Quantum feedback engineering, bosonic codes and quantum error correction, by Pierre Rouchon (Mines Paris – PSL)

Quantum error correction relies on a feedback loop. This feedback generally corresponds to a classical controller. Quantum error correction can also exploit the dissipation associated with the phenomenon of decoherence. Called autonomous correction by physicists, it then uses feedback where the controller is a dissipative quantum auxiliary system. This talk focuses on the development of such quantum controllers to stabilize logical qubits encoded in harmonic oscillators (bosonic code). Two types of encoding will be considered: cat-qubit encoded in two coherent states of opposite phases for which bit-flip errors induced by usual noises can be experimentally almost suppressed ; GKP-qubit encoded in finite energy grid-states approximating position/impulsion Dirac combs where, in principle, both bit-flips and phase-flips could be almost suppressed.

Bio: Pierre Rouchon is a professor with the Centre Automatique et Systèmes at Mines-Paris, Université PSL and a member of the French Academy of Sciences. Since 2015, he has been part of the Quantic Research team, a collaboration between Inria, Ecole Normale Supérieure and Ecole des Mines. His fields of interest include nonlinear control and system theory with applications to physical systems. His contributions include differential flatness and its extension to infinite dimensional systems, non-linear observers and symmetries, quantum filtering, and feedback control. In 2017, he was awarded the Grand Prix IMT by the Académie des sciences de Paris. He is the principal investigator of the ERC Advanced Grant « Quantum Feedback Engineering » (2021-2026).