Back-action in the measurement of “macroscopic quantum superpositions” in microwave cavities

Abstract

We analyze the back-action of nonlinear atomic homodyning measurements on steady-state “macroscopic superpositions” that can be generated in high-Q microwave cavities. We show that a full characterization of the state requires measurements such that the macroscopic superposition is irreversibly destroyed, that is, it cannot be reconstructed by using the scheme that was used to generate it in the first place.