Dynamic Decoupling In Solid State Spin Ensembles

• US 20150048822A1
• Filed: 06/13/2012
• Published: 02/19/2015
• Est. Priority Date: 06/13/2011
• Status: Active Grant

• Current Assignee: President and Fellows of Harvard College (Harvard Corporation)
• Original Assignee: President and Fellows of Harvard College (Harvard Corporation)
• Inventors: Walsworth, Ronald, Pham, Linh My
• Granted Patent: US 9,784,804 B2
• Time in Patent Office: Days
• US Class Current: 324/309
• CPC Class Codes: G01N 24/08 by using nuclear magnetic resonance G01N24/12 takes precedence
• CPC Class Codes: G01R 33/24 for measuring direction or magnitude of magnetic fields or magnetic flux
• CPC Class Codes: G01R 33/323 Detection of MR without the use of RF or microwaves, e.g. force-detected MR, thermally detected MR, MR detection via electrical conductivity, optically detected MR
• CPC Class Codes: G01R 33/60 using electron paramagnetic resonance G01R33/24, G01R33/62 take precedence

Abstract

Long spin coherence lifetimes are realized for ensembles of electronic spin impurities in solid state spin systems, for example NV color centers in diamond, by using spin-control RF pulse sequences to provide dynamic decoupling of the ensembles of spin impurities from environmental sources of decoherence such as dipolar and hyperfine interactions with proximal spin and other paramagnetic impurities in diamond. In this way, the measurement sensitivity of the coherent evolution of ensembles of solid state spin impurities are increased. Using the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence, the spin coherence lifetimes of NV ensembles can be extended to more than 2 ms in room temperature diamond, and sensitivity of magnetometry that uses NV ensembles can be increased.

Claims

1. A method comprising:

applying a series of periodic microwave control pulses to an ensemble of electronic spin impurities in a spin-bath environment of a solid-state spin system, so as to decouple the spin impurities from one or more sources of decoherence in the spin-bath environment to thereby increase coherence times of the spin impurities.

6. The method of claim 1, wherein the ensemble of spin impurities has a density of at least about 10¹²/cm³.

7. The method of claim 1, wherein the series of microwave pulses comprises at least one of

a Hahn spin-echo pulse sequence;

a CPMG (Carr Purcell Meiboom Gill) pulse sequence; and

a MREVB pulse sequence.

8. The method of claim 1, wherein the series of microwave pulses comprises at least one of:

an XY pulse sequence and a CPMG-n pulse sequence; and

wherein the XY pulse sequence and the CPMG-n pulse sequence are configured to decouple single NV spins from higher frequency bath fluctuations.

2. The method of claim 2, wherein the ensemble of electronic spin impurities comprise an ensemble of NV (nitrogen-vacancy) centers in the diamond crystal.

3. The method of claim 2, further comprising an act of applying optical radiation to the NV centers before applying the microwave pulses, so as to prepare the NV centers into m_s=0 ground states, and generate spin-dependent fluorescence signals from the NV center.

4. The method of claim 2, wherein the spin-bath environment comprises ¹³C (carbon 13) nuclear spin impurities and N (nitrogen atom) electronic spin impurities, and wherein the solid-state spin system comprises a diamond crystal.

5. The method of claim 4, wherein the sources of decoherence in the spin bath environment include fluctuating magnetic fields generated by the ¹³C and N spin impurities, and wherein the magnetic field fluctuations are slow compared to time period between the pulses.

9. The method of claim 3, further comprising an act of detecting a magnetic field by measuring a Zeeman shift in energy levels that the spin impurities undergo in response to the optical radiation and the microwave pulses applied thereto.

10. The method of claim 9, further comprising an act of optimizing the number of microwave pulses to be applied to the spin impurities so as to maximize sensitivity of the magnetic field detection;

and wherein the optimized number n_opt of microwave pulses is given by;

11. A system comprising:

a pulsed microwave source configured to generate a series of microwave control pulses and apply them to a sample containing an ensemble of electronic spin impurities in a spin-bath environment of a solid-state spin system, so as to dynamically decouple the spin impurities from one or more sources of decoherence in the spin-bath environment to thereby increase coherence times of the spin impurities.

12. The system of claim 11, wherein the ensemble of electronic spin impurities comprise an ensemble of NV centers in the diamond crystal.

13. The system of claim 12, wherein the spin-bath environment comprises ¹³C nuclear spin impurities and N electronic spin impurities, and wherein the solid-state spin system comprises a diamond crystal.

14. The system of claim 13, further comprising an optical source configured to generate optical radiation that prepares the NV centers into m_s=0 ground states and drive spin-dependent fluorescence detection from the NV centers, when applied thereto.

15. The system of claim 13, wherein the sources of decoherence in the spin bath environment include fluctuating magnetic fields generated by the ¹³C and N spin impurities, and wherein the magnetic field fluctuations are slow compared to time period between the pulses.

16. The system of claim 11, wherein the ensemble of spin impurities has a density of at least about 10¹²/cm³.

17. The system of claim 11, wherein the series of microwave pulses comprises at least one of:

a Hahn spin-echo pulse sequence;

a CPMG (Carr Purcell Meiboom Gill) pulse sequence; and

a MREVB pulse sequence.

18. The system of claim 11, wherein the series of microwave pulses comprises at least one of:

an XY pulse sequence; and

a CPMG-n pulse sequence.

19. The system of claim 14, further comprising a detector configured to detect output optical radiation from the spin impurities after being exposed to the optical excitation signal and the series of microwave control pulses.

20. The system of claim 11, further comprising the sample containing the ensemble of electronic spin impurities in the spin-bath environment of the solid-state spin system.

21. The system of claim 11, wherein the microwave source comprises a loop antenna.

22. The system of claim 14, wherein the optical source is a laser tunable to a frequency of about 532 nm.