Granted Patent B2

US 12,206,422 · App. 18/029,207 · Granted Jan 21, 2025

Inventors: Shaoyi Xu (Anhui, CN); Tianyu Xie (Anhui, CN); Zhiyuan Zhao (Anhui, CN); Fazhan Shi (Anhui, CN); Jiangfeng Du (Anhui, CN)

Assignee: University of Science and Technology of China

H03L7/26G04F5/14

Abstract

Claims (33)

1. A method for implementing an atomic clock based on NV- 15 N coupling spin system in diamond, the method comprising:

comparing a RF frequency with a 15 N hyperfine coupling through Ramsey interferometry;

reading out a difference value between the RF frequency and the 15 N hyperfine coupling by collecting a fluorescence signal at NV centers so as to feedback and lock the RF frequency;

outputting the RF frequency as a frequency standard,

wherein the Ramsey interferometry comprises performing a Ramsey interference sequence using π/2 radiofrequency pulses, and

wherein reading out the difference value comprises applying a selective π second-microwave pulse to entangle a nuclear spin and an electron spin, applying a laser pulse, simultaneously collecting the fluorescence signal from the NV centers, and converting the fluorescence signal into an electrical signal.

2. The method according to claim 1 , comprising:

initialization: applying a laser pulse to initialize NV electron spins in a preceding initialization process, simultaneously applying a DC bias square wave and a selective π first-microwave pulse and applying a π radiofrequency pulse to initialize 15 N nuclear spins, applying the laser pulse to reinitialize the NV electron spins, and finally applying a selective π second-microwave pulse to complete an overall initialization process;

frequency feedback and locking: calculating a frequency difference between the RF frequency and the 15 N hyperfine coupling according to the electrical signal, and adjusting the RF frequency according to a calculation result until the RF frequency is locked to the 15 N hyperfine coupling;

output: using a locked RF frequency as a frequency standard to output a clock signal of the atomic clock.

3. The method according to claim 2 , wherein the initialization comprises:

applying the laser pulse to initialize the NV electron spins to ═m S =0>, simultaneously applying the DC bias square wave and the selective π first-microwave pulse and applying the π radiofrequency pulse to initialize the nuclear spins to |m l −−1/2>;

applying the laser pulse to reinitialize the electron spins; and

applying the selective π second-microwave pulse, so as to prepare the NV electron spins and the 15 N nuclear spins to a state |m S =+1, m l =−1/2>.

4. The method according to claim 2 , wherein the preceding initialization process is performed multiple times to obtain an optimal polarization.

5. The method according to claim 2 , wherein two states used for the Ramsey interference are |m l =−1/2> and |m l =+1/2>.

6. The method according to claim 2 , wherein the RF frequency is calibrated through a proportional-integral-differential algorithm.

7. An atomic clock device based on NV- 15 N coupling spin system in diamond, comprising:

a light source configured to emit a laser for exciting NV centers and causing the NV centers to emit a fluorescence;

an optical filter configured to filter out a stray light outside a fluorescence spectrum;

a microwave signal generator configured to generate a selective π first-microwave pulse and a selective π first-microwave pulse;

a radiofrequency signal generator configured to generate a radiofrequency;

a DC signal generator configured to generate a DC bias;

power amplifiers configured to boost a power of the microwave and a power of the radiofrequency, respectively;

a double split-ring resonator configured to transmit the selective π first-microwave pulse and the selective π first-microwave pulse to a spatial range of the laser-excited NV centers in diamond and form a uniform microwave field to manipulate electron spin states of NVs;

a low frequency coil configured to transmit the radiofrequency to the spatial range of the laser-excited NV centers in diamond and form a uniform radiofrequency field to manipulate nuclear spin states of 15 Ns, and configured to transmit the DC bias to the spatial range of the laser-excited NV centers in diamond and form a uniform magnetic field to split energy levels of NV electron spins;

a magnetic shield configured to shield a disturbance of an external magnetic field and improve stability and accuracy of the device;

a photoelectric detector configured to collect a fluorescence signal radiated from the NV centers and convert the fluorescence signal into an electrical signal;

a frequency feedback and locking module configured to receive the electrical signal transmitted by the photoelectric detector, calculate a frequency difference between a RF frequency and a 15 N hyperfine coupling based on the electrical signal, feedback and control the RF frequency in real time according to the frequency difference, and lock the RF frequency to the 15 N hyperfine coupling; and

a sample module configured to provide NV- 15 N coupling spin systems, wherein a coherence time T 2 * of the NV centers in the sample module is greater than 1 μs.

8. The atomic clock device according to claim 7 , comprising: a fluorescence waveguide configured to collect and transmit the fluorescence emitted by the NV centers.

9. The atomic clock device according to claim 7 , comprising: a Bragg reflector configured to be arranged around the diamond for forming an optical cavity, so as to improve an excitation efficiency of the NV centers and reduce a requirement of a laser power.

10. The atomic clock device according to claim 7 , wherein the number of NV centers of the sample module is greater than 10 12 .

Assignments (1)

Continuity (1)

References Cited (11)