Quantum frequency combs for quantum information protocols

Light offers a vast potential in the development of modern quantum technologies due to its intrinsic resilience to decoherence effects. One avenue for employing light to process quantum information focuses on the continuous variable regime, where the observables of interest are the quadratures of the electric field. They have proven their worth as a platform for creating huge entangled states (entangling up to one million optical modes). Additionally, this entanglement can be created in a deterministic fashion and easily manipulated with standard techniques in optics [1,2].

To reach a quantum advantage, and perform a task that cannot be efficiently simulated with a classical device, we require more than just entanglement. The additional ingredient is non-Gaussian statistics in the outcomes of the quadrature measurements. More specifically, we must create quantum states with a negative Wigner function. At LKB, we have recently developed a mode- tunable photon subtractor as a device for creating such states [3,4]. As such, we now have the possibility to produce large entangled states and to render them non-Gaussian. This opens up a whole new realm of research, where a vast amount of questions on the interplay between entanglement and non-Gaussian effects remain unanswered [4,5].

The experiment consists in manipulating the spectral modes of a frequency comb to engineer entangled Gaussian states, and use photon-subtraction through mode-dependent sum-frequency to induce non-Gaussian features in these states. We implement experimental techniques from optical cavities, non-linear optics, ultra-short optical pulses manipulation and highly sensitive and multiplexed detection.

Gradually, more and more non-Gaussian elements will be added to the experimental setup. On the level of state engineering, we will aim at the subtraction of multiple tailored photons. On the detection stage, we will incorporate photon-number detection schemes, mesoscopic detectors and double homodyne detection.

All of these elements will make the experiment a platform for quantum information protocols. On the one hand, it will be possible to explore non-Gaussian quantum steering and to implement elaborated tests of required quantum properties, necessary for any quantum advantage. This will be done in collaboration with the QI group at LIP6 [6]. Then, we will study how to implement elementary quantum protocols, for instance linked to error correction.

Contact to submit your application :
Nicolas Treps, nicolas.treps@upmc.fr

[1] J. Roslund, R. M. de Araujo, S. Jiang, C. Fabre, N. Treps, Nature Photonics 8, 109 (2014).

[2] Y. Cai, J. Roslund, G. Ferrini, F. Arzani, X. Xu, C. Fabre, N. Treps, Nature Communication 8, 15645

(2017).
[3] Y.-S. Ra, C. Jacquard, A. Dufour, C. Fabre, N. Treps, Phys. Rev. X, 7, 031012 (2017).


[4] Y.-S. Ra, A Dufour, M. Walschaers, C. Jacquard, T. Michel, C. Fabre, N. Treps, Nature Physics 11, 1 (2019).


[5] M. Walschaers and N. Treps, Phys Rev Lett 124, 150501 (2020).

[6] U. Chabaud, G. Roeland, M. Walschaers, F. Grosshans, V. Parigi, D. Markham, and N. Treps, ArXiv:2011.04320 [Quant-Ph] (2020).