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TT: Tiefe Temperaturen

TT 15: Poster der Symposien SYQI und SYQD

TT 15.9: Poster

Mittwoch, 26. März 2003, 14:30–19:00, P2d

A random matrix approach to fidelity and decoherence — •Thomas Gorin — Theoretische Quantendynamik, Albert-Ludwigs-Universität, Hermann-Herder-Str. 3, D-79104 Freiburg

A simple concept for quantum information processing would devide the task into three steps: 1) Load the quantum register (containing a fixed number of qubits) with an arbitrary initial state. 2) Perform a user-defined sequence of elementary unitary transformations (the quantum protocol). 3) Readout the result by suitable measurments.

In this approach, it is essential to keep the deviations from the quantum protocol, in the time evolution of the quantum register (loss of fidelity), small. It is equally important to avoid entanglement with the environment (loss of coherence). In practice, the protection against both effects must be effective for all possible states of the quantum register and all quantum protocols, a user might wish to apply.

We introduce a random matrix model to describe the dynamics of the total system: quantum register plus environment. This is motivated by the fact that random matrix theory naturally provides methods to deal with ensembles of quantum states and/or evolution operators. We assume the time evolution of the total system to be unitary, and measure the decoherence of the state of the quantum register by tracing out the environmental degrees of freedom.