Quantum chem

Abstract

To provide a quantum sensor with a simple structure. [Solution] The quantum sensor comprises an element body layer having a color center, a signal line, and a ground line. The signal line has a first parallel line and a second parallel line that extend in parallel and through which high-frequency currents flow in parallel. When the element body layer is viewed from above, at least one color center is located within the opening between the first parallel line and the second parallel line in the element body layer.

Description

[Technical Field]

[0001] The technologies disclosed herein relate to quantum sensors. [Background technology]

[0002] Development is underway on quantum sensors that detect physical quantities (e.g., magnetic fields, electric fields, temperature, or pressure) using optically detected magnetic resonance (ODMR). Patent document 1 discloses an example of this type of quantum sensor. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-128554 [Overview of the project] [Problems that the invention aims to solve]

[0004] In quantum sensors utilizing photodetection magnetic resonance, an alternating magnetic field is applied to the element body layer containing the color center in order to excite the electrons present in the color center. It is desirable that the alternating magnetic field be applied in a direction parallel to the main surface of the element body layer. Patent Document 1 discloses a technique for applying an alternating magnetic field in a direction parallel to the main surface of the element body layer by passing high-frequency currents with opposite phases through a pair of coils arranged vertically above and below the element body layer. However, such quantum sensors suffer from the problem of having a complex structure. This specification aims to provide a quantum sensor with a simple structure. [Means for solving the problem]

[0005] The quantum sensor disclosed herein may comprise an element body layer having a color center, a signal line, and a ground line. The signal line may have a first parallel line and a second parallel line extending in parallel and carrying high-frequency currents in parallel. When the element body layer is viewed from above, at least the color center may be provided within an opening between the first parallel line and the second parallel line in the element body layer.

[0006] When high-frequency currents flow in parallel through the first and second parallel transmission lines, which extend parallel to each other, an alternating magnetic field is applied to the element body layer directly below the aperture between the first and second parallel transmission lines, in a direction parallel to the main surface of the element body layer. In the above quantum sensor, a color center exists in the element body layer directly below the aperture. Therefore, electrons present in the color center are excited by the alternating magnetic field applied in a direction parallel to the main surface of the element body layer. Furthermore, the above quantum sensor can allow at least one of the excitation light irradiated onto the color center and the fluorescence emitted from the color center to pass through the aperture between the first and second parallel transmission lines. Thus, the above quantum sensor has the necessary functions to utilize photodetection magnetic resonance and has a simple structure. [Brief explanation of the drawing]

[0007] [Figure 1] This diagram illustrates the operating principle of detecting physical quantities using optical magnetic resonance. [Figure 2] This diagram provides a schematic overview of the configuration of a quantum sensor system. [Figure 3] This figure schematically shows a plan view of a quantum sensor according to one embodiment. [Figure 4] This is a cross-sectional view of a quantum sensor according to one embodiment, schematically showing the cross-sectional view corresponding to line IV-IV in Figure 3. [Figure 5] This is a cross-sectional view of a quantum sensor according to one embodiment, schematically showing a cross-sectional view corresponding to the VV line in Figure 3. [Figure 6] This figure shows an example of how the excitation light generation unit and the photodetector unit are connected to the quantum sensor 10. [Figure 7]It is a diagram showing an example in which an excitation light generation unit and a light detection unit are connected to a quantum sensor 10. [Figure 8] It is a diagram showing an example in which an excitation light generation unit and a light detection unit are connected to a quantum sensor 10. [Figure 9] It is a diagram for explaining an alternating magnetic field generated around a signal line. [Figure 10] It is a diagram showing an example in which a quantum sensor is arranged directly below an object to be measured. [Figure 11] It is a diagram schematically showing a (A) plan view and a (B) cross-sectional view of a modified example of a quantum sensor. [Figure 12] It is a diagram schematically showing a (A) plan view and a (B) cross-sectional view of a modified example of a quantum sensor. [Figure 13] It is a diagram schematically showing a (A) plan view and a (B) cross-sectional view of a modified example of a quantum sensor. [Figure 14] It is a diagram schematically showing a plan view of a quantum sensor having a modified example of a signal line. [Figure 15] It is a diagram schematically showing a cross-sectional view of a quantum sensor having a modified example of a signal line.

Mode for Carrying Out the Invention

[0008] (Operating Principle of Photo-Detection Magnetic Resonance) Before explaining the configuration of the quantum sensor disclosed in this specification, the operating principle of detecting a physical quantity using photo-detection magnetic resonance will be explained. Hereinafter, the case where the magnetic resonance material is diamond and the physical quantity to be measured is an external magnetic field will be described as an example.

[0009] FIG. 1 shows the energy levels of the NV center of diamond. The electrons existing in the NV center form an electron spin triplet state of m s = 0, +1, -1. The electrons in the ground state are excited by green excitation light of 515 nm. The electrons in the excited state are relaxed to the ground state by a direct transition accompanied by red light emission of 637 nm or an indirect transition (i.e., a non-light-emitting process) via a spin singlet state. m sElectrons in the state of m = 0 are highly likely to relax to the ground state by direct transition. On the other hand, s electrons in the state of m = ±1 have a higher probability of relaxing to the ground state via a non-radiative process than electrons in the state of m s = 0. Therefore, when the ground state is m s = 0, the luminescence during relaxation is strong, and when the ground state is m s = ±1, the luminescence during relaxation is weak.

[0010] Here, when no external magnetic field is applied, as shown in Fig. 1(a), the states of electrons with m s = ±1 are degenerate. In this case, the resonance frequencies when the ground state of the electron is excited from m s = 0 to m s = ±1 are both 2.87 GHz. Therefore, as shown in Fig. 1(c), the luminescence intensity is observed to be weak at the resonance frequency of f + = f - . On the other hand, when an external magnetic field is applied, as shown in Fig. 1(b), the degeneracy of the states of electrons with m s = +1 and m s = -1 is lifted by the Zeeman splitting. In this case, the resonance frequency f s when the ground state of the electron is excited from m s = 0 to m + = +1 becomes a frequency higher than 2.87 GHz, and the resonance frequency f s when the ground state of the electron is excited from m s = 0 to m - = -1 becomes a frequency lower than 2.87 GHz. Therefore, as shown in Fig. 1(d), the luminescence intensity is observed to be weak at each of the two resonance frequencies f + , f - . The difference between the two resonance frequencies (f + - f - ) is proportional to the magnitude of the external magnetic field.

[0011] A quantum sensor utilizing optical magnetic resonance measures the strength of an external magnetic field based on the above operating principle. The quantum sensor applies an external magnetic field, irradiates a diamond NV center with green excitation light, and sweeps with microwaves. It acquires the ODMR spectrum of the red fluorescence emitted from the NV center and measures the strength of the external magnetic field based on the resonance frequency of the acquired ODMR spectrum. An embodiment of the quantum sensor based on the above operating principle is described below. Note that the operating principle for detecting physical quantities remains the same even when the magnetic resonance material is a material other than diamond (e.g., silicon carbide), and even when the physical quantity being measured is a physical quantity other than an external magnetic field. For example, if the physical quantity is temperature, the temperature change is m s =0 state and m s Because it causes a change in the magnitude of the energy difference in the ±1 state, i.e., a shift in the resonance frequency, it can be measured in the same way as an external magnetic field.

[0012] (Configuration of the quantum sensor system) As shown in Figure 2, the quantum sensor system 1 comprises a quantum sensor 10, an excitation light generation unit 20, a high-frequency signal generation unit 30, a photodetection unit 40, and a control unit 50.

[0013] The quantum sensor 10 is a sensor element that includes a magnetic resonance material having a color center, as will be described later. The quantum sensor 10 is not particularly limited, but may be attached to the tip of a sensor probe, for example, or it may be integrated into a device such as a power device.

[0014] The excitation light generation unit 20 is configured to generate excitation light and irradiate the quantum sensor 10 with the generated excitation light. The excitation light generation unit 20 may include a light source such as a light-emitting diode.

[0015] The high-frequency signal generation unit 30 is configured to generate a high-frequency current for generating microwaves and to supply the generated high-frequency current to the quantum sensor 10. The high-frequency signal generation unit 30 may also include, for example, a high-frequency signal source.

[0016] The photodetector 40 is configured to detect fluorescence emitted from the color center. The photodetector 40 may include, for example, a photodetector such as a photodiode.

[0017] The control unit 50 controls the operation of the excitation light generation unit 20, the high-frequency signal generation unit 30, and the photodetection unit 40. The control unit 50 may be composed of a computer having, for example, memory and an arithmetic unit. The memory stores a physical quantity detection program. The arithmetic unit is composed of a microprocessor including a CPU. The arithmetic unit performs the physical quantity detection process by executing the physical quantity detection program stored in the memory.

[0018] As shown in Figures 3 to 5, the quantum sensor 10 includes an element body layer 12 having a color center 18 (i.e., a light-emitting point defect), a signal line 14, and a ground line 16. The quantum sensor 10 in this example is configured as a microstrip line. The material of the element body layer 12 is not particularly limited, but may be, for example, diamond having NV centers consisting of substituted nitrogen and vacancies, or silicon carbide (SiC) having VSi centers of silicon vacancies. The element body layer 12 is a flat plate-shaped member and has a first main surface S1 and a second main surface S2. The signal line 14 and the ground line 16 are not particularly limited, but may be metal foils such as aluminum. The signal line 14 and the ground line 16 are not particularly limited, but may be formed by depositing a film on the surface of the element body layer 12 using, for example, sputtering or vapor deposition technology.

[0019] Here, for the sake of explanation, we define a coordinate system. The direction parallel to the first principal plane S1 and the second principal plane S2 is defined as the X direction, the direction parallel to the first principal plane S1 and the second principal plane S2 and perpendicular to the X direction is defined as the Y direction, and the direction perpendicular to both the X and Y directions is defined as the Z direction. Furthermore, the first principal plane S1 is defined as the top surface, and the second principal plane S2 is defined as the bottom surface.

[0020] The signal line 14 is arranged on a part of the first main surface S1 of the element body layer 12. The signal line 14 extends linearly along the Y direction, from one side to the other of the element body layer 12 in the Y direction. The signal line 14 has a first end 22 and a second end 24 at both ends in the Y direction. A high-frequency current generated by the high-frequency signal generation unit 30 is input to either the first end 22 or the second end 24. Therefore, the high-frequency current transmitted through the signal line 14 flows in the direction connecting the first end 22 and the second end 24, that is, along the Y direction.

[0021] An opening 15 is formed in the signal line 14 in a portion between the first end 22 and the second end 24. The opening 15 is not particularly limited, but may be a rectangular shape with its longer side extending in the Y direction, for example. A first parallel line 14a is arranged on one side of the opening 15 in the X direction, and a second parallel line 14b is arranged on the other side of the opening 15 in the X direction. The first parallel line 14a and the second parallel line 14b extend parallel to each other with the opening 15 in between. In this example, each of the first parallel line 14a and the second parallel line 14b further extends in a straight line parallel to the longitudinal direction of the signal line 14, i.e., the Y direction. The first parallel line 14a and the second parallel line 14b are identical in shape and are symmetrical with respect to the center line of the signal line 14 extending in the Y direction.

[0022] The width 15W of the aperture 15 (see Figure 3), measured in a direction perpendicular to the direction of the high-frequency current flowing through the signal line 14, i.e., along the X direction, is appropriately adjusted according to the wavelength of the high-frequency current transmitted through the signal line 14. The width 15W of the aperture 15 is not particularly limited, but may be as large as, for example, several tens of micrometers.

[0023] A color center 18 exists in at least a portion of the element body layer 12. When the element body layer 12 is viewed from above, that is, when viewed from the Z direction, the color center 18 is at least located within the opening 15 of the signal line 14 within the element body layer 12. Furthermore, the color center 18 is formed closer to the first main surface S1 than to the second main surface S2 within the element body layer 12. More specifically, the color center 18 is formed in the area of ​​the element body layer 12 that includes the first main surface S1.

[0024] The grounding line 16 is arranged across the entire surface of the second main surface S2 of the element body layer 12. The grounding line 16 is fixed at GND potential.

[0025] Figures 6 to 8 show connection examples in which the excitation light generation unit 20 and the photodetector unit 40 are connected to the quantum sensor 10. In the quantum sensor 10, at least one of the excitation light emitted from the excitation light generation unit 20 and the fluorescence emitted from the color center 18 passes through the aperture 15 of the signal line 14. The example in Figure 6 is one in which both the excitation light and fluorescence pass through the aperture 15 of the signal line 14. The excitation light and fluorescence may be separated using an optical system such as a beam splitter 60. The example in Figure 7 is one in which the excitation light passes through the aperture 15 of the signal line 14 and the fluorescence passes through the side surface of the element body layer 12. The example in Figure 8 is one in which the fluorescence passes through the aperture 15 of the signal line 14 and the excitation light passes through the side surface of the element body layer 12.

[0026] (Effects of quantum sensors) As shown in Figure 9, when the high-frequency current generated by the high-frequency signal generation unit 30 propagates through the signal line 14, an alternating magnetic field is generated within the element body layer 12. In the basic mode (i.e., the lowest-order propagation mode) of the signal line 14, which is a planar waveguide, the alternating magnetic field is generated to circulate around the signal line 14, as indicated by the dashed arrow. As described above, the width 15W of the aperture 15 of the signal line 14 is appropriately adjusted according to the wavelength of the high-frequency current transmitted through the signal line 14, and is adjusted to be sufficiently small. As a result, even though an aperture 15 is formed in the signal line 14, an alternating magnetic field is generated in the element body layer 12 directly below the aperture 15 in a direction parallel to the main surfaces S1 and S2 of the element body layer 12, that is, in a direction parallel to the XY plane. In the quantum sensor 10, a color center 18 exists in the element body layer 12 directly below the aperture 15. Therefore, an alternating magnetic field is applied to the electrons present in the color center 18 in a direction parallel to the XY plane. Furthermore, in the quantum sensor 10, the signal line 14 and the color center 18 are located in close proximity. As a result, the amplitude of the alternating magnetic field is large and applied to the color center 18 without significant attenuation.

[0027] For the alternating magnetic field applied to the element body layer 12 directly below the aperture 15 to be parallel to the XY plane, it is desirable that the phases of the high-frequency current propagating through the first parallel line 14a and the high-frequency current propagating through the second parallel line 14b coincide in the X direction. In other words, it is desirable that no electric field is generated between the first parallel line 14a and the second parallel line 14b. In the quantum sensor 10, when the element body layer 12 is viewed from above, the first parallel line 14a and the second parallel line 14b have the same shape. Therefore, the above state is obtained in the quantum sensor 10, and the alternating magnetic field applied to the element body layer 12 directly below the aperture 15 is parallel to the XY plane.

[0028] Furthermore, in the quantum sensor 10, as shown in Figures 6 to 8, at least one of the excitation light irradiated from the excitation light generation unit 20 and the fluorescence emitted from the color center 18 passes through the aperture 15 of the signal line 14. Therefore, when the excitation light passes through the aperture 15 of the signal line 14, it becomes possible to efficiently irradiate the color center 18 with the excitation light. When the fluorescence passes through the aperture 15 of the signal line 14, it becomes possible to detect the fluorescence emitted from the color center 18 with high sensitivity.

[0029] Thus, the quantum sensor 10 has the necessary functions to utilize photodetection magnetic resonance and has a simple structure. Furthermore, because of its simple structure, the quantum sensor 10 can be placed close to the object to be measured. For example, as shown in Figure 10, the quantum sensor 10 can be placed directly below the object to be measured. In this case, the distance between the color center 18 and the object to be measured is shortened, and the physical quantity being measured (e.g., magnetic field) can be detected with high sensitivity.

[0030] The quantum sensor 10 is not limited to being placed directly beneath the object to be measured; the object to be measured may be integrated with the element body layer 12. The material of the element body layer 12 is the same as that of the semiconductor layer of a power device, such as diamond or silicon carbide. Therefore, by forming the signal line 14 and the ground line 16 in the region of interest within the semiconductor layer of the power device, the quantum sensor 10 can be integrated into the semiconductor layer of the power device. Thus, because the quantum sensor 10 has a simple structure, it can be integrated into other devices.

[0031] The quantum sensor 10 generates an alternating magnetic field using a waveguide-type transmission line. Compared to conventionally used resonator structures (i.e., antennas), such waveguide-type transmission lines have a wider frequency range over which impedance matching is possible. Therefore, the quantum sensor 10 can handle cases where the difference between two resonance frequencies (see Figure 1) is wide, and has the characteristic of having a wide detection range for physical quantities.

[0032] The quantum sensor 10 is configured as a microstrip line, and its characteristic impedance can be designed based on the line width of the signal line 14 and the thickness of the element body layer 12. Compared to conventionally used resonant structures (i.e., antennas), it has a small structure while still being able to sufficiently suppress the reflection of high-frequency currents from several hundred MHz to several GHz. For example, conventionally used resonant structures (i.e., antennas) require a size of several millimeters to several centimeters to suppress the reflection of high-frequency currents from several hundred MHz to several GHz. On the other hand, waveguide-type transmission lines can suppress the reflection of high-frequency currents from several hundred MHz to several GHz even with a line width of tens of micrometers to several hundred micrometers.

[0033] (Variable example of a quantum sensor) The following are examples of several variations of the quantum sensor. Components that share common functions with the quantum sensor 10 described above are denoted by the same reference numeral, and their explanations are omitted. Furthermore, the features of each variation described below can be combined as appropriate.

[0034] The quantum sensor 10A shown in Figure 11 and the quantum sensor 10B shown in Figure 12 are configured as coplanar lines. Quantum sensors 10A and 10B configured as coplanar lines can have their characteristic impedance designed based on the ratio of the line width of the signal line 14 to the distance between the signal line 14 and the ground line 16. Therefore, quantum sensors 10A and 10B are useful when there is no flexibility in the thickness of the element body layer 12. Alternatively, as shown in the quantum sensor 10C in Figure 13, they may be configured as grounded coplanar lines.

[0035] The quantum sensor 10D shown in Figure 14 is configured such that the first parallel line 14a and the second parallel line 14b extend over the entire range between the first end 22 and the second end 24 of the signal line 14. Therefore, the opening 15 formed in the signal line 14 also extends over the entire range between the first end 22 and the second end 24 of the signal line 14. A quantum sensor 10D having a signal line 14 configured in this way can secure a wide sensing area.

[0036] The quantum sensor 10E shown in Figure 15 is configured with a signal line 14 embedded within the element body layer 12. Alternatively, a ground line 16 may be embedded within the element body layer 12, or both the signal line 14 and the ground line 16 may be embedded within the element body layer 12. A quantum sensor 10E with such a configuration can also exhibit the same effects as the quantum sensor described above.

[0037] In each of the quantum sensors described above, the aperture 15 formed in the signal line 14 was rectangular. Various shapes can be used for the aperture 15. The shape of the aperture 15 may be, for example, circular, elliptical with the signal propagation direction as the major axis, rhombic, or elongated, meandering along the signal propagation direction. When the width 15W of the aperture 15 (see Figure 3) is constant along the signal propagation direction (for example, when the aperture 15 is rectangular), the distribution of the AC magnetic field applied to the element body layer 12 directly below the aperture becomes uniform. Therefore, the sensing position can be arbitrarily set within the aperture 15.

[0038] The following summarizes the features of the technology disclosed in this specification. Note that each of the technical elements described below is an independent technical element, and exhibits technical usefulness either individually or in various combinations.

[0039] (Aspect 1) It is a quantum sensor, A main element layer having a color center, It comprises a signal line and a grounding line, The aforementioned signal line has a first parallel line and a second parallel line that extend in parallel and through which high-frequency currents flow in parallel. A quantum sensor wherein, when the element body layer is viewed in plan view, at least the color center is located within the opening between the first parallel line and the second parallel line in the element body layer.

[0040] (Aspect 2) It also includes a light detection unit, The quantum sensor according to embodiment 1, wherein the light detection unit is configured to detect the fluorescence emitted from the color center that has passed through the aperture.

[0041] (Aspect 3) It is further equipped with an excitation light generation unit, The quantum sensor according to embodiment 1 or 2, wherein the excitation light generating unit is configured to irradiate the color center with excitation light by passing it through the aperture.

[0042] (Aspect 4) The element body layer has a first main surface and a second main surface, The signal line is arranged on the first main surface of the element body layer, The quantum sensor according to any one of embodiments 1 to 3, wherein the grounding line is arranged on the second main surface of the element body layer.

[0043] (Appendix 5) The element body layer has a first main surface and a second main surface, The signal line is arranged on the first main surface of the element body layer, The quantum sensor according to any one of embodiments 1 to 3, wherein the grounding line is also disposed on the first main surface of the element body layer.

[0044] (Aspect 6) A quantum sensor according to any one of embodiments 1 to 3, wherein at least one of the signal line and the ground line is embedded within the element body layer.

[0045] (Aspect 7) The aforementioned signal line is a conductive film including a first end and a second end, The quantum sensor according to any one of embodiments 1 to 6, wherein the first parallel line and the second parallel line extend on both sides of the opening provided in a part of the conductive film between the first end and the second end.

[0046] (Pattern 8) The signal line extends in a straight line between the first end and the second end, The quantum sensor according to embodiment 7, wherein each of the first parallel line and the second parallel line extends parallel to the longitudinal direction of the signal line.

[0047] (Aspect 9) The quantum sensor according to embodiment 8, wherein the first parallel line and the second parallel line are configured to have the same shape.

[0048] (Aspect 10) A quantum sensor according to any one of embodiments 1 to 9, wherein the object to be measured is integrated with the element body layer.

[0049] Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. Furthermore, the technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technologies illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives itself constitutes technical usefulness. [Explanation of Symbols]

[0050] 10: Quantum sensor, 12: Element body layer, 14: Signal line, 14a: First parallel line, 14b: Second parallel line, 15: Aperture, 16: Ground line, 18: Color center, S1: First main surface, S2: Second main surface

Claims

1. It is a quantum sensor, A main element layer having a color center, It comprises a signal line and a grounding line, The aforementioned signal line has a first parallel line and a second parallel line that extend in parallel and through which high-frequency currents flow in parallel. A quantum sensor wherein, when the element body layer is viewed in plan view, at least the color center is located within the opening between the first parallel line and the second parallel line in the element body layer.

2. It also includes a light detection unit, The quantum sensor according to claim 1, wherein the light detection unit is configured to detect the fluorescence emitted from the color center that has passed through the aperture.

3. It is further equipped with an excitation light generation unit, The quantum sensor according to claim 1, wherein the excitation light generating unit is configured to irradiate the color center with excitation light by passing it through the aperture.

4. The element body layer has a first main surface and a second main surface. The signal line is arranged on the first main surface of the element body layer, The quantum sensor according to claim 1, wherein the grounding line is disposed on the second main surface of the element body layer.

5. The element body layer has a first main surface and a second main surface. The signal line is arranged on the first main surface of the element body layer, The quantum sensor according to claim 1, wherein the grounding line is also disposed on the first main surface of the element body layer.

6. The quantum sensor according to claim 1, wherein at least one of the signal line and the ground line is embedded within the element body layer.

7. The signal line is a conductive film including a first end and a second end, The quantum sensor according to claim 1, wherein the first parallel line and the second parallel line extend on both sides of the opening provided in a portion of the conductive film between the first end and the second end.

8. The signal line extends in a straight line between the first end and the second end, The quantum sensor according to claim 7, wherein each of the first parallel line and the second parallel line extends parallel to the longitudinal direction of the signal line.

9. The quantum sensor according to claim 8, wherein the first parallel line and the second parallel line are configured to have the same shape when the element body layer is viewed in plan view.

10. The quantum sensor according to any one of claims 1 to 9, wherein the object to be measured is integrated with the element body layer.

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