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Exceptional seminars of Pierre ROUCHON on Quantum Systems - GIPSA-lab June 21th

2017-06-09

In the context of the ERC-AdG Scale-FreeBack, Pierre ROUCHON, professor at MinesParisTech, will be giving two seminars on quantum systems (open to all public) and on quantum control and experimental tests.

Pierre Rouchon is professor at Centre Automatique et Systèmes, MinesParisTech, PSL Research University. He is a member of QUANTIC team-project at Inria (ENS-Paris, Mines-ParisTech, UPMC, CNRS). He was student of Ecole polytechnique, Ingénieur général des Mines and professor at Ecole polytechnique (1993-2005).

Seminars will be organised in 2 times:
10:30 am – 11:30 am : Une introduction au contrôle quantique pour automaticiens familiers du monde classique – GIPSA-lab, salle des séminaires B208 (2e étage, bâtiment B).

14:00 pm – 15:00 pm : On the first experimental realization of a quantum state feedback – GIPSA-lab, salle des séminaires B208 (2e étage, bâtiment B).


Abstract: At the quantum level, feedback loops have to take into account measurement back-action. The goal of this talk is to explain, in a tutorial way and on the first experimental realization of a quantum-state feedback, how such purely quantum effect can be exploited in models and stabilization control schemes. This closed-loop experiment was conducted in 2011 by the group of Serge Haroche (Physics Nobel Prize 2012). The control goal was to stabilize a small number of micro-wave photons trapped between two super-conducting mirrors and subject to quantum non-demolition measurement via probe off-resonant Rydberg atoms. The implemented control scheme was decomposed into two parts. The first part estimates in real-time the quantum state of the trapped photons via a discrete-time Belavkin quantum filter. The second part is a nonlinear quantum-state feedback based on control Lyapunov functions. It stabilizes via suitable coherent displacements the number of photon(s) towards its set-point, namely an integer less than 5 in the experiment. This control scheme relies on a hidden control Markov model whose structure combines three quantum rules: unitary deterministic Schrödinger evolution; stochastic collapse of the wave packet induced by the measurement; tensor product for the composite systems. These basic quantum rules characterize the structure of all Markovian models describing open-quantum systems. These rules explain also the existence to two kinds of feedback schemes currently developed for quantum error correction: measurement-based feedback where an open quantum system is stabilized by a classical controller; coherent or autonomous feedback (reservoir engineering) where an open quantum system is passively stabilized through its coupling with another highly dissipative quantum system, namely the quantum controller.

>> Pierre ROUCHON website


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