Superconducting Parametric Cavities as an “Optical” Quantum Computation Platform

Quantum information may be encoded into systems of discrete variables (DV) or continuous variables (CV). CV quantum computation has typically been studied at optical frequencies using linear quantum optics to realize Gaussian operations. To achieve universal computation, however, non-Gaussian resources such as the photon number measurements or the cubic phase state are necessary. In superconducting circuits, DV quantum computation is dominant. Here, we propose and study the superconducting parametric cavity for optical quantum computation using microwave photons. At optical frequencies, the qumodes are often separated spatial modes. Here we use the orthogonal frequency modes of the cavity. Gaussian operations between the modes are achieved via standard parametric interactions. In addition, the recent realization of three-photon spontaneous parametric downconversion in this system provides access to both a non-Gaussian gate and resource state, which provides a path to universality. We will present preliminary results towards the development of the parametric cavity for optical quantum computation starting with demonstrations of simple algorithms. One such algorithm is a quantum machine learning algorithm called Quantum Kitchen Sinks.