High-rate generation and state tomography of non-gaussian quantum states for ultra-fast clock frequency quantum processors

Quantum information processors greatly benefit from high clock frequency. All-optical systems offer unique advantages due to their inherent 100 THz carrier frequency, permitting one to develop THz clock frequency processors. In practice, the bandwidth of the quantum light sources and the measurement devices has been limited to the MHz range and the generation rate of nonclassical states to kHz order In this work, we go beyond this limitation by utilizing optical parametric amplifier (OPA) as a squeezed-light source and optical phase-sensitive amplifiers (PSA) to realize high-rate generation of broadband non-Gaussian states and their quantum tomography. Our system consists of a 6-THz squeezed-light source, a 6-THz PSA, and a 66-GHz homodyne detector. We have successfully demonstrated non-Gaussian state generation at a 0.9 MHz rate---almost three orders of magnitude higher than the current state-of-the-art experiments---with a sub-nanosecond wave packet using continuous-wave laser. The performance is constrained only by the superconducting detector's jitter which currently limits the usable bandwidth of the squeezed light to 1 GHz.

Methods
This data was collected by homodyne measurement on photon-subtracted state generated. The photon-subtracted state is generated by tapping a small portion of squeezed light generated from an optical parametric amplifier, and then send the tapped light to a photon counter. The data processed by integration of the real-time data collected from the oscilloscope into the quadrature of each wave packet.