Confining the state of light to a quantum manifold by engineered two-photon loss
Zaki Leghtas, Steven Touzard, Ioan M. Pop, Angela Kou, Brian Vlastakis, Andrei Petrenko, Katrina Sliwa, A. Narla, Shyam Shankar, Michael Hatridge, Matthew J. Reagor, Luigi Frunzio, Robert J. Schoelkopf, Mazyar Mirrahimi, Michel Devoret · Science · 2015
Physical systems usually exhibit quantum behavior, such as superpositions and entanglement, only when they are sufficiently decoupled from a lossy environment. Paradoxically, a specially engineered interaction with the environment can become a resource for the generation and protection of quantum states. This notion can be generalized to the confinement of a system into a manifold of quantum states, consisting of all coherent superpositions of multiple stable steady states. We have confined the state of a superconducting resonator to the quantum manifold spanned by two coherent states of opposite phases and have observed a Schrödinger cat state spontaneously squeeze out of vacuum before decaying into a classical mixture. This experiment points toward robustly encoding quantum information in multidimensional steady-state manifolds.