Nonclassicality of Propagating States From 3-Photon Interactions in a Superconducting Parametric Cavity

Abstract

The multimode superconducting parametric cavity has proven to be a powerful and versatile system for producing nonclassical states of light in the microwave regime. Utilizing its ability to realize nonlinear and multimode Hamiltonians, we can produce strongly correlated propagating signals from the cavity at different frequencies including entangled photons. In this thesis, we study the generation of photon triplets using a cubic Hamiltonian in the cavity under a parametric drive. We demonstrate the implementation of 3-photon Spontaneous Parametric Down-Conversion (SPDC) into different frequency modes of the cavity and study the non-Gaussian statistics of the outputted photon triplets through purely linear detection. We detail our methodology for performing absolutely calibrated measurements of the cavity output using a Shot Noise Tunnel Junction (SNTJ) as well as our use of a near quantum-limited Travelling-Wave Parametric Amplifier (TWPA). In addition to the primary results of this thesis, we present calibrated measurements of the noise temperature of the Crescendo TWPA from QuantWare. Through the use of this TWPA and SNTJ, we are able to obtain the correlations between frequencies with low uncertainty up to the 4th moments. From these moments, we can compute a nonlinear entanglement witness on the propagating triplets and demonstrate the non-Gaussian genuine tripartite entanglement between photons with over 15 sigmas of certainty.