Quantum Sources and Detectors for Quantum Information

Quantum computing offers the potential to solve complex problems beyond the reach of classical systems, with applications in cryptography, optimization, and scientific simulation. Photonic continuous-variable (CV) quantum computing harnesses light’s properties to enable scalable, fault-tolerant quantum computation. This dissertation contributes to this field through developing high performing optical parametric oscillators (OPOs) and photon-number-resolving detectors (PNRDs). These efforts improve the generation and detection of quantum states, providing practical tools for quantum information processing. I built two triply resonant optical parametric oscillators—a nondegenerate design which demonstrated 6 dB gain and a degenerate one achieving 24 dB gain—demonstrating strong potential for record quantum squeezing as the squeezing record is 15dB. These OPOs are sources of two-mode squeezed states, entangled photon pairs, and CV cluster states, supporting measurement based quantum computing (MBQC) and related applications. As for PNRDs, I significantly enhanced the photon number resolution of the superconducting transition edge sensor (TES) system in our lab, increasing it from 8 to 37 photons per channel, enabling the resolution of up to 100 photons setting a new record up from the previous record of 16. I also modeled segmented detectors using single avalanche photodiodes, offering additional design insights. PNR detectors enable numerous applications, two of which I explore in this dissertation: a quantum random number generator which I experimentally demonstrated and Fock state interferometry, which I theoretically modeled including losses, validating its use for phase discrimination. Together, the high-gain OPOs and refined TES bolster photonic CV quantum computing, by paving the way for cubic phase gate realization and by extension universal CV quantum computing.