# US 10,371,763 B2 · Systems and methods for low power magnetic field generation for atomic sensors using electro-permanent magnets > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,371,763 B2 - Document ID: US10371763B2 - Status: Granted - Kind: B2 - Application number: 14/802,818 - Filed: 2015-07-17 - Published: 2017-01-19 - Granted: 2019-08-06 - Earliest claimed: 2015-07-17 - Assignees: Honeywell International Inc. - Applicants: Honeywell International Inc. - Inventors: Kenneth Salit - Web page: https://patentgrep.com/patent/US10371763B2 ## CPC - G01R 33/24: for measuring direction or magnitude of magnetic fields or magnetic flux - G01R 33/26: using optical pumping - G01R 33/383: using permanent magnets - H01F 7/0273: {Magnetic circuits with PM for magnetic field generation} - H01F 7/0284: {using a trimmable or adjustable magnetic circuit, e.g. for a symmetric dipole or quadrupole magnetic field} - G01C 19/58: Turn-sensitive devices without moving masses - G01C 19/62: with optical pumping - G01R 33/389: Field stabilisation {, e.g. by field measurements and control means or indirectly by current stabilisation} - G04F 5/14: using atomic clocks - G21K 1/30: for confining neutral particles or handling confined neutral particles, e.g. atom traps - H01F 13/00: Apparatus or processes for magnetising or demagnetising ({devices for holding workpieces using magnetic or electric force acting directly on the workpieces B23Q3/15} ; for degaussing ships B63G9/06; for clocks or watches G04D9/00; {recording or erasing of information on magnetic record carriers G11B5/00} ; demagnetising arrangements for colour television H04N9/29) - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES - G01C: MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY (measuring liquid level G01F; radio navigation, determining distance or velocity by use of propagation effects, e.g. Doppler effects, propagation time, of radio waves, analogous arrangements using other waves G01S) - G04F: TIME-INTERVAL MEASURING (measuring pulse characteristics G01R, e.g. G01R29/02; in radar or like systems G01S) - G21K: HANDLING OF PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES ## Abstract Systems and methods for low power magnetic field generation for atomic sensors using electro-permanent magnets are provided. In one embodiment, a method for magnetic field generation for an atomic sensor comprises: laser cooling a sample of atoms in a chamber; and trapping the sample of atoms in a magneto-optical trap within the chamber by applying an atom trapping field across the sample of atoms using at least one pair of electro-permanent magnet units. ## Claims ### Claim 1 A method of magnetic field generation with an atomic sensor, the method comprising: laser cooling a sample of atoms in a chamber; and trapping the sample of atoms in a magneto-optical trap within the chamber by applying an atom trapping field across the sample of atoms using at least one pair of electro-permanent magnet units; wherein each electro-permanent magnet unit of the at least one pair of electro-permanent magnet units comprises: a first magnetic ring of a first magnetic material; a second magnetic ring of a second magnetic material; and a coil of magnet wire that is wrapped around one or both of the first magnetic ring and the second magnetic ring; wherein applying an atom trapping magnetic field across the sample of atoms further comprises applying a first pulse of current having a first duration and amplitude to the coil of magnetic wire, wherein the applied first pulse of current also switches each electro permanent magnet unit of the at least one pair of electro-permanent magnet units from an off state to an on state by switching a magnetic polarity of the second magnetic ring without switching a polarity of the first magnetic ring. ### Claim 2 (depends on 1) The method of claim 1, further comprising: performing an atomic interrogation scheme on the sample of atoms while momentarily de-energizing the atom trapping magnetic field across the sample of atoms. ### Claim 3 (depends on 1) The method of claim 1, wherein the sample of atoms comprises one of atomic Rubidium (Rb), Cesium (Cs), atomic Calcium (Ca) or atomic Ytterbium (Yb). ### Claim 4 (depends on 1) The method of claim 1, wherein in the off state, a first magnetic field of the first magnetic ring and a second magnetic field of the second magnetic ring are oppositely polarized in order to offset each other, and wherein, in the on state, the first magnetic field of the first magnetic ring and the second magnetic field of the second magnetic ring are similarly polarized in order to add to each other. ### Claim 5 (depends on 1) The method of claim 1, the first magnetic material having a first magnetic hardness sufficient to not change polarity in response to the first pulse of current; and the second magnetic material having a second magnetic hardness that is less than the magnetic hardness of the first magnetic material such that the second magnetic material will change its polarity in response to the first pulse of current, but wherein the second magnetic material has a hardness that is sufficient in order to not change polarity in response to the first magnetic pulse of current applied to the first magnetic ring. ### Claim 6 (depends on 1) The method of claim 1, wherein the least one pair of electro-permanent magnet units comprises a first electro-permanent magnet unit having a first center ring hole and a second electro-permanent magnet unit having a second center ring hole; wherein the laser cooling further comprises: launching a first laser beam provided by a first laser source through the first center ring hole towards the second center ring hole, and launching a second laser beam provided by a second laser source through the second center ring hole towards the first center ring hold, wherein the first laser beam and the second laser beam are collinear with one another and intersect at the magneto-optical trap. ### Claim 7 (depends on 1) The method of claim 1, wherein laser cooling further comprises applying a first laser beam and a second laser beam into the magneto-optical trap with each laser beam being aligned to an axis of an anti-Helmholtz magnetic field. ### Claim 8 (depends on 1) The method of claim 1, further comprising: probing the sample of atoms in order to measure a net magnetic field; and calibrating at least a first electro-permanent magnet unit of the at least one pair of electro-permanent magnet units based on the net magnetic field measured by the probing. ### Claim 9 (depends on 8) The method of claim 8, wherein the first electro-permanent magnet unit further comprising: at least one shim coil; and wherein calibrating at least the first electro-permanent magnet unit comprises controlling a feedback current to the at least one shim coil based on the net magnetic field measured by the probing. ### Claim 10 A cold atom sensor, the cold atom sensor comprising: a vacuum chamber having a sample of atoms sealed within the vacuum chamber; at least one pair of electro-permanent magnet units arranged across the vacuum chamber, the least one pair of electro-permanent magnet units comprising a first electro-permanent magnet unit having a first center ring hole and a second electro-permanent magnet unit having a second center ring hole; a first laser source configured to launch a first laser beam through the first center ring hole and towards the second center ring hole, and a second laser source configured to launch a second laser beam through the second center ring hole and towards the first center ring hold, wherein the first laser beam and the second laser beam are collinear; wherein the first laser source and the second laser source are configured to laser cool the sample of atoms when the first laser beam and the second laser beam are energized and the first electro-permanent magnet unit and the second electro-permanent magnet unit are configured to produce an atom trapping magnetic field that holds the sample of atoms in an magneto-optical trap; wherein each electro-permanent magnet unit of the at least one pair of electro-permanent magnet units comprises: a first magnetic ring of a first magnetic material; a second magnetic ring of a second magnetic material; and a coil of magnet wire that is wrapped around one or both of the first magnetic ring and the second magnetic ring; wherein the at least one pair of electro-permanent magnet units are configured to produce the atom trapping magnetic field across the sample of atoms by applying a first pulse of current having a first duration and amplitude to the coil of magnetic wire, wherein the applied first pulse of current also switches each electro-permanent magnet unit of the at least one pair of electro-permanent magnet units from an off state to an on state by switching a magnetic polarity of the second magnetic ring without switching a polarity of the first magnetic ring. ### Claim 11 (depends on 10) The cold atom sensor of claim 10, wherein the cold atom sensor is configured to perform an atomic interrogation on the sample of atoms while momentarily de-energizing the atom trapping magnetic field across the sample of atoms by switching a polarity of the second magnetic ring. ### Claim 12 (depends on 10) The cold atom sensor of claim 10, wherein when switched to an off state, a first magnetic field of the first magnetic ring and a second magnetic field of the second magnetic ring are oppositely polarized in order to offset each other, and wherein when switched to an on state, the first magnetic field of the first magnetic ring and the second magnetic field of the second magnetic ring are similarly polarized in order to add to each other. ### Claim 13 (depends on 10) The cold atom sensor of claim 10, the first magnetic material having first magnetic hardness sufficient to not change polarity in response to the first pulse of current; and the second magnetic material having a second magnetic hardness that is less than the magnetic hardness of the first magnetic material such that the second magnetic material will change its polarity in response to the first pulse of current, but wherein the second magnetic material has a hardness that is sufficient hi order to not change polarity in response to the first magnetic pulse of current applied to the first magnetic ring. ### Claim 14 The cold atom sensor of now, wherein the first laser beam and the second laser beam are each aligned to an axis of the atom trapping magnetic field. ### Claim 15 (depends on 10) The cold atom sensor of claim 10, wherein the sample of atoms comprise one of atomic Rubidium (Rb), Cesium (Cs), atomic Calcium (Ca) or atomic Ytterbium (Yb). ### Claim 16 (depends on 10) The cold atom sensor of claim 10, further comprising: an atom characterization function configured to probe the sample of atoms in order to measure a net magnetic field; and wherein the atom characterization function is configured to calibrate at least a first electro-permanent magnet unit of the at least one pair of electro-permanent magnet units based on the net magnetic field measured by the probing performed by the atom characterization function. ### Claim 17 (depends on 16) The cold atom sensor of claim 16, wherein the at least one of the pair of electro-permanent magnet units comprises a shim coil; and wherein the atom characterization function is configured to control a feedback current supplied to the at least one shim coil based on the net magnetic field measured by the probing performed by the atom characterization function. ### Claim 18 (depends on 10) The cold atom sensor of claim 10, wherein the at least one pair of electro-permanent magnet units comprise: a first pair of electro-permanent magnet units producing a first anti-Helmholtz magnetic field gradient across the magneto-optical trap.