Atom interferometry with quantized light pulses

TL;DR

This paper investigates how atom interferometry behaves with different quantum states of light, revealing that low photon numbers encode which-way information, reducing interference visibility, unlike classical light.

Contribution

It demonstrates the impact of quantum light states, especially low photon number states, on atom interferometry interference patterns and visibility.

Findings

Diffraction patterns are identical for classical and quantum light fields.

Interference visibility decreases with low photon numbers due to which-way information.

High photon number coherent states approach classical interference behavior.

Abstract

The far-field patterns of atoms diffracted from a classical light field, or from a quantum one in a photon-number state are identical. On the other hand, diffraction from a field in a coherent state, which shares many properties with classical light, displays a completely different behavior. We show that in contrast to the diffraction patterns, the interference signal of an atom interferometer with light-pulse beam splitters and mirrors in intense coherent states does approach the limit of classical fields. However, low photon numbers reveal the granular structure of light, leading to a reduced visibility since Welcher-Weg (which-way) information is encoded into the field. We discuss this effect for a single photon-number state as well as a superposition of two such states.