Multi-photon quantum interferometry

Dirk Bouwmeester

Richard J. Birrittella, Jihane Mimih, Christopher C. Gerry

Hugo Sanabria, B. M. Rodríguez-Lara

"Quantum interferometry uses the quantum properties of light to surpass the Rayleigh diffraction limit inherent in classical interferometry. We have used Fock and coherent states, which describe the electromagnetic input field, a multi-photon counting apparatus, and an operator-based approach to a multi-slit Young’s experiment to present the principles behind quantum interferometry. Our calculations show interference fringes that depend on the wavelength of the source h, the number of slits in the Young’s screen-both characteristics present in the classical scheme-, and the number of photons m, that the measurement apparatus detects. The latter dependence generates an effective de Broglie wavelength, h/m, a phenomenon that can only be observed by taking advantage of the quantum properties of light."

P. Hariharan

Aephraim M. Steinberg

Recent advances make it possible to entangle multiple photons, despite the absence of strong photon-photon interactions. We present experiments generating “noon” states applicable to quantum interferometry, and complete quantum tomography of such states.

Young-Sik Ra, Malte C. Tichy, Hyang‐Tag Lim +4 more

The coherence time constitutes one of the most critical parameters that determines whether or not interference is observed in an experiment. For photons, it is traditionally determined by the effective spectral bandwidth of the photon. Here we report on multi-photon interference experiments in which the multi-photon coherence time, defined by the width of the interference signal, depends on the number of interfering photons and on the measurement scheme chosen to detect the particles. A theoretical analysis reveals that all multi-photon interferences with more than two particles feature this dependence, which can be attributed to higher-order effects in the mutual indistinguishability of the particles. As a striking consequence, a single, well-defined many-particle quantum state can exhibit qualitatively different degrees of interference, depending on the chosen observable. Therefore, optimal sensitivity in many-particle quantum interferometry can only be achieved by choosing a suitable detection scheme. The coherence time describes the timescale over which particles can still display wave-like interference and is important for quantum optics. Using multi-photon interference experiments, Ra et al. show that the multi-photon coherence time depends on both the number of photons and the detection scheme used.