Mainz 2017 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 54: Ultracold atoms and BEC - V (with A)
Q 54.5: Talk
Friday, March 10, 2017, 12:00–12:15, N 1
Cavity-assisted measurement and coherent control of collective atomic spin oscillators — •Nicolas Spethmann1,2, Jonathan Kohler2, Sydney Schreppler2, and Dan Stamper-Kurn2,3 — 1Department of Physics and Research Center OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany — 2Department of Physics, University of California, Berkeley, CA 94720, USA — 3Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
I will present experiments of continuous measurement and coherent control of the collective spin of an atomic ensemble trapped and evolving in a high-finesse cavity. We employ autonomous optical feedback onto the atomic spin dynamics, conditioned by the cavity spectrum, as a feedback mechanism to stabilize the spin in either its high- or low-energy state. We measure the effective spin temperature from the asymmetry between the Stokes and anti-Stokes sidebands. We demonstrate that such a feedback-stabilized spin ensemble remains in a nearly pure quantum state, in spite of measurement back-action due to the continuous interaction with the probe field. Here, the high-energy spin state corresponds to a state with negative effective temperature. The system realized in our work paves the way for applications in the quantum regime, as for example quantum-limited, phase-preserving spin amplifiers or coherent quantum noise cancellation techniques.