Nicolas Gisin

Introduction to guided-wave quantum optics (GWQO): science, technology, and magic

In this paper we propose various applications of guided wave optics to quantum optics experiments. As quantum optics moves on to multiparticle and multiport configurations, guided wave optics, incorporating both integrated optics and fiber optics, could provide a realistic means of constructing experiments and devices.

Generating non-classical correlations between photons and spins in a crystal

We perform the experimental generation of pairs of photons on a solid-state rare-earth ion doped crystal of Eu3+:Y2SiO5, by using a DLCZ-like protocol designed for inhomogeneously broadened media. The idea relies on the use of the atomic frequency comb technique, in order to rephase the atoms for the emission of the photons. A specificity of this protocol is its high temporal multimode capacity, as many pairs of photons can be emitted at different instants in time. A Cauchy-Schwarz inequality violation of 2.88>1 is witnessed, proving the non-classical correlations of the photon pairs that we produce. A detailed analysis of the source and detection imperfections is conducted, revealing ways of increasing the quality of the pairs that are produced.

A long-lived solid-state quantum memory at the single photon level

We show storage of a few photon optical pulse as a spin-wave in a crystal, preserving the states’ coherence. We show how it is possible to extend the storage time and increase the process efficiency.

Towards Multimode Memories with Atomic Ensembles in the Solid State

Atomic ensembles in the solid state using rare-earth ion doped materials can be used to implement a quantum memory for the storage of multiple temporal modes. First experimental steps will be presented.

Photon-bunching measurement after two25−km-long optical fibers

To show the feasibility of a long distance partial Bell-State measurement, a Hong-Ou-Mandel experiment with coherent photons is reported. Pairs of degenerate photons at telecom wavelength are created by parametric down conversion in a periodically poled lithium niobate waveguide. The photon pairs are separated in a beam-splitter and transmitted via two fibers of 25km. The wave-packets are relatively delayed and recombined on a second beam-splitter, forming a large Mach-Zehnder interferometer. Coincidence counts between the photons at the two output modes are registered. The main challenge consists in the trade-off between low count rates due to narrow filtering and length fluctuations of the 25km long arms during the measurement. For balanced paths a Hong-Ou-Mandel dip with a visibility of 47.3% is observed, which is close to the maximal theoretical value of 50% developed here. This proves the practicability of a long distance Bell state measurement with two independent sources, as e.g. required in an entanglement swapping configuration in the scale of tens of km.