Laboratoire Kastler Brossel
Large Continuous Variable quantum networks for quantum information technologies
Photonics quantum networks are essential resources for quantum communication and information protocols, they represent an essential part of the future quantum internet where quantum states of light will allow for the efficient distribution and manipulation of information. We explore continuous-variable (CV) entangled states, where entanglement correlations appear between quadratures of the electromagnetic field. Such states can be deterministically generated by mixing several squeezed optical modes via linear-optics operations or, more generally, via mode-basis changes. We recently demonstrated the generation of spectrally multimode squeeze states of light at telecommunication wavelengths involving more that 21 frequency modes . For all transfer of information over appreciable distances, telecommunication wavelengths offer the most reliable solution. The generated resource can then be used for frequency multiplexed cryptographic protocols . Moreover, the resource shows promise as a compact solution for scalable entangled states in quantum computing. The 21 squeezed modes are in fact generated in a the single-pass configuration based on non-linear waveguides and a femtosecond laser source: this allows for supplemental pulse-based multiplexing . Large three-dimensional structures, necessary for fault tolerant quantum computing  can then be explored along with non-Gaussian operations  for quantum information protocols.
In this context the internship will concern the test of the pulse-resolving homodyne detection, that will allow for the temporal multiplexing, and/or the design of non-Gaussian operations (like single-photon subtraction) via photon counting with nanowire detectors.
The internship can be followed by a PhD project. The project fits with the purposes of ERC project COCQOoN, the national acceleration strategy PEPR OQULUS ( ‘ordinateur quantique à base de lumière en variables discrètes et continues’) and the EU projet veriqub.
 V. Roman-Rodriguez, D. Fainsin, G. L Zanin, N. Treps, E. Diamanti, V. Parigi Spectrally multimode squeezed states generation at telecom wavelengths, arXiv:2306.07267 (2023)
 O. Kovalenko, Y.-S. Ra, Y Cai, V. C. Usenko , C. Fabre N. Treps, and R. Filip, Frequency-multiplexed entanglement for continuous-variable quantum key distribution Photonics Research Vol. 9, pp. 2351-2359 (2021)
 T. Kouadou, F. Sansavini, M. Ansquer, J. Henaff, N. Treps, V. Parigi, Spectrally shaped and pulse-by-pulse multiplexed multimode squeezed states of light, APL Photonics 8, 086113 (2023)
 J. E., Bourassa, et al. Quantum 5, 392 (2021).
 Ra, Y.-S., Dufour, A., Walschaers, M., Jacquard, C., Michel, T., Fabre, C., and Treps, N., Non-Gaussian quantum states of a multimode light field, Nat. Phys. 16, 144–147 (2020)
The candidate must have a strong interest for experimental work and quantum optics, interest for continuous variable quantum information encoding may be valuable.
Level: M1 obtenu (en cours de M2)
Duration: 3-6 months
Work place: LKB Sorbonne Université, 4 Place Jussieu, 75005 Paris