Single Photon Nonlinearities and Macroscopic Entanglement
Rob Thew, Natalia Bruno, Thiago Guerreiro, Enrico Pomarico, Anthony Martin, Bruno Sanguinetti, Pavel Sekatski, Nicolas Sangouard, Jason S. Pelc, Carsten Langrock, M. M. Fejer, Hugo Zbinden, Nicolas Gisin · The Rochester Conferences on Coherence and Quantum Optics and the Quantum Information and Measurement meeting · 2013
I will discuss a couple of recent experiments that are at opposite extremes of quantum photonics. We have demonstrated an integrated nonlinear optics scheme – based on sum-frequency generation - capable of photon-photon interactions. This approach has the potential for significant impact in quantum communication, e.g. for heralding entanglement over large distances and providing a significant step towards device-independent quantum key distribution. It also has the added advantage that it is incredibly flexible in terms of the wavelengths and bandwidths that can be incorporated, thus providing a potential solution for a wide range of experiments and applications beyond quantum communication. In a more fundamental experiment, we have tested a way of characterising macroscopic entanglement – the approach firstly amplifies a “microscopic” - single photon - entangled state, to the level of ~500 photons, before reducing this state back to the microscopic regime where a well known entanglement witness can be used to characterise the macroscopic state.