Leader : Tanzilli Sébastien
Collaborators within LPMC : Alibart Olivier, Kastberg Anders, Labonté Laurent
External Collaborators : Chanelière T. (Laboratoire Aimé Cotton (LAC), UPR 3321 du CNRS, Orsay)
PhD/Post-doctoral fellows : Aktas Djeylan, Bin-Ngah Lutfi-Arif, Issautier Amandine
Financial supports financiers : Foundation Simone & Cino Del Duca (Institut de France) ; Foundation iXCore for Scientific Research
Entanglement, which lies at the heart of quantum physics, finds nowadays applications in quantum information. It is, indeed, an essential resource for quantum key distribution experiments and manipulation of information through teleportation and storage of quantum states.
In the framework of long distance quantum networks, the realization of quantum nodes allowing the storage of quantum information (qubits) represents today an essential but difficult task. Those interconnecting nodes, or quantum repeaters, are generally based on light/matter interactions where a photon induces a collective excitation in an atomic ensemble such as a cold-atom cloud or a rare-earth ions doped crystal.
Among the various ionic and atomic species that the whole international scientific community has been studying, three of them seem to stand out. On one hand, we can find thulium (Tm) and erbium (Er) ions that can interact with light at the respective wavelength of 793 and 1538 nm, and on the other hand, cold atoms of rubidium (Rb) operate at 795 nm.
We also aim at studying the generation of entangled photon pairs emitted within a comb of twin DWDW telecom channels, in order to achieve high-speed quantum key distribution for cryptography applications.
The aim of this project is the demonstration of an ultra-narrow (10 MHz) photon pairs source at telecom wavelength or at a frequency corresponding to the DWDM canals of optical telecommunications entangled in an hybrid manner upon the observables time of emission and polarization . And concerning the ultra-narrow spectral bandwidth :
- The production of photon pairs will reside on parametric down conversion inside a non-linear integrated optical waveguide with the use of photon pairs in a non degenerated way (two different wavelength photons entanglement, one at 1538 while the other is at 1560 nm). The emission in an ultra-narrow bandwidth will only be possible due to the use of the latest technology, like state of the art fibered Bragg filters, to be compatible with the considered quantum memories.
- From a fundamental point of view, it will be necessary to demonstrate both theoretically and experimentally the feasibility of such an hybrid entanglement. An extension based on two waveguides in parallel will also be studied for states entangled solely in polarization.
- Also from a fundamental point of view, we aim to couple (inside the laboratory), the photon at 1560 nm with a cold-atom ensemble of Rb view as a quantum memory, but used as a deterministic single photon source at 795 nm (see project Remote entanglement of two quantum memories). The idea is to build an experiment where two photons are sent on a beam-splitter, one coming from the entangled photons source while the other would come from the single photons source, where they would interfere maximally (Hong-Ou-Mandel effect). In order to observe this, both photons must be indiscernible regarding their wavelength. This will be possible by converting the wavelength of the single photon with a Difference Frequency Generation (DFG) process in a non-linear integrated optical waveguide (795 nm -> 1560 nm).
- Finally, from a quantum information applications point of view, the 1538 nm photon will be directly compatible with a quantum memory based on a doped erbium crystal (available through a collaboration with laboratory Aimé Cotton (LAC) in Orsay). Furthermore, the photon at 1560 nm will also be compatible with other quantum memories based on cold atoms of Rb (LPMC) or thulium ions doped crystals (LAC) through a process of Sum Frequency Generation (SFG) in an integrated optical non-linear Crystal.
Also note that this project represents the natural of the e-QUANET project that was supported by both the ANR (ANR-09-BLAN-0333-01 [2009-2012]) and the Région PACA through its "exploratory project" call.
 "A versatile source of polarization entanglement for quantum network applications", F. Kaiser, A. Issautier, O. Alibart, A. Martin, and ST,
Laser Phys. Lett. 10, 045202 (2013).