Optical Parametric Amplification for the Detection of Quantum States
Mahmoud Kalash
Optical quantum information science plays a central role in the development of advanced photonic technologies, with applications ranging from quantum imaging and communication to continuous-variable (CV) quantum computing. The efficient realization of these technologies depends not only on the generation of nonclassical states of light but also on their proper detection. Optical parametric amplification (OPA) has long been known as both a fundamental nonlinear process for generating nonclassical light and as a method to boost detection efficiency through pre-amplification. Recently, OPA has been revisited as a tool for all-optical quadrature detection, offering a powerful alternative to conventional homodyne detection by enabling broadband, loss-tolerant squeezing measurements across various optical platforms. In this thesis, I establish optical parametric amplification as a versatile tool for the detection of CV quantum states through all-optical quadrature detection. I extend squeezing detection to high-dimensional scenarios by exploiting the intrinsic multimode nature of OPA, thereby enabling, for the first time to the best of my knowledge, the real-time monitoring of multimode squeezed light, a long-standing challenge in quantum optics. This approach further permits the simultaneous monitoring of multiple CV Einstein–Podolsky–Rosen (EPR) mode pairs, providing a framework for scalable detection of multimode entanglement, namely optical cluster states, which constitute essential resources for CV quantum computing. Furthermore, I demonstrate OPA as a platform for loss-tolerant and broadband quantum state tomography, applying it to both Gaussian and non-Gaussian states. This paves the way for the scalable tomography of multimode quantum states. Finally, I show that OPA enables the certification of the non-Gaussian and nonclassical character of quantum states without the need for photon-number-resolving detectors, relying instead on post-amplification intensity statistics. In particular, I amplify a single photon sufficiently strongly that its non-Gaussian character becomes accessible through conventional intensity detectors. Altogether, this work establishes optical parametric amplification as a powerful and scalable platform for high-dimensional continuous-variable optical quantum technologies.
•Jan 1, 2026•0 citations