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Entangled photons in a III-V chip

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Photonics is to play a central role in the development of quantum information and communication technologies. Integrability, room temperature operation and compatibility with the telecom network constitute some key issues for future quantum components. A. Orieux and colleagues at ‘Matériaux et Phénomènes Quantiques’ Laboratory (Paris Diderot University and CNRS) in the framework of a collaboration with Laboratory LPN and ISMO report in Physical Review Letters the first III-V semiconductor source of entangled photons working at room temperature and telecom wavelength.
The device is an AlGaAs microcavity waveguide in which a transverse pump beam generates polarization-entangled photon pairs by parametric down conversion. The state of the system is characterized through a complete quantum tomography that demonstrates fidelity of 83% to a maximally entangled state and a consequent violation of Bell’s inequality. The approach employed by the authors avoids post-manipulation of the generated photons and is thus particularly suitable for large-scale quantum photonic architectures. A theoretical model taking into account the experimental details provides ways to understand and control the amount of entanglement.
The compatibility of the device with electrical injection, together with the high versatility of the generated two-photon states, makes the reported source a promising candidate for fully integrated quantum photonics.
This work is the result of a collaboration between the DON and the THEORY team of Laboratory MPQ.

Figure :

Scheme of the set-up for the direct generation of Bell states : a ridge micorcavity is elluminated with a transverse pump beam passing through a Fresnel biprism. Entangled pairs of counterpropagating photons are emitted and collected at both facets.

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Référence :

Direct Bell States Generation on a III-V Semiconductor Chip at Room Temperature.
A. Orieux, A. Eckstein, A. Lemaître, P. Filloux, I. Favero, G. Leo, T. Coudreau, A. Keller, P. Milman, and S. Ducci Physical Review Letters 110, 160502 (2013).