Light scattering in an open quantum system

H. J. Carmichael

The quantum trajectory theory of an open quantum system driven by a photoemissive source is formulated. The formalism is illustrated by applying it to photon scattering from an atom driven by strongly focused coherent light.

Alexander A. Lisyansky, E. S. Andrianov, Alexey P. Vinogradov +1 more

N. G. van Kampen

Ben Q. Baragiola

In this dissertation, I explore interactions between matter and propagating light. The electromagnetic field is modeled as a reservoir of quantum harmonic oscillators successively streaming past a quantum system. Each weak and fleeting interaction entangles the light and the system, and the light continues its course. Within the framework of open quantum systems, the light is eventually traced out, leaving the reduced quantum state of the system as the primary mathematical subject. Two major results are presented. The first is a master equation approach for a quantum system interacting with a traveling wave packet prepared with a definite number of photons. In contrast to quasi-classical states, such as coherent or thermal fields, these N-photon states possess temporal mode entanglement, and local interactions in time have nonlocal consequences. The second is a model for a three-dimensional light-matter interface for an atomic ensemble interacting with a paraxial laser beam and its application to the generation of QND spin squeezing. Both coherent and incoherent dynamics due to spatially inhomogeneous atom-light coupling across the ensemble are accounted for. Measurement of paraxially scattered light can generate squeezing of an atomic spin wave, while diffusely scattered photons lead to spatially local decoherence.

B. R. Mollow

Ziting Chen, Yifei He, Mingchen Huang +4 more

Superradiance is the coherent spontaneous emission from a many-body system, owing to its origin in the simultaneous cooperative interaction among its constituents, initially predicted by R. H. Dicke in 1954. It has been a subject of intense study in various systems, especially in atomic systems. In this poster, we will present our recent observation on superradiant light scattering in a dipolar Bose-Einstein condensate (BEC) of Er atoms [1]. We systematically investigate how s-wave and dipolar interactions affect superradiant light scattering. Our finding opens a new way of characterizing many-body quantum states with light scattering. As an example, we examine the collective light scatter across the phase transition from a dipolar BEC to a quantum droplet.