Quantum feedback control for the deterministic generation of Schrödinger-cat states

Continuous measurement and feedback hold tremendous potential for producing non-Gaussian quantum states that are useful for quantum communication and computation. We present a new feedback scheme to deterministically produce quantum non-Gaussian states from linear optical elements and feedback. In our scheme, measurement outcomes are used in two different ways. One implements a multiplicative feedback control which produces nonlinear effects in the system. The other stabilizes the system to produce a desired state deterministically. A design example of the multi-loop feedback structure is demonstrated for the deterministic generation of Schrodinger-cat states as the practical use of quantum feedback control.