Atomic physics: Quantum theory verified by experiment

Abstract

Systems of quantum objects can be characterized by the correlations between the objects. A technique that precisely measures even the most delicate of these correlations allows models of quantum systems to be tested.

Figure 1. Observing correlations in a quantum system

Schweigler et al. report a method to probe the underlying physics of quantum systems. Their experiment consists of a pair of weakly interacting one-dimensional quantum fluids — thousands of rubidium-87 atoms at ultracold (nanokelvin-scale) temperatures. Each fluid acts like a wave whose shape can be described by a fluctuating phase (defining the position of the crest of the wave). The authors use a measurement technique called matter–wave interferometry to determine the relative phase between the fluids at various positions (dotted lines) along the length of the waves. They then use these measured correlations to test theoretical models of such systems.