Synthetic diamond materials for quantum and optical applications and methods of making the same

1. A synthetic diamond material comprising one or more spin defects having a full width half maximum intrinsic inhomogeneous zero phonon line width of no more than 100 MHz,

wherein the full width half maximum intrinsic inhomogeneous zero phonon line width is averaged over one or both of: at least 10 seconds; and at least 10 spectral scans,

wherein the synthetic diamond material is chemical vapor deposited (CVD) synthetic diamond material, and

wherein the one or more spin defects are negatively charged nitrogen vacancy (NV − ) spin defects, and

wherein the one or more s in defects have a decoherence time T 2 at room temperature of at least 500 μs.

2. A synthetic diamond material according to claim 1 , wherein the full width half maximum intrinsic inhomogeneous zero phonon line width is no more than 40 MHz.

3. A synthetic diamond material according to claim 1 , wherein the full width half maximum intrinsic inhomogeneous zero phonon line width is averaged over at least 100 seconds.

4. A synthetic diamond material according to claim 1 , wherein the full width half maximum intrinsic inhomogeneous zero phonon line width is averaged over at least 100 spectral scans.

5. A synthetic diamond material according to claim 1 , wherein the synthetic diamond material comprises a layer of said spin defects, the layer comprising at least 10 5 spin defects/cm 2 and having a thickness no more than 1 μm.

6. A synthetic diamond material according to claim 1 , wherein at least 50% of the spin defects have a total spectral line width of less than 100 MHz.

7. A synthetic diamond material according to claim 1 , further comprising one or more photonic structures fabricated in the synthetic diamond material.

8. A diamond-based quantum system comprising:

a synthetic diamond material according to claim 1 ;

an excitation arrangement configured to optically excite one or more spin defects in the synthetic diamond material; and

a detector arrangement configured to detect photon emission from the one or more spin defects.

9. A synthetic diamond material comprising one or more spin defects having a full width half maximum intrinsic inhomogeneous zero phonon line width of no more than 100 MHz,

wherein the full width half maximum intrinsic inhomogeneous zero phonon line width is averaged over one or both of: at least 10 seconds; and at least 10 spectral scans,

wherein the synthetic diamond material is chemical vapor deposited (CVD) synthetic diamond material, and

wherein the one or more spin defects are negatively charged nitrogen vacancy (NV − ) spin defects, and

wherein the one or more spin defects are located no more than 1 μm from a surface of the synthetic diamond material.

10. A synthetic diamond material according to claim 9 , wherein said layer comprises 10 5 spin defects/cm 2 to 10 11 spin defects/cm 2 .

11. A synthetic diamond material comprising one or more spin defects having a full width half maximum intrinsic inhomogeneous zero phonon line width of no more than 100 MHz,

wherein the full width half maximum intrinsic inhomogeneous zero phonon line width is averaged over one or both of: at least 10 seconds; and at least 10 spectral scans,

wherein the synthetic diamond material is chemical vapor deposited (CVD) synthetic diamond material, and

wherein the one or more spin defects are negatively charged nitrogen vacancy (NV − ) spin defects,

wherein the synthetic diamond material comprises a layer of said spin defects, the layer comprising at least 10 5 spin defects/cm 2 and having a thickness no more than 1 μm, and

wherein the thickness of said layer is no more than 100 nm.

12. A synthetic diamond material comprising one or more spin defects having a full width half maximum intrinsic inhomogeneous zero phonon line width of no more than 100 MHz, and

one or more photonic structures fabricated in the synthetic diamond material,

wherein the full width half maximum intrinsic inhomogeneous zero phonon line width is averaged over one or both of: at least 10 seconds; and at least 10 spectral scans,

wherein the synthetic diamond material is chemical vapor deposited (CVD) synthetic diamond material, and

wherein the one or more spin defects are negatively charged nitrogen vacancy (NV) spin defects, and

wherein the one or more spin defects are located no more than 1 μm from the one or more photonic structures or within the one or more photonic structures.

13. A method of fabricating a synthetic diamond material, the method comprising:

selecting a synthetic diamond material comprising a single substitutional nitrogen concentration of no more than 100 ppb; and

annealing the synthetic diamond material using a multi-stage annealing process comprising:

a first annealing step at a temperature in a range 350 to 450° C. for at least 2 hours;

a second annealing step at a temperature in a range 750 to 900° C. for at least 2 hours; and

a third annealing step at a temperature in a range 1150° C. to 1550° C. for at least 2 hours; said synthetic diamond comprising

one or more spin defects having a full width half maximum intrinsic inhomogeneous zero phonon line width of no more than 100 MHz,

wherein the full width half maximum intrinsic inhomogeneous zero phonon line width is averaged over one or both of: at least 10 seconds; and at least 10 spectral scans,

wherein the synthetic diamond material is chemical vapor deposited (CVD) synthetic diamond material, and

wherein the one or more spin defects are negatively charged nitrogen vacancy (NV − ) spin defects.

14. A method according to claim 13 , further comprising implanting a layer of nitrogen into the synthetic diamond material prior to the multi-stage annealing process.

15. A method according to claim 13 , further comprising irradiating the synthetic diamond material prior to the multi-stage annealing process to form vacancy defects.