A bright source of entangled photon pairs
lundi 7 octobre 2019 15:47:44
M2/PhD offer, Institut Néel, Grenoble

Entangled photons pairs are a key resource for quantum information processing, in particular for quantum communications. For example, they enable the realization of quantum relays that can extend the distance of quantum key distribution. To be useful, a source of entangled photon pairs has to be bright and tunable, emit indistinguishable photons, and operate on-demand to allow scaling up to many pairs.

This project targets the first demonstration of such a source. On-demand, polarization-entangled photon pairs will be emitted by a semiconductor quantum dot, by exploiting the biexciton-exciton radiative cascade. The cancelation of the excitonic fine structure splitting will be obtained by applying suitable strain [1,2], using piezo-electric actuators and an original electrostatic technique. A tapered nanocavity will simultaneously ensure the efficient extraction of both exciton and biexciton photons [3,4] and provide a broadband spontaneous emission speed-up, in order to achieve photon indistinguishability.

This is a starting project connected to a recently obtained ANR grant (IPOD). During the M2 internship, the work will consist in setting up the ultra-sharp spectroscopic tools for the separation of the two-photon excitation laser, and the two quantum dot lines that will be used to generate the entangled photons. Most of the equipement (cryostat, lasers, spectrometer) is already available and will be complemented thanks to the ANR support. The internship is meant to go on with a PhD, during which a post-doc will be recruited to team up.
The samples are fabricated by our colleagues (J. Claudon and J.M. Gérard) from CEA Grenoble. The project involves original samples, and it will therefore be carried out in very close interaction with them.

[1] I. Yeo et al, Nature Nanotechnology 9, 106 (2014)
[2] D. Tumanov et al, Appl. Phys. Lett. 112, 123102 (2018)
[3] M. Munsch et, Phys. Rev. Lett. 110, 177402 (2013)
[4] H.A. Nguyen et al, Phys. Rev. B 97, 201106(R) (2018)