Coherent backscattering of ultracold atoms

Area of Science:

• Quantum physics
• Atomic physics
• Condensed matter physics

Background:

• Coherent backscattering (CBS) is a quantum interference effect observed in disordered media.
• It is a signature of weak localization, a precursor to Anderson localization.
• Ultracold atoms provide a controllable system to study quantum transport phenomena.

Purpose of the Study:

• To directly observe coherent backscattering (CBS) of ultracold atoms.
• To investigate the build-up of the momentum scattering pattern and the CBS peak.
• To determine microscopic transport quantities and study the time evolution of the CBS peak.

Main Methods:

• Utilizing a quasi-two-dimensional configuration of ultracold atoms.
• Launching atoms with well-defined momentum into a laser speckle disordered potential.
• Monitoring the depletion of the initial momentum component and the formation of the angular ring profile.

Main Results:

• Direct observation of the coherent backscattering (CBS) peak in the backward direction.
• Observation of a ring associated with multiple elastic scattering.
• Determination of microscopic transport quantities from scattering pattern evolution.
• Time evolution of the CBS peak agrees with theoretical predictions at both short and long times.

Conclusions:

• The direct observation of CBS in ultracold atoms confirms its role as a signature of coherence in quantum transport.
• This finding provides experimental evidence for weak localization phenomena in disordered quantum systems.
• The study offers insights into the fundamental mechanisms underlying Anderson localization.