The Quantum Statistics of Light Scattering and Propagation Effects

Jan Pefina

Juha Javanainen, Janne Ruostekoski

We study interactions of light with a sample of two-level atoms, with full inclusion of angular momentum degeneracy, at temperatures and densities such that the quantum statistics of the atoms may have an effect. Coupled propagation equations are given for light and matter fields, and plausible general simplifications are enumerated. In particular, the motion of the atoms during the excited-state lifetime may often be ignored. The propagation equations of light and matter fields are decoupled within the assumption that the detuning of the driving light from atomic resonance is large, and the spectrum of scattered light is studied for ideal Bose and Fermi gases. In addition to the expected image of the velocity distribution, the spectra contain qualitatively distinct features that depend on the statistics of the atoms. This is because for bosons (fermions), those scattering events in which an atom recoils to an already occupied state are enhanced (inhibited).

C. W. McCombie

Mateo Restrepo, Ángela M. Guzmán, William T. Rhodes +1 more

We analyze the quantum statistical properties of light scattered by an acousto-optic modulator. From the perspective of quantum mechanics, the acousto-optic effect arises from a nonlinear interaction between three bosonic fields: the laser light, the Brillouin-scattered light, and an acoustic wave. The Hamiltonian coincides with that of sum-frequency generation, where the sum-frequency mode is known to exhibit sub-Poissonian statistics. We calculate the free temporal evolution of the Fano factor for Brillouin backscattered light and determine that sub-Poissonian statistics are obtained when faint laser light is scattered by a counter-propagating coherent acoustic wave with low average phonon number. The use of sub-Poissonian light would lead to an increase of the security for quantum key distribution.

R. Graham, Fritz Haake

Chenglong You, Ashe Miller, Roberto de J. León‐Montiel +1 more

Abstract Recent progress on quantum state engineering has enabled the preparation of quantum photonic systems comprising multiple interacting particles. Interestingly, multiphoton quantum systems can host many complex forms of interference and scattering processes that are essential to perform operations that are intractable on classical systems. Unfortunately, the quantum coherence properties of multiphoton systems degrade upon propagation leading to undesired quantum-to-classical transitions. Furthermore, the manipulation of multiphoton quantum systems requires nonlinear interactions at the few-photon level. Here, we introduce the quantum van Cittert-Zernike theorem to describe the scattering and interference effects of propagating multiphoton systems. This fundamental theorem demonstrates that the quantum statistical fluctuations, which define the nature of diverse light sources, can be modified upon propagation in the absence of light-matter interactions. The generality of our formalism unveils the conditions under which the evolution of multiphoton systems can lead to surprising photon statistics modifications. Specifically, we show that the implementation of conditional measurements may enable the all-optical preparation of multiphoton systems with attenuated quantum statistics below the shot-noise limit. Remarkably, this effect cannot be explained through the classical theory of optical coherence. As such, our work opens new paradigms within the established field of quantum coherence.