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Quantum photonics

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Photonics is playing a central role in the development of quantum information technologies. Quantum key distribution systems are already commercially available and, taking benefit from the high-speed transmission and low-noise properties of photons, continuous progresses are under way towards large-scale secure networks, metrological systems and quantum processors. The main challenge on the way towards large-scale applications is the miniaturization and integration of all major components on a single chip operating at room temperature. Our team works on the conception, fabrication and characterization of III-V semiconductor sources of entangled photons at room temperature at telecom wavelength ; thanks to its direct band gap, this platform present en evident interest for electrical injection opening the way to the generation, manipulation and detection of non classical states of light in a single chip. Here we give a short summary of our main results.

Counterpropagating entangled photons sources

Partie réelle de la matrice densité de photons intriqués en polarisation

These devices are based on a counterpropagating phase-matching scheme : in this geometry, a pump field (775 nm) impinges on top of the waveguide generating two counterpropagating, orthogonally polarized guided-wave signal/idler field (around 1550 nm) [1]. This kind of source has led to several major results : indistinguishable photons have been demonstrated through a Hong-Ou-Mandel experiment [2] and entangled photons at room temperature through the reconstruction of the density matrix [3]. We are currently working on the study of degrees of freedom displaying a high-dimensional Hilbert space such as frequency or orbital angular momentum and on the integration of the sources with quantum photonic circuits.

Intégration de la source avec des séparateurs de faisceau 50/50

Electrically injected photon pair sources at room temperature

Taking advantage of the direct band-gap of GaAs we have designed and demonstrated the first twin photon laser pointer [4] : this electrically driven device works at room temperature and has been engineered for simultaneous lasing around 775 nm and efficient internal parametric down-conversion with photon pairs around 1.55 μm. Such achievement is an important improvement of the state of the art since all the photon pairs sources demonstrated up to now are either optically injected (nonlinear dielectric crystals or fibers) or working at cryogenic temperature (quantum dots). Indistinguishabilty and energy-time entanglement has been demonstrated on a passive device [5]. Work is going on to characterize the bi-photon state emitted by the electrically driven device and to use the source in fibered quantum networks.

Sketch du premier pointeur laser à photons jumeaux

Quantum state engineering and measurement

In collaboration with theoreticians, we work on the development of new methods to reconstruct and engineer bi-photon states for quantum information applications. Our sources provide a bench test for the experimental demonstration of these novel techniques.

Simulations numériques d’un état compas pouvant être généré avec un de nos dispositifs

For example, we have recently shown that a simple modification in the HOM experiment provides a measurement of the Wigner function ; this open the way to the generation of Schrödinger cats and compass states with our devices [6].

Reconstruction expérimentale de la densité spectrale jointe d’un état à deux photons émis par une de nos sources

We have also shown that the spectral characterization of the quantum correlations generated by two-photon sources can be directly performed classically with an unprecedented spectral resolution. This streamlined technique has the potential to speed up design and testing of massively parallel integrated sources by providing a fast and reliable quality control procedure [7].

[1] L. Lanco et al. "Semiconductor waveguide source of counterpropagating twin photons", Phys. Rev. Lett. 97, 173901 (2006).
[2] X. Caillet et al. "Two-photon interference with a semiconductor integrated source at room temperature", Optics Express 18, 9967 (2010).
[3] A. Orieux et al. "Direct Bell States Generation on a III-V Semiconductor Chip at Room Temperature", Phys. Rev. Lett. 110, 160502 (2013).
[4] F. Boitier et al. "An electrically injected photon-pair source at room temperature", Phys. Rev. Lett. 112, 183901 (2014). Editor’s choice & Viewpoint on
[5] C. Autebert et al. " Integrated AlGaAs source of highly indistinguishable and energy-time entangled photons", Optica 3, 143 (2016).
[6]G. Boucher et al. "Toolbox for continuous-variable entanglement production and measurement using spontaneous parametric down-conversion", Phys. Rev. A 92, 023804 (2015).
[7] A. Eckstein et al. “High-resolution spectral characterization of two photon states via classical measurements”, Laser Photon. Rev., 8, 76 (2014).

Main collaborators

- Laboratoire de Photonique et Nanostructures : A. Lemaître, X. Lafosse, F. Raineri.
- University of Oxford : I. Walmsley’s team
- University of Geneva : H. Zbinden’s team.
- University of Pavia : M. Liscidini
- University of Toronto : J. Sipe