Observation of Entanglement between Itinerant Microwave Photons and a Superconducting Qubit
Christopher Eichler, Christian B. Lang, J. M. Fink, Joonas Govenius, Stefan Filipp, Andreas J. Wallraff · Physical Review Letters · 2012
A localized qubit entangled with a propagating quantum field is well suited to study nonlocal aspects of quantum mechanics and may also provide a channel to communicate between spatially separated nodes in a quantum network. Here, we report the on-demand generation and characterization of Bell-type entangled states between a superconducting qubit and propagating microwave fields composed of zero-, one-, and two-photon Fock states. Using low noise linear amplification and efficient data acquisition we extract all relevant correlations between the qubit and the photon states and demonstrate entanglement with high fidelity.