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Q: Fachverband Quantenoptik und Photonik

Q 17: Fermi Quantum Gas

Q 17.8: Vortrag

Dienstag, 15. März 2011, 12:15–12:30, BAR Schön

Loschmidt Echo of a Trapped Fermi Gas — •Thomas Fogarty¹, Thomas Busch¹, and John Goold² — ¹Physics Department, University College Cork, Ireland — ²Department of Atomic & Laser Physics, Clarendon Laboratory, University of Oxford

The process of decoherence in quantum systems is an substantial area of study with implications for quantum computing. This importance has led to a rich area of study that encompasses decoherence in spin environments. It has been shown that the coherence of a qubit coupled to an environment directly influences the entanglement of the qubit with the environment and can result in quantum phase transitions. Here we study the decoherence of a one dimensional Fermi gas in a harmonic trap undergoing a sudden perturbation. The decoherence is studied by calculating the Loschmidt echo which is the overlap of the initial state evolving according to two different hamiltonians, one with and one without the perturbation. We show that revivals of the coherence occur based on the trap frequency of the harmonic oscillator and that the decoherence is directly influenced by the Anderson orthogonality catastrophe. Anderson proved that the overlap of two many body ground states tends to zero as the number of fermions are increased and here we provide detailed analysis of the catastrophe and derive a perturbative scheme which holds for a small perturbation.