Dresden 2011 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 42: Critical Phenomena and Phase Transitions
DY 42.5: Vortrag
Freitag, 18. März 2011, 11:15–11:30, ZEU 255
Speeding up critical system dynamics through optimized evolution — •Tommaso Caneva1, Tommaso Calarco1, Rosario Fazio3, Giuseppe E. Santoro2,4,5, and Simone Montangero1 — 1Institut für Quanteninformationsverarbeitung, Universität Ulm, D-89069 Ulm, Germany — 2International School for Advanced Studies (SISSA), Via Beirut 2-4, I-34014 Trieste, Italy — 3NEST, Scuola Normale Superiore & Istituto di Nanoscienze - CNR, Piazza dei Cavalieri 7, I-56126 Pisa, Italy — 4CNR-INFM Democritos National Simulation Center, Via Beirut 2-4, I-34014 Trieste, Italy — 5nternational Centre for Theoretical Physics (ICTP), P.O.Box 586, I-34014 Trieste, Italy
The number of defects which are generated on crossing a quantum phase transition can be minimized by choosing properly designed time-dependent pulses. In this talk we show what are the ultimate limits of this optimization. We discuss under which conditions the production of defects across the phase transition is vanishing small. Furthermore we show that the minimum time required to enter this regime is T=π/Δ, where Δ is the minimum spectral gap, unveiling an intimate connection between an optimized unitary dynamics and the intrinsic measure of the Hilbert space for pure states. Surprisingly, the dynamics is non-adiabatic; this result can be understood by assuming a simple two-level dynamics for the many-body system.