Observation of Entanglement Between Itinerant Microwave Photons and a Superconducting Qubit

  1. C. Eichler,
  2. C. Lang,
  3. J. M. Fink,
  4. J. Govenius,
  5. S. Filipp,
  6. and A. Wallraff
A localized qubit entangled with a propagating quantum field is well suited to study non-local 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.