Hannover 2013 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 30: Quantum effects
Q 30.3: Vortrag
Dienstag, 19. März 2013, 14:45–15:00, F 128
Decoherence-assisted transport in quantum critical systems — •Gian Luca Giorgi1 and Thomas Busch2 — 1AG Theoretische Quantenphysik, Theoretische Physik, Universität des Saarlandes, D-66123 Saarbrücken, Germany and Department of Physics, University College Cork, Cork, Republic of Ireland — 2Quantum Systems Unit, Okinawa Institute of Science and Technology, Okinawa 904-0411, Japan
A two-level system interacting with an external bath is unavoidably subject to coherence loss. On the other hand, decoherence can be used to enhance the transport properties between the two levels of the systems. The bath is modelled as an XY spin chain in the presence of an external magnetic field, and is subject to a quantum phase transition by changing the intensity of the external field itself.
Driving the bath from the paramagnetic towards the ferromagnetic region, the dynamics of the qubit is studied. The transition probability from the lower level to the upper level is enhanced by the bath, and this noise-assisted phenomenon is sensitive to the change of the quantum phase of the environment.
First, we discuss the case of an isotropic chain. In the zero-temperature case, the bath renormalizes the system Hamiltonian, making it possible to improve the transition probability. Even if the mechanism is more complicated, the same qualitative enhancement can be observed for finite temperatures regime and by releasing the isotropic assumption.
G. L. Giorgi and Th. Busch, Physical Review A 86, 052112 (2012)