Use of Nuclear Spin Impurities to Suppress Electronic Spin Fluctuations and Decoherence in Composite Solid-State Spin Systems

• US 20140306707A1
• Filed: 11/30/2012
• Published: 10/16/2014
• Est. Priority Date: 11/30/2011
• Status: Active Grant

• Current Assignee: President and Fellows of Harvard College (Harvard Corporation)
• Original Assignee: President and Fellows of Harvard College (Harvard Corporation)
• Inventors: Bar-Gill, Nir, Belthangady, Chinmay, Pham, Linh My, Walsworth, Ronald L.
• Granted Patent: US 9,720,067 B2
• Time in Patent Office: Days
• US Class Current: 324/309
• CPC Class Codes: G01R 33/1284 Spin resolved measurements; Influencing spins during measurements, e.g. in spintronics devices G01R33/093 takes precedence; semiconductor devices using spin polarized carriers H01L29/66984
• CPC Class Codes: G01R 33/24 for measuring direction or magnitude of magnetic fields or magnetic flux
• CPC Class Codes: G01R 33/4616 using specific RF pulses or specific modulation schemes, e.g. stochastic excitation, adiabatic RF pulses, composite pulses, binomial pulses, Shinnar-le-Roux pulses, spectrally selective pulses not being used for spatial selection
• CPC Class Codes: G01R 33/58 Calibration of imaging systems, e.g. using test probes , Phantoms; Calibration objects or fiducial markers such as active or passive RF coils surrounding an MR active material
• CPC Class Codes: G01R 33/60 using electron paramagnetic resonance G01R33/24, G01R33/62 take precedence

Abstract

A solid state electronic spin system contains electronic spins disposed within a solid state lattice and coupled to an electronic spin bath and a nuclear spin bath, where the electronic spin bath composed of electronic spin impurities and the nuclear spin bath composed of nuclear spin impurities. The concentration of nuclear spin impurities in the nuclear spin bath is controlled to a value chosen so as to allow the nuclear spin impurities to effect a suppression of spin fluctuations and spin decoherence caused by the electronic spin bath. Sensing devices such as magnetic field detectors can exploit such a spin bath suppression effect, by applying optical radiation to the electronic spins for initialization and readout, and applying RF pulses to dynamically decouple the electronic spins from the electronic spin bath and the nuclear spin bath.

Claims

1. A system comprising:

a solid state electronic spin system containing one or more electronic spins disposed within a solid state lattice and coupled to an electronic spin bath and a nuclear spin bath, the electronic spin bath composed of electronic spin impurities and the nuclear spin bath composed of nuclear spin impurities;

wherein concentration of the nuclear spin impurities in the nuclear spin bath is chosen so that the nuclear spin impurities effect a suppression of spin fluctuations and spin decoherence of the one or more electronic spins caused by the electronic spin bath;

an optical source configured to generate optical excitation radiation for initialization and readout of the electronic spins in the solid state lattice;

an RF source configured to generate RF pulse sequences configured to dynamically decouple the electronic spins from the electronic spin bath and the nuclear spin bath; and

a detector configured to detect output optical radiation correlated with the electronic spins, after the electronic spins have been subject to the optical excitation radiation and the RF pulse sequences, so as to detect a variable of interest.

2. The system of claim 1, wherein the solid state lattice comprises diamond, the electronic spins comprise NV centers in the diamond, the electronic spin impurities comprise N atoms in the diamond, and the nuclear spin impurities comprise ¹³C isotopes within the diamond.

3. The system of claim 2, wherein the electronic spins of the N atoms are configured to magnetically interact with each other and with the electronic spins of the NV centers, so as to cause spin flipping and spin decoherence of the N atom electronic spins and the NV center electronic spins;

and

wherein the nuclear spins of the ¹³C isotopes are configured to magnetically interact with the N atom electronic spins and with the NV center electronic spins thereby reducing spin flipping and increasing spin coherence of the electronic spins of the NV centers.

4. The system of claim 2, wherein the concentration of the ¹³C isotopes within the diamond lattice is chosen so that the magnetic interactions between the ¹³C nuclear spins and the N atom electronic spins shift the energy levels of the N atom electronic spins relative to each other and remove the degeneracy in these energy levels, thereby substantially suppressing the spin flipping and spin decoherence of the N atom electronic spins and the NV center electronic spins.

5. The system of claim 2, wherein a ratio of single substitutional nitrogen to ¹³C given by [N](ppm)/¹³C(%) is in a range 1 to 500, 10 to 400, 20 to 300, 30 to 200, 40 to 150, or 50 to 150.

6. The system of claim 2, wherein a single substitutional nitrogen concentration is equal to or greater than 150 ppm, 200 ppm, 300 ppm, 500 ppm, 750 ppm, or 1000 ppm.

7. The system of claim 6, wherein the single substitutional nitrogen concentration is equal to or less than 10000 ppm, 5000 ppm, 2000 ppm, or 1000 ppm.

8. The system of claim 6, wherein a ¹³C concentration is equal to or greater than 1.5%, 2%, 3%, 5%, 7%, or 10%.

9. The system of claim 7, wherein the ¹³C concentration may be equal to or less than 100%, 75%, 50%, 30%, 20%, or 15%.

10. The system of claim 2, wherein a single substitutional nitrogen concentration is equal to or greater than greater than 1 ppm, 5 ppm, 10 ppm, 20 ppm, 50 ppm, or 70 ppm.

11. The system of claim 10, wherein the single substitutional nitrogen concentration is equal to or less than 80 ppm, 60 ppm, 40 ppm, 20 ppm, or 10 ppm.

12. The system of claim 2, wherein a ¹³C concentration is equal to or greater than 0.02%, 0.05%, 0.10%, 0.2%, 0.3%, 0.5% or 0.7%.

13. The system of claim 12, wherein the ¹³C concentration is equal to or less than 0.8%%, 0.6%%, 0.4%, 0.25%, 0.15%, 0.10% or 0.75%.

14. The system of claim 2, wherein a ratio of [NV](ppm)/[N](ppm) is equal to or greater than 1×

10<sup>−

3</sup>, 5×

10<sup>−

3</sup>, 1×

10<sup>−

2</sup>, or 5×

10<sup>−

2</sup>.

15. The system of claim 14, wherein the ratio of [NV](ppm)/[N](ppm) is equal to or less than 1, 5×

10<sup>−

1</sup>, or 1×

10<sup>−

1</sup>.

16. The system according to claim 1, wherein T₂(n) scales with the number of pulses n according to the equation:

T₂(n)=T₂(1)×

n^(SF)

where T₂(n) is the T₂ for an n pulse RF sequence, T₂(1) is the T₂ for one RF pulse, and SF is a scaling factor, wherein the scaling factor SF is equal to or greater than 0.55 or 0.6.

17. The system according to claim 1, wherein a figure of merit (FOM) given by NV×

T₂(n) [ms/cm³] is equal to or greater than 5×

10¹⁴, 1×

10¹⁵, 5×

10¹⁵, 1×

10¹⁶, 5×

10¹⁶ or 1×

10¹⁷ using an RF pulse sequence with a number of pulses n less than or equal to 1000, 800, 600, 400, 200, 100, 80 or 60.

18. The system of claim 17, wherein NV×

T₂(n) is equal to or greater than 1×

10¹⁶ with a number of pulses n less than or equal to 400, 200, 100, 80, or 60.

19. The system according to claim 1, wherein NV×

T₂(n)>

5×

10¹⁵×

n^(0.55).

20. The system according to claim 1, wherein the RF pulse sequences comprise at least one of:

a Hahn-echo sequence; and

a CPMG sequence.

21. The system according to claim 1, wherein the variable of interest an external magnetic field, and the system a magnetometer.

22. The system according to claim 1, wherein the variable of interest is an external electric field, and the system is an electric field detector.

23. A method comprising:

introducing nuclear spin impurities into a solid state spin system that includes electronic spins coupled to a spin bath of electronic spin impurities and nuclear spin impurities;

wherein the concentration of the nuclear spin impurities is chosen so as to allow the magnetic interactions between the nuclear spin impurities and the electronic spin impurities to shift the energy levels of the electronic spin impurities relative to each other and remove the degeneracy in the energy levels, thereby substantially suppressing the spin flipping caused by the electronic spin impurities and substantially increasing the spin coherence lifetime of the electronic spins.

24. The method of claim 23, wherein the electronic spins comprise NV centers in diamond, the electronic spin impurities comprise N atoms in diamond, and the nuclear spin impurities comprise ¹³C isotopes in diamond.

25. The method of claim 23, wherein the act of introducing the nuclear spin impurities into the solid state spin system comprises performing chemical vapor deposition.

26. A synthetic diamond material comprising:

a plurality of NV (nitrogen-vacancy) centers within a diamond lattice;

an electronic spin bath including a plurality of N (nitrogen) atoms disposed within the diamond lattice, the electronic spins of the N atoms configured to magnetically interact with each other and with the electronic spins of the NV centers, so as to cause spin flipping and spin decoherence of the N atom electronic spins and the NV center electronic spins; and

a nuclear spin bath including a plurality of ¹³C isotopes within the diamond lattice, the nuclear spins of the ¹³C isotopes configured to magnetically interact with the N atom electronic spins and with the NV center electronic spins;

wherein the concentration of the ¹³C isotopes within the diamond lattice is chosen so as to allow the magnetic interactions between the ¹³C nuclear spins and the N atom electronic spins to shift the energy levels of the N atom electronic spins relative to each other and remove the degeneracy in these energy levels, thereby substantially suppressing the spin flipping and spin decoherence of the N atom electronic spins and the NV center electronic spins.

27. (canceled)

28. A solid state spin system comprising:

one or more electronic spins within a lattice;

a plurality of electronic spin impurities within the lattice, the electronic spin impurities configured to magnetically interact with each other and with the one or more electronic spins so as to cause spin flipping and spin decoherence of the electronic spin impurities and the one or more electronic spins; and

a plurality of nuclear spin impurities within the lattice, the nuclear spin impurities configured to magnetically interact with the electronic spin impurities and the one or more electronic spins;

wherein the concentration of the nuclear spin impurities within the lattice is chosen so as to allow the magnetic interactions between the nuclear spin impurities and the electronic spin impurities to shift the energy levels of the electronic spin impurities relative to each other and remove the degeneracy in the energy levels, thereby suppressing the spin flipping caused by the electronic spin impurities and increasing the spin coherence lifetime of the one or more electronic spins.

29. The solid state spin system of claim 28, comprising one of:

quantum dots, and phosphorous donors in silicon.