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Q: Fachverband Quantenoptik und Photonik

Q 14: Quanteninformation (Quantencomputer I)

Q 14.1: Group Report

Tuesday, March 11, 2008, 14:00–14:30, 1B

Simulation of a Quantum Magnet — •Axel Friedenauer¹, Hektor Schmitz¹, Jan Glueckert¹, Lutz Petersen², and Tobias Schaetz¹ — ¹Max Planck Institut für Quantenoptik, Garching, Deutschland — ²ETH Zuerich

Simulating quantum mechanical systems is a hard task since the amount of degrees of freedom scale exponentially with the number of constituents. We are aiming to circumvent this difficulty by introducing a quantum simulator based on the idea that systems governed by the same Hamiltonian evolve alike.

Our system for a feasibility study is a linear chain of magnesium ions. External fields and interactions between the ions are simulated/controled via rf- and laser-fields respectively. To initialize our system, we cool up to three ions close to the axial-motional ground state n<0.05.To calibrate our operational fidelities, we implemented a geometric phase gate¹ and prepared an entangled Bell state of two ions with a fidelity exceeding 95%. Subsequently, we were able to simulate an adiabatic evolution of two spins described by the Quantum-Ising-Hamiltonian from paramagentic into ferromagnetic order^2,3 with an fidelity of 95%. We proof that this transition is driven by quantum (not thermal) fluctuations providing us even an entangled state with a lower bound for the fidelity of 70%. We discuss these results and comment on the possibilities to increase the size of our system.

[1] D. Leibfried et al., Nature 422, 412 (2003)

[2] D. Porras and J.I. Cirac, Phys. Rev. Lett. 92, 207901 (2004)

[3] to be published