Francesca Sansavini (LKB): Femtosecond parametric processes for the generation of continuous variables quantum networks

Femtosecond parametric processes are at the heart of quantum light generation. In particular, multimode squeezed states of light have emerged as a promising tool for creating quantum networks and advancing continuous-variable (CV) quantum information technologies, where information is encoded in the phase and amplitude of the electromagnetic field [1]. In our approach, the nodes of the network represent the temporal/frequency modes of the electromagnetic field, while the links correspond to tailored entanglement correlations. Our configuration is based on a series of ultra-short pulses that drive a single-pass spontaneous parametric down-conversion process in a nonlinear waveguide. With this device, we can generate multimode squeezed states that are multiplexed both in the time domain (pulse by pulse) and spectral domain: this paves the way for the generation of entangled structures at the laser repetition rate [2]. While time multiplexing has already enabled the generation of the largest CV entangled networks [3,4], multimode compression in the spectral modes of a femtosecond source offers complete reconfigurability of the entanglement network [5].

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[2] T. Kouadou, F. Sansavini, M. Ansquer, Johan Henaff, N. Treps, and V. Parigi, Spectrally shaped and pulse-by-pulse multiplexed multimode squeezed states of light, APL Photonics 8, 086113 (2023)
[3] W. Asavanant, Y. Shiozawa, S. Yokoyama, B. Charoensombutamon, H. Emura, R. N. Alexander, S. Takeda, J.-i. Yoshikawa, N. C. Menicucci, H. Yonezawa, and A. Furusawa, Generation of time-domain-multiplexed two-dimensional cluster state, Science 366, 373 (2019).
[4] M. V. Larsen, X. Guo, C. R. Breum, J. S. Neergaard-Nielsen, and U. L. Andersen, Deterministic generation of a two-dimensional cluster state, 366, 369 (2019).
[5] J. Roslund, R. Medeiros de Araujo, S. Jiang, C. Fabre and N. Treps, Wavelength-multiplexed quantum networks with ultrafast frequency combs, Nat. Photon. 8, 109 (2014).