Diamond quantum sensor, diamond anvil cell-type quantum sensor, and measuring equipment

Abstract

To provide a diamond quantum sensor with high durability and reproducibility, a diamond anvil cell-type quantum sensor including the same, and measuring equipment.SOLUTION: In an embodiment of the disclosure, there is provided a diamond quantum sensor 10 that includes: a nitrogen-vacancy center-containing diamond 11 including a nitrogen-vacancy center; and an impurity-doped diamond 12 that functions as a microwave taxiway for guiding a microwave to the nitrogen-vacancy center. The impurity-doped diamond 12 has an electrical conductivity and is chemically bonded to the nitrogen-vacancy center-containing diamond.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a diamond quantum sensor, a diamond anvil cell type quantum sensor, and a measuring device.

Background Art

[0002] A nitrogen-vacancy center (NV center) in which nitrogen and a defect in diamond are combined to form a new energy level is expected as a next-generation quantum sensing technology because the quantum state of its spin responds sensitively to an external magnetic field.

[0003] As a sensor using an NV center-containing diamond containing an NV center, for example, there is known a sensor that sandwiches a sample to be measured between opposing diamond anvils and compresses the sample to be measured with the diamond anvils to measure the physical properties of the sample to be measured (see, for example, Non-Patent Document 1).

[0004] Here, in order to drive the NV center, it is necessary to irradiate microwaves from the outside. In Non-Patent Document 1, a platinum microwave wire (MW wire) is placed on a top cuvette, and the NV center is irradiated with microwaves by the MW wire.

[0005] Also, there is known a sensor that sandwiches a sample to be measured between diamond anvils and has an electrode pattern formed of a boron-doped diamond thin film on one of the diamond anvils, although it does not use an NV center-containing diamond (see, for example, Patent Document 1).

Prior Art Documents

Non-Patent Documents

[0006]

Non-Patent Document 1

Patent Document

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, in the technology of Non-Patent Document 1, the MW wire is placed on the top culet and the NV center is irradiated with microwaves by the MW wire. However, the MW wire may be crushed by the diamond anvil, the shape of the MW wire may change, or the MW wire may be cut. In addition, since the MW wire is placed manually, it is difficult to place the MW wire at the same position every time, and the reproducibility is poor.

[0009] In addition, the technology of Patent Document 1 uses boron-doped diamond, but boron-doped diamond is not for inducing microwaves to the NV center.

[0010] The present invention has been made to solve the above problems. That is, an object of the present invention is to provide a diamond quantum sensor with high durability and reproducibility, a diamond anvil cell type quantum sensor including the same, and a measuring device.

Means for Solving the Problems

[0011] [1] A diamond quantum sensor comprising a nitrogen-vacancy center-containing diamond containing a nitrogen-vacancy center and an impurity-doped diamond functioning as a microwave induction path for inducing microwaves in the nitrogen-vacancy center, wherein the impurity-doped diamond has conductivity and is chemically bonded to the nitrogen-vacancy center-containing diamond.

[0012] [2] The diamond quantum sensor according to [1] above, wherein the impurity in the impurity-doped diamond is boron.

[0013] [3] The diamond quantum sensor according to [2] above, wherein the concentration of the boron in the impurity-doped diamond is 1×10 20 cm -3 or more.

[0014] [4] The diamond quantum sensor according to any one of [1] to [3] above, wherein the impurity-doped diamond includes an annular portion having a notch and two end portions separated by the notch, and terminal portions continuously extending from each of the end portions of the annular portion.

[0015] [5] The diamond quantum sensor according to [4] above, wherein the annular portion is circular.

[0016] [6] A diamond anvil cell type quantum sensor comprising the diamond quantum sensor according to any one of [1] to [5] above and a diamond pressure cell disposed on the surface side of the impurity-doped diamond and sandwiching a sample to be measured with the diamond quantum sensor.

[0017] [7]The measurement device includes the diamond quantum sensor according to any one of [1] to [5] above, or the diamond anvil cell type quantum sensor according to [6] above, a green laser light irradiation system that irradiates the nitrogen-vacancy center with green laser light that excites the nitrogen-vacancy center, a microwave introduction system that introduces microwaves into the impurity-doped diamond, and a detection system that detects red light emitted from the nitrogen-vacancy center.

Advantages of the Invention

[0018] According to the present invention, it is possible to provide a diamond quantum sensor, a diamond anvil cell type quantum sensor, and a measurement device with high durability and reproducibility.

Brief Description of the Drawings

[0019]

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DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, a diamond quantum sensor and a measurement device according to an embodiment of the present invention will be described. FIG. 1 is a schematic plan view of the diamond quantum sensor according to the present embodiment, and FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1. FIG. 3 is a schematic plan view of another diamond quantum sensor according to the present embodiment, and FIG. 4 is a cross-sectional view taken along line B-B of FIG. 3. FIGS. 5 and 6 are schematic configuration diagrams of the diamond anvil cell type quantum sensor according to the present embodiment, and FIG. 7 is a schematic configuration diagram of the measurement device according to the present embodiment.

[0021] <<Diamond Quantum Sensor>> As shown in FIGS. 1 and 2, the diamond quantum sensor 10 includes a nitrogen-vacancy center-containing diamond (hereinafter referred to as "NV center-containing diamond") 11 containing a nitrogen-vacancy center (hereinafter referred to as "NV center"), and an impurity-doped diamond 12 that functions as a microwave induction path for inducing microwaves to the NV center.

[0022] <Diamond containing NV centers> The diamond 11 containing NV centers is a diamond containing nitrogen (N)-vacancy (V) pairs. The NV center has a structure in which two adjacent carbon atoms are replaced by a pair of a nitrogen atom and an atomic vacancy, and one N and one V exist adjacent to each other.

[0023] The diamond 11 containing NV centers may have a portion that does not contain NV centers even if there is a portion that contains NV centers. The diamond 11 containing NV centers shown in FIGS. 1 and 2 is composed only of portions that contain NV centers.

[0024] The concentration of NV centers in the diamond 11 containing NV centers is 1.77×10 16 cm -3 or more and 1.77×10 18 cm -3 or less. If the concentration of NV centers is 1.77×10 16 cm -3 or more, sufficient light emission from the NV centers is observed when the NV centers are irradiated with green laser light and microwaves. If the concentration of NV centers is 1.77×10 18 cm -3 or less, a decrease in the measurement accuracy due to the interaction between NV centers can be suppressed. The lower limit of the concentration of the above NV centers is 5.32×10 16 cm -3 or more or 1.77×10 17 cm -3 or more is more preferable, and the upper limit of the concentration of the above NV centers is 1.42×10 18 cm -3 or less is more preferable. The concentration of NV centers can be measured by electron spin resonance method.

[0025] The shape of the NV center-containing diamond 11 is not particularly limited, and for example, it may be in the form of a polygonal plate such as a rectangle or a square. When the NV center-containing diamond 11 is in the form of a plate, the thickness of the NV center-containing diamond 11 is preferably 100 nm or more. If this thickness is 100 nm or more, a sufficient number of NV centers can be ensured for measuring a magnetic field or the like.

[0026] <Impurity-doped diamond> The impurity-doped diamond 12 is chemically bonded to the NV center-containing diamond 11. The impurity-doped diamond 12 can be chemically bonded to the NV center-containing diamond 11, for example, by epitaxially growing the impurity-doped diamond 12 on the surface 11A of the NV center-containing diamond 11.

[0027] The impurity-doped diamond has conductivity. The impurities contained in the impurity-doped diamond are not particularly limited as long as they impart conductivity to the impurity-doped diamond. Examples of such impurities include boron, phosphorus, and the like. Among these, boron is preferred from the viewpoint of low electrical resistivity. When the impurity is boron, the impurity-doped diamond becomes a boron-doped diamond, and when the impurity is phosphorus, the impurity-doped diamond becomes a phosphorus-doped diamond.

[0028] When boron is used as the impurity in the impurity-doped diamond (in the case of a boron-doped diamond), the concentration of boron in the boron-doped diamond is preferably 1×10 20 cm -3 or more. Although the electrical resistivity of the boron-doped diamond is temperature-dependent, if the above boron concentration is 1×10 20 cm -3 or more, the electrical resistivity is low at least on the high-temperature side (for example, room temperature or higher), so it can be used as a diamond quantum sensor on the high-temperature side. The above boron concentration is 2×10 20 cm -3More preferably, it is as described above, and even more preferably 3×10 20 cm -3 or more. If the concentration of the above boron is 2×10 20 cm -3 or more, the temperature dependence of the electrical resistivity of boron-doped diamond is small, so it can be used as a diamond quantum sensor not only on the high-temperature side but also on the low-temperature side, that is, in a wide temperature range. From the perspective of the limit value of the amount of boron that can be contained in impurity-doped diamond, the concentration of the above boron may be 8×10 21 cm -3 or less.

[0029] The concentration of boron in boron-doped diamond can be determined, for example, by comparing it with the graph showing the relationship between the concentration of boron and the electrical resistivity in the boron-doped diamond in FIG. 3 of Julie V. Macpherson, “A practical guide to using boron doped diamond in electrochemical research”, Phys.Chem.Chem.Phys., 2015, 17, 2935-2949 (hereinafter referred to as this document as “Non-Patent Document 2”). Specifically, first, in FIG. 3 of Non-Patent Document 2, draw an approximate line based on the plot (see FIG. 9). Also, since the graph in FIG. 3 of Non-Patent Document 2 shows the relationship between the boron concentration and the electrical resistivity at room temperature, measure the electrical resistivity of boron-doped diamond at room temperature (for example, 25°C). Then, in FIG. 3 of Non-Patent Document 2, find the point where the measured electrical resistivity intersects the above approximate line. The boron concentration at this intersection point is taken as the boron concentration of boron-doped diamond.

[0030] The shape of the impurity-doped diamond 12 shown in FIG. 1 is rectangular, but it is not particularly limited and may be, for example, a polygonal shape such as a square or circular. When the diamond quantum sensor is for measuring the physical properties of the sample to be measured, the sample to be measured is placed on the surface of the NV center-containing diamond. However, in order to uniformly propagate microwaves through the sample to be measured, it is preferable to have an annular portion 31 as in the impurity-doped diamond 30 of the diamond quantum sensor 20 shown in FIG. 3.

[0031] The diamond quantum sensor 20 shown in FIGS. 3 and 4 includes an annular portion 31 having a notch 31A and two end portions 31B separated by the notch 31A, and a terminal portion 32 extending continuously from each end portion 31B of the annular portion 31. The sample to be measured is disposed inside the annular portion 31.

[0032] The annular portion 31 may be a substantially polygonal ring such as a triangular ring, a square ring, or a pentagonal ring, but is preferably a circular ring from the viewpoint of uniformly irradiating the sample to be measured with microwaves. When the annular portion 31 is a circular ring, the inner diameter of the annular portion 31 is preferably 1 μm or more and 1000 μm or less, although it also depends on the size of the sample to be measured.

[0033] The terminal portion 32 preferably has a portion where the width of the terminal portion 32 gradually increases toward the side opposite to the annular portion 31. The maximum width W max (see FIG. 3) is preferably 1 μm or more and 1000 μm or less. The maximum width W max of the terminal portion 32 is 1 μm or more, the connection between the terminal portion 32 and the wire can be made easily and reliably by a conductive paste. Also, when the maximum width W max of the terminal portion 32 is 1000 μm or less, the formation of unnecessary portions of the terminal portion 32 can be suppressed. The upper limit of the maximum width of the terminal portion 32 is more preferably 99 μm or less in order to lower the electrical resistance value at the connection portion between the terminal portion 32 and the wire. Note that the lower limit of the maximum width of the terminal portion 32 may be 100 μm or more.

[0034] The thickness of the impurity-doped diamond 12 is preferably 10 nm or more and 1000 nm or less. If this thickness is 10 nm or more, a low electrical resistance value can be obtained. Also, if it is 1000 nm or less, since the distance between the non-measured sample and the NV center is sufficiently close, the physical properties of the non-measured sample can be accurately measured. The lower limit of the thickness of the impurity-doped diamond 12 is more preferably 30 nm or more, 50 nm or more, or 100 nm or more. Further, the upper limit of the impurity-doped diamond 12 is not limited to the above preferred range and may be, for example, 10 μm or less, 5 μm or less, or 99 nm or less. If the thickness of the impurity-doped diamond 12 is 99 nm or less, the time of the film formation process can be shortened. The thickness of the impurity-doped diamond 12 can be measured by an atomic force microscope. Note that the thickness of the impurity-doped diamond 30 is also the same as that of the impurity-doped diamond 12.

[0035] <Method for manufacturing diamond quantum sensor> The diamond quantum sensor 10 can be manufactured as follows. First, prepare a diamond 11 containing an NV center. The diamond containing an NV center can be obtained, for example, as follows. First, a diamond is manufactured while incorporating nitrogen. Then, the nitrogen-containing diamond is annealed at a temperature of 600 °C or more and 1000 °C or less. Thereby, a nitrogen-vacancy pair is formed, and a diamond containing an NV center is formed. Alternatively, a nitrogen-containing diamond is formed on the diamond surface, and then annealed at a temperature of 600 °C or more and 1000 °C or less. Thereby, a diamond containing an NV center is formed.

[0036] Next, an impurity-doped diamond 12 is formed. Specifically, a mask made of metal or the like is formed on the surface 11A of the NV center-containing diamond 11 by, for example, a lift-off method using an electron beam lithography method. Then, a thin film of an impurity-doped diamond is formed on the NV center-containing diamond 11 on which the mask is formed by, for example, a microwave plasma chemical vapor deposition method. Specifically, as a gas for the impurity-doped diamond, for example, a mixed gas in which methane and trimethylboron are diluted with hydrogen is flowed, and an impurity-doped diamond is formed on the NV center-containing diamond 11 by epitaxial growth. When epitaxially grown, it grows while maintaining the crystal structure of diamond from the NV center-containing diamond. Then, acid cleaning using nitric acid or sulfuric acid is performed to remove the mask. Thereby, an impurity-doped diamond 12 chemically bonded to the NV center-containing diamond 11 is formed, and the diamond quantum sensor 10 is fabricated.

[0037] In the above, after forming a mask on the surface 11A of the NV center-containing diamond 11, the impurity-doped diamond 12 is formed. However, an impurity-doped diamond may be formed on the entire surface 11A of the NV center-containing diamond 11, and then unnecessary portions may be removed to form the impurity-doped diamond 12.

[0038] <<Diamond Anvil Cell Type Quantum Sensor>> When measuring the physical properties of the sample to be measured, instead of the diamond quantum sensor 10, the diamond anvil cell type quantum sensors 40 and 70 shown in FIGS. 5 and 6 may be used.

[0039] The diamond anvil cell type quantum sensor 40 includes, as shown in FIG. 5, the diamond quantum sensor 10, a diamond anvil 50 that sandwiches the sample to be measured between the diamond quantum sensors 10, and a gasket 60 disposed between the diamond quantum sensor 10 and the diamond anvil 50. Note that the diamond anvil cell type quantum sensor 40 may not include the gasket 60.

[0040] <Diamond quantum sensor> The diamond quantum sensor 10 is the same as that described in the column of the diamond quantum sensor. However, when it is used as the diamond anvil cell type quantum sensor 40, the thickness of the NV center-containing diamond 11 is preferably 0.1 mm or more. If this thickness is 0.1 mm or more, for example, sensing under a high pressure of 0.1 MPa or more and 20 GPa or less becomes possible. The lower limit of the thickness of the NV center-containing diamond 11 is more preferably 0.5 mm or more, 1 mm or more, or 2 mm or more, and the upper limit may be 2 mm or less.

[0041] <Diamond anvil> The diamond anvil 50 is, for example, a brilliants-cut diamond, and includes a flat table surface 50A at the top, a crown 50B provided on the upper side surface, a girdle 50C that is the boundary between the upper and lower parts, a pavilion 50D provided on the lower side surface, and a culet 50E having a flat surface formed at the tip of the diamond anvil 50. The flat surface of the culet 50E is pressed against the sample to be measured (not shown), and the size of the flat surface is determined to match the size of the measurement sealing space according to the shape of the sample to be measured.

[0042] <Gasket> The gasket 60 holds the state in which the sample to be measured is sandwiched between the diamond quantum sensor 10 and the diamond anvil 50, and is compressed when pressed by the flat surface portion of the culet 50E of the diamond anvil 50, maintaining the high-pressure state of the sealed space formed by the flat surface portion of the culet 50E and the wall of the through-hole 60A at the central portion of the gasket 60. For this gasket 60, a generally rectangular plate material is used, and for example, a plastic material, a ceramic material, or a metal material is used. The through-hole 60A is provided in the central portion of the gasket 60. When pressed at high pressure by the flat surface portion of the culet 50E, the peripheral portion of the through-hole 60A is crushed to form a sealed space inside. The sample to be measured is accommodated in this sealed space and its physical properties under high-pressure conditions are evaluated.

[0043] As shown in FIG. 6, the diamond anvil cell type quantum sensor 70 includes a diamond quantum sensor 80, a diamond anvil 50 that sandwiches the sample to be measured between the diamond quantum sensors 80, and a gasket 60 disposed between the diamond quantum sensor 80 and the diamond anvil 50. Note that the diamond anvil cell type quantum sensor 70 may not include the gasket 60.

[0044] <Diamond quantum sensor> The shape of the diamond quantum sensor 80 is different from the shape of the diamond quantum sensor 10. Specifically, the NV center-containing diamond 81 of the diamond quantum sensor 80 shown in FIG. 6 is, for example, a brilliante-cut diamond, and has a table surface 81A with a flat top, a crown 81B provided on the lower side surface, a girdle 81C that is the boundary between the upper and lower parts, a pavilion 81D provided on the upper side surface, and a culet 81E having a flat surface portion formed at the tip of the NV center-containing diamond 81.

[0045] The impurity-doped diamond 82 of the diamond quantum sensor 80 has, similar to the impurity-doped diamond 30, an annular portion 82A having a notch and two end portions separated by the notch, and terminal portions 82B extending continuously from each end portion of the annular portion 82A. Since the annular portion 82A is the same as the annular portion 31 and the terminal portions 82B are the same as the terminal portions 32, the description thereof will be omitted here.

[0046] <<Measurement Device>> The diamond quantum sensor 10 is incorporated into and used in a measurement device 90 shown in FIG. 7. Note that not only the diamond quantum sensor 10 but also the diamond quantum sensors 20, and the diamond anvil cell type quantum sensors 40, 70 can be incorporated into the measurement device 90. The measurement device 90 measures, for example, magnetism, temperature, physical properties of a sample to be measured, and the like.

[0047] As shown in FIG. 7, the measurement device 90 includes the diamond quantum sensor 10, a green laser light irradiation system 100 that irradiates the NV center with green laser light for exciting the NV center, a microwave introduction system 110 that introduces microwaves into the impurity-doped diamond, and a detection system 120 that detects red light emitted from the NV center.

[0048] <Green Laser Light Irradiation System> The green laser light irradiation system 100 includes a laser light source 101 that generates green laser light, an acousto-optic modulator (AOM) 102, a half mirror 103, a Galilean beam expander (GBE) 104, and an objective lens 105. The green laser light irradiation system 100 may not include other members as long as it includes the laser light source 101. The AOM 102 has a function of modulating the green laser light by diffracting it into only the primary light component, and the GBE 104 has a function of adjusting the beam diameter.

[0049] <Microwave Introduction System> The microwave introduction system 110 includes a microwave generation source (SG) 111, an amplifier 112, a wire 113, and a conductive paste (not shown). The wire 113 is for electrically connecting the microwave generation source 111 and the impurity-doped diamond 12, and the conductive paste is for fixing the wire 113 to the impurity-doped diamond 12 and electrically connecting them.

[0050] <<Detection system>> The detection system 120 includes a dichroic mirror 121, a low-pass filter 122, and a CCD camera 123. The dichroic mirror 121 has a function of transmitting green laser light and reflecting only the red light emitted from the NV center, and the low-pass filter 122 has a function of transmitting only the red light from the NV center.

[0051] In such a measuring device 90, first, the green laser light generated from the laser light source 101 is irradiated onto the diamond 11 containing the NV center of the diamond quantum sensor 10 through the AOM 102, the half mirror 103, the GBE 104, the dichroic mirror 121, and the objective lens 105. When the diamond 11 containing the NV center is irradiated with the green laser light, only the red light from the NV center excited by the green laser light is reflected by the dichroic mirror 121 and imaged by the CCD camera 123 through the low-pass filter 122.

[0052] On one hand, the microwave signal generated by the microwave source 111 is amplified by the amplifier 112 and transmitted to the impurity-doped diamond 12 of the diamond quantum sensor 10. Here, while irradiating the NV center with green laser light and sweeping the microwave frequency around 2.87 GHz, a dip where the emission intensity decreases is confirmed, and the frequency at this time is the magnetic resonance frequency. When the magnetic field applied to the NV center is zero, mS = ±1 among the spin triplet energy levels of the NV center is degenerate, and the dip is single. When a magnetic field is applied, the dip splits into magnitudes corresponding to the applied magnetic field. Thereby, the magnetic field of the surrounding environment can be measured.

[0053] According to this embodiment, since the impurity-doped diamond 12 is chemically bonded to the NV center-containing diamond 11, it is mechanically and chemically stable. Therefore, it is possible to suppress disconnection due to secular deterioration such as shape change like an MW wire and metal fatigue, and it is possible to suppress the position with respect to the NV center-containing diamond 11 from changing every measurement. Thereby, it is excellent in durability and reproducibility.

[0054] Since the impurity-doped diamond can obtain a desired shape by patterning using a microfabrication technique such as lithography, the impurity-doped diamond 12 can be fabricated in a shape suitable for the diamond quantum sensor 10.

Example

[0055] To describe the present invention in detail, examples will be given below for illustration, but the present invention is not limited to these descriptions. FIG. 8 is an optical micrograph of the diamond quantum sensor according to Example 1, FIG. 9 is a graph used to calculate the boron concentration of the boron-doped diamond of the diamond quantum sensors according to Examples 2 to 4, FIG. 10 is a graph showing the relationship between the temperature and the electrical resistivity of the diamond quantum sensors according to Examples 3 to 5, and FIG. 11 is a graph showing the result of sensing magnetism with the magnetic sensing measurement device according to Example 5. FIG. 12 is a configuration diagram of the Rabi oscillation measurement device, FIG. 13 is a mapping diagram of the Rabi oscillation frequency when the Rabi oscillation frequency is measured at each point inside the annular portion of the diamond quantum sensor according to Example 2, FIG. 14A is a graph of the Rabi oscillation frequency at position 4 in FIG. 13, and FIG. 14B is a graph of the Rabi oscillation frequency at position 55 in FIG. 13. FIG. 15 is a graph showing the Rabi oscillation frequency with respect to the boron concentration of the diamond quantum sensors according to Examples 2 to 4.

[0056] <Example 1> In Example 1, two types of boron-doped diamonds with different shapes were fabricated on an NV center-containing diamond substrate to fabricate a diamond quantum sensor.

[0057] The method for fabricating the microwave waveguide made of boron-doped diamond was as follows. First, an NV center-containing diamond substrate was prepared. Here, the NV center-containing diamond (manufactured by Element Six) is a (100)-oriented nitrogen-containing diamond substrate, which was fabricated by chemical vapor deposition (CVD). The size of the NV center-containing diamond was 3.0 mm in length × 3.0 mm in width × 0.5 mm in thickness.

[0058] Next, using the microwave plasma chemical vapor deposition (MPCVD) method, a thin film of boron-doped diamond was formed on the NV center-containing diamond. First, the NV-containing diamond was boiled and washed with a mixed acid obtained by mixing nitric acid and sulfuric acid at a ratio of 1:3 and heating it to 200°C. Then, a metal mask for forming boron-doped diamond composed of titanium and gold was formed by a lift-off process using electron beam lithography. Thereafter, the NV center-containing diamond with the metal mask was annealed at 450°C for 1 hour in a vacuum atmosphere.

[0059] Thereafter, under the conditions of a chamber pressure of 70 Torr (9332 Pa), a microwave power of 500 W, and a substrate temperature of 500 to 600°C, a thin film of boron-doped diamond was formed using a mixed gas of trimethylboron diluted with methane and hydrogen. The concentration of boron with respect to carbon in the source gas was 3%. After 60 minutes of deposition, a thin film with a thickness of approximately 1 μm was obtained. The boron concentration in the formed boron-doped diamond was about 1×10 21 cm -3 . The boron concentration was calculated by the same method as the method described in Examples 2 to 4 described later.

[0060] Thereafter, by dissolving the metal mask composed of titanium and gold by acid cleaning using a mixed acid obtained by mixing nitric acid and sulfuric acid at a ratio of 1:3 and heating it to 200°C, two types of thin-film boron-doped diamonds functioning as microwave conduction paths were formed.

[0061] One of the boron-doped diamonds was rectangular as shown in FIG. 8. The other boron-doped diamond included an annular portion having a notch and two end portions separated by the notch, and terminal portions continuously extending from each end portion of the annular portion. These boron-doped diamonds were fabricated using metal masks of different shapes.

[0062] <Examples 2 to 4> In Examples 2 to 4, the temperature dependence of the electrical resistivity of boron-doped diamond prepared by varying the boron concentration was evaluated. Specifically, in the MPCVD process of the process of preparing boron-doped diamond, except that the flow rate of trimethylboron gas diluted with hydrogen was changed to 7 sccm (Example 2), 2 sccm (Example 3), and 1 sccm (Example 4) to prepare boron-doped diamond functioning as a microwave waveguide, a diamond quantum sensor including a notch and an annular portion having two end portions separated by the notch, and terminal portions continuously extending from each end portion of the annular portion was obtained by the same procedure as in Example 1.

[0063] In the diamond quantum sensors according to Examples 2 to 4, when the boron concentration of the boron-doped diamond was measured, in Example 2, the boron concentration was about 3×10 21 cm -3 , in Example 3, the boron concentration was about 4×10 20 cm -3 , and in Example 4, the boron concentration was about 1×10 20 cm -3 .

[0064] The boron concentration was calculated as follows. First, in FIG. 3 of Non-Patent Document 2, an approximate line was drawn based on the plot (see FIG. 9). Also, the electrical resistivity of the formed boron-doped diamond at room temperature (25°C) was measured. Specifically, a gold wire was attached to the formed boron-doped diamond using silver paste and connected to a measuring device, and the electrical resistivity at each temperature was measured. A PPMS device (manufactured by Quantum Design) was used for the measurement of the electrical resistivity and the temperature control. Then, in FIG. 9, the point where the measured electrical resistivity intersects the above approximate line was found, and the boron concentration at this intersection point was taken as the boron concentration of the formed boron-doped diamond.

[0065] In addition, in the diamond quantum sensors according to Examples 2 to 4, when the electrical resistivity at each temperature when the temperature was changed was measured, the results shown in FIG. 10 were obtained. A PPMS device (manufactured by Quantum Design) was used for the measurement of the electrical resistivity and the temperature control.

[0066] From the results of Examples 2 and 3 in FIG. 10, it can be seen that the electrical resistivity of boron-doped diamond with a boron concentration of 3×10 20 cm -3 or more hardly changes from room temperature to extremely low temperature. That is, in the diamond quantum sensors according to Examples 2 and 3, since microwaves can be stably propagated with respect to temperature changes, microwaves can be propagated in a wide temperature range. On the other hand, from the results of Example 4 in FIG. 10, it can be seen that the electrical resistivity of boron-doped diamond with a boron concentration of 1×10 20 cm -3 or less increases exponentially with decreasing temperature. That is, in the diamond quantum sensor according to Example 4, microwaves can be induced only on the high-temperature side. As these data show, considering use in a wide temperature range, it can be said that diamond doped with boron at a high concentration of 3×10 20 cm -3 or more is preferable.

[0067] <Optical Detection Magnetic Resonance Measurement> Using the rectangular diamond quantum sensor according to Example 1, a magnetic sensing test was conducted. The magnetic sensing measurement device had the same configuration as that in FIG. 7. Specifically, the green laser light with a wavelength of 532 nm generated from a laser light source (Coherent's "Verdi G5") was modulated by an acousto-optic modulator (AOM) (manufactured by Gooch & Housego) into only the first-order light component, and was guided through a half mirror to a Galilean beam expander (GBE) (manufactured by Thorlab), and adjusted to a desired beam diameter. The green laser light was irradiated onto the diamond containing the NV center through a dichroic mirror and an objective lens. Only the red light derived from the NV center excited by the green laser light was reflected by the dichroic mirror and detected by a CCD camera through a low-pass filter. At the same time, the microwave signal generated by a microwave source (manufactured by Keysight) was amplified by an amplifier, and the microwave was transmitted to the boron-doped diamond of the diamond quantum sensor according to Example 1.

[0068] Using the above measurement device, optically detected magnetic resonance (ODMR) measurement, which is the most common sensing method by the NV center, was carried out. The results are shown in FIG. 11. When the microwave frequency was swept around 2.87 GHz while irradiating the NV center with the green laser light, a dip where the emission intensity decreased was observed. The frequency at this time was the magnetic resonance frequency. When the magnetic field applied to the NV center was zero as described above, the dip was single, but as shown in FIG. 11, it was clearly seen from the ODMR results that the dip split under the influence of the geomagnetism. Therefore, it was confirmed that the measurement device of Example 5 can perform magnetic field sensing by the NV center using the boron-doped diamond.

[0069] <Rabi Oscillation Frequency Measurement (1)> Using the diamond quantum sensor including an annular portion and a terminal portion according to Example 2, a Rabi oscillation measurement test was conducted. The Rabi oscillation measurement device 130 was configured as shown in FIG. 12. First, the green pulsed laser light with a wavelength of 532 nm generated from the laser light source (CNI laser "MGL-III-532-200mW", "PSU-III-FDA") 131 shown in FIG. 12 passed through the mirror 132, the quarter-wave plate 133, the p-polarized beam splitter (PBS) 134, and the lens 135, and then was modulated by the acousto-optic modulator (AOM) 136 only for the primary light component. The green laser light modulated only for the primary component passed through the iris 137, the lens 138, and the λ / 2 plate 139, was reflected by the mirror 140, passed through the AOM 136 again, was reflected by the mirrors 141 and 142, and was introduced into the optical fiber 143. Then, the green pulsed laser light extracted from the optical fiber 143 passed through the low-pass filter 144, was reflected by the mirror 145, and then passed through the λ / 2 plate 146, the λ / 4 plate 147, the p-polarized beam splitter (PBS) 148, the λ / 4 plate 149, and the mirror 150, and was irradiated to the region inside the annular portion of the NV center-containing diamond S according to Example 2 through the dichroic mirror 151 and the objective lens 152. Only the red light derived from the NV center excited by the green pulsed laser light was reflected by the dichroic mirror 151, passed through the confocal system of the two low-pass filters 153 and 154, the mirrors 155, the lenses 156, 158, 159, and the pinhole 157, and then was detected by the avalanche photodiode (APD, "SPCM-780-33-BR1" manufactured by Excelitas Technologies) 160. At the same time, the microwave signal generated by the microwave signal source ("AWG 70002A" manufactured by Tektronics and "SMW200A" manufactured by Rohde&Schwarz) 161 was amplified by the amplifier 162, and the microwave was transmitted to the boron-doped diamond S of the diamond quantum sensor according to Example 2.

[0070] Using the above Rabi oscillation measurement device, a Rabi oscillation frequency measurement test was conducted in the region inside the annular portion of the diamond quantum sensor according to Example 2. Here, as shown in FIG. 13, the region inside the annular portion of the diamond quantum sensor according to Example 2 was divided into 10×10, numbered starting from the upper left as the first, and numbered so that the numbers increase as moving rightward and downward. When the Rabi oscillation frequency was measured at each position, the Rabi oscillation frequency was the highest at the fourth position near the peripheral edge of the annular portion, which was 21.8 MHz, and the lowest at the 55th position near the center of the annular portion, which was 7.48 MHz. Therefore, a Rabi oscillation frequency about three times faster was observed near the peripheral edge of the annular portion than near the center of the annular portion, and it was confirmed that quantum operations are possible using the diamond quantum sensor according to Example 2. Also, differences due to the intensity of the applied magnetic field and the position of its gradient could be confirmed from the center to the peripheral edge of the annular portion. Note that FIG. 13 was created based on the measurement results of the Rabi oscillation frequency such as FIGS. 14A and 14B, and the white portions in FIG. 13 are locations where red light could be observed but the Rabi oscillation frequency could not be calculated due to the influence of noise or the like.

[0071] <Rabi Oscillation Frequency Measurement (2)> Using diamond quantum sensors having annular portions and terminal portions with different boron concentrations according to Examples 2 to 4, respective Rabi oscillation frequency measurement tests were conducted. As the Rabi oscillation measurement device, the Rabi oscillation measurement device 130 used in the above Rabi oscillation frequency measurement (1) was used. The measurement position was the center of the annular portion of the diamond quantum sensor in each case.

[0072] The results are shown in FIG. 15. From FIG. 15, it was measured that the higher the boron concentration of the diamond quantum sensor, the higher the Rabi oscillation frequency.

Explanation of Reference Numerals

[0073] 10, 20, 80... Diamond quantum sensor 11... NV center-containing diamond 12, 30... Impurity-doped diamond 31…Annular part 31A…Notch part 31B…End part 32…Terminal part 40, 70…Diamond anvil cell type quantum sensor 50…Diamond pressure device 60…Gasket 90…Measuring device

Claims

1. A nitrogen-vacancy center-containing diamond including a nitrogen-vacancy center, and an impurity-doped diamond functioning as a microwave induction path for inducing microwaves in the nitrogen-vacancy center, comprising: The diamond quantum sensor, wherein the impurity-doped diamond has conductivity and is chemically bonded to the nitrogen-vacancy center-containing diamond.

2. The diamond quantum sensor according to claim 1, wherein the impurity in the impurity-doped diamond is boron.

3. The concentration of the boron in the impurity-doped diamond is 1×10 ２０ cm －３ or more. The diamond quantum sensor according to claim 2.

4. The diamond quantum sensor according to any one of claims 1 to 3, wherein the impurity-doped diamond includes an annular portion having a notch and two end portions separated by the notch, and terminal portions continuously extending from each of the end portions of the annular portion.

5. The diamond quantum sensor according to claim 4, wherein the annular portion is circular.

6. A diamond quantum sensor according to any one of claims 1 to 5, and a diamond anvil cell disposed on the surface side of the impurity-doped diamond and sandwiching a sample to be measured with the diamond quantum sensor. A diamond anvil cell type quantum sensor comprising:

7. A diamond quantum sensor according to any one of claims 1 to 5 or a diamond anvil cell type quantum sensor according to claim 6, and a green laser light irradiation system for irradiating the nitrogen-vacancy center with green laser light that excites the nitrogen-vacancy center, a microwave introduction system for introducing microwaves into the impurity-doped diamond, a detection system for detecting red light emitted from the nitrogen-vacancy center. A measuring device comprising:

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