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.
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