laboratoire pierre aigrain
électronique et photonique quantiques
laboratoire pierre aigrain

Seminar, December 22, 2014

Michel Devoret (Applied Physics, Yale University)
Friction and measurements that preserve rather than destroy quantum entanglement

Entangled states constitute a key resource in quantum
cryptography, quantum computation and quantum sensing. It has generally
been assumed that the creation of such states requires the system to avoid
contact with a dissipative environment, and the suppression of all sources
of dephasing. Some recent theoretical studies have shown, however, that
dissipative interactions combined with an adequately chosen drive can be
employed to preserve coherence. Following these ideas, we have built
experimentally an autonomous feedback scheme that counteracts both
dissipation and dephasing. This led to the stabilization of an entangled
Bell state of a quantum register of two superconducting qubits for an
arbitrary time [1]. Furthermore, fidelity of the Bell state can be
increased by continuously monitoring one dissipative channel involved in
the stabilization. The general approach we are following may help building
a logical qubit holding quantum information in a fault-tolerant way and
with minimal hardware [2].

[1] Shankar et al., Nature *504*, 419 (2013)

[2] Mirrahimi et al., New J. Phys*.* *16,* 045014 (2014)