Dresden 2011 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 42: Critical Phenomena and Phase Transitions

DY 42.5: Talk

Friday, March 18, 2011, 11:15–11:30, ZEU 255

Speeding up critical system dynamics through optimized evolution — •Tommaso Caneva¹, Tommaso Calarco¹, Rosario Fazio³, Giuseppe E. Santoro^2,4,5, 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.