Photon tomography of a Josephson Parametric Amplifier

Josephson Parametric Amplifiers (JPAs) are an important resource for quantum limited measurement, feedback and nonclassical state generation. To study the JPA transformation, we use a superconducting qubit-cavity system to launch single photons or, n=1 Fock states, into a JPA, which measures the state. From repeated measurements, we can infer the state's loss of purity as a results of the JPA transformation. We will present our estimates of the JPA's efficiency as a photon detector along with progress toward measuring arbitrary superpositions of n=0 and n=1 Fock states.