# Quantum Metrology with Bose Einstein Condensates

### Monday, 19 Jan. 2015, 17:30 - 19:00

**Presenter:** Markus Oberthaler

**Host:** Jörg Schmiedmayer

**Where:** Lise-Meitner-Hörsaal, 1. Stck. Strudelhofgasse 4, Wien

One aspect of metrology, the science of measurement, is the exploration of the ultimate precision limit. It is known for quite some time that the new possibilities in quantum mechanics allow the surpassing of the ultimate classical precision limit given by counting statistics. Quantum metrology is about the exploration of these new limits. The goal is the generation and characterization of useful quantum mechanical resources for going beyond the classical precision limits. Since the gain in precision is intimately connected to quantum entanglement in many particle systems these investigations are also interesting from the fundamental point of view.

In the colloquium I will discuss in detail how Bose Einstein condensates can be used to generate entangled many particle states which push atom interferometry beyond the classical limits. I will use the system of two component atomic condensates as a model system for explaining how quantum correlations arise and how they can be used for improved estimation of a phase shift in an atom interferometer. The simplest form of useful many particle quantum states are spin squeezed states which can be classified as Gaussian states. I will also report on the latest results revealing that Bose Einstein condensates make it possible to generate deterministically non-gaussian states. The experimental extraction of a bound of the quantum Fisher information implies that these states also surpass the classical limits of the phase estimation precision.