Atomic interferometer system

Patent metadata

Field	Value
Publication number	US-11133117-B2
Application number	US-202016866931-A
Country	US
Kind code	B2
Filing date	May 5, 2020
Priority date	May 8, 2019
Publication date	Sep 28, 2021
Grant date	Sep 28, 2021

Abstract

An atom interferometer system includes a sensor cell comprising alkali metal atoms. An optical system generates first and second interrogation beams having respective first and second frequencies and a circular polarization. The optical system includes optics that provide the first and second interrogation beams through the sensor cell in a first direction and reflect the first and second interrogation beams back through the sensor cell in a second direction opposite the first direction and in a same circular polarization to drive the alkali metal atoms from a first energy state to a greater energy state during an interrogation stage of sequential measurement cycles. A detection system detects a state distribution of a population of the alkali metal atoms between the first energy state and the second energy state during the interrogation stage based on an optical response.

First claim

What is claimed is:

1. An atom interferometer system comprising:
a sensor cell comprising alkali metal atoms;
an optical system that generates a first interrogation beam having a first frequency and a first circular polarization and a second interrogation beam having a second frequency and the first circular polarization, the second frequency being different from the first frequency, the optical system comprising optics that provide the first and second interrogation beams through the sensor cell in a first direction and reflect the first and second interrogation beams back through the sensor cell in a second direction opposite the first direction and in the first circular polarization to drive an energy transition of the alkali metal atoms between a first energy state and a second energy state during an interrogation stage in each of sequential measurement cycles;
a magnetic field generator configured to provide a uniform magnetic field in the sensor cell, the uniform magnetic field having a magnitude to provide for a transition frequency of the alkali metal atoms that is approximately centered on a quadratic Zeeman-shift of the energy transition of the alkali metal atoms from the first energy state to the second energy state; and
a detection system that detects a state distribution of the alkali metal atoms between the first energy state to the second energy state during the interrogation stage based on an optical response during a state readout stage in each of the sequential measurement cycles.

2. The system of claim 1 , wherein the optical system is configured to provide the first and second interrogation beams through the alkali metal atoms to provide for absorption of photons in a population of the alkali metal atoms via the first frequency of the first interrogation beam in the first circular polarization to provide a first photon momentum of the population of the alkali metal atoms in a first momentum direction, and to provide the reflected first and second interrogation beams through the alkali metal atoms to provide for emission of photons in the population of the alkali metal atoms via the second frequency of the second interrogation beam in the first circular polarization to provide a second photon momentum of the population of the alkali metal atoms in the first momentum direction.

3. The system of claim 1 , wherein the optics comprises a quarter-wave plate and a mirror, the mirror being configured to reflect the first and second interrogation beams and the quarter-wave plate being configured to maintain the first circular polarization for each of the first and second interrogation beams in each of the first and second direction.

4. The system of claim 1 , wherein the optical system is configured to provide the first and second interrogation beams in each of a first π/2-pulse, a π-pulse, and a second π/2-pulse during the interrogation stage, wherein the detection system is configured to determine at least one measurable parameter based on changes associated with a population of the alkali metal atoms after the second π/2-pulse during the state readout stage.

5. The system of claim 1 , wherein the optical system comprises a trapping beam source configured to generate an optical trapping beam, the system further comprising a magneto-optical trapping (MOT) system, the MOT system comprising:
a first magnetic field generator configured to generate a trapping magnetic field configured to trap the alkali metal atoms in the cell in response to the optical trapping beam; and
a second magnetic field generator configured to generate the uniform magnetic field during the interrogation stage, the uniform magnetic field having an amplitude based on Zeeman-shift characteristics of the alkali metal atoms to drive interrogation of a population of the alkali metal atoms from the first energy state to the second energy state.

6. The system of claim 5 , wherein the alkali metal atoms are 87-rubidium atoms, and wherein the uniform magnetic field has a magnitude of approximately 3.23 Gauss.

7. The system of claim 6 , wherein the uniform magnetic field has a magnitude to provide for a transition frequency that is approximately centered on an interrogation energy transition of the alkali metal atoms from the first energy state of <1,−1> to the second energy state of <2,1>, or from the first energy state of <1,1> to the second energy state of <2,−1>.

8. The system of claim 5 , wherein the optics are configured to provide the first and second interrogation beams and the optical trapping beam through the sensor cell along the same optical path.

9. The system of claim 1 , wherein the optical system comprises:
a trapping beam source configured to provide a first optical trapping beam, a second optical trapping beam, and a third optical trapping beam along respective approximate X, Y, and Z orthogonal axes through the sensor cell via the optics; and
a first interrogation beam source configured to generate the first interrogation beam and to provide the first interrogation beam along at least one of the respective approximate X, Y, and Z orthogonal axes through the sensor cell via the optics during a respective approximate X, Y, or Z-axis interrogation stage along a same optical path as a respective one of the first, second, and third optical trapping beams; and
a second interrogation beam source configured to generate the second interrogation beam and to provide the second interrogation beam along the at least one of the respective approximate X, Y, and Z orthogonal axes through the sensor cell via the optics during the respective approximate X, Y, or Z-axis interrogation stage along the same optical path as the respective one of the first, second, and third optical trapping beams.

10. A sensor system comprising the atom interferometer system of claim 1 , the sensor system further comprising:
a sensor controller comprising at least one sensor configured to determine a first measurement of at least one measurable parameter, wherein the atom interferometer system is further configured to provide a second measurement of the at least one measurable parameter and to provide the second measurement to the sensor controller, wherein the sensor controller is configured to refine the first measurement of the at least one measurable parameter based on the second measurement.

11. The sensor system of claim 10 , wherein the sensor controller is configured to provide at least one tuning signal to the atom interferometer system to configure the atom interferometer system to adjust at least one parameter associated with the optical system to enable the atom interferometer system to provide the second measurement of one of a plurality of predefined measurable parameters for which the atom interferometer system is configured to provide.

12. The system of claim 11 , wherein the plurality of predefined measurable parameters comprises frequency, frequency difference, time, time difference, and at least one inertial parameter.

13. The system of claim 1 , further comprising a calibration controller configured to change at least one characteristic associated with at least one of the uniform magnetic field and the first and second interrogation beams in each of at least one measurement cycle to implement calibration of the atom interferometer system during normal operating conditions of the atom interferometer system.

14. The system of claim 13 , wherein the calibration controller is configured to change a circular polarization of each of the first and second interrogation beams in each of the at least one measurement cycle to implement the calibration of the atom interferometer syst

Assignees

• Larsen Michael S
• Walker Thad G
• Brown Justin M
• Northrop Grumman Systems Corp

Inventors

• Larsen Michael S
• Walker Thad G
• Brown Justin M

Classifications

• G21K1/30 Primary

  for confining neutral particles or handling confined neutral particles, e.g. atom traps · CPC title

• G01R33/26

  using optical pumping · CPC title

• G01R33/032

  using magneto-optic devices, e.g. Faraday {or Cotton-Mouton effect} · CPC title

• G01C21/24

  specially adapted for cosmonautical navigation · CPC title

• G01C19/58 Primary

  Turn-sensitive devices without moving masses · CPC title