US 12,339,332 B2
Automated resonance control for nv magnetometers
Ferdinand Schiller, Korntal Münchingen (DE); Robert Roelver, Calw (DE); and Katharina Jag-Lauber, Winterbach (DE)
Assigned to Q.ANT GMBH, Stuttgart (DE)
Filed by Q.ant GmbH, Stuttgart (DE)
Filed on Nov. 27, 2024, as Appl. No. 18/961,530.
Application 18/961,530 is a continuation of application No. PCT/EP2023/063409, filed on May 17, 2023.
Claims priority of application No. 10 2022 113 754.6 (DE), filed on May 31, 2022.
Prior Publication US 2025/0093432 A1, Mar. 20, 2025
Int. Cl. G01R 33/032 (2006.01); G01R 33/26 (2006.01)
CPC G01R 33/032 (2013.01) [G01R 33/26 (2013.01)] 14 Claims
OG exemplary drawing
 
1. A method for determining an external magnetic field with a nitrogen-vacancy (NV) magnetometer with automated resonance control, wherein the NV magnetometer comprises a sensor material with NV centers with respective spin states ms=0, ±1 and resonance frequencies f± for transitions between the spin states ms=0↔±1, wherein a difference f+−f− of the resonance frequencies f± depends on the external magnetic field B, the method comprising:
recording single resonance signals VSR-LIA for determining the resonance frequencies f± by using frequency-modulated microwave radiation emitted onto the sensor material in frequency bands based on a microwave frequency fMW and a carrier frequency fSB, wherein the microwave frequency fMW and the carrier frequency fSB are selected such that the frequency bands address two magnetic resonances in succession;
recording a double resonance signal VDR-LIA with a dispersive form and a linear range around the resonance frequencies f±, wherein the microwave frequency fMW and the carrier frequency fSB are selected such that fMW±fSB=f± applies so that the two magnetic resonances are excited simultaneously;
determining a slope of the linear range as a scalar factor α from the double resonance signal VDR-LIA;
observing a detuning ΔB=VDR-LIA/α of the resonance frequencies f± via the double resonance signal VDR-LIA with resonant emission of the microwave radiation due to external magnetic field changes by using an evaluation unit;
controlling the frequency bands fMW±fSB with a controller comprising a control algorithm based on the observed detuning ΔB so that the frequency bands fMW±fSB remain in the range of the resonance frequencies f± of the NV centers present at the detuning ΔB even after the detuning ΔB has occurred; and
determining the external magnetic field B from a distance 2*fSB of the frequency bands and the detuning ΔB by using the evaluation unit.