Description

2009/09/30,  Prof. Morgan W. Mitchell (ICFO, Barcelona)

Place: Sala de Seminarios del Departamento de Física Teórica e Historia de la Ciencia
Time: 12h.
Title: Quantum non-demolition measurements of cold atoms and
quantum-enhanced atomic sensing

Abstract
Atomic ensembles, collections of many identical atoms, are interesting
systems for studying the quantum physics of light-matter interactions.
 The ensemble behaves as a macroscopic quantum system, interacting
strongly with the light field and robust against the loss or
decoherence of individual atoms in the ensemble.  Using laser-cooled
rubidium-87 in an optical dipole trap, we demonstrate an atomic
ensemble with very strong light-matter interactions (an effective
optical depth of ~50 with only 10^6 atoms).  Using paramagnetic
Faraday rotation to probe the spin polarization, we demonstrate
quantum non-demolition measurement with quantum-limited sensitivity.
In parallel, we develop quantum light sources suitable for atomic
probing.  I will discuss applications to entanglement generation,
atom-based magnetometry and possibly more exotic topics such as
non-linear measurements that 'beat' the 1/N Heisenberg scaling limit.