Diamond nanocrystal single-photon source with wavelength converter

1 . A single-photon source, comprising:

a color-centered diamond-nanocrystal (CCDN) single-photon source (SPS) adapted to emit input photons of wavelength λ 1 ;

a non-linear optical medium arranged to receive the input photons;

a pump light source in optical communication with the non-linear optical medium and adapted to generate pump photons having a wavelength λ 2 that pump the non-linear optical medium so as allow the non-linear optical medium to optically downconvert said first photons passing through the non-linear optical medium to form output photons having a wavelength λ 3 ; and

an optical filter arranged downstream of the non-linear optical medium and adapted to substantially block the pump photons and to substantially transmit said output photons.

2 . The single-photon source of claim 1 , wherein the non-linear optical medium is a periodically poled lithium niobate waveguide.

3 . The single-photon source, wherein λ 1 ˜637 nm, λ 2 ˜1080 nm and λ 3 ˜1550 nm.

4 . The single-photon source, wherein λ 1 ˜637 nm, λ 2 ˜1310 nm and λ3˜1310 nm.

5 . The single-photon source of claim 1 , wherein the CCDN includes one of either a nitrogen vacancy (NV) or a nickel center (NE8).

6 . A quantum key distribution (QKD) system, comprising:

a first QKD station having the SPS of claim 1 and adapted to generate once-selectively-randomly-modulated quantum signals from the output photons;

a second QKD station optically coupled to the first QKD station and adapted to receive and selectively randomly modulate the once-selectively-randomly modulated quantum signals so as to form twice-selectively-randomly modulated quantum signals and detect same in a manner that provides information about the overall modulation imparted to the twice-selectively-randomly-modulated quantum signals; and

wherein the first and second QKD stations are adapted to create a common key based on the exchanged quantum signals.

7 . A method of generating single photons, comprising:

generating input photons having a wavelength λ 1 using a color-center diamond nanocrystal (CCDN) single-photon source;

inputting the input photons into a non-linear optical material that is pumped so as to downconvert the input photons; and

forming from the downconverted input photons output photons having an output wavelength λ 3 .

8 . The method of claim 7 , wherein the input photon wavelength λ 1 is outside of a telecommunication wavelength band, and wherein the output photon wavelength λ 3 is within a telecommunication wavelength band.

9 . The method of claim 7 , including forming the input photons so that the input photon wavelength λ 1 is ˜637 nm and pumping the non-linear optical medium so that the output photon wavelength λ 3 is either ˜1550 nm or ˜1310 nm.

10 . The method of claim 7 , including providing a periodically poled non-linear waveguide for the non-linear optical medium.

11 . The method of claim 7 , including:

pumping the non-linear optical medium with pump photons of wavelength λ 2 .

11 . The method according to claim 10 , including filtering out pump photons that exit the non-linear optical medium so that substantially only output photons in an output beam.

12 . A method of forming a quantum key, comprising:

forming output photons according to the method of claim 7 at a first QKD station ALICE;

selectively randomly modulating the output photons to form once-modulated quantum signals;

transmitting the once-modulated quantum signals to a second QKD station BOB;

at BOB, selectively randomly modulating the once-modulated quantum signals so as to form twice-modulated quantum signals;

detecting the twice modulated quantum signals so as to determine an overall phase imparted thereto; and

communicating between BOB and ALICE information concerning the modulation and detection of the quantum signals so as to form the quantum key.