Quantum measuring processes for trapped ultracold bosonic gases

TL;DR

This paper investigates quantum measurement processes in ultracold bosonic gases, revealing that common experimental techniques correspond to a generalized quantum measure that affects the observed atomic density profiles.

Contribution

It introduces a quantum measurement framework based on POVMs for ultracold gases, highlighting differences from traditional density expectation values.

Findings

Absorption imaging corresponds to a generalized quantum measure.

The measured density profile differs from the standard expectation value.

Interference patterns suggest a fixed-phase, coherent-like state measurement.

Abstract

The standard experimental techniques usually adopted in the study of the behaviour of ultracold atoms in optical lattices involve extracting the atom density profile from absorption images of the atomic sample after trap release. Quantum mechanically this procedure is described by a generalized measure (POVM); interference patterns found in absorption images suggest a generalized measure based on fixed-phase, coherent-like states. We show that this leads to an average atomic density which differs from the usually adopted one, obtained as the expectation value of the atom density operator in the many-body state.