Tue February 3, 2015 4:00 pm
Detecting entanglement of non-gaussian atomic states & upscaling of squeezing to large atom numbers
Location:Harvard Jefferson 250
Professor Dr. Markus Oberthaler,
Kirchhoff-Institute for Physics/Universitat Heidelberg
Ten Minute Talk:"Single Proton NMR Spectroscopy Using Quantum Logic" by
Igor Lovchinsky
Spin squeezed states in atomic systems have already been generated and detected in various different physical systems employing different methods. We report on the generation of spin squeezed states building on the quantum dynamics close to an unstable fixed point of the underlying classical dynamics. This new method allows the generation of 6dB squeezed states on short time scale. Since the squeezed states can be described as slightly distorted gaussian states the observation of variances is sufficient to verify the presence of entanglement. Our new way of squeezing generation also allows the exploration of transient states towards the generation of cat states. We will report on our results preparing and characterizing these transient non-gaussian states. They reveal variances which are larger than the classical shot noise limit thus suppression of fluctuations cannot be employed as an entanglement witness. We therefore developed a novel method for detecting the presence of entanglement by extracting from the experimentally detected distribution functions a bound of the Fisher information present in the system. With that we confirm that the entanglement is still present although the states are not spin squeezed. Furthermore interferometry beyond classical limits with these states is demonstrated which can be achieved by maximum likelihood estimation of the interferometric phase [1]. We will also present a general approach which allows the upscaling of squeezed states to large atom numbers by employing the concept – divide and conquer. We explicitly demonstrate 5dB squeezing for more than 13000 particles. We use this resource and combined this with swapping the squeezing to magnetically sensitive states for demonstration of quantum enhanced magnetometry with high spatial resolution [2]. I will also give a short overview of the current topics we are investigating ranging from probing quantum critical points with quenches, Poincare Birkhoff scenario for many particle systems and the implementation of SU(1,1) interferometry. References [1] H. Strobel, W. Muessel, D. Linnemann, T. Zibold, D.B. Hume, L. Pezzè, A. Smerzi, M.K. Oberthaler, Science 345, 424 (2014). [2] W. Muessel, H. Strobel, D. Linnemann, D.B. Hume, M.K. Oberthaler, Phys. Rev. Lett. August (2014).