Nonclassical Field Correlations in Quantum Optics

Roman V. Zakharov, Olga V. Tikhonova

Kisik Kim

We generate multi-mode nonclassical correlations in the output field from the single-mode nonclassicality in the input field with a unitary optical device. It is shown that, according to the invariance of nonclassicality, the decrement of the single-mode nonclassicality is compensated for by the appearance of multi-mode nonclassical correlations. We demonstrate a complete transfer of single-mode nonclassicality to a multi-mode nonclassical correlation for a 1 × 2 array of beam splitters, when chaotic lights are taken as auxiliary classical fields of the input.

V. V. Dodonov, Igor Dremin, Olga V. Man’ko +2 more

Rupamanjari Ghosh

Jhoan Eusse, Esteban Vasquez, Tom Rivlin +1 more

Nonclassical states of light and their correlations lie at the heart of quantum optics, serving as fundamental resources that underpin both the exploration of quantum phenomena and the realisation of quantum information protocols. These lecture notes provide an accessible yet rigorous introduction to the foundations of quantum optics, emphasising their relevance to quantum information science and technology. Starting from the quantisation of the electromagnetic field and the bosonic formalism of Fock space, the notes develop a unified framework for describing and analysing quantum states of light. Key families of states -- thermal, coherent, and squeezed -- are introduced as paradigmatic examples illustrating the transition from classical to nonclassical behaviour. The concepts of convexity, classicality, and quasiprobability representations are presented as complementary tools for characterising quantumness and defining operational notions such as P-nonclassicality. The discussion extends naturally to Gaussian states, composite systems, and continuous-variable entanglement, highlighting how nonclassicality serves as a resource for generating and quantifying quantum correlations. Theoretical developments are complemented by computational and experimental perspectives, including simulations of optical states using the Python library Strawberry Fields and data analysis from simulated data. Together, these notes aim to bridge the foundational concepts of quantum optics and modern quantum information, offering both conceptual insight and practical tools for students and researchers entering the field.

Chanseul Lee, Tai Hyun Yoon

We discuss nonclassical light properties, in particular, focused on multi-photon quantum correlations in quantum optics. We analyze two-mode fields from a nondegenerate optical parametric oscillator below threshold using criteria introduced by Agarwal1 and Lee. Additionally, we identify that system parameters like pump and seed coherent amplitudes influence the nonclassicality of the output quantum state.