 24 are turned on. The control unit 31 then divides the luminance B by the reference value A to obtain B / A. For example, the control unit 31 acquires the luminance B of red light using microwaves with a frequency of 2.87 GHz and divides it by the reference value A to obtain the contrast value B / A. In this way, the control unit 31 calculates the magnetic field from the contrast value of the microwaves with a frequency of 2.87 GHz.

[0034] FIG. 3 is a schematic diagram illustrating an example of control in a magnetic field detection device. Laser indicates the timing of emission of green light from the light-emitting element 12. The light-emitting element 12 constantly emits green light while detecting the magnetic field of the circuit under test 100. MW1 indicates the timing of microwave oscillation from the first microwave source 21. The first microwave source 21 repeatedly oscillates (on) and stops (off) the microwave while detecting the magnetic field of the circuit under test 100. MW2 indicates the timing of microwave oscillation from the second microwave source 23. The second microwave source 23 repeatedly oscillates (on) and stops (off) the microwave in synchronization with the first microwave source 21 while detecting the magnetic field of the circuit under test 100. CCD frames indicate the timing of light reception by the light-receiving element 13. The light-receiving element 13 repeatedly receives (on) and stops (off) red light while detecting the magnetic field of the circuit under test 100. The light receiving element 13 receives light at least when the reference value A is obtained and when the emission intensity B is obtained.

[0035] Fig. 4 is a schematic diagram illustrating another example of control in the magnetic field detection device. In the example shown in Fig. 4, the first microwave source 21 constantly oscillates (turns on) microwaves while detecting the magnetic field of the circuit 100 under test.

[0036] The magnetic field detection process is not limited to the above. For example, the magnetic field may be detected by taking the difference between the resonant frequencies at two points by sweeping the frequency of the microwave applied from the second radiator 24 to the NV center 11 using a known method.

[0037] When obtaining a current image of a circuit under measurement using the magnetic field detection device 1, the detection may be performed by the method described with reference to FIGS.

[0038] In this way, a microwave is applied to the circuit under test 100 by the first radiator 22, thereby exciting a current in the circuit under test 100. Then, a microwave is applied to the NV center 11 by the second radiator 24, thereby measuring the magnetic field.

[0039] (effect) As described above, in this embodiment, a current is excited by applying microwaves to the circuit under test 100. In this embodiment, there is no need to physically contact a probe or the like with the circuit under test 100. According to this embodiment, the magnetic field of the minute circuit under test 100 can be efficiently measured.

[0040] In this embodiment, the strength of the detected magnetic field can be confirmed on an image. According to this embodiment, the magnetic field of the circuit 100 under test can be confirmed efficiently.

[0041] In contrast, in the technology described in Patent Document 1, in order to pass an AC current through an object to be measured, a probe extending from an AC power source must be physically brought into contact with the object to be measured. However, the smaller the circuit to be measured, the more difficult it becomes to bring the probe into contact with the circuit.

[0042] Furthermore, in the technology described in Patent Document 1, the diamond NV center sensor needs to be sandwiched between electrodes in order to apply an electric field. If it is desired to set the energy difference between |Br> and |Da> to a large value, the width between the electrodes needs to be narrowed to strengthen the electric field. However, in that case, it becomes difficult to increase the width of the diamond NV center sensor. If the width of the diamond NV center sensor is small, the measurement surface of the sensor becomes small.

[0043] As such, there is room for improvement in magnetic field detection devices that use diamond substrates with NV centers, which are small and have high magnetic field measurement efficiency.

[0044] [Second embodiment] 5 is a block diagram illustrating an example of a magnetic field detection device according to the second embodiment. In this embodiment, the magnetic field detection device 1 is different from the first embodiment in that it includes a diamond substrate 10, a light-emitting element 12, a light-receiving element 13, a first and second microwave source 25, and a first and second radiator 26.

[0045] The first and second microwave source 25 implements the functions of the first microwave source 21 and the second microwave source 23 of the first embodiment. In other words, in this embodiment, the first and second microwave source 25 implements the first microwave source 21 and the second microwave source 23 of the first embodiment as the same radiator.

[0046] The first and second radiators 26 implement the functions of the first radiators 22 and the second radiators 24 of the first embodiment.

[0047] The control unit 31 controls the generation of microwaves from the first and second microwave source 25. The control unit 31 outputs an operation control command that controls the on / off switching operation of the microwaves from the first and second microwave source 25.

[0048] (effect) As described above, in this embodiment, the first and second microwave source 25 is implemented as the same radiator as the first microwave source 21 and the second microwave source 23 of the first embodiment. According to this embodiment, since there is only one radiator in the magnetic field detection device 1, the device can be made space-saving.

[0049] [Third embodiment] FIG. 6 is a block diagram illustrating an example of a magnetic field detection device according to the third embodiment. FIG. 7 is a graph showing another example of the relationship between the microwave frequency and the brightness of red light. FIG. 8 is a schematic diagram illustrating another example of control in the magnetic field detection device. FIG. 9 is a graph showing another example of the relationship between the microwave frequency and the brightness of red light. FIG. 10 is a graph showing the relationship between the microwave frequency and the brightness of red light. In this embodiment, the magnetic field detection device 1 differs from the first embodiment in that it includes a diamond substrate 10, a light-emitting element 12, a light-receiving element 13, a microwave source 23, a radiator 24, a static magnetic field generating unit 27, and an AC circuit 28.

[0050] The microwave source 23 is configured in the same manner as the second microwave source 23 of the first embodiment.

[0051] The radiator 24 is configured in the same manner as the second radiator 24 of the first embodiment. The radiator 24 applies microwaves of a specific frequency to the NV centers 11 of the diamond substrate 10.

[0052] The static magnetic field generating unit 27 applies a static magnetic field to the NV centers 11 of the diamond substrate 10. The static magnetic field generating unit 27 is, for example, a magnet.

[0053] The static magnetic field is applied perpendicular to the NV axis of the NV center 11 .

[0054] The AC circuit 28 applies an AC current of a frequency that causes electron spin double resonance to the circuit 100 under test. The frequency of the double resonance (9.63 MHz in the example shown in FIG. 9) may be, for example, 0.1 MHz or more and 100 MHz or less, or 1 MHz or more and 10 MHz or less. The lower limit of the double resonance frequency is determined by the lower limit of the magnitude of the strain inherent to diamond. This is set to several hundred kHz, so the lowest limit is 100 kHz (0.1 MHz). The upper limit is considered to be about 1 / 10 of the splitting width of a zero magnetic field, so 100 MHz is the highest limit.

[0055] The control unit 31 applies an AC current to the circuit 100 under test using the AC circuit 28. The control unit 31 applies a microwave to the NV center 11 using the radiator 24, thereby measuring the magnetic field emitted from the circuit 100 under test.

[0056] More specifically, the control unit 31 determines the red light intensity of the NV center 11 obtained when a static magnetic field is applied to the NV center 11, a microwave is applied to the NV center 11, and an AC current is applied as the first emission intensity.The control unit 31 determines the red light intensity of the NV center 11 obtained when a static magnetic field is applied to the NV center 11, a microwave is applied to the NV center 11, and no AC current is applied as the second emission intensity.The control unit 31 then measures the magnetic field emitted from the circuit 100 under measurement based on the first emission intensity and the second emission intensity.

[0057] In this embodiment, the control unit 31 uses the red light intensity of the NV center 11 when no microwaves are applied as a reference value. Then, the control unit 31 corrects the first emission intensity and the second emission intensity using the reference value. Then, the control unit 31 may measure the magnetic field emitted from the circuit under test 100 by determining the difference between the corrected first emission intensity and the corrected second emission intensity.

[0058] The magnetic field detection method in the signal control unit 30 will be described in more detail using FIG. 7. In FIG. 7, the solid line graph represents the red light luminance contrast value when the microwave frequency is changed, or swept, while a static magnetic field is applied to the NV center 11. The dashed line graph represents the red light luminance contrast value when the microwave frequency is swept while a static magnetic field and an AC current (in this example, a frequency of 9.67 MHz) are applied to the NV center 11. The red light luminance is obtained as a reference value A when the microwave from the radiator 24 to the NV center 11 is turned off. Then, the red light luminance B1 is obtained when a static magnetic field and a microwave are applied to the NV center 11 and an AC current is applied. Then, the red light luminance B2 is obtained when a static magnetic field and a microwave are applied to the NV center 11 and the AC current is turned off. The microwave frequency used here may be, for example, one of the frequencies of the double resonance generated when an AC current is applied to the circuit under test 100. In the example shown in FIG. 7, for example, 2.888 GHz is used. The frequency of the microwave used is not limited to this. In the example shown in FIG. 7, the frequency of the AC current is 9.67 MHz. Then, B1 / A and B2 / A are calculated to obtain a contrast value. Next, (B1 / A)-(B2 / A) is calculated, and the magnetic field is calculated based on this value.

[0059] The static magnetic field conditions are explained below. By setting the static magnetic field conditions, the energy difference of the electron spin at the NV center 11 between |Br〉 and |Da〉 is ensured. This energy difference appears as the width between two dips on the solid line in the graph shown in Figure 7. The static magnetic field conditions here refer to the magnetization amount of the magnet used as the static magnetic field generating unit 27, the distance from the magnet to the NV center 11, the orientation of the magnet with respect to the NV center 11, etc. These conditions adjust the strength component of the static magnetic field along the direction perpendicular to the direction in which N and V are aligned at the NV center 11. The larger this component, the larger the width between the dips. In the example shown in Figure 7, the width between the dips is adjusted to 9.67 MHz by adjusting the above conditions.

[0060] |Br〉 is expressed by the following formula:

[0061]

number

[0062] |Da〉 is expressed by the following formula:

[0063]

number

[0064] The frequency of the AC current will now be explained. The frequency of the AC current is set to a frequency that corresponds to the width between dips. In the example shown in FIG. 7, the width between dips is 9.67 MHz, so the frequency of the AC current is set to 9.67 MHz. In the example shown in FIG. 7, a static magnetic field is applied under conditions that result in a width between dips of 9.67 MHz, and a 9.67 MHz AC current is applied to the circuit under measurement, resulting in a graph like the dashed line in FIG. 7. Note that if the AC current is turned off and only the static magnetic field is applied to the NV center 11, the graph will be shown as a solid line.

[0065] Control in the magnetic field detection device will be described using FIG. 8. Static magnetic field indicates the timing at which the static magnetic field is generated by the static magnetic field generating unit 27. The static magnetic field generating unit 27 constantly generates a magnetic field while detecting the magnetic field of the circuit under test 100. MW indicates the timing at which microwaves are generated from the microwave source 23. The microwave source 23 repeatedly oscillates (on) and stops (off) the microwaves while detecting the magnetic field of the circuit under test 100. RF indicates the timing at which AC current is applied from the AC circuit 28. The AC circuit 28 repeatedly applies (on) and stops (off) the AC current while detecting the magnetic field of the circuit under test 100. The light receiving element 13 receives light at least when acquiring the reference value A, when acquiring the first emission intensity B1, and when acquiring the second emission intensity B2. In an embodiment, the AC current may be turned on later than the microwave, and the AC current may be turned off at the same time.

[0066] Fig. 9 shows the case where the double resonance frequency is 9.63 MHz. In Fig. 9, the solid line graph shows the red light luminance contrast value when the microwave frequency is changed, in other words, swept, while a static magnetic field is applied to the NV center 11. The dashed line graph shows the red light luminance contrast value when the microwave frequency is swept while a static magnetic field and an AC current, in this example a frequency of 9.63 MHz, are applied to the NV center 11. The frequency range in Fig. 9 is set, for example, from the graph shown in Fig. 10.

[0067] (effect) As described above, in this embodiment, the static magnetic field generator 27 applies a static magnetic field to the NV centers 11 of the diamond substrate 10, and the AC circuit 28 applies an AC current of a frequency that causes electron spin double resonance to the circuit 100 under test. According to this embodiment, no electrodes are used to apply the static magnetic field. According to this embodiment, there is no restriction on the width of the NV centers 11 of the diamond substrate 10, and the measurement surface can be made larger.

[0068] In this embodiment, the magnetic field can be measured simply by turning the AC current on and off. This embodiment can measure the magnetic field at a large number of point positions in a short time, even if the measurement surface of the circuit under test 100 is large. This embodiment can efficiently sweep and detect the magnetic field in one or two dimensions.

[0069] In this embodiment, the magnetic field emitted from the measurement target circuit 100 is measured by determining the difference between the first emission intensity when no microwave is applied after the correction and the second emission intensity after the correction. According to this embodiment, the accuracy of magnetic field detection can be improved.

[0070] In this embodiment, the AC current is turned on later than the microwave is turned on, and the AC current and the microwave are turned off at the same time. This embodiment improves the signal-to-noise ratio and improves sensitivity.

[0071] In this embodiment, the strength of the detected magnetic field can be confirmed on an image. According to this embodiment, the magnetic field of the circuit 100 under test can be confirmed efficiently.

[0072] The embodiments disclosed in the present application can be modified without departing from the spirit and scope of the invention. Furthermore, the embodiments disclosed in the present application and their modifications can be combined as appropriate.

[0073] Although specific embodiments have been described to fully and clearly disclose the claimed technology, the appended claims should not be limited to the above-described embodiments, but should be construed to embody all modifications and alternative arrangements that may be made by those skilled in the art within the scope of the basic concept presented herein. [Explanation of symbols]

[0074] 1. Magnetic field detection device 10 Diamond substrate 11 NV Center 12 Light-emitting element 13 Photodetector 21 First microwave source 22 First Radiator 23 Second microwave source 24 Second Radiator 100 Circuit to be measured

Claims

1. a diamond substrate having an NV center; a light emitting element that irradiates the diamond substrate with green light; a light receiving element for receiving red light generated by inputting green light to the diamond substrate; a first radiator for applying microwaves to the circuit under test; a second radiator for applying microwaves to the NV center of the diamond substrate; Equipped with applying microwaves to the circuit under test by the first radiator to excite a current in the circuit under test; a microwave is applied to the NV center by the second radiator, thereby measuring a magnetic field emitted from the circuit under test; Magnetic field detection device.

2. the first radiator and the second radiator are the same radiator; The magnetic field detection device according to claim 1 .

3. an image processing unit that creates an image based on the detected magnetic field; The magnetic field detection device according to claim 1 or 2, comprising:

4. a diamond substrate having an NV center; a light emitting element that irradiates the diamond substrate with green light; a radiator for applying microwaves of a specific frequency to the NV center of the diamond substrate; a light receiving element for receiving red light generated by inputting green light to the diamond substrate; an AC circuit that applies an AC current of a frequency that causes electron spin double resonance to the circuit under test; a static magnetic field generating unit that applies a static magnetic field to the NV center of the diamond substrate; Preparation, applying an AC current to the circuit under test by the AC circuit; a microwave is applied to the NV center by the radiator, and a magnetic field emitted from the circuit under test is measured; Magnetic field detection device.

5. The static magnetic field is applied perpendicular to the NV axis. The magnetic field detection device according to claim 4 .

6. a first light emission intensity is a red light intensity of the NV center obtained when the static magnetic field is applied to the NV center, the microwave is applied to the NV center, and the AC current is applied; the red light intensity of the NV center obtained when the static magnetic field is applied to the NV center, the microwave is applied to the NV center, and the AC current is not applied is defined as a second light emission intensity; measuring a magnetic field emitted from the circuit under measurement based on the first light emission intensity and the second light emission intensity; The magnetic field detection device according to claim 4 .

7. The red light intensity of the NV center when the microwave is not applied is set as a reference value, correcting the first emission intensity and the second emission intensity using a reference value; measuring the magnetic field emitted from the circuit under test by determining a difference between the corrected first emission intensity and the corrected second emission intensity; The magnetic field detection device according to claim 6.

8. The timing at which the AC current is turned on is later than the timing at which the microwave is turned on, and the timing at which the AC current is turned off is the same as the timing at which the microwave is turned off. The magnetic field detection device according to claim 6 or 7.

9. an image processing unit that creates an image based on the detected magnetic field; The magnetic field detection device according to claim 4 , comprising:

Images