Toward surface plasmon polariton quantum-state tomography

We report the direct excitation and detection of single-photon surface plasmon polariton (SPP) using a SPP tomography arrangement. Temporally spaced photons produced by spontaneous parametric downconversion were used to excite single-photon SPPs. The quantum statistics of the leakage radiation was studied using a Hanbury-Brown Twiss correlator arrangement. We observed a violation of the second order coherence test indicating leakage of temporally spaced photons. This demonstrates that leakage radiation associated with SPPs excited by single photons is composed of temporally spaced photons. Reaching the quantum regime of SPP tomography opens the door for further advances in SPP quantum state determination using SPP tomography.