@article{1784, abstract = {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.}, author = {Eichler, Christopher and Lang, C and Johannes Fink and Govenius, J and Filipp, Stefan and Wallraff, Andreas}, journal = {Physical Review Letters}, number = {24}, publisher = {American Physical Society}, title = {{Observation of entanglement between itinerant microwave photons and a superconducting qubit}}, doi = {10.1103/PhysRevLett.109.240501}, volume = {109}, year = {2012}, }