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Tomographic reconstruction of the Wigner function of an itinerant microwave field.

Francois Mallet, Joint Institute for Laboratory Astrophysics

(Session 9 : Saturday from 5:00-5:30)

Abstract. Francois Mallet, Manuel Castellanos-Beltran, Hsiang-Sheng Ku, Kent Irwin, Leila Vale, Gene Hilton, Konrad Lehnert. In an increasing number of experiments, the desired information (for example the state of nanomechanical resonators or of superconducting qubits) is successfully encoded into the state of a coherent microwave field. However these experiments suffer from the lack of high efficiency detectors at microwave frequencies: the best commercially available amplifiers add twenty times more noise than the intrinsic quantum fluctuations of the field. Our group has made a crucial step to overcome this important limitation by developing quantum limited Josephson Parametric Amplifiers (JPAs) [1]. In this talk I will show how we dramatically increase the performance of the Quantum State Tomography of a squeezed state of the microwave field by using our JPAs. The achieved degree of squeezing and the quantum efficiency of the state tomography will be presented from the point of view of using these squeezed states as building blocks of a more global strategy to perform Quantum Information experiments. Indeed it has been shown in the field of Continuous Variables Quantum Information that theses squeezed states, can be combined to create EPR-like entangled states. Conveniently, the non-classical squeezed states are themselves created by the JPAs. [1] Amplification and squeezing of quantum noise with a tunable Josephson metamaterial, M. Castellanos-Beltran et al., Nat. Phys. 4, 929-931 (2008).