Heidelberg 2015 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 18: Poster: Ultra-cold atoms, ions and BEC (with Q)

A 18.13: Poster

Dienstag, 24. März 2015, 17:00–19:00, C/Foyer

Cavity-Optomechanics with Cold Atoms: Coupled Quantum Oscillators and Quantum Limited Force Sensing — •Nicolas Spethmann1,2, Jonathan Kohler1, Sydney Schreppler1, Lukas Buchmann1, and Dan Stamper-Kurn11University of California, Berkeley — 2Universität Kaiserslautern

Cavity opto-mechanics with cold atoms provides a system with unique properties for studying quantum physics: Highly tunable and controllable oscillators, close to their thermal groundstate, with excellent isolation from the environment and quantum-limited optical detection.

The limit of sensitivity of a force measurement dictated by quantum mechanics, the standard quantum limit, is reached when measurement imprecision from photon shot-noise is balanced against disturbance from measurement back-action. To observe this quantum limit, we apply a known external force to the center-of-mass motion of an ultracold atom cloud in a high-finesse optical cavity. We achieve a sensitivity of (42±13yN)2/Hz, consistent with theoretical predictions and a factor of 4 above the absolute standard quantum limit.

The flexibility of our approach furthermore allows us to study cavity-optomechanics with multiple, coupled oscillators. We demonstrate cavity mediated coupling between two near-groundstate oscillators. We observe the oscillating coherent transfer of excitation between the oscillators. At the same time, we detect the motional noise of the oscillators to monotonously increase due to back-action caused by the coupling. Our results point to the potential, and also the challenge, of coupling quantum objects with light.

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