Photonic quantum information

Linda Sansoni

Sébastien Tanzilli, Wolfgang Tittel, Hugo Zbinden +3 more

The experiment performed aims to transfer the quantum information (QI) carried by "telecom photons" at 1310 nm to "visible photons". This is a necessary step to realize a quantum interface between photons and atoms. To this end, in the most general case, entanglement produced by parametric down-conversion is preserved when submitting one photon out of an entangled pair to a wavelength up-conversion process (i.e. sum frequency generation SFG) in a nonlinear crystal.

Sylvain Borderieux, Arnaud Coatanhay, Ali Khenchaf

The quantum illumination radar uses pairs of entangled photons to enhance the detection sensitivity of a reflecting target.In this paper, we worked on a quantum illumination radar using a pair of entangled photons in polarization in the microwave frequency range in the atmosphere.We studied the quantum information evolution modeling the propagation of a photon in the atmosphere while building two binary decision strategies for the QI radar.We focused on the quantum information evolution showing that the quantum discord representing quantum correlations beyond entanglement could represent an interesting resource to explore for the subject of quantum radar.In addition, we made an approximative estimation of the entanglement survival distance in the atmosphere.Results showed that an optimization should be found to favour the survival of quantum correlations or the signal-to-noise ratios calculated with the binary decision strategy.

Sebastian Malewicz

Sébastien Tanzilli, Wolfgang Tittel, M. Halder +4 more

Radhika Rangarajan, Luis Edgar Vicent, Alfred B. U’Ren +1 more

The eventual success of optical quantum information (QI) processing depends critically on the available technologies. Photons produced via the nonlinear process of spontaneous parametric downconversion (SPDC) have now been used in a vast array of experiments in optical quantum computing and long-distance quantum communication. However, almost no source to date has been fully optimized. Here, we describe our progress in engineering an ideal photon-pair source for optical quantum information processing – polarization-entangled photons made indistinguishable by engineering spatio-spectral unentanglement at the source. We present solutions for several key challenges encountered in the development of the indistinguishable source. We expect such a source to directly translate into significantly enhanced QI protocols with higher rates, fidelities and efficiencies.