A new way to correlate photons

Zachary Walton, Ayman F. Abouraddy, Mark C. Booth +3 more

We present a new quantum cryptography implementation that uses frequency-correlated photon pairs to combine one-way operation with an autocompensating feature that has hitherto only been available in implementations that require the signal to make a round trip between the users. Furthermore, we describe a new scheme for creating frequency-correlated photon pairs (auto-phase-matched spontaneous parametric down-conversion). The new scheme offers several advantages over previous schemes, including the ability to generate frequency-correlated photon pairs regardless of the dispersion characteristics of the system.

Ling-an, Wu

Deborah Jackson, George Hockney, Jonathan Dowling

This paper describes a completely new way to perform noise rejection using a two-photon sensitive detector and taking advantage of the properties of correlated photons to improve an optical communications link in the presence of uncorrelated noise. In particular, a detailed analysis is made of the case where a classical link would be saturated by an intense background, such as when a satellite is in front of the sun, and identifies a regime where the quantum correlating system has superior performance.

I. K. Karpenko

Christophe Galland, Santiago Tarrago Velez, Mitchell D. Anderson

We present a new experiment, in which we measure quantum correlations between single photons that are mediated by the exchange of a single phonon. We create and annihilate a single optical phonon in bulk diamond using two ultrashort laser pulses at two different wavelengths, generated by a Ti:Sapph oscillator and a frequency-doubled optical parametric oscillator (APE Berlin). During Stokes Raman scattering, the first pulse creates a photon-phonon pair, while the second pulse convert the same phonon into an anti-Stokes photon. Using spectral filtering and photon counting, we measure the cross-correlations between the Stokes and anti-Stokes photons with a few hundred femtoseconds time resolution. As expected, the non-classical correlation (g(2) much larger than the classical bound) decays within a few picosecond, following to the dynamics of the phonon mode. Our results demonstrate a new source of broadly tunable quantum correlated photons, and can be extended to provide a new way of measuring non-classical dynamics in nanoscale systems — down to individual nanostructures.

Edward R. Pike