Atomic electron state splitter, atomic interferometer, atomic transition frequency measuring device, atomic oscillator, optical lattice clock, quantum computer, and method for generating an atomic electron state superposition state

Abstract

An atomic electron state splitter 1 is provided with an atom supply unit 11, an atom movement path 12, a probe laser light source 13, and a magnetic field generating unit M. The atom supply unit 11 supplies an atom that moves along the atom movement path 12 at a constant speed. The probe laser light source 13 supplies, into the atom movement path 12, probe laser that propagates coaxially with the atom movement path 12 in an opposite direction to, or in the same direction as, the motion of the atom. The magnetic field generating unit M generates, in the atom movement path 12, a magnetic field orthogonal to the atom movement path 12, and mixes an electric dipole transition-permitting electron state and a wave function, enabling pulse excitation of clock transition by a temporally and spatially uniform probe laser. Alternatively, a magnetic shield shields the magnetic field being applied on the atom movement path 12, and spatially varies a Zeeman shift, enabling pulse excitation of clock transition by a temporally and spatially uniform probe laser. As a result, it becomes possible to continuously perform atomic transition spectroscopy and probe laser frequency control, thereby increasing the stability of an atomic clock.

Description

Technical Field

[0001] The present invention relates to an atomic electron state splitter, an atomic interferometer, an atomic transition frequency measuring device, an atomic oscillator, an optical lattice clock, a quantum computer, and a method for generating an atomic electron state superposition state.

[0002] This application claims priority based on US Provisional Patent Application No. 63153434 and Japanese Patent Application No. 2021-116217. The specification of the application is incorporated herein by reference in its entirety.

Background Art

[0003] As methods for measuring the atomic transition frequency with high precision, Rabi spectroscopy and Ramsey spectroscopy are known (see, for example, Non-Patent Document 1). In this specification, a transition between states including atoms, molecules, and ions is referred to as an "atomic transition".

[0004] In these spectroscopic methods, an atom is excited by irradiating the atom with coherent excitation light (probe light) in pulses. The transition probability of an atom changes sensitively according to the frequency of the probe light. Therefore, by measuring the transition probability, the transition frequency can be observed with high accuracy.

[0005] In addition, a "moving optical lattice" has been proposed in which an atom is trapped near the lattice points of an optical lattice and moved and transported on an atomic movement path (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Non-Patent Documents

[0007]

Non-Patent Document 1

[0008] In Ramsey spectroscopy, an atom interacts with the excitation light twice. At this time, the greater the temporal or spatial interval during which the atom interacts with the excitation light, the higher the measurement accuracy of the spectroscopic measurement. However, when the excitation light is spatially separated, the coherence of the excitation light deteriorates due to the mechanical stability of the mirrors that split and reflect the light. Therefore, the wider the interval is increased in an attempt to improve the accuracy, the higher the mechanical stability of the mirrors must be enhanced. In this case, it becomes difficult to maintain coherence. On the other hand, when the excitation light is temporally separated, it is liberated from the problem of the mechanical stability of the mirrors. However, on the other hand, it becomes necessary to separate Ramsey spectroscopy and the state detection of the atom in time. In this case, due to the inability to perform continuous frequency measurement, it is impossible to perform phase-sensitive stabilization of the light. The time required for the generation, capture, and state detection of ultracold atoms becomes wasted time for Ramsey spectroscopy, and it is known that a stability limit called the Dick limit occurs (see, for example, Non-Patent Document 2). Thus, in the conventional methods using Rabi spectroscopy or Ramsey spectroscopy, it is difficult to continuously perform high-precision frequency measurement. Furthermore, the longer the interaction time between the atom and the laser light is increased for the purpose of improving the measurement accuracy, the higher the frequency stability required for the laser light. For the generation of such laser light, it is indispensable to refer to an optical resonator with a length of several tens of centimeters, which causes the apparatus to become large. That is, in the conventional spectroscopic methods, it is difficult to perform high-precision atomic transition frequency measurement with a compact apparatus.

[0009] The present invention has been made in view of such problems, and an object thereof is to realize high-precision spectroscopic measurement using a compact apparatus.

Means for Solving the Problems

[0010] To solve the above problems, an atomic electron state splitter according to an aspect of the present invention includes an atom supply unit, an atomic movement path, a probe laser light source, and a magnetic field generation unit. The atom supply unit supplies atoms that move along the atomic movement path at a constant speed. The probe laser light source supplies a probe laser that propagates coaxially with the atomic movement path in the atomic movement path in a direction opposite to or the same as the movement of the atoms. The magnetic field generation unit generates a magnetic field orthogonal to the atomic movement path in the atomic movement path to mix an electronically dipole transition - allowed electron state and a wave function, enabling the excitation of clock transitions by the probe laser.

[0011] According to this aspect, excitation with an arbitrary pulse area can be realized using a temporally and spatially uniform probe laser. Therefore, an atomic electron state splitter capable of branching the internal state of an atom into an arbitrary superposition state can be realized. The atomic electron state splitter of this aspect can be applied to various applications such as an atomic transition frequency measurement device, an atomic oscillator, an optical lattice clock, and a quantum computer.

[0012] In a certain embodiment, the atomic electron state splitter may include a first optical lattice laser light source and a second optical lattice laser light source. The first optical lattice laser light source and the second optical lattice laser light source form an optical lattice formed by a standing wave by supplying a pair of optical lattice lasers that travel in opposite directions to each other along the atomic movement path. The frequencies of the pair of optical lattice lasers are shifted from each other. The optical lattice thus formed is a moving optical lattice that moves along the atomic movement path. The moving optical lattice transports atoms along the atomic movement path.

[0013] In a certain embodiment, each optical lattice laser may be set to a magic frequency that does not cause a Stark shift in clock transitions.

[0014] In a certain embodiment, the magnetic field may be a magic - frequency AC magnetic field (for example, a magnetic field having a magnetic field component of laser light adjusted to the magic frequency).

[0015] Another aspect of the present invention is an atomic interferometer. This atomic interferometer includes an atomic supply unit, an atomic movement path, a probe laser light source, a first magnetic field generation unit, and a second magnetic field generation unit. The atomic supply unit supplies atoms that move along the atomic movement path at a constant speed. The probe laser light source supplies a probe laser that propagates coaxially with the atomic movement path within the atomic movement path in a direction opposite to or the same as the movement of the atoms. The first magnetic field generation unit and the second magnetic field generation unit generate a magnetic field that is orthogonal to the atomic movement path and parallel to the electric field of the probe light in the atomic movement path, thereby mixing the electric dipole transition - allowed electron states and wave functions, and installing a plurality of atomic electron state splitters that enable excitation by the probe laser light.

[0016] According to this aspect, a compact and highly accurate atomic interferometer can be realized.

[0017] In one embodiment, the atomic interferometer includes a detection laser light source that supplies a detection laser for projection - measuring the electron state of the atoms after the electron state operation by the electron state splitter, and the first magnetic field generation unit and the second magnetic field generation unit may be arranged with an interval corresponding to the interaction length between the atoms and the probe laser. At this time, the first magnetic field generation unit and the second magnetic field generation unit may each realize Ramsey spectroscopy by causing an excitation with a pulse area of π / 2 to occur in the atoms by a combination of the magnetic field and the probe laser.

[0018] In one embodiment, the first magnetic field generation unit and the second magnetic field generation unit may be arranged adjacent to each other without an interval. At this time, the first magnetic field generation unit, the second magnetic field generation unit, and the probe laser each give a pulse with a pulse area of π / 2 to the atoms, and the combined pulse area is π, realizing Rabi spectroscopy.

[0019] Another aspect of the present invention is an atomic transition frequency measurement apparatus. This apparatus includes an atom supply unit, an atom movement path, a probe laser light source, a first magnetic field generation unit, a second magnetic field generation unit, a detection laser light source, and a detector. The atom supply unit supplies atoms that move along the atom movement path at a constant speed. The probe laser light source supplies a probe laser that propagates coaxially with the atom movement path within the atom movement path in a direction opposite to or the same as the movement of the atoms. The first magnetic field generation unit and the second magnetic field generation unit are arranged with an interval corresponding to the interaction length between the atom and the probe laser. The first magnetic field generation unit and the second magnetic field generation unit generate a magnetic field that is orthogonal to the atom movement path and parallel to the electric field of the probe light in the atom movement path, thereby mixing the electric dipole transition - allowed electron state and the wave function and enabling excitation by the probe laser light. The first magnetic field generation unit and the second magnetic field generation unit each realize Ramsey spectroscopy by generating an excitation with a pulse area of π / 2 in the atom through a combination of the magnetic field and the probe laser. The detection laser light source supplies a detection laser for projective measurement of the electronic state of the atoms after receiving pulse irradiation. The detector measures the fluorescence intensity proportional to the occupancy number of a certain electronic state of the atoms.

[0020] According to this aspect, a compact and highly accurate atomic transition frequency measurement apparatus can be realized.

[0021] In an embodiment, the atomic transition frequency measurement apparatus may include a magnetic field generation unit for Rabi spectroscopy measurement before or after the first magnetic field generation unit and the second magnetic field generation unit. The interval between the first magnetic field generation unit and the second magnetic field generation unit is longer than the interaction length of the magnetic field generation unit for Rabi spectroscopy measurement.

[0022] In an embodiment, the atomic transition frequency measurement apparatus may include a pair of a plurality of magnetic field generation units having different lengths from each other.

[0023] In one embodiment, the atomic transition frequency measuring apparatus may include a magnetic field generator for Rabi spectrum measurement before or after the first magnetic field generator and the second magnetic field generator. At this time, the distance between the first magnetic field generator and the second magnetic field generator is longer than the interaction length of the magnetic field generator for Rabi spectrum measurement.

[0024] In one embodiment, the atomic movement path may be an optical waveguide of a hollow core fiber.

[0025] In one embodiment, atoms may be transported along the atomic movement path by a moving optical lattice.

[0026] In one embodiment, an optical lattice trapping atoms may be fixed within the atomic movement path. At this time, the magnetic field generated by the pair of magnetic field generators moves along the atomic movement path.

[0027] Yet another aspect of the present invention is an optical lattice clock and an atomic oscillator. This optical lattice clock and atomic oscillator include the aforementioned atomic electron state splitter, an atomic state detector, and a frequency control circuit according to the output thereof.

[0028] In one embodiment, the optical lattice clock and the atomic oscillator may include a Doppler shift compensation unit including a ring resonator, a beat frequency detector, a first DDS (Direct Digital Synthesizer), a second DDS, a third DDS, a first optical frequency modulator, a second optical frequency modulator, and a third optical frequency modulator.

[0029] According to this aspect, a compact and highly accurate optical lattice clock and atomic oscillator can be realized.

[0030] Yet another aspect of the present invention is a quantum computer. This quantum computer includes the aforementioned atomic electron state splitter.

[0031] According to this aspect, a compact and large-scale quantum computer can be realized.

[0032] Still another aspect of the present invention is a method for generating a superposition state of atomic electronic states using an atomic electronic state splitter. The atomic electronic state splitter includes an atomic supply unit, an atomic movement path, a probe laser light source, and a magnetic field generation unit. This method includes supplying, using the atomic supply unit, atoms that move along the atomic movement path at a constant speed; supplying, using the probe laser light source, a probe laser that propagates coaxially with the atomic movement path and in a direction opposite to or the same as the movement of the atoms within the atomic movement path; and generating, using the magnetic field generation unit, a magnetic field orthogonal to the atomic movement path in the atomic movement path, thereby mixing an electronically dipole-transition-allowed electronic state and a wave function and enabling excitation by the probe laser light.

[0033] According to this aspect, an arbitrary pulse area can be realized using a uniform probe laser. Therefore, it is possible to realize an atomic electronic state that can branch the internal state of an atom into an arbitrary superposition state. The method for generating a superposition state of atomic electronic states in this aspect can be applied to various applications such as an atomic transition frequency measuring device, an atomic oscillator, an optical lattice clock, and a quantum computer.

[0034] Still another aspect of the present invention is an atomic electronic state splitter for an atom having a non-zero total angular momentum (F≠0). This atomic electronic state splitter includes an atomic supply unit, an atomic movement path, a probe laser light source, a magnetic field source, and a magnetic shield. The atomic supply unit supplies atoms that move along the atomic movement path at a constant speed. The magnetic shield is configured to surround the atomic movement path. This magnetic shield reduces an external magnetic field within the shielded portion. The probe laser light source supplies a probe laser that resonates with a Zeeman-shifted atomic transition within the shield into the atomic movement path. Thereby, the atoms can be excited at the shield position.

[0035] According to this aspect, in the atomic electronic state splitter, · Excitation can be controlled by a first-order Zeeman shift ·Measure the Zeeman shifts ±f corresponding to the positive and negative magnetic sub-levels (±m states), and take the average to compensate for the first-order Zeeman shift. ·Also, estimate the magnetic field from the first-order Zeeman shift, and compensate for the second-order Zeeman shift from the result. ·As a result, calibration of the magnetic field and the drive power supply is unnecessary. ·Compared with the magnetic field-induced method, the second-order Zeeman shift and the optical lattice light shift can be reduced to about 1 / 1000. It can be made.

[0036] Another aspect of the present invention is an atomic interferometer. This atomic interferometer includes a plurality of electronic state splitters for atoms having a non-zero total angular momentum (F≠0). That is, this atomic interferometer includes an atomic supply unit, an atomic movement path, a probe laser light source, a magnetic field source, a first magnetic shield, and a second magnetic shield. The atomic supply unit supplies atoms that move along the atomic movement path at a constant speed. The first magnetic shield and the second magnetic shield are configured to surround the atomic movement path. The first magnetic shield and the second magnetic shield reduce the external magnetic field at the first shield position and the second shield position of the portions they surround, respectively. The probe laser light source supplies a probe laser that resonates with the atomic transition with a Zeeman shift within the shield into the atomic movement path. Thereby, atoms can be excited at the first shield position and the second shield position.

[0037] According to this aspect, in the atomic interferometer, ·The excitation can be controlled by the first-order Zeeman shift. ·Measure the Zeeman shifts ±f corresponding to the positive and negative magnetic sub-levels (±m states), and take the average to compensate for the first-order Zeeman shift. ·Also, estimate the magnetic field from the first-order Zeeman shift, and compensate for the second-order Zeeman shift from the result. ·Compared with the magnetic field-induced method, the second-order Zeeman shift and the optical lattice light shift can be reduced to about 1 / 1000. It can be made.

[0038] Yet another aspect of the present invention is an atomic transition frequency measurement device. This atomic transition frequency measurement device includes an atomic supply unit, an atomic movement path, a first magnetic shield, a second magnetic shield, a probe laser light source, a magnetic field source, a detection laser light source, and a detector. The atomic supply unit supplies atoms that move along the atomic movement path at a constant speed. The first magnetic shield and the second magnetic shield are configured to surround the atomic movement path. The first magnetic shield and the second magnetic shield reduce the external magnetic field at the first shield position and the second shield position of the portions they surround, respectively. The probe laser light source supplies a probe laser that resonates with the Zeeman-shifted atomic transition within the shield into the atomic movement path, thereby exciting the atoms at the first shield position and the second shield position. The first magnetic shield and the second magnetic shield realize Ramsey spectroscopy by causing excitation with a pulse area of π / 2 to occur in the atoms at the first shield position and the second shield position. The detection laser light source supplies a detection laser for projective measurement of the electronic state of the atoms after receiving pulse irradiation. The detector measures a signal proportional to the occupancy number of the electronic state of the atoms.

[0039] According to this aspect, in Ramsey spectroscopy, · Excitation can be controlled by the first-order Zeeman shift · Measurement of the Zeeman shifts ±f corresponding to the positive and negative magnetic sublevels (±m states) is performed, and the average is taken to enable compensation for the first-order Zeeman shift · Further, the magnetic field is estimated from the first-order Zeeman shift, and compensation for the second-order Zeeman shift is possible from the result · Compared with the magnetic field-induced method, the second-order Zeeman shift and the optical lattice light shift can be reduced to about 1 / 1000 can be achieved.

[0040] In addition, any combination of the above components, and those obtained by converting the expression of the present invention among devices, methods, systems, recording media, computer programs, etc. are also effective as aspects of the present invention.

Advantages of the Invention

[0041] According to the present invention, high-precision atomic transition frequency measurement can be realized using a compact device.

Brief Description of the Drawings

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Embodiments for Carrying Out the Invention

[0043] Hereinafter, the present invention will be described with reference to the drawings based on preferred embodiments. The embodiments are illustrative rather than limiting the invention, and not all features and combinations thereof described in the embodiments are necessarily essential to the invention. The same or equivalent components, members, and processes shown in each drawing are denoted by the same reference numerals, and repeated explanations are appropriately omitted. Also, the scales and shapes of the respective parts shown in each figure are set for convenience in order to facilitate the explanation, and are not to be construed restrictively unless otherwise specified. Further, when terms such as "first", "second", etc. are used in this specification or claims, these terms do not represent any order or importance unless otherwise specified, and are only for distinguishing one configuration from another. Also, in each drawing, some of the members that are not important in explaining the embodiments are omitted from the display.

[0044] Before describing specific embodiments, the underlying knowledge will be described. FIG. 1 is a schematic diagram of an atomic transition frequency measuring apparatus 100 by Ramsey spectroscopy of a conventional method. The atomic transition frequency measuring apparatus 100 includes an oven 101 for heating atoms, four parallel probe lasers 102a, 102b, 102c, and 102d, and a detector 103. The atomic beam heated in the oven 101 moves with a velocity v in the rightward direction of the paper plane. The probe lasers 102a and 102b are upward in the paper plane, and the probe lasers 102c and 102d are downward in the paper plane, but all of these are orthogonal to the movement direction of the atoms. Atoms in the ground state interact with the probe laser 102a and transition to a superposition state of the ground state and the excited state. When transitioning to the excited state among these, as a result of the momentum of the probe photons being imparted, the atomic orbit also branches into two. As a result of similar transitions of the electron state and the motion state occurring between 102b - c, two closed atomic orbits Tr1 and Tr2 are formed (shown as two trapezoids in FIG. 1). These form two independent interferometers. Using this interferometer, the frequency of the atomic transition can be measured. At this time, the longer the interaction time between the atoms and the probe laser, the higher the measurement accuracy, but on the other hand, the mechanical stability of the probe laser irradiation is impaired. As a result, there is a problem that the measurement accuracy deteriorates. That is, the more the measurement accuracy is to be increased, the more difficult it is to mechanically perform phase control between the four probe lasers, resulting in a trade-off. This limits the improvement of the measurement accuracy. Furthermore, when such an interferometer is used in an atomic clock, since the interferometer encloses a finite area, a rotational acceleration due to the Sagnac effect is detected. This becomes noise for the atomic interferometer.

[0045] [First Embodiment] FIG. 2 is a schematic diagram of an atomic electron state splitter 1 according to the first embodiment. The atomic electron state splitter 1 includes an atom supply unit 11, an atomic movement path 12, a probe laser light source 13, and a magnetic field generation unit M.

[0046] The atom supply unit 11 includes an atom supply source and a laser light source for laser cooling. The atom supply source supplies atoms (for example, 88 Sr) that move along the atom movement path 12 at a constant speed. Specifically, the atoms are cooled by interacting with the laser light source for laser cooling in the atom supply unit 11 and then sent to the atom movement path 12. These atoms move along the atom movement path 12 at a constant speed v.

[0047] The atom movement path 12 functions as a guide for the movement of atoms. The atom movement path 12 can be formed using, for example, a standing wave in free space, a standing wave in an optical resonator, or a standing wave in an optical waveguide. The optical lattice laser that constitutes these standing waves may be set to a magic frequency that does not cause the Stark shift of the clock transition. Alternatively, the atom guide may be formed by a two-dimensional magnetic field trap or a two-dimensional electric field trap (see, for example, Non-Patent Document 4).

[0048] The probe laser light source 13 supplies a probe laser that propagates coaxially with the atom movement path 12 within the atom movement path 12 in a direction opposite to or the same as the movement of the atoms. That is, the propagation direction of the probe laser is parallel or anti-parallel to the movement direction of the atoms. In FIG. 2, as an example, a probe laser that propagates in a direction opposite to the movement of the atoms (that is, semi-parallel to the movement direction of the atoms) is shown.

[0049] The magnetic field generation unit M is configured to surround the atom movement path 12. The magnetic field generation unit M generates a magnetic field B that is orthogonal to the atom movement path 12 and parallel to the probe laser electric field within the atom movement path 12. Atoms moving along the atom movement path 12 at a constant speed v become electric dipole transition allowed at the location of the magnetic field generation unit M. Thereby, a probe laser uniformly irradiated coaxially with the atom movement path 12 can give an arbitrary pulse area to the atoms.

[0050] The magnetic field generation unit M can be formed using, for example, a permanent magnet, an electromagnet, or a combination thereof.

[0051] Let the intensity of the probe laser be I p and assume that the magnitude B of the magnetic field parallel to the probe laser electric field is given. The Rabi frequency Ω B is expressed as follows. Ω B = 2πα√I p |B| ···(1) Here, the parameter α is called the coupling coefficient. Assuming that the polarization of the probe laser and the magnetic field B are parallel, the coupling coefficient α for strontium atoms is α = 198 Hz / (√(mW / cm 2 )) (see, for example, Non-Patent Document 3).

[0052] Suppose an atom in state 1 (ground state) is irradiated with resonant probe light for a time t. At this time, the probability P1(t) of finding the atom in state 1 and the probability P2(t) of finding the atom in state 2 (excited state) are respectively expressed using the pulse area Ω B ·t as P1(t) = |a1| 2 = 1 / 2(1 + cos Ω B ·t) ···(2) P2(t) = |a2| 2 = 1 / 2(1 - cos Ω B ·t) ···(3) where a1 and a2 are the probability amplitudes of states 1 and 2, respectively.

[0053] In this way, an atom that has moved along the atomic movement path 12 at a constant speed v becomes a quantum mechanical superposition state at the location of the magnetic field generation unit M. In other words, this device functions as a state splitter that branches the internal state of the atom into a quantum mechanical superposition state. Furthermore, this device can arbitrarily change the pulse area Ω P ·t shown in equations (2) and (3) according to the atomic movement speed v, the excitation light intensity I B and the magnetic field shape.

[0054] According to this embodiment, an arbitrary pulse area can be realized using a uniform probe laser. Therefore, an atomic electronic state splitter capable of branching the internal state of an atom into an arbitrary superposition state can be realized. This atomic electronic state splitter can be applied to various applications such as an atomic transition frequency measurement device, an atomic oscillator, an optical lattice clock, and a quantum computer.

[0055] In the Ramsey spectroscopy of the conventional method shown in FIG. 1, the propagation direction of the probe laser is orthogonal to the movement direction of the atom. As a result, the atom is "transversely excited". As described above, in such a case, it was necessary to provide a plurality of probe lasers with a fixed device phase relationship. In contrast, in this embodiment, the propagation direction of the probe laser and the movement direction of the atom are coaxial. As a result, the atom is "longitudinally excited". In this way, in this embodiment, since the atom is longitudinally excited, there is a remarkable feature that the entire area of the atomic beam can be covered by a single probe laser. Therefore, it is possible to eliminate the mechanical stability for determining the phase relationship between a plurality of probe lasers as in the conventional method.

[0056] [Second Embodiment] FIG. 3 is a schematic diagram of an atomic electronic state splitter 2 according to the second embodiment. The atomic electronic state splitter 2 includes an atom supply unit 11, an atom movement path 12, a probe laser light source 13, a magnetic field generation unit M, a first optical lattice laser light source 161, and a second optical lattice laser light source 162. That is, the atomic electronic state splitter 2 includes a first optical lattice laser light source 161 and a second optical lattice laser light source 162 in addition to the configuration of the atomic electronic state splitter 1 of FIG. 2. The other configurations of the atomic electronic state splitter 2 are common to the configuration of the atomic electronic state splitter 1.

[0057] The first grating laser light source 161 and the second grating laser light source 162 form a standing-wave grating in the atomic movement path 12 by supplying a pair of grating lasers (grating laser 1 and grating laser 2) that travel in opposite directions to each other. The frequency of the grating laser may be set to a frequency shifted from the magic frequency by the Doppler shift amount.

[0058] The frequencies of grating laser 1 and grating laser 2 are shifted from each other. As a result, the formed grating is a moving grating that moves along the atomic movement path 12. This moving grating transports the aforementioned atoms at a constant speed along the atomic movement path 12.

[0059] According to this embodiment, by confining the atoms in a moving grating, the atoms can be transported at a constant speed v. At this time, if the interaction length is l R then the observation time T is l R / v. The measurement accuracy of the frequency improves in proportion to the -1 power of the observation time T.

[0060] In this case, each grating laser may be set to a magic frequency that does not cause the Stark shift of the clock transition.

[0061] As a further effect obtained by this embodiment, since the atoms are confined in the Lamb Dicke region, the Doppler effect may disappear. As a result, two excitation locations are sufficient, and it is not necessary to perform excitation at three or more locations as in the conventional Ramsey spectroscopy in the optical region.

[0062] As a further effect obtained from the above embodiment using the moving grating, since an aperture for incidentally irradiating the probe from the lateral direction is not required, it may be possible to more completely shield from an external field (blackbody radiation, electric field, magnetic field, etc.).

[0063] [Third Embodiment] Figure 4 is a schematic diagram of the atomic interferometer 3 according to the third embodiment. This atomic interferometer 3 performs splitting (branching) and combining of the electronic states of atoms by combining a plurality of the atomic electronic state splitters of the above-described embodiments. Specifically, the atomic interferometer 3 includes an atomic supply unit 11, an atomic movement path 12, a probe laser light source 13, a first magnetic field generation unit M1, and a second magnetic field generation unit M2. A pair of the first magnetic field generation unit M1 and the second magnetic field generation unit M2 is denoted as MP. The atomic electronic state splitter 1 in FIG. 2 includes one magnetic field generation unit M, whereas the atomic interferometer 3 is different in that it includes two magnetic field generation units (that is, the first magnetic field generation unit M1 and the second magnetic field generation unit M2).

[0064] According to the present embodiment, a compact and highly accurate atomic interferometer can be realized.

[0065] The first magnetic field generation unit M1 and the second magnetic field generation unit M2 are arranged at an interval of l from each other. R l gives the interaction length between the atom and the probe laser. The first magnetic field generation unit M1 and the second magnetic field generation unit M2 generate a magnetic field B that is orthogonal to the atomic movement path 12 and parallel to the electric field of the probe laser within the atomic movement path 12. An atom moving along the atomic movement path 12 at a constant speed v becomes dipole transition allowed at the locations of the first magnetic field generation unit M1 and the second magnetic field generation unit M2. The pulse area Ω·t in the first magnetic field generation unit M1 and the second magnetic field generation unit M2 can be arbitrarily given. In particular, in this example, this pulse area is π / 2. R B

[0066] [Fourth Embodiment] In the atomic interferometer 3 of FIG. 4, the first magnetic field generation unit M1 and the second magnetic field generation unit M2 are arranged at an interval of l from each other. However, the present invention is not limited to this, and the first magnetic field generation unit M1 and the second magnetic field generation unit M2 may be arranged adjacent to each other without an interval. Also in this case, the pulse area Ω in the first magnetic field generation unit M1 and the second magnetic field generation unit M2 R B ​​​·t can be arbitrarily given. In particular, in this example, similar to the second embodiment, the pulse area is π / 2. Also in this case, the probe laser applies a π / 2 pulse to the atom by the first magnetic field generation unit M1 and the second magnetic field generation unit M2. As a result, the atom is irradiated with π / 2 pulses continuously at substantially one location without a time interval. This corresponds to the atom being irradiated with a π pulse once. Thus, this embodiment can realize Rabi spectroscopy.

[0067] [Fifth Embodiment] FIG. 5 is a schematic diagram of an atomic transition frequency measurement device 4 according to the fifth embodiment. The atomic transition frequency measurement device 4 includes an atom supply unit 11, an atom movement path 12, a probe laser light source 13, a first magnetic field generation unit M1, a second magnetic field generation unit M2, a detection laser light source 14, and a detector 15. That is, the atomic transition frequency measurement device 4 includes a detection laser light source 14 and a detector 15 in addition to the configuration of the atom interferometer 3 in FIG. 3. Other configurations of the atomic transition frequency measurement device 4 are common to the configuration of the atom interferometer 3.

[0068] The detection laser light source 14 supplies a detection laser for projective measurement of the electronic state of the atom after receiving pulse irradiation. The propagation direction of this detection laser is orthogonal to the atom movement path 12 (in the example of FIG. 5, the detection laser is assumed to propagate from the back to the front of the paper surface).

[0069] The detector 15 measures the occupation number of the excited state of the atom resulting from the interference of the probability amplitudes of atomic transitions in the first magnetic field generation unit M1 and the second magnetic field generation unit M2.

[0070] Hereinafter, 88 Forbidden transition of Sr 1 S0- 3 Based on P0, the atomic transition frequency measurement using the atomic transition frequency measurement device 4 will be described. FIG. 6 is an enlarged view of a part (near the first magnetic field generation unit M1 and the second magnetic field generation unit M2) of the atomic transition frequency measurement device 4 in FIG. 5. The atom supply unit 11 supplies atoms (in this example, 88Supply Sr). The distance l between the first magnetic field generation unit M1 and the second magnetic field generation unit M2 R is 30 mm. The atoms move at a speed v = 40 mm / s in the rightward direction (x-direction) of the paper surface. The magnitude (magnetic flux density) of the magnetic field B generated by the first magnetic field generation unit M1 and the second magnetic field generation unit M2 is 1 mT. Here, the first magnetic field generation unit M1 and the second magnetic field generation unit M2 may each be composed of two substantially square coils (side length b = 2 mm, interval d = 0.54·b ≒ 1.1 mm). The grating lasers 1 and 2 have a diameter of 2·w0 = 320 μm and a Rayleigh length of 100 mm.

[0071] Fig. 7 shows the distribution of the magnetic field B in the x-direction and the second-order Zeeman shift in the configuration of Fig. 6. It can be seen that the magnetic field B exists substantially only in the vicinity of the first magnetic field generation unit M1 and the second magnetic field generation unit M2. The magnetic field B has an intensity I P = 900 mW / cm 2 gives a π / 2 pulse with respect to the probe laser. The second-order Zeeman shift Δ B (t) changes spatially corresponding to the magnetic field B and takes a maximum value of -23.3 Hz.

[0072] Fig. 8 shows the time variation of the excited state occupancy of the atoms in the configuration of Fig. 6. However, the probe detuning Δ P from the resonance frequency of the atoms is set to -21.3 Hz. The atoms trapped by the moving grating undergo a superposition of the ground state and the excited state electron states due to the π / 2 pulse at the first magnetic field generation unit M1. After a time elapse of T R = l R / v = 750 ms, the atoms reach the second magnetic field generation unit M2. Due to the π / 2 pulse here, the excited state occupancy becomes almost 100%. This corresponds to Ramsey interference when the probe laser frequency resonates with the Zeeman-shifted electron state. Also, the superposition of quantum states by the π / 2 pulse can be used, for example, as an Hadamard gate in a quantum computer.

[0073] As shown in Fig. 6, the diameter of the detection laser is 1 mm, and the distance l between the second magnetic field generation unit M2 and the detection laserd Let it be 1 mm. At this time, the light detection efficiency of the detector 15 becomes 10%. As a result, 1 S0- 3 When attempting fluorescence observation by exciting the P1 transition, since 10 or more photons can be observed per atom, the number of atoms can be observed at the shot noise limit. On the other hand, the 1S0-3P1 transition of the atoms in the M2 region is greatly Zeeman-shifted with respect to its natural width of 7.5 kHz, so it is non-resonant with the detection light. Therefore, the optical shift of the atoms due to this fluorescence can be suppressed to the -18 level of 10.

[0074] Fig. 9 shows the excited state occupancy of the atoms in the configuration of Fig. 6 as a function of the frequency detuning (the difference between the optical frequency and the resonance frequency). The excited state occupancy of the atoms irradiated with the π / 2 pulse by the first magnetic field generation unit M1 and the second magnetic field generation unit M2 is shown by the Ramsey spectrum. As shown in the figure, the width 1 / T R of the Ramsey spectrum is 1.33 Hz, and the center frequency is detuned by Δ P = -21.3 Hz due to the Zeeman shift. On the other hand, the excited state occupancy irradiated with the π / 2 pulse by the first magnetic field generation unit M1 is shown by the Rabi spectrum. The transition time δt when the atoms pass through the first magnetic field generation unit M1 and the second magnetic field generation unit M2 is estimated to be δt = b / v = 50 ms. Therefore, the linewidth is estimated to be 1 / δt = 20 Hz.

[0075] As described above, the Ramsey spectrum is Zeeman-shifted by Δ P = -21.3 Hz. Actually, this value depends on the spatial shape of the first magnetic field generation unit M1 and the second magnetic field generation unit M2. However, this frequency shift can be stabilized with an accuracy of -18 10 by controlling the magnetic field. The frequency sensitivity ξ1 with respect to the change δB of the magnetic field is estimated to be -3.2 Hz / mT. The magnitude of this value is the value δν predicted from the second-order Zeeman shift ZIt is one order of magnitude smaller than / δB≒-46.6Hz / mT. This is the result of the atoms being exposed to the magnetic field only at specific locations (the locations of the first magnetic field generating unit M1 and the second magnetic field generating unit M2). That is, the length of this specific location is approximately one order of magnitude smaller than the total interaction length. Due to this low sensitivity, with magnetic field control of sub-μT or 100 ppm, 10 -18 of accuracy can be achieved.

[0076] According to this embodiment, the magnetic field B exists limited to a specific location (that is, the locations of the first magnetic field generating unit M1 and the second magnetic field generating unit M2), rather than the entire atomic movement path 12. Therefore, the spatial interval for Ramsey spectroscopy can be arbitrarily designed by changing the interaction length l R . For example, by increasing the interaction length l R , the interaction time T = l R / v is extended, and as a result, the frequency resolution is improved to 1 / T. Also, since the atomic excitation region and the state observation region are spatially separated, continuous observation of atomic transitions becomes possible. As described above, since there is one probe, even if the interaction length l R is increased, the coherence of the probe laser does not deteriorate, and the effect that high-precision frequency measurement can be continuously performed is obtained. However, in reality, it should be noted that the interaction length l R is limited by the Rayleigh length of the laser constituting the optical lattice or the coherence time of the probe laser.

[0077] The above description was made for an example using 88 Sr as the atom. However, the atom used in this method is not limited to this. It is applicable to atoms having a forbidden transition that becomes allowed due to state mixing by the application of a magnetic field. For example, this method is also applicable to Group IIA elements other than Sr such as Mg and Ca, Group IIB elements such as Zn, Cd, Hg, or Yb.

[0078] [Sixth Embodiment] FIG. 10 is a schematic diagram of an optical lattice clock or an atomic oscillator 5 according to the sixth embodiment (a frequency control circuit for a probe laser is added to FIG. 5). The optical lattice clock or the atomic oscillator 5 includes, in addition to the configuration of the atomic transition frequency measuring device 4 in FIG. 5, a third magnetic field generating unit M3 before or after the pair MP of the magnetic field generating unit. As will be described later, the third magnetic field generating unit M3 is a magnetic field generating unit for measuring a Rabi spectrum. The third magnetic field generating unit M3 generates a magnetic field B2 orthogonal to the atomic movement path 12 within the atomic movement path 12. Here, the interaction length l s with respect to the atom and the magnetic field B2 is 4 mm. The first magnetic field generating unit M1 and the second magnetic field generating unit M2 are configured by being arranged at intervals from each other. In contrast, the third magnetic field generating unit M3 is configured by arranging the first magnetic field generating unit M1 and the second magnetic field generating unit M2 adjacent to each other without an interval.

[0079] FIG. 11 shows the Ramsey spectrum regarding the interaction length l R (between the first magnetic field generating unit M1 and the second magnetic field generating unit M2) and the Rabi spectrum regarding the interaction length l s (the third magnetic field generating unit M3). An atom moving at a speed v = 40 mm / s on the axis of the probe laser is subjected to a π pulse by the probe laser in the region of the magnetic field B2 for a time T s = l s / v = 0.1 s. Therefore, the line width of the Rabi spectrum is 1 / T sIt becomes ≒10 Hz. The frequency sensitivity ξ2 with respect to the magnetic field change δB at this time is estimated to be -35.6 Hz / mT. This value is one order of magnitude larger than the sensitivity ξ1 = -3.2 Hz / mT in the case of the Ramsey spectrum. By applying a magnetic field B2 = 0.99 mT, the shoulder of the Rabi excitation spectrum can be adjusted to the frequency locking point Δ1 = -21.59 Hz. However, this frequency locking point is determined by the Ramsey spectrum where the excitation probability p1 is 0.5. The magnitude of the magnetic field |B2| can be controlled by compensating for the long-term drift of the magnetic field so that the Rabi excitation probability p2 is 0.5. By simultaneously measuring the Ramsey spectrum and the Rabi spectrum in this way, the measurement range of the Ramsey spectrum can be extended. Fig. 11 shows an example of extending the measurement range of the Ramsey spectrum, which was 0.66 Hz, by about three times by using this method. This extended range can be up to 10 Hz, which is the linewidth of the Rabi spectrum.

[0080] As shown in Fig. 11, in the Ramsey spectrum, the cumulative phase R of the measurement time T [Number] results in an excitation state occupancy p proportional to the frequency change within the range of |θ| ≦ π / 2. However, beyond this range, the proportional relationship is inverted and behaves oscillatory. Therefore, the effective range of the Ramsey spectrum is limited, which is 0.66 Hz in Fig. 11. By simultaneously measuring the Rabi spectrum, information on the temporal fluctuation ν(t) of the laser frequency can be obtained. By using this, it becomes possible to estimate the cumulative phase due to the laser frequency fluctuation during Ramsey spectroscopy even for |θ| > π / 2. Using this result, by setting p = 2 - p when π / 2 ≦ θ ≦ 3π / 2 and p = -p when -3π / 2 < θ < -π / 2, the measurement range of the Ramsey spectrum can be extended. Fig. 11 shows an example of extending the measurement range of the Ramsey spectrum, which was 0.66 Hz, by about three times by using this method. By applying this method, the extended range can be up to 10 Hz, which is the linewidth of the Rabi spectrum.

[0081] Figure 12 shows simulation results for confirming the effects of the present embodiment. The horizontal axis represents the average time, and the vertical axis represents the Allan variance. The unfilled plots (□, ○, △) indicate the stability of the lasers used. The filled plots (■, ●, ▲) indicate the simulation results of the stability of the atomic clock obtained according to the present embodiment. In this simulation, it is assumed that measurements are made with 10,000 atoms per second. As a result of the expansion of the measurement region by the Ramsey spectrum and continuous measurement, for a laser (□) with a flicker floor of 1×10 -15 it can be seen that a stability of 19 digits is reached with an average time of about 1000 seconds (■). This result is comparable to the results obtained conventionally using extremely high-precision lasers (●, ▲).

[0082] According to the present embodiment, the measurement region of the Ramsey spectrum can be expanded.

[0083] [Seventh Embodiment] FIG. 13 is a schematic diagram of an optical lattice clock or an atomic oscillator 6 according to the seventh embodiment (a frequency control circuit for the probe laser is added with respect to FIG. 5). While the atomic transition frequency measurement device 4 in FIG. 5 includes one pair MP of the magnetic field generation unit, the optical lattice clock or the atomic oscillator 6 includes three pairs MP1, MP2, and MP3 of the magnetic field generation units. Each of the pairs MP1, MP2, and MP3 of the magnetic field generation units is configured to include two magnetic field generation units. The interaction length L1 of the pair MP1 of the magnetic field generation units, the interaction length L2 of the pair MP2 of the magnetic field generation units, and the interaction length L3 of the pair MP3 of the magnetic field generation units are different from each other. In this example, L1 < L2 < L3.

[0084] There is an uncertainty relation of Δν·Δt = 1 between the frequency measurement uncertainty Δν and the observation time Δt. Therefore, in the pair of magnetic field generating units (MP1) with a short interaction length, the measurement time of the excitation probability is short (Δt is small), but the measurement accuracy is low (Δν is large). Conversely, in the pair of magnetic field generating units (MP3) with a long interaction length, the measurement accuracy is high (Δν is small), but the measurement time of the excitation probability is long (Δt is large). By making it possible to select the measurement results of MP1 to MP3 for each feedback frequency band, the feedback band and the feedback accuracy can be balanced. In this embodiment, since multiple measurements are required for one atom, it is preferable to perform the measurement while maintaining the atom in the optical lattice without heating it. An example of this is the method of exciting the 1 S0- 3 P1 transition and performing fluorescence observation while laser cooling.

[0085] According to this embodiment, the measurement accuracy and the measurement time can be balanced, and the dynamic range of the feedback control can be expanded.

[0086] [Embodiment 8] FIG. 14 is a schematic diagram of an optical lattice clock or an atomic oscillator 7 according to the eighth embodiment (a frequency control circuit for a probe laser is added to FIG. 5). The optical lattice clock or the atomic oscillator 7 includes a fourth magnetic field generating unit M4 before or after the pair of magnetic field generating units MP in addition to the configuration of the atomic transition frequency measuring device 4 in FIG. 5. The optical lattice clock or the atomic oscillator 7 is characterized in that the probe light includes sidebands instead of a single frequency. That is, in this embodiment, sidebands are also used for atomic transition frequency measurement. By generating a strong magnetic field B4 with M4 to increase the mixing by the magnetic field, the transition dipole moment is increased. At this time, the second-order Zeeman shift also increases. Therefore, in order to probe this atomic transition, sidebands are generated for the probe light using an electro-optic element or the like. Using this sideband, this transition can be measured independently of the clock transition of the main band.

[0087] According to this embodiment, by shortening the observation time and performing high-speed feedback control, it becomes possible to improve the high stability of the optical lattice clock.

[0088] [Embodiment 9] FIG. 15 is a schematic diagram of the atomic movement path of the atomic transition frequency measurement apparatus according to the ninth embodiment. This atomic movement path is constituted by an optical waveguide using a hollow-core fiber. In this embodiment, the magnetic field is fixed and the optical lattice is moved. That is, the optical lattice moves in the hollow-core fiber and transports atoms. The magnetic field can be realized by a magnetic disk, a magnetic tape, a loop current of a printed circuit board, etc. Since the radial distribution of the atoms can be limited to a region of about 10 μm, the uniformity of the magnetic field in the radial direction only needs to cover about 10 μm.

[0089] According to this embodiment, the entire apparatus can be miniaturized.

[0090] [Embodiment 10] FIG. 16 is a schematic diagram of the atomic movement path of the atomic transition frequency measurement apparatus according to the tenth embodiment. This atomic movement path is also constituted by an optical waveguide using a hollow-core fiber. In this embodiment, contrary to the ninth embodiment, the optical lattice is fixed and the magnetic field is moved. The magnetic field can be realized by a magnetic disk, a magnetic tape, etc. Since the radial distribution of the atoms can be limited to a region of about 10 μm, the uniformity of the magnetic field in the radial direction only needs to cover about 10 μm.

[0091] According to this embodiment, the entire apparatus can be miniaturized.

[0092] [Embodiment 11] FIG. 17 is a schematic diagram of an optical lattice clock 20 according to the eleventh embodiment. The optical lattice clock 20 includes an atomic electron state splitter according to any of the foregoing embodiments. The optical lattice clock itself may use existing technologies (see, for example, Non-Patent Document 8), and the part for measuring the atomic transition frequency may be replaced with the configuration of the foregoing embodiments. In this case, the magnetic field can be generated by two magnets or two sets of Helmholtz coils.

[0093] According to this embodiment, a compact and highly accurate optical lattice clock can be realized.

[0094] [Twelfth Embodiment] FIG. 18 is an enlarged schematic diagram of a part of a quantum computer 30 according to the twelfth embodiment. The quantum computer 30 includes atoms trapped in a moving optical lattice and an atomic electron state splitter according to any of the foregoing embodiments. That is, the superposition of quantum states by the π / 2 pulse of the atomic electron state splitter can be used as the Hadamard gate of the quantum computer 30. Each atom trapped in the optical lattice functions as a quantum bit. Note that in order to configure a quantum computer, it is necessary to realize basic arithmetic functions for quantum bits, but this can be realized as follows using the configuration of this embodiment. · The quantum bit is represented by whether the atom is in the ground state or the excited state. · Each atom is a flying quantum bit moving at a speed v, and undergoes a spatial quantum operation during the movement. · A probe laser is arranged in each moving optical lattice, and the state of the atom is manipulated using a local magnetic field. · Using an excitation with a pulse area of π / 2, a superposition state of bit 0 and bit 1 is generated. · Using an excitation with a pulse area of π, the excited state of the atom is inverted, that is, the bit is inverted. · By changing the Zeeman shift amount according to the position and magnitude of the applied magnetic field, individual addresses of the quantum bits are performed by the frequency of the probe laser. · By means of the resonator quantum electrodynamics (CQED) method, a quantum entanglement state is formed between adjacent atoms in the same moving optical lattice. · The moving optical lattice in which atoms are trapped and the corresponding probe laser can be extended to N columns. · A quantum entanglement state can be formed by means of the resonator quantum electrodynamics (CQED) method between atoms in different columns. Thereby, a two-dimensional quantum entanglement state can be formed. · Each probe light and local magnetic field can be changed temporally. · After a series of quantum operations, the state of each atom is measured by projective measurement.

[0095] According to this embodiment, a compact and highly scalable quantum computer for qubits can be realized.

[0096] [Embodiment 13] Embodiment 13 is a voltage / current-controlled atomic oscillator. This atomic oscillator includes the atomic transition frequency measurement device of any of the foregoing embodiments. A Helmholtz coil is used to generate a magnetic field. As an example, if the radius of the Helmholtz coil is 0.5 mm, a magnetic field with a magnetic flux density of 1.9 mT / A can be generated according to the current. Since a current noise of 5 μA corresponds to a frequency error of about 0.4 mHz, by suppressing the current noise to about 5 μA or less (a sufficiently practical accuracy), a voltage-controlled atomic oscillator with a relative uncertainty of 10 -18 can be realized.

[0097] According to this embodiment, a compact and highly accurate atomic oscillator can be realized.

[0098] [Embodiment 14] FIG. 19 is a flowchart of a method for generating a superposed state of atomic electron states according to the 14th embodiment. This method for generating a superposed state of atomic electron states uses the atomic electron state splitter of the above-described embodiment. That is, the atomic electron state splitter includes an atom supply unit, an atomic movement path, a probe laser light source, and a magnetic field generation unit. The method for generating a superposed state of atomic electron states includes a step S1 of supplying atoms moving at a constant speed along the atomic movement path using the atom supply unit, a step S2 of supplying a probe laser propagating coaxially with the atomic movement path in the atomic movement path in a direction opposite to or the same as the movement of the atoms using the probe laser light source, and a step S3 of generating a magnetic field orthogonal to the atomic movement path in the atomic movement path using the magnetic field generation unit to mix an electronically dipole transition-allowed electron state and a wave function. As shown in FIG. 19, as a result of being developed in space, these three steps proceed in parallel.

[0099] This method may further include a step of observing the atoms and performing feedback control on the probe laser frequency.

[0100] According to this embodiment, an arbitrary pulse area can be realized using a uniform probe laser. Therefore, an atomic electron state splitter capable of branching the internal state of an atom into an arbitrary superposed state can be realized. The method for generating a superposed state of atomic electron states in this aspect can be applied to various applications such as an atomic transition frequency measuring device, an atomic oscillator, an optical lattice clock, and a quantum computer.

[0101] [15th Embodiment] In an embodiment of the present invention, compensation for frequency changes (hereinafter referred to as Doppler shifts) caused by the Doppler effect is an important issue. For example, when the moving speed of an optical lattice is 40 mm / s, the Doppler effect is 57 kHz. At this time, in order to obtain a measurement accuracy of 18 digits, it is necessary to perform compensation for the Doppler effect up to 0.4 mHz. This compensation is extremely important for realizing a highly accurate vertical excitation Ramsey clock. The device of the 15th embodiment includes a Doppler shift compensation device.

[0102] FIG. 20 is a schematic diagram of a Doppler shift compensation device 40 according to the 15th embodiment. FIG. 21 is a schematic diagram of an optical measurement system 42 in the Doppler shift compensation device 40 of FIG. 20. In addition to the configuration of the atomic electron state splitter 2 described in the second embodiment (that is, the longitudinal excitation Ramsey region 401, the probe laser light source 402 that supplies the probe laser, the first grating laser light source 403 that supplies the grating laser 1, and the second grating laser light source 404 that supplies the grating laser 2), the Doppler shift compensation device 40 includes a ring resonator 405 for the probe laser and the grating laser, a beat frequency detector 406 for the grating lasers 1 and 2, a first DDS 407, a second DDS 408, a third DDS 409, a first optical frequency modulator 410, a second optical frequency modulator 411, and a third optical frequency modulator 412. Here, DDS refers to a Direct Digital Synthesizer.

[0103] Compensation for the Doppler shift is performed by three DDSs (that is, the first DDS 407, the second DDS 408, and the third DDS 409) that refer to the same reference clock. The frequencies ν1 of the first DDS 407, ν2 of the second DDS 408, and ν3 of the third DDS 409 are as follows, respectively. ν1 = 2·(v / c)·f1 ν2: Driving frequency of the optical frequency modulator (arbitrary) ν3 = ν2+(v / c)·f2 Here, f1 is the frequency of the grating laser known as the magic frequency, and this frequency is a known value with 9 digits. f2 is the frequency of the probe laser, and this frequency is a known value with 15 digits. v is the speed of the moving grating (arbitrary set value). c is the speed of light. Note that the frequency of the grating laser 1 is given by f1(1) = f1(1 + v / c), and the frequency of the grating laser 2 is given by f1(2) = f1(1 - v / c), respectively.

[0104] The operation procedure of the Doppler shift compensation device 40 is as follows (see FIGS. 20 and 21). (1) Determine the moving speed v by ν1. (2) Set the frequency ν2 of the optical frequency modulator. (3) Using the frequency ν1 of the first DDS 407 and the frequency ν2 of the second DDS 408, set the frequency ν3 of the third DDS 409 according to the relationship ν3 = ν2 + (ν1 / 2)·(f2 / f1).

[0105] According to this embodiment, the Doppler shift can be effectively compensated.

[0106] In the embodiments described above, what was the DC magnetic field may be an AC magnetic field. In particular, an AC magnetic field at the magic frequency (for example, a magnetic field having a magnetic field component of laser light adjusted to the magic frequency) is an effective embodiment.

[0107] In the first to fifteenth embodiments, atoms moving at a constant speed by a moving optical grating at the magic wavelength are made to interact with a local magnetic field. By utilizing the state mixing with the allowed transition by this local magnetic field, continuous Rabi or Ramsey spectroscopy becomes possible. However, this method has · the atomic spectrum is perturbed by a large second-order Zeeman shift · magnetic field calibration is required to determine the value of this second-order Zeeman shift · the heat generation of the coil for generating the magnetic field causes non-uniform blackbody radiation such problems.

[0108] [Sixteenth Embodiment] To solve such problems, in the embodiments described below, clock transitions resulting from hyperfine mixing occurring in isotopes of alkaline-earth-like atoms having nuclear spins (including Yb atoms in addition to alkaline-earth metal atoms) are utilized. Hereinafter, the method of inducing transitions by state mixing with a local magnetic field, such as the aforementioned first to fifteenth embodiments, may be referred to as a "magnetic field-induced type". In contrast, a method of performing local excitation by utilizing a spatially varying first-order Zeeman shift due to magnetic field shielding, using the clock transitions resulting from the following hyperfine mixing, may be referred to as a "magnetic field shielding type".

[0109] FIG. 22 is a schematic diagram of an atomic transition frequency measuring apparatus 8 according to the sixteenth embodiment. The atomic transition frequency measuring apparatus 8 includes an atomic supply unit 11, an atomic movement path 12 extending in the x direction, a probe laser light source 13, a magnetic field source 17, a first magnetic shield Sh1, a second magnetic shield Sh2, a detection laser light source 14, a detector 15, and a pump light source 16. The spectroscopic region is defined between the first magnetic shield Sh1 and the second magnetic shield Sh2. In the spectroscopic region, a bias magnetic field B b is applied using the magnetic field source 17 in a direction orthogonal to the atomic movement path 12. The bias magnetic field B b in FIG. 22 is a uniform magnetic field with a magnitude of about 2 mT and directed in the z direction. However, the bias magnetic field B b is not limited to this. That is, the bias magnetic field B b does not have to have a strength of 2 mT and does not have to be uniform.

[0110] As described above, the atomic supply unit 11 supplies atoms moving in the x direction along the atomic movement path 12 as a moving optical lattice. However, the atoms here are alkaline-earth-like atoms having a nuclear spin I (in this example, Sr with I = 9 / 2). 87 The moving optical lattice of Sr supplied by the atomic supply unit 11 moves along the atomic movement path 12 at a constant speed v (for example, v = 40 mm / s). 87

[0111] ​The probe laser light source 13 supplies a probe laser that propagates coaxially with the atomic movement path 12 within the atomic movement path 12, in the direction opposite to or the same as the movement of the atoms (i.e., in the -x direction or +x direction). That is, the propagation direction of the probe laser is parallel or anti-parallel to the movement direction of the atoms. In the example of FIG. 22, 87 a probe laser that propagates in the direction opposite to the movement of Sr is shown. The probe laser resonates with the Zeeman-shifted clock transition in 87 Sr with I = 9 / 2. In the example of FIG. 22, as the probe laser, 1 S0(m = ±I) → 3 a two-frequency laser corresponding to the transition of P0(m = ±I) is incident.

[0112] The first magnetic shield Sh1 and the second magnetic shield Sh2 are configured to surround the atomic movement path 12. In the example of FIG. 22, the first magnetic shield Sh1 and the second magnetic shield Sh2 are composed of, for example, an annular ring made of permalloy. Their dimensions are, for example, an outer diameter of 10 mm, an inner diameter (aperture diameter) of 1 mm, and a thickness of 2 mm (it goes without saying that they are not limited to these numerical values). The atomic movement path 12 passes through the apertures of the first magnetic shield Sh1 and the second magnetic shield Sh2. The magnetic field is reduced inside the area surrounded by the first magnetic shield Sh1 and the second magnetic shield Sh2 (hereinafter also referred to as the "magnetic shield position"). A weak magnetic field (for example, about 32 μT at minimum in the configuration of FIG. 22) also exists at the magnetic shield position, and the Zeeman shift depending on the magnetic sub-level m is utilized thereby.

[0113] The detection laser light source 14 87 for Sr 1 S0(F = I, m = ±I) → 3 incides a detection laser that excites P1(F = I + 1, m = ±(I + 1)) at the detection position. By making the Zeeman shift sufficiently large with respect to the natural width of the transition of about 7.5 kHz, the atoms in the state of m = ±I can be separated by the Zeeman shift and measured. In the example of FIG. 22, the detection position is at a distance l d away from the second magnetic shield Sh2.

[0114] Detector 15 measures the interference of probability amplitudes, which is caused by the excitation of atomic transitions in magnetic shield Sh1 and the second magnetic shield Sh, as the atomic excited state occupancy. Here, for reducing the collision shift, the atomic occupancy per photon is set to 1 or less.

[0115] The pump light source 16 emits pump light at the pump light incident position. Thereby, the π transition of the F = I → I - 1 transition is excited, and optical pumping is performed on two magnetic sublevels of m = ±I. In the configuration of FIG. 22, the magnetic field is shielded so that the Zeeman broadening is about the saturation width of excitation (magnetic shield Sh0).

[0116] FIG. 23 shows the Zeeman shift in the spectral region of FIG. 22 (Zeeman sublevel m = 9 / 2). However, the bias magnetic field B b is a uniform magnetic field with a strength of 2 mT. The atoms moving along the atomic movement path are 87 Sr having a nuclear spin I = 9 / 2. The moving speed of the atoms is about 40 mm / s, and the first magnetic shield Sh1 and the second magnetic shield Sh2 are separated from each other by about 30 mm. Therefore, it takes about 750 ms for the atoms to move from the first magnetic shield Sh1 to the second magnetic shield Sh2. As a result of the presence of a weak magnetic field (for example, about 32 μT at minimum in the configuration of FIG. 22) also at the magnetic shield positions, the Zeeman shift depending on the magnetic sublevel m is utilized. This first-order Zeeman shift is about 150 Hz when m = 9 / 2, which is converted at m × 1.06 × 10 6 Hz / T. As shown in FIG. 23, a large Zeeman shift occurs at the position outside the magnetic shield, and the atoms are non-resonant with respect to the light of the probe laser.

[0117] FIG. 24 schematically shows the principle of measuring the state occupancy of each state of the magnetic sublevels of m = ±I. The upper figure is 87 of 1 Sr 3 showing the energy levels in the S0(F = I, m = ±I) → bHaving linearly polarized light orthogonal thereto (i.e., a superposition of right-handed circularly polarized light and left-handed circularly polarized light with respect to the quantization axis taken in the direction of the bias magnetic field B b ), the laser frequency of the detection laser is modulated by ±ν z (period T), and fluorescence measurement is performed in synchronization with this. Note that when B = 2 mT, the Zeeman shift of adjacent magnetic sublevels excited by right-handed circularly polarized light and left-handed circularly polarized light is 16 MHz (>> 7 kHz, natural width). As a result, the excitation of the magnetic sublevel to the ground state during detection by the detection light that causes optical pumping can be made sufficiently small.

[0118] Figure 25 shows the time changes of the atomic excited state occupancy and the Zeeman shift in the configuration of Figure 22. As described above, at the first shield position, the Zeeman shift is about 32 μT, and since the resonance condition with the probe laser is satisfied, the excited state occupancy increases from 0 to 50% (π / 2 pulse). When passing through the first shield position, the system develops freely with the excited state occupancy remaining at 50% because of non-resonance with the probe light due to the large Zeeman shift. At the second shield position, the Zeeman shift becomes about 32 μT again, and the excited state occupancy increases from 50% to 100% again by the π / 2 pulse.

[0119] Figure 26 shows the Ramsey spectra of m = -9 / 2 (left side of the figure) and m = 9 / 2 (right side of the figure) in the configuration of Figure 22. As shown in the figure, the spectral waveform is almost symmetric about the frequency 0. Therefore, by taking the average from the observation results of m = -9 / 2 and m = 9 / 2, Ramsey spectroscopy that cancels the value of the first-order Zeeman shift becomes possible.

[0120] Figure 27 is an enlarged view of Figure 26. As shown, since the spectra of the -m magnetic sublevel and the +m magnetic sublevel are Zeeman-shifted symmetrically with respect to the spectrum center when there is no Zeeman shift, the point where the frequency becomes 0 can be obtained by taking this average. On the other hand, the effective magnetic field felt by the atom can be estimated from the frequency difference between the spectra of the -m magnetic sublevel and the +m magnetic sublevel. Using this value, a minute second-order Zeeman shift can be estimated and compensated for.

[0121] As described above, according to the 16th embodiment (magnetic field shielding type), in Ramsey spectroscopy that uses an alkaline earth-like metal having a nuclear spin and performs π / 2 pulse excitation at a magnetically shielded position, · Measurement and compensation of the first-order Zeeman shift can be performed by observing the spectra of the positive and negative magnetic sublevels m = ±I states · Estimation and compensation of the second-order Zeeman shift can be performed using this value · As a result, detailed magnetic field setting becomes unnecessary · The second-order Zeeman shift and the optical lattice light shift can be reduced to about 1 / 1000 compared to the magnetic field-induced method And the like effects can be obtained.

[0122] Although the 16th embodiment was an atomic transition frequency measuring device, using the same principle, an atomic electron state splitter and an atom interferometer can also be realized as follows.

[0123] [17th Embodiment] The 17th embodiment is an electronic state splitter for an atom having non-zero total angular momentum (F≠0). This electronic state splitter for an atom includes an atom supply unit, an atomic movement path, a probe laser light source, a magnetic field source, and a magnetic shield. The atom supply unit supplies atoms that move along the atomic movement path at a constant speed. The magnetic shield is configured to surround the atomic movement path. This magnetic shield reduces an external magnetic field within the shielded portion that it surrounds. The probe laser light source supplies a probe laser that resonates with a Zeeman-shifted atomic transition within the shield into the atomic movement path. Thereby, atoms can be excited at the shield position.

[0124] [18th Embodiment] The 19th embodiment is an atomic interferometer. This atomic interferometer includes a plurality of electronic state splitters for an atom having non-zero total angular momentum (F≠0). That is, this atomic interferometer includes an atom supply unit, an atomic movement path, a probe laser light source, a magnetic field source, a first magnetic shield, and a second magnetic shield. The atom supply unit supplies atoms that move along the atomic movement path at a constant speed. The first magnetic shield and the second magnetic shield are configured to surround the atomic movement path. The first magnetic shield and the second magnetic shield each reduce an external magnetic field within the shielded portion that it surrounds. The probe laser light source supplies a probe laser that resonates with a Zeeman-shifted atomic transition within the shield into the atomic movement path. Thereby, atoms can be excited at the first shield position and the second shield position.

[0125] Note that all of the various numerical values used in the above description are for illustrative purposes only and do not limit the scope of the present invention.

[0126] As described above, the present invention has been described based on embodiments. It is understood by those skilled in the art that these embodiments are examples, and that various modifications are possible for each combination of their respective components and each processing process, and that such modifications are also within the scope of the present invention.

Industrial Applicability

[0127] The present invention relates to an atomic electron state splitter, an atomic interferometer, an atomic transition frequency measuring device, an atomic oscillator, an optical lattice clock, a quantum computer, and a method for generating an atomic electron state superposition state.

[0128] This application claims priority based on U.S. Provisional Patent Application No. 63153434. The specification of the provisional application is hereby incorporated by reference in its entirety.

Description of Reference Numerals

[0129] 1 ··· Atomic electron state splitter. 2 ··· Atomic electron state splitter. 3 ··· Atomic interferometer. 4 ··· Atomic transition frequency measuring device. 5 ··· Atomic transition frequency measuring device. 6 ··· Atomic transition frequency measuring device. 7 ··· Atomic transition frequency measuring device. 8 ··· Atomic transition frequency measuring device. 11 ··· Atomic supply unit. 12 ··· Atomic movement path. 13 ··· Probe laser light source. 14 ··· Detection laser light source. 15 ··· Detector. 16 ··· Pump light light source. 17 ··· Magnetic field source. 161 ··· First optical lattice laser light source. 162 ··· Second optical lattice laser light source. 20 ··· Optical lattice clock. 30 ··· Quantum computer. 40 ··· Doppler shift compensation device. 42 ··· Measurement system of the Doppler shift compensation device. 401 ··· Longitudinal excitation Ramsey region. 402 ··· Probe laser light source. 403 ··· First optical lattice laser light source. 404 ··· Second optical lattice laser light source. 405 ··· Ring resonator. 406 ·· Beat frequency detector. 407 ·· First DDS. 408 ·· Second DDS. 409 ·· Third DDS. 410 ·· First optical frequency modulator. 411 ·· Second optical frequency modulator. 412 ·· Third optical frequency modulator. M ·· Magnetic field generation unit. M1 ·· First magnetic field generation unit. M2 ·· Second magnetic field generation unit. M3 ·· Third magnetic field generation unit. M4 ·· Fourth magnetic field generation unit. MP ·· Pair of magnetic field generation units. MP1 ·· Pair of magnetic field generation units. MP2 ·· Pair of magnetic field generation units. MP3 ·· Pair of magnetic field generation units. Sh1 ·· First magnetic shield. Sh2 ·· Second magnetic shield. S0 ·· Magnetic shield.

Claims

1. An atomic state splitter comprising an atomic supply unit, an atomic movement path, a probe laser light source, and a magnetic field generation unit, wherein the atomic supply unit supplies atoms that move along the atomic movement path at a constant speed, the probe laser light source supplies a probe laser that propagates coaxially within the atomic movement path in a direction opposite to or the same as the movement of the atoms, and the magnetic field generation unit generates a magnetic field orthogonal to the atomic movement path in the atomic movement path, and enables excitation of clock transitions by a probe laser by causing mixing of wave functions with an electronically dipole transition-permitted electronic state.

2. An atomic state splitter comprising a first grating laser light source and a second grating laser light source, wherein the first grating laser light source and the second grating laser light source form a grating formed by a standing wave by supplying a pair of grating lasers that travel along the atomic movement path in opposite directions, the frequencies of the pair of grating lasers are shifted from each other, the grating is a moving grating that moves along the atomic movement path, and the moving grating carries the atoms along the atomic movement path, according to Claim 1.

3. The atomic state splitter according to Claim 2, wherein each of the grating lasers is set to a magic frequency that does not cause a Stark shift in clock transitions.

4. An atomic interferometer comprising an atomic supply unit, an atomic movement path, a probe laser light source, a first magnetic field generation unit, and a second magnetic field generation unit, wherein the atomic supply unit supplies atoms that move along the atomic movement path at a constant speed, the probe laser light source supplies a probe laser that propagates coaxially within the atomic movement path in a direction opposite to or the same as the movement of the atoms, and the first magnetic field generation unit and the second magnetic field generation unit generate a magnetic field orthogonal to the atomic movement path in the atomic movement path, and a plurality of atomic state splitters that enable excitation of clock transitions by a probe laser by causing mixing of wave functions with an electronically dipole transition-permitted electronic state are installed.

5. The atomic interferometer according to claim 4, characterized in that the first magnetic field generating unit and the second magnetic field generating unit are arranged with an interval corresponding to the interaction length between the atom and the probe laser.

6. It includes a detection laser light source that supplies a detection laser for projective measurement of the electronic state of the atom after the electronic state operation by the electronic state splitter. The atomic interferometer according to claim 5, characterized in that each of the first magnetic field generating unit and the second magnetic field generating unit realizes Ramsey spectroscopy by generating an excitation having a pulse area of π / 2 in the atom by a combination of a magnetic field and a probe laser.

7. It includes an atom supply unit, an atom movement path, a probe laser light source, a first magnetic field generating unit, a second magnetic field generating unit, a detection laser light source, and a detector. The atom supply unit supplies atoms that move along the atom movement path at a constant speed. The probe laser light source supplies a probe laser that propagates coaxially with the atom movement path within the atom movement path in a direction opposite to or the same as the movement of the atom. The first magnetic field generating unit and the second magnetic field generating unit are arranged with an interval corresponding to the interaction length between the atom and the probe laser. The first magnetic field generating unit and the second magnetic field generating unit generate a magnetic field orthogonal to the atom movement path in the atom movement path, and by causing mixing of the wave functions with the electronically dipole-transition-allowed electronic states, enable the atom to be excited by the probe laser. Each of the first magnetic field generating unit and the second magnetic field generating unit realizes Ramsey spectroscopy by generating an excitation having a pulse area of π / 2 in the atom by a combination of a magnetic field and a probe laser. The detection laser light source supplies a detection laser for projective measurement of the electronic state of the atom after pulsed irradiation. The detector measures a signal proportional to the occupancy number of the electronic state of the atom, and is an atomic transition frequency measuring device.

8. An atomic oscillator, characterized in that it includes an electronic state splitter for an atom according to any one of claims 1 to 3.

9. An optical lattice clock, characterized in that it includes an electronic state splitter for an atom according to any one of claims 1 to 3.

10. A quantum computer, characterized in that it includes an electronic state splitter for an atom according to any one of claims 1 to 3.

11. A method for generating a superposition state of atomic electronic states using an atomic electronic state splitter, comprising: The atomic electronic state splitter includes an atomic supply unit, an atomic movement path, a probe laser light source, and a magnetic field generation unit; Supplying an atom that moves along the atomic movement path at a constant speed using the atomic supply unit; Supplying a probe laser that propagates coaxially with the atomic movement path and in a direction opposite to or the same as the movement of the atom within the atomic movement path using the probe laser light source; Mixing an electronically dipole-transition allowed electronic state and a wave function by generating a magnetic field orthogonal to the atomic movement path in the atomic movement path using the magnetic field generation unit. A method for generating a superposition state of atomic electronic states is characterized by comprising the above steps.

12. An atomic supply unit, an atomic movement path, a probe laser light source, a magnetic field source, and a magnetic shield; The atomic supply unit supplies an atom that moves along the atomic movement path at a constant speed; The magnetic shield is configured to surround the atomic movement path and reduce an external magnetic field within the shielded portion; The probe laser light source excites the atom at the shield position by supplying a probe laser that resonates with a Zeeman-shifted atomic transition within the shield into the atomic movement path. An atomic electronic state splitter is characterized by the above.

13. An atomic supply unit, an atomic movement path, a probe laser light source, a magnetic field source, a first magnetic shield, and a second magnetic shield; The atomic supply unit supplies an atom that moves along the atomic movement path at a constant speed; The first magnetic shield and the second magnetic shield are configured to surround the atomic movement path and reduce an external magnetic field at the first shield position and the second shield position of the portions they respectively surround; An atomic interferometer characterized by installing a plurality of atomic electronic state splitters that excite the atom at the first shield position and the second shield position by supplying a probe laser that resonates with a Zeeman-shifted atomic transition within the shield into the atomic movement path.

14. An atomic supply unit, an atomic movement path, a first magnetic shield, a second magnetic shield, a probe laser light source, a magnetic field source, a detection laser light source, and a detector; The atom supply unit supplies atoms that move along the atom movement path at a constant speed. The first magnetic shield and the second magnetic shield are configured to surround the atom movement path, and reduce the external magnetic field at the first shield position and the second shield position of the portions they respectively surround. The probe laser light source supplies a probe laser that resonates with the atomic transition that has undergone Zeeman shift within the shield into the atom movement path, thereby causing the excitation of the clock transition at the first shield position and the second shield position. The first magnetic shield and the second magnetic shield realize Ramsey spectroscopy by causing excitation with a pulse area of π / 2 to occur in the atoms at the first shield position and the second shield position. The detection laser light source supplies a detection laser for projective measurement of the electronic state of the atoms after receiving pulse irradiation. The detector measures a signal proportional to the occupancy number of the electronic state of the atoms, and is an atomic transition frequency measurement device characterized by this.

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