JP2014197734A - Quantum interference device, atomic oscillator, magnetic sensor, and method for manufacturing quantum interference device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a quantum interference device in which the long-term stability can be enhanced more than conventional, an atomic oscillator, a magnetic sensor, and a method for manufacturing the quantum interference device.SOLUTION: An atomic oscillator 1 comprises: metal atoms; a gas cell 13 for encapsulating metal atoms; a semiconductor laser 10 for irradiating the gas cell 13 with light containing a pair of resonance light generating electromagnetic induction transmission phenomenon in the metal atoms; a photodetector 14 for detecting the light transmitted through the gas cell 13; and a magnetic field generating part 15 for generating the magnetic field in the gas cell 13. When the intensity of the pair of resonance light irradiated from the semiconductor laser 10 changes, the magnetic field in the gas cell 13 is set so that a frequency difference at which the output signal of the photodetector 14 becomes a maximum value, shifts to the direction in which Stark shift is offset.

Description

  The present invention relates to a quantum interference device, an atomic oscillator, a magnetic sensor, and a method for manufacturing the quantum interference device.

As shown in FIG. 15, a cesium atom which is a kind of alkali metal atom is known to have a ground level of 6S _1/2 and two excited levels of 6P _1/2 and 6P _3/2. ing. Furthermore, each level of 6S _1/2 , 6P _1/2 , 6P _3/2 has a hyperfine structure divided into a plurality of energy levels. Specifically, 6S _1/2 has two ground levels of F = 3 and 4, 6P _1/2 has two excitation levels of F ′ = 3 and 4, and 6P _3/2 has F It has four excitation levels' = 2, 3, 4, and 5.

For example, a cesium atom in the ground level of F = 3 of 6S _1/2 transitions to the excited level of either F ′ = 2, 3 or 4 of 6P _3/2 by absorbing the D2 line. However, it is not possible to transition to the excitation level of F ′ = 5. The cesium atom in the ground level of F = 4 of 6S _1/2 must transition to the excited level of F ′ = 3, 4, 5 of 6P _3/2 by absorbing the D2 line. However, it is not possible to transition to the excitation level of F ′ = 2. These are based on the transition selection rule when electric dipole transition is assumed. Conversely, a cesium atom in the excited level of either F ′ = 3, 4 of 6P _3/2 emits a D2 line, and the ground level of F = 3 or F = 4 of 6S _1/2 ( Transition to either the original ground level or the other ground level. Here, three levels (two base levels and two ground levels of F = 3, 4 of 6S _1/2 and excitation levels of F ′ = 3, 4 of 6P _3/2 ) (Consisting of one excitation level) is called a Λ-type three-level because it can make a Λ-type transition by absorption and emission of the D2 line. Similarly, three levels consisting of two ground levels of F = 3, 4 of 6S _1/2 and an excited level of F ′ = 3, 4 of 6P _1/2 are the absorption level of the D1 line. Since a Λ-type transition by light emission is possible, a Λ-type three level is formed.

On the other hand, the cesium atom in the excitation level of F ′ = 2 of 6P _3/2 emits the D2 line, and the ground level of F = 3 of 6S _1/2 is always (original ground level). Similarly, the cesium atom in the excitation level of F ′ = 5 of 6P _3/2 emits the D2 line, and the ground level of F = 4 of 6S _1/2 (the original ground level) ). That is, three levels consisting of two ground levels of F = 3, 4 of 6S _1/2 and an excited level of F ′ = 2 or F ′ = 5 of 6P _3/2 are the absorption and emission of the D2 line. The Λ-type three-level is not formed because Λ-type transition by is impossible. It is known that alkali metal atoms other than cesium atoms also have two ground levels and excited levels that form Λ-type three levels.

By the way, the first ground level (in the case of a cesium atom, F = 3 ground level of 6S _1/2 ) and the excited level (cesium atom in a gaseous alkali metal atom). In this case, for example, resonant light (resonant light 1) having a frequency (frequency) corresponding to an energy difference from 6P _3/2 F ′ = 4 excitation level) and a second ground level ( In the case of a cesium atom, when simultaneously irradiating resonance light (resonance light 2) having a frequency (frequency) corresponding to an energy difference between 6S _1/2 F = 4 ground level and an excitation level. An electromagnetically induced transmission (EIT) phenomenon (CPT (Coherent Population Trapping) phenomenon) in which two ground levels are superposed, that is, a quantum coherence state (dark state), and excitation to the excited level stops. Sometimes called)) is known to happen The frequency difference between the resonance light pair (resonance light 1 and resonance light 2) that causes this EIT phenomenon exactly coincides with the frequency corresponding to the energy difference ΔE ₁₂ between the two ground levels of the alkali metal atom. For example, since the frequency corresponding to the energy difference between the two ground levels of cesium atoms is 9.192631770 GHz, two kinds of D1 line or D2 line laser light having a frequency difference of 9.192631770 GHz are simultaneously applied to the cesium atoms. When irradiated, the EIT phenomenon occurs.

Accordingly, as shown in FIG. 16, when light having a frequency of ω ₁ and light having a frequency of ω ₂ are simultaneously irradiated onto a gaseous alkali metal atom, the two light waves become a resonance light pair, and the alkali metal atom becomes EIT. The intensity of the light transmitted through the alkali metal atom changes sharply depending on whether or not the phenomenon occurs. The signal indicating the intensity of the transmitted light that changes sharply is called an EIT signal (resonance signal), and when the frequency difference ω ₁ −ω _{2 of} the resonance light pair exactly matches the frequency ω ₁₂ corresponding to ΔE _12. The level of the EIT signal shows a peak value. Therefore, the atomic cell (gas cell) in which gaseous alkali metal atoms are sealed is irradiated with two light waves, and the peak top of the EIT signal is detected by the photodetector, that is, the frequency difference ω ₁ −ω ₂ between the two light waves. Is controlled so as to exactly match the frequency ω ₁₂ corresponding to ΔE ₁₂ , a highly accurate oscillator can be realized. A technique related to such an atomic oscillator is disclosed in Patent Document 1, for example.

US Pat. No. 6,320,472

By the way, when the intensity of light irradiated to alkali metal atoms decreases due to aging deterioration of the light source or the gas cell, the frequency of the atomic oscillator shifts in a low direction such as f ₁ → f ₂ → f ₃ due to the Stark shift. (FIG. 17). The Stark shift occurs whenever atoms and light interact. However, the conventional atomic oscillator has a problem that it is difficult to achieve high long-term stability because frequency fluctuations due to Stark shift are not canceled or insufficient.

  The present invention has been made in view of the above problems, and according to some aspects of the present invention, a quantum interference device, an atomic oscillator, A method of manufacturing a magnetic sensor and a quantum interference device can be provided.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following aspects or application examples.

[Application Example 1]
The quantum interference device according to this application example includes a metal atom, a cell enclosing the metal atom, a light source that irradiates the cell with a resonant light pair that generates an electromagnetically induced transmission phenomenon in the metal atom, and the cell A light detection unit that detects light transmitted through the cell, and a magnetic field generation unit that generates a magnetic field inside the cell, and the output of the light detection unit when the intensity of the resonant light pair irradiated by the light source changes The magnetic field inside the cell is set so that the frequency difference of the resonant light pair when the signal reaches a maximum value shifts in a direction that cancels the Stark shift.

  According to the quantum interference device according to this application example, when the intensity of the resonant light pair decreases with time, the peak position of the EIT signal fluctuates and the frequency of the atomic oscillator shifts. Since the magnetic field inside the cell is set so as to cancel, the frequency shift can be reduced as a result. Therefore, the long-term stability of the atomic oscillator can be improved.

[Application Example 2]
In the quantum interference device according to the application example described above, the magnetic field inside the cell may have a deviation in the irradiation direction of the resonant light pair generated by the light source to the cell.

[Application Example 3]
In the quantum interference device according to the application example described above, the position where the magnetic field inside the cell is strongest may be different from the center of the cell.

[Application Example 4]
In the quantum interference device according to the application example described above, the intensity of the magnetic field inside the cell may be different between a position where light generated by the light source is incident on the cell and a position where the light is emitted from the cell.

[Application Example 5]
In the quantum interference device according to the application example described above, the magnetic field generation unit may also be used as a means for Zeeman splitting energy levels of the metal atoms.

  For example, the means for Zeeman splitting the energy level of a metal atom may be a c-field coil.

  According to the quantum interference device according to this application example, it is not necessary to provide a dedicated means for generating a magnetic field for reducing the Stark shift, which is advantageous for miniaturization of atomic oscillation.

[Application Example 6]
In the quantum interference device according to the application example described above, the magnetic field deviation generation unit may be provided separately from a means for causing Zeeman splitting of the energy level of the metal atom.

  According to the quantum interference device according to this application example, by separately providing a means for generating a magnetic field for reducing the Stark shift and a means for generating a magnetic field for causing Zeeman splitting of the energy level of the metal atom, Since the degree of freedom of adjustment of each magnetic field is high, the Stark shift can be canceled with high accuracy.

[Application Example 7]
The atomic oscillator according to this application example includes any of the quantum interference devices described above.

[Application Example 8]
The magnetic sensor according to this application example includes any of the quantum interference devices described above.

[Application Example 9]
A method of manufacturing a quantum interference device according to this application example includes a metal atom, a cell enclosing the metal atom, a light source that generates light including two light waves and irradiates the cell, and transmits the cell. A physical package preparation step of preparing a physical package including a light detection unit that detects light, and a magnetic field generation unit that generates a magnetic field inside the cell; and when the intensity of the two light waves changes, And a magnetic field setting step of setting a magnetic field generated by the magnetic field generator so that the frequency difference between the two light waves when the output signal reaches a maximum value shifts in a direction to cancel the Stark shift.

The figure which shows the specific structural example of the atomic oscillator of 1st Embodiment. FIG. 2A is a diagram showing energy levels obtained by Zeeman splitting, and FIG. 2B is a diagram showing an example of split EIT signals. Schematic which shows an example of the frequency spectrum of the emitted light of a semiconductor laser. Explanatory drawing of the detection principle by a detection circuit. Explanatory drawing of the detection principle by a detection circuit. Explanatory drawing about the relationship between the light transmittance (EIT signal intensity) and a lock frequency. Explanatory drawing about the relationship between the light transmittance (EIT signal intensity) and a lock frequency. The figure which shows an example of the method of making an EIT signal left-right asymmetric. FIG. 9A is a diagram of experimental results regarding the relationship between the intensity of magnetic fields having deviations and frequency sensitivity, and FIG. 9B is a diagram of experimental results regarding the relationship between uniform magnetic field strengths and frequency sensitivity. Figure. The flowchart figure which shows an example of the manufacturing method of the atomic oscillator of this embodiment. The figure which shows the specific structural example of the atomic oscillator of 2nd Embodiment. The figure which shows an example of the method of making an EIT signal left-right asymmetric. The figure which shows the structural example of the magnetic sensor of this embodiment. Schematic which shows the frequency spectrum of the emitted light of the semiconductor laser in a modification. The figure which shows the energy level of a cesium atom typically. Schematic which shows an example of an EIT signal. Explanatory drawing of a Stark shift.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unduly limit the contents of the present invention described in the claims. Also, not all of the configurations described below are essential constituent requirements of the present invention.

1. Atomic oscillator 1-1. First Embodiment [Configuration of Atomic Oscillator]
FIG. 1 is a diagram illustrating a configuration example of the atomic oscillator according to the first embodiment. As shown in FIG. 1, the atomic oscillator 1 of the first embodiment includes a semiconductor laser 10, a neutral density filter (ND filter) 11, a quarter wavelength plate 12, a gas cell 13, a photodetector 14, a magnetic field generator 15, Detection circuit 16, voltage controlled crystal oscillator (VCXO) 17, modulation circuit 18, low frequency oscillator 19, frequency conversion circuit 20, detection circuit 21, modulation circuit 22, low frequency oscillator 23, drive circuit 24, magnetic field setting circuit 25, bias A setting circuit 26, a memory 27, and a frequency conversion circuit 28 are included. Note that the atomic oscillator 1 of the present embodiment may have a configuration in which some of the components (parts) in FIG. 1 are omitted or changed as appropriate, or other components are added.

  The semiconductor laser 10 (an example of a light source) is, for example, a surface emitting laser such as a vertical cavity surface emitting laser (VCSEL) or an edge emitting laser, and the semiconductor laser 10 is generated. The light thus made is incident on the neutral density filter 11.

  The neutral density filter 11 transmits only part of the light emitted from the semiconductor laser 10, and the light transmitted through the neutral density filter 11 enters the quarter-wave plate 12.

  The quarter-wave plate 12 transmits incident light as σ + circularly polarized light, and the light transmitted through the quarter-wave plate 12 enters the gas cell 13.

The gas cell 13 (an example of a cell) includes neon (Ne) together with gaseous alkali metal atoms (sodium (Na) atoms, rubidium (Rb) atoms, cesium (Cs) atoms, etc.) in a container made of a transparent member such as glass. ) And argon (Ar) or other buffer gas is enclosed. A part of the light incident on the gas cell 13 passes through the gas cell 13 and enters the photodetector 14.

  The light detector 14 (an example of a light detection unit) detects light transmitted through the gas cell 13 and outputs a detection signal corresponding to the detected light intensity. The light detection unit 14 can be realized using, for example, a photodiode (PD) that outputs a detection signal corresponding to the intensity of received light. The output signal of the photodetector 14 is input to the detection circuit 16 and the detection circuit 21.

  The magnetic field generator 15 generates a magnetic field in at least a part of the gas cell 13. The magnetic field generator 15 can be realized by, for example, a coil, and a desired magnetic field can be achieved by adjusting the position and shape of the coil (for example, the direction in which the coil is wound, the number of turns, the diameter, etc.), the current magnitude and direction, and the like. Can be generated.

When a magnetic field is applied, each energy level of the alkali metal atom splits into 2F + 1 pieces (Zeeman splitting). For example, in the case of a cesium atom, as shown in FIG. 2A, the ground level of 6S _1/2 and F = 3 and the excited level of 6P _3/2 and F ′ = 3 are represented by the magnetic quantum number mF = It splits into seven levels corresponding to 0, ± 1, ± 2, ± 3, and the 6S _1/2 , F ′ = 4 ground level and 6P _3/2 , F = 4 excited level are magnetic The quantum number is divided into nine levels corresponding to mF = 0, ± 1, ± 2, ± 3, ± 4. When σ + circularly polarized light is incident on the cesium atom, excitation is performed according to the selection rule of ΔmF = + 1. For example, the ground level of 6S _1/2 , F = 3, 4 and the excitation level of 6P _3/2 , F ′ = 4 Seven Λ-type three levels are formed between the positions. Therefore, in this state, when the frequency difference between the two light waves is swept, seven EIT signals are observed as shown in FIG. In particular, the Λ-type 3 level formed between the ground level of mF = 0 of 6S _1/2 , F = 3, 4 and the excitation level of mF = + 1 of 6P _3/2 , F ′ = 4 Since the intensity of the corresponding EIT signal is the highest, it is effective to control the frequency difference of the resonant light pair so as to generate this EIT signal.

  The semiconductor laser 10, the neutral density filter 11, the quarter-wave plate 12, the gas cell 13, the photodetector 14, and the magnetic field generator 15 are housed in one housing and constitute a physical package 100.

  The detection circuit 16 detects the output signal of the photodetector 14 using the oscillation signal of the low frequency oscillator 19 that oscillates at a low frequency of about several Hz to several hundred Hz. Then, the oscillation frequency of the voltage controlled crystal oscillator (VCXO) 17 is finely adjusted according to the magnitude of the output signal of the detection circuit 16. The voltage controlled crystal oscillator (VCXO) 17 oscillates at about several MHz to several tens of MHz, for example.

  The modulation circuit 18 uses the oscillation signal of the low frequency oscillator 19 (the same signal as the oscillation signal supplied to the detection circuit 16) as a modulation signal in order to enable detection by the detection circuit 16, and a voltage controlled crystal oscillator (VCXO) 17 Modulate the output signal. The modulation circuit 18 can be realized by a frequency mixer (mixer), a frequency modulation (FM) circuit, an amplitude modulation (AM) circuit, or the like.

  The frequency conversion circuit 20 converts the frequency of the output signal of the modulation circuit 18 at a constant frequency conversion rate and outputs the converted signal to the drive circuit 24. The frequency conversion circuit 20 can be realized by, for example, a PLL (Phase Locked Loop) circuit.

  The detection circuit 21 detects the output signal of the photodetector 14 using the oscillation signal of the low frequency oscillator 23 that oscillates at a low frequency of about several Hz to several hundred Hz.

The modulation circuit 22 modulates the output signal of the detection circuit 21 using the oscillation signal of the low frequency oscillator 23 (the same signal as the oscillation signal supplied to the detection circuit 21) as a modulation signal in order to enable detection by the detection circuit 21. And output to the drive circuit 24. The modulation circuit 22 can be realized by a frequency mixer (mixer), a frequency modulation (FM) circuit, an amplitude modulation (AM) circuit, or the like.

  The magnetic field setting circuit 25 performs processing for setting the strength of the magnetic field generated by the magnetic field generator 15 according to the setting information stored in the memory 27. For example, the magnetic field generation unit 15 may be realized by a coil, and the magnetic field setting circuit 25 may set the amount of current flowing through the coil according to setting information stored in the memory 27.

  The bias setting circuit 26 sets a bias current in the semiconductor laser 10 according to the setting information stored in the memory 27 via the drive circuit 24 (processing for setting the center wavelength of light generated by the semiconductor laser 10). )I do.

  The memory 27 is a non-volatile memory, and stores setting information for the intensity of the magnetic field generated by the magnetic field generator 15 and setting information for the bias current of the semiconductor laser 10. The memory 27 can be realized by, for example, a flash memory such as a MONOS (Metal-Oxide-Nitride-Oxide-Silicon) memory, an EEPROM (Electrically Erasable Programmable Read-Only Memory), or the like.

The drive circuit 24 sets the bias current of the semiconductor laser 10 and finely adjusts the bias current according to the output signal of the modulation circuit 22 and supplies the bias current to the semiconductor laser 10. That is, by a feedback loop (first feedback loop) passing through the semiconductor laser 10, the neutral density filter 11, the quarter wavelength plate 12, the gas cell 13, the photodetector 14, the detection circuit 21, the modulation circuit 22, and the drive circuit 24, The center wavelength λ ₀ (center frequency f ₀ ) of the light generated by the semiconductor laser 10 is finely adjusted.

Further, the drive circuit 24 superimposes the current (modulation current) of the output frequency component (modulation frequency f _m ) of the frequency conversion circuit 20 on the bias current, and supplies it to the semiconductor laser 10. With this modulation current, the semiconductor laser 10 is frequency-modulated, and with the light having the center frequency f ₀ (center wavelength λ ₀ ), the frequencies f ₀ ± f _m and f ₀ ± 2f are shifted from each other by f _m on both sides. _m ,... light is generated. The semiconductor laser 10, the neutral density filter 11, the quarter wave plate 12, the gas cell 13, the photodetector 14, the detection circuit 16, the voltage controlled crystal oscillator (VCXO) 17, the modulation circuit 18, the frequency conversion circuit 20, and the drive circuit the feedback loop through 24 (second feedback loop), the frequency f ₀ + f _m of the light and the frequency f ₀ -f light resonant light pair for generating EIT phenomenon in the alkali metal atom enclosed in the gas cell 13 of the _m It is finely adjusted so that

For example, the second feedback loop, an alkali metal atom with a ground level of the magnetic quantum number mF = 0 is to undergo EIT phenomenon, the modulation frequency f _m is feedback controlled. Specifically, the second feedback loop, the frequency difference of the light of the light and the frequency f ₀ -f _m of frequency f ₀ + f _m is a first-order sideband (= 2f _m) is magnetic alkali metal atom Feedback control is applied so as to accurately match the frequency ω ₁₂ corresponding to the energy difference ΔE ₁₂ between the two ground levels of the quantum number mf = 0. For example, if the alkali metal atom is a cesium atom, ω ₁₂ is 9.192631770 GHz + ΔHz (Δ is a frequency expressed by a quadratic function of the magnetic field strength), so the modulation frequency f _m exactly matches 4.59631585 GHz + Δ / 2 Hz. . FIG. 3 shows an example of the frequency spectrum of the emitted light from the semiconductor laser 10. In FIG. 3, the horizontal axis represents the light frequency, and the vertical axis represents the light intensity.

In this way, by using the EIT phenomenon of alkali metal atoms, the output signal of the frequency conversion circuit 20 and the voltage controlled crystal oscillator (VCXO) 1 included in the second feedback loop.
7 output signals are stabilized at a predetermined frequency.

  The frequency conversion circuit 28 converts the output signal of the voltage controlled crystal oscillator (VCXO) 17 at a constant frequency conversion rate, and generates a clock signal having a desired frequency (for example, 10.00... MHz). This clock signal is output externally. The frequency conversion circuit 20 can be realized by, for example, DDS (Direct Digital Synthesizer).

  In FIG. 1, the components (circuits) excluding the physical package 100 can be realized by, for example, a one-chip integrated circuit (IC).

  In FIG. 1, the semiconductor laser 10, the neutral density filter (ND filter) 11, the quarter wavelength plate 12, the gas cell 13, the photodetector 14, the magnetic field generator 15, the detection circuit 16, and the voltage controlled crystal oscillator (VCXO) 17, a modulation circuit 18, a low-frequency oscillator 19, a frequency conversion circuit 20, a detection circuit 21, a modulation circuit 22, a low-frequency oscillator 23, a drive circuit 24, a magnetic field setting circuit 25, a bias setting circuit 26, and a memory 27. 200 is configured. However, the quantum interference device 200 of the present embodiment may be configured such that some of the components (each unit) in FIG. 1 are omitted or changed as appropriate, or other components are added.

[Detection principle]
Next, the principle of detection by the detection circuit 16 will be described. As described above, in the present embodiment, the modulation circuit 18 uses the sine wave of about several tens Hz to several hundreds Hz generated by the low frequency oscillator 19 as the modulation signal, and uses the oscillation signal of the voltage controlled crystal oscillator (VCXO) 17 as the frequency. Modulated and input to the frequency conversion circuit 20. As a result, the frequency difference between the two light waves generated by the semiconductor laser 10 is swept within a range of about several hundred Hz to several kHz determined by the amplitude of the sine wave, and the output signal of the photodetector 14 is detected by the sine wave by the detection circuit 16. By performing synchronous detection, the area where the left and right areas of the EIT signal appearing in the output of the photodetector 14 are equal is detected as a peak. When the EIT signal is symmetric, as shown in FIG. 4A, zero cross points a, c, e of a sine wave (sweep signal) having a frequency of f _s (period is 1 / f _s ) are peaks of the EIT signal. In the state where it coincides with the top, the output signal of the photodetector 14 includes a DC component and a low frequency component having a constant amplitude of 2 f _s (period is 1/2 f _s ), but the frequency is f _s. The low-frequency component with a period of 1 / f _s is extremely small. Therefore, the frequency component of f _s is hardly detected by the detection circuit 16. On the other hand, as shown in FIG. 4B, when the zero cross points a, c, e of the sine wave having the frequency f _s (period is 1 / f _s ) are shifted in a direction lower than the peak top of the EIT signal. , the output signal of the photodetector 14, the frequency (the period 1 / 2f _s) is 2f _s amplitude changes every 1 / f _s period in. That is, the output signal of the photodetector 14, in addition to the frequency component of the DC component and 2f _s, the frequency component of f _s are also included. Therefore, the frequency component of f _s is detected by the detection circuit 16, and the voltage value of the output signal of the detection circuit 16 is higher than the voltage value (reference voltage value) in the case of FIG. Since the output signal of the detection circuit 16 is input to the voltage controlled crystal oscillator (VCXO) 17, the oscillation frequency of the voltage controlled crystal oscillator (VCXO) 17 is higher (the direction in which the frequency difference between the two light waves approaches ω ₁₂ ). Change. On the other hand, although not shown, in the state where the zero cross points a, c, e of the sine wave having the frequency f _s (period is 1 / f _s ) are shifted in a direction higher than the peak top of the EIT signal, the photodetector The output signal 14 is a signal that is 180 degrees out of phase with the signal in FIG. Therefore, the voltage value of the output signal of the detection circuit 16 becomes negative (voltage value lower than the reference voltage value), and the oscillation frequency of the voltage controlled crystal oscillator (VCXO) 17 is low (the frequency difference between the two light waves approaches ω ₁₂₎ . Direction).

Due to such a detection principle, when the EIT signal is symmetrical, the peak top of the EIT signal is locked. On the other hand, when the EIT signal is asymmetrical, as shown in FIG. 5A, zero cross points a, c, e of a sine wave (sweep signal) having a frequency of f _s (period is 1 / f _s ) are EIT. in the state to match the signal of the peak top, the output signal of the photodetector 14, in addition to the frequency component of the DC component and 2f _s, the frequency component of f _s are also included. Therefore, the frequency component of f _s is detected by the detection circuit 16, and the voltage value of the output signal of the detection circuit 16 becomes a voltage value lower than the voltage value (reference voltage value) in the case of FIG. Further, as shown in FIG. 5B, the zero cross points a, c, e of the sine wave having a frequency of f _s (period is 1 / f _s ) are shifted by a predetermined amount in a direction lower than the peak top of the EIT signal. In this state, the output signal of the photodetector 14 includes a DC component and a low-frequency component having a constant amplitude with a frequency of 2 f _s (cycle is 1/2 f _s ), but the frequency is f _s (cycle is 1 / cycle). The low frequency component of f _s ) is very small. Therefore, the frequency component of f _s is hardly detected by the detection circuit 16 and is stabilized in this state. That is, when the EIT signal is asymmetrical, the position is shifted from the peak top of the EIT signal.

[Improved long-term stability of frequency]
Since the detection circuit 16 has a property of locking the frequency by regarding the area where the left and right areas of the EIT signal are equal as a peak, if the EIT signal is symmetrical, the frequency that locks should not be shifted even if the strength of the EIT signal is reduced. It is. However, when the intensity of the light applied to the gas cell 13 is reduced, the actual locking frequency changes due to the Stark shift. Therefore, if the EIT signal is symmetrical, it is difficult to achieve high long-term stability.

On the other hand, when the EIT signal is distorted asymmetrically, the frequency that is locked when the intensity of the EIT signal decreases is also shifted. FIGS. 6A and 6B are examples of graphs in which the EIT signal (output signal of the photodetector 14)) and the lock frequency (frequency difference between the resonant light pairs) are plotted. 6 (A) and 6 (B), the vertical axis represents the transmittance of light transmitted through the gas cell 13 (the output signal intensity of the detector 14), and the horizontal axis represents the frequency (frequency difference between the resonant light pair). is there. For example, as shown in FIG. 6A, when the EIT signal is tilted to the left side (low frequency side), the lock frequency decreases as f ₁ → f ₂ → f ₃ as the intensity of the EIT signal decreases. To go. Conversely, as shown in FIG. 6B, when the EIT signal is tilted to the right side (high frequency side), the lock frequency increases as f ₁ → f ₂ → f ₃ as the intensity of the EIT signal decreases. To go.

However, if the intensity of the light applied to the gas cell 13 is reduced, the frequency is also reduced due to the Stark shift. Therefore, as shown in FIG. 6 (A), the EIT signal may be inclined to the left side (low frequency side). For example, the frequency shift is further increased by the Stark shift, but as shown in FIG. 6B, if the EIT signal is tilted to the right side (high frequency side) and is asymmetrical, the frequency shift is the Stark shift. Get smaller. In other words, the Stark shift can be canceled by tilting the EIT signal to the right side (high frequency side) to be asymmetric. As a result, as shown in FIG. 7, even EIT signal is reduced due to a decrease in the intensity of the light emitted from the light source 13, the lock frequency can be prevented from being varied while the initial frequency f _1. Thereby, high long-term stability can be realized.

Therefore, in the present embodiment, the magnetic field generator 15 generates a magnetic field having a deviation inside the gas cell 13 in order to make the EIT signal asymmetrical. That is, in the present embodiment, the magnetic field generation unit 15 uses a means (for example, a c-field coil) for splitting the energy level of alkali metal atoms accommodated in the gas cell 13 as a magnetic field inside the gas cell 13. It is also used for giving deviation. By giving a deviation to the magnetic field, the gas cell 13 can have a large magnetic field and a small magnetic field. When a magnetic field is applied, the energy level of the alkali metal atom causes Zeeman splitting, but the splitting width depends on the magnitude of the magnetic field. Therefore, if the magnetic field has a deviation, each atom causes an EIT phenomenon. Is different depending on the strength of the magnetic field (proportional to the square of the magnetic field strength). Since the EIT signal is a superposition of signals due to the EIT phenomenon of each atom, the result is left-right asymmetry. In particular, if the distribution of the magnetic field is set so that the number of atoms receiving a relatively strong magnetic field is larger than the number of atoms receiving a relatively weak magnetic field, the EIT signal tilts to the right (high frequency side) and becomes asymmetric. It becomes possible to cancel the shift.

  As a method of making the EIT signal left-right asymmetric, for example, the methods shown in FIGS. 8A to 8E can be considered. 8A to 8E are views of the gas cell 13 viewed from a direction perpendicular to the light traveling direction (optical axis direction).

  For example, as shown in FIG. 8A, if only a part of the gas cell 13 is covered with the coil 30 and a predetermined current is passed through the coil 30, the space covered with the coil 30 is relatively relative to the inside of the gas cell 13. The magnetic field strength of the space that is not covered by the coil 30 decreases as the distance from the coil 30 increases. Thereby, a deviation can be given to the magnetic field inside the gas cell 13, and by adjusting the magnitude of the current flowing through the coil 30, the number of turns and the diameter of the coil 30, and the length and position of the coil 30 in the optical axis direction. It is also possible to have a magnetic field distribution that cancels the Stark shift. In FIG. 8A, the coil 30 corresponds to the magnetic field generator 15 in FIG.

  Further, for example, as shown in FIG. 8B, if the gas cell 13 is covered with one coil 30 having a different number of turns and a predetermined current is supplied to the coil 30, the inside of the gas cell 13 A space having a larger number of turns has a relatively higher magnetic field strength, and a space having a smaller number of turns of the coil 30 has a relatively lower magnetic field strength. Thereby, a deviation can be given to the magnetic field inside the gas cell 13, and a magnetic field that cancels the Stark shift by adjusting the magnitude of the current flowing through the coil 30, the number of turns and the diameter of the coil 30, and the like. A distribution is also possible. In FIG. 8B, the coil 30 corresponds to the magnetic field generator 15 in FIG.

  Further, for example, as shown in FIG. 8C, the gas cell 13 is covered with two coils 30 and 31 (may be three or more coils), and for example, a predetermined current flowing through the coil 30 is flown through the coil 31. In the gas cell 13, the space covered with the coil 30 has a relatively high magnetic field strength, and the space covered with the coil 31 has a relatively low magnetic field strength. Thereby, a deviation can be given to the magnetic field inside the gas cell 13, the magnitude and direction of the current flowing through the coils 30 and 31, the number of turns and the diameter of the coils 30 and 31, and the length of the coils 30 and 31 in the optical axis direction. By adjusting the sheath position and the like, it is possible to obtain a magnetic field distribution that cancels the Stark shift. In FIG. 8C, the coil 30 and the coil 31 correspond to the magnetic field generator 15 in FIG.

  Further, for example, as shown in FIG. 8D, if the gas cell 13 is covered with one coil 30 having a different diameter for each part and a predetermined current is passed through the coil 30, the diameter of the coil 30 is within the gas cell 13. The shorter the space, the larger the magnetic field strength, and the longer the coil 30 diameter, the smaller the magnetic field strength. Thereby, a deviation can be given to the magnetic field inside the gas cell 13, and a magnetic field that cancels the Stark shift by adjusting the magnitude of the current flowing through the coil 30, the number of turns and the diameter of the coil 30, and the like. A distribution is also possible. In FIG. 8D, the coil 30 corresponds to the magnetic field generator 15 in FIG.

  Further, for example, as shown in FIG. 8E, Helmholtz coils in which two coils 30 and 31 are opposed to each other on the light incident side and the light emitting side of the gas cell 13 are arranged. By varying some or all of the parameters such as the size, the direction of current, the number of turns, the diameter, the length in the optical axis direction, and the position, the magnetic field inside the gas cell 13 can have a deviation. By adjusting these parameters, it is possible to obtain a magnetic field distribution that cancels the Stark shift. In FIG. 8E, the coil 30 and the coil 31 correspond to the magnetic field generator 15 in FIG.

  8A to 8E, the magnetic field generated by the magnetic field generator 15 is deviated in the irradiation direction of the light generated by the semiconductor laser 10 to the gas cell 13 (alkali metal atom). The intensity of the magnetic field is different between the position where the light enters the gas cell 13 and the position where the light exits from the gas cell 13. Further, the position where the magnetic field generated by the magnetic field generator 15 is the strongest is different from the center of the gas cell 13 (center of the container containing the alkali metal atoms). Thus, in this embodiment, when the intensity of the emitted light from the semiconductor laser 10 changes, the frequency difference of the resonant light pair that causes the EIT phenomenon in the alkali metal atoms is shifted in the opposite direction to the Stark shift. A magnetic field (magnetic field deviation) inside the gas cell 13 is set.

  In FIG. 9A, as shown in FIG. 8A, only a part of the gas cell is covered with a coil, the magnitude of the current flowing through the coil is set in five ways, and the emitted light of the semiconductor laser (of the gas cell) It is a graph of the experimental result which acquired the relationship between the intensity | strength of incident light), and the frequency deviation of an atomic oscillator. In FIG. 9B, for comparison, the entire gas cell is covered with a coil, the magnitude of the current flowing through the coil is set in five ways, the intensity of the emitted light of the semiconductor laser (incident light of the gas cell) and the atomic oscillator It is a graph of the experimental result which acquired the relationship with a frequency deviation.

  In the graph of FIG. 9B, when the magnetic field inside the gas cell is uniform, the frequency changes due to the Stark shift if the light intensity changes even if the current flowing through the coil (that is, the strength of the magnetic field inside the gas cell) is changed. It shows that it will end. On the other hand, the graph of FIG. 9A shows that the amount of change in frequency (frequency sensitivity) with respect to the change in light intensity can be reduced if the magnetic field inside the gas cell has a deviation and its intensity is changed. . Therefore, if the deviation and strength of the magnetic field are adjusted, the Stark shift can be almost canceled, and the long-term stability of the atomic oscillator can be improved as compared with the conventional case.

[Method of manufacturing an atomic oscillator]
FIG. 10 is a flowchart showing an example of a method for manufacturing the atomic oscillator 1 of the present embodiment.

  First, the physical package 100 shown in FIG. 1 is prepared (S10). For example, an existing physical package 100 may be prepared, or the semiconductor package 10, the neutral density filter 11, the quarter wavelength plate 12, the gas cell 13, the photodetector 14, and the magnetic field generator 15 may be prepared. May be assembled.

  Next, parameters for determining the distribution of the magnetic field inside the gas cell 10 such as the position and shape of the magnetic field generator 15 (coils, etc.) are initialized (S20).

Then swept in a low-frequency modulation frequency f _m of the semiconductor laser 10 around the omega _12/2, a bias current of the semiconductor laser 10 is changed in a predetermined range to measure the frequency to be locked, respectively (S30). Low frequencies sweeping the modulation frequency f _m may be brought into coincidence with the frequency of the low frequency oscillator 19 in FIG. 1. Signal to sweep at low frequencies the modulation frequency f _m around the omega _12/2, for example, can be generated by a signal generator.

  Next, the frequency sensitivity with respect to the light intensity is calculated from the frequency measurement result at each bias current value in step S30 (S40).

  If the frequency sensitivity is greater than the threshold value (N in S50), the setting of the parameter that determines the distribution of the magnetic field inside the gas cell 10 is changed until the frequency sensitivity is equal to or less than the threshold value (S60), and the processing after step S30 Repeat.

  If the frequency sensitivity is equal to or lower than the threshold value (Y in S50), finally, the physical package 100 and the circuit (IC) are connected, and the atomic oscillator 1 is assembled (S50).

  As described above, according to the atomic oscillator of the first embodiment, the EIT signal is asymmetric, so that the frequency fluctuation due to the Stark shift is canceled to some extent when the intensity of the emitted light from the semiconductor laser 100 is reduced. Therefore, long-term stability can be improved.

1-2. Second Embodiment In the first embodiment, the magnetic field generator 15 uses a means (for example, a c-field coil) for splitting the energy levels of alkali metal atoms accommodated in the gas cell 13 inside the gas cell 13. In the atomic oscillator of the second embodiment, a means for generating a uniform magnetic field (for example, c−) is used to cause Zeeman splitting of the energy level of the alkali metal atom. field coil) and means for giving a deviation to the magnetic field inside the gas cell 13 are provided separately.

  FIG. 11 is a diagram illustrating a configuration example of the atomic oscillator according to the second embodiment. In FIG. 11, the same components as those in the first embodiment (FIG. 1) are denoted by the same reference numerals. As shown in FIG. 11, in the atomic oscillator 1 of the second embodiment, the magnetic field generator 15 is replaced with a stationary magnetic field generator 40 and a magnetic field deviation generator 41, compared to the atomic oscillator of the first embodiment. Other configurations are the same.

  The stationary magnetic field generator 40 generates a stationary magnetic field (uniform magnetic field) inside the gas cell 13. The magnetic field generator 15 can be realized by, for example, a coil, and a desired magnetic field can be achieved by adjusting the position and shape of the coil (for example, the direction in which the coil is wound, the number of turns, the diameter, etc.), the current magnitude and direction, and the like. Can be generated.

  The magnetic field deviation generating unit 41 (an example of a magnetic field generating unit) is for giving a deviation to the magnetic field inside the gas cell 13. The magnetic field deviation generating unit 41 can be realized by, for example, a magnet or a coil, and the position, shape, strength, etc. of the magnet, or the position, shape of the coil (for example, the direction in which the coil is wound, the number of turns, the diameter, etc.) A desired magnetic field can be generated by adjusting the magnitude and direction of the current.

  The magnetic field setting circuit 25 performs processing for setting the strengths of the magnetic fields generated by the stationary magnetic field generation unit 40 and the magnetic field deviation generation unit 41 in accordance with the setting information stored in the memory 27. For example, the stationary magnetic field generation unit 40 and the magnetic field deviation generation unit 41 are realized by separate coils, and the magnetic field setting circuit 25 sets the amount of current that flows through each coil according to the setting information stored in the memory 27. May be.

  Other configurations in FIG. 11 are the same as those in the first embodiment (FIG. 1), and thus description thereof is omitted.

  In the present embodiment, as a method for making the EIT signal asymmetrical, for example, the methods shown in FIGS. 12A to 12C are conceivable. 12A to 12C are views of the gas cell 13 viewed from a direction perpendicular to the light traveling direction (optical axis direction).

For example, as shown in FIG. 12A, the gas cell 13 is covered with a coil 50, and a predetermined current is passed through the coil 50 to generate a uniform magnetic field inside the gas cell 13. Furthermore, by arranging the magnet 60 near the gas cell 13, the magnetic field strength is relatively increased in the space closer to the magnet 60 in the gas cell 13, and the magnetic field strength is relatively decreased in the space farther from the magnet 60. . Thereby, a deviation can be given to the magnetic field inside the gas cell 13, and by adjusting the position, shape, strength of the magnet 60, the current flowing through the coil 50, the number of turns and the diameter of the coil 50, etc. It is also possible to have a magnetic field distribution that cancels the Stark shift. In FIG. 12A, the coil 50 corresponds to the stationary magnetic field generation unit 40 in FIG. 11, and the magnet 60 corresponds to the magnetic field deviation generation unit 41 in FIG.

  For example, as shown in FIG. 12B, the gas cell 13 is covered with a coil 50, and a predetermined current is passed through the coil 50 to generate a uniform magnetic field inside the gas cell 13. Furthermore, by arranging the coil 52 on the light incident side or the light emission side (or both) of the gas cell 13 and flowing a predetermined current, the magnetic field strength is relatively larger in the space closer to the coil 52 inside the gas cell 13. Thus, the magnetic field strength becomes relatively smaller as the space is farther from the coil 52. Thereby, a deviation can be given to the magnetic field inside the gas cell 13, and the Stark shift is canceled by adjusting the magnitude of the current flowing through the coil 50 and the coil 52, the number of turns and the diameter of the coil 30, and the like. It is also possible to have a uniform magnetic field distribution. In FIG. 12B, the coil 50 corresponds to the stationary magnetic field generation unit 40 in FIG. 11, and the coil 52 corresponds to the magnetic field deviation generation unit 41 in FIG.

  Further, for example, as shown in FIG. 12C, Helmholtz coils having two coils 50 and 51 facing each other are arranged on the light incident side and the light emitting side of the gas cell 13, and a predetermined current is supplied to the coil 50 and the coil 51. To generate a uniform magnetic field inside the gas cell 13. Furthermore, only a part of the gas cell 13 is covered with the coil 52 and a predetermined current is passed through the coil 50, so that the space covered with the coil 52 has a relatively large magnetic field strength inside the gas cell 13. In the uncovered space, the magnetic field strength is relatively small. Thereby, a deviation can be given to the magnetic field inside the gas cell 13, and the magnitude of the current flowing through the coil 50, the coil 51, and the coil 52, the number of turns and the diameter of the coil 50, the coil 51, and the coil 52 are adjusted. Thus, it is possible to obtain a magnetic field distribution that cancels the Stark shift. In FIG. 12C, the coil 50 and the coil 51 correspond to the stationary magnetic field generation unit 40 in FIG. 11, and the coil 52 corresponds to the magnetic field deviation generation unit 41 in FIG.

  In any of the methods shown in FIGS. 12A to 12C, the magnetic field generated by the magnetic field deviation generation unit 41 is in the irradiation direction of the light generated by the semiconductor laser 10 to the gas cell 13 (alkali metal atom). There is a deviation, and the intensity of the magnetic field is different between the position where the light is incident on the gas cell 13 and the position where the light is emitted from the gas cell 13. Further, the position where the magnetic field generated by the magnetic field deviation generator 41 is the strongest is different from the center of the gas cell 13 (center of the container containing the alkali metal atoms). Thus, in this embodiment, when the intensity of the emitted light from the semiconductor laser 10 changes, the frequency difference of the resonant light pair that causes the EIT phenomenon in the alkali metal atoms is shifted in the opposite direction to the Stark shift. A magnetic field (magnetic field deviation) inside the gas cell 13 is set.

  In addition, for example, the coil 50 in FIG. 12C may be replaced with a coil having a different number of turns or a diameter depending on a position or a plurality of coils having different amounts of current, similarly to FIGS. 8B to 8D. Good.

  In addition, since the flowchart of the manufacturing method of the atomic oscillator of 2nd Embodiment is the same as that of the flowchart of FIG. 10, the illustration and description are abbreviate | omitted.

  As described above, according to the atomic oscillator of the second embodiment, when the EIT signal becomes asymmetric by causing a deviation in the magnetic field inside the gas cell 13 and the intensity of the emitted light from the semiconductor laser 100 is reduced, Since the fluctuation of the frequency due to the shift can be canceled to some extent, the long-term stability can be improved.

  Furthermore, according to the atomic oscillator of the second embodiment, the means for generating a stationary magnetic field and the means for generating a magnetic field deviation are separately provided in the gas cell 13, so that the degree of freedom of adjustment is improved and the Stark shift It is possible to cancel the frequency fluctuation due to the above with high accuracy.

2. Magnetic Sensor When the intensity of the magnetic field around the gas cell 13 shown in FIG. 1 changes, the Zeeman splitting level in the ground level and the excited level of the alkali metal atoms accommodated in the gas cell 13 changes. In accordance with the change in the Zeeman splitting level, the frequency difference ω ₁₂ of the resonant light pair that causes the EIT phenomenon in the alkali metal atom also changes. This ω ₁₂ is known to be proportional to the square of the magnetic field strength B. Since the frequency of the voltage controlled crystal oscillator (VCXO) 17 is proportional to ω ₁₂ , the magnetic field strength can be calculated from the frequency of the voltage controlled crystal oscillator (VCXO) 17. Therefore, a magnetic sensor can be realized by arranging a magnetic measurement object in the vicinity of the gas cell 13.

  FIG. 13 is a diagram illustrating a configuration example of the magnetic sensor of the present embodiment. In FIG. 11, the same components as those in FIG. As shown in FIG. 11, in the magnetic sensor 2 of the present embodiment, the frequency conversion circuit 28 of the atomic oscillator 1 shown in FIG. 1 is replaced with a magnetic field strength information generation circuit 29, and other configurations are shown in FIG. Similar to the atomic oscillator 1.

  The magnetic field strength information generation circuit 29 measures the oscillation frequency of the voltage controlled crystal oscillator (VCXO) 17 and generates magnetic field strength information indicating the strength of the external magnetic field based on the measurement result. Since the magnetic field is applied to the gas cell 13 by the magnetic field generator 15, for example, information on the oscillation frequency of the voltage controlled crystal oscillator (VCXO) 17 when the external magnetic field is 0 (only the stationary magnetic field) is stored in the memory 27 in advance. The magnetic field strength information generation circuit 29 may compare the measured frequency with the oscillation frequency stored in the memory 27 to calculate the strength of the external magnetic field. Alternatively, a correspondence table between the oscillation frequency of the voltage controlled crystal oscillator (VCXO) 17 and the intensity of the external magnetic field is stored in the memory 27, and the magnetic field strength information generation circuit 29 refers to the correspondence table and sets the measured frequency to the measured frequency. You may obtain | require the intensity | strength of a corresponding external magnetic field by complementary calculation etc.

  The other configuration of the magnetic sensor 2 shown in FIG. 13 is the same as that of the atomic oscillator 1 shown in FIG.

  Note that a magnetic sensor can be realized by replacing the frequency conversion circuit 28 with a magnetic field strength information generation circuit 29 in the atomic oscillator 1 shown in FIG.

3. The present invention is not limited to this embodiment, and various modifications can be made within the scope of the present invention.

[Modification 1]
The atomic oscillator and the magnetic sensor of the present embodiment, the first feedback loop, the light (frequency f ₀ + f _m of the two first-order sideband included in the output light of the semiconductor laser 10 light and the frequency f ₀ -f _m like the light) becomes resonant light pair for generating EIT phenomenon in the alkali metal atom, ie control as the modulation frequency f _m is equal to omega _12/2 is applied, not limited to this. For example, FIG. 14 (A) and 14 (B), the light of one primary sideband (frequency f ₀ + f _m of the light or the frequency f ₀ -f light _m) and the central wavelength lambda ₀ ( Control may be performed so that light of frequency f ₀ ) forms a resonant light pair, that is, modulation frequency f _m matches ω ₁₂ .

[Modification 2]
The atomic oscillator and the magnetic sensor of the present embodiment may be modified to a configuration using an electro-optic modulator (EOM). That is, the semiconductor laser 10 is not modulated by the output signal (modulation signal) of the frequency conversion circuit 20, and generates light having a single wavelength λ ₀ (frequency f ₀ ) corresponding to the set bias current. The light having the wavelength λ ₀ enters an electro-optic modulator (EOM) and is modulated by an output signal (modulation signal) of the frequency conversion circuit 20. As a result, light having a frequency spectrum similar to that in FIG. 3 can be generated. Then, the gas cell 13 is irradiated with light generated by the electro-optic modulator (EOM). In this atomic oscillator and magnetic sensor, a light source is constituted by the semiconductor laser 10 and an electro-optic modulator (EOM). Note that an acousto-optic modulator (AOM) may be used instead of the electro-optic modulator (EOM).

[Modification 3]
In the atomic oscillator and the magnetic sensor of the present embodiment, two primary sideband lights included in the light emitted from one semiconductor laser 10 are used as resonance light pairs. Wavelength light may be generated and used as a resonant light pair. Also in this case, the bias currents of the two semiconductor lasers may be set so that the intermediate wavelength of the resonant light pair is a wavelength between λa and λb.

  Note that the quantum interference device of the present embodiment can be applied to applications other than atomic oscillators and magnetic sensors. For example, since the quantum interference state (quantum coherence state) of alkali metal atoms can be created with the configuration of the quantum interference device of this embodiment, a quantum computer can be obtained by extracting the resonant light pair incident on the gas cell 13. It is also possible to realize a light source used for quantum information equipment such as a quantum memory and a quantum cryptography system.

  The above-described embodiments and modifications are merely examples, and the present invention is not limited to these. For example, it is possible to appropriately combine each embodiment and each modification.

  The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

DESCRIPTION OF SYMBOLS 1 Atomic oscillator, 2 Magnetic sensor, 10 Semiconductor laser, 11 Neutral filter, 12 1/4 wavelength plate, 13 Gas cell, 14 Photo detector, 15 Magnetic field generation part, 16 Detection circuit, 17 Voltage control crystal oscillator (VCXO), 18 modulation circuit, 19 low frequency oscillator, 20 frequency conversion circuit, 21 detection circuit, 22 modulation circuit, 23 low frequency oscillator, 24 drive circuit, 25 magnetic field setting circuit, 26 bias setting circuit, 27 memory, 28 frequency conversion circuit, 29 Magnetic field strength information generation circuit, 30 coils, 31 coils, 40 stationary magnetic field generator, 41 magnetic field deviation generator, 50 coils, 51 coils, 52 coils, 60 magnets, 100 physical package, 200 quantum interference device

Claims (9)

Metal atoms,
A cell enclosing the metal atom;
A light source that irradiates the cell with a resonant light pair that generates an electromagnetically induced transmission phenomenon in the metal atom;
A light detection unit for detecting light transmitted through the cell;
A magnetic field generator for generating a magnetic field inside the cell,
When the intensity of the resonant light pair irradiated by the light source is changed, the frequency difference of the resonant light pair when the output signal of the light detection unit reaches a maximum value is shifted in a direction to cancel the Stark shift. A quantum interference device in which the magnetic field inside the cell is set.   The quantum interference device according to claim 1, wherein the magnetic field inside the cell has a deviation in the irradiation direction of the resonance light pair generated by the light source to the cell.   The quantum interference device according to claim 1, wherein a position where the magnetic field inside the cell is strongest is different from a center of the cell.   The quantum interference according to any one of claims 1 to 3, wherein the magnetic field in the cell has different intensities between a position where light generated by the light source is incident on the cell and a position where the light is emitted from the cell. apparatus. The magnetic field generator is
The quantum interference device according to any one of claims 1 to 4, wherein a unit for Zeeman splitting the energy level of the metal atom is also used. The magnetic field generator is
6. The quantum interference device according to claim 1, wherein the quantum interference device is provided separately from means for splitting the energy level of the metal atom with Zeeman splitting.   An atomic oscillator including the quantum interference device according to claim 1.   The magnetic sensor containing the quantum interference apparatus as described in any one of Claims 1 thru | or 6. A metal atom, a cell enclosing the metal atom, a light source that generates light including two light waves and irradiates the cell, a light detection unit that detects light transmitted through the cell, and an inside of the cell A physics package preparation step of preparing a physics package including a magnetic field generation unit that generates a magnetic field;
When the intensity of the two light waves changes, the magnetic field generation unit generates the frequency difference between the two light waves when the output signal of the light detection unit reaches a maximum value in a direction that cancels the Stark shift. And a magnetic field setting step for setting a magnetic field.

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