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SYQD: Quantum decoherence in solid state physics

SYQD 3: Postersitzung

SYQD 3.4: Poster

Mittwoch, 26. März 2003, 14:30–19:00, P2

Non-Markovian dynamics of macroscopic flux-state in SQUIDs — •Wolfgang Pfersich — Albert-Ludwig-Universität, Physikalisches Institut, Herman-Herder-Straße 3a, 79104 Freiburg

My poster relates to the investigation of the Non-Markovian dynamics of open quantum systems. Friedman et al. have shown experimentally that a super-conducting quantum interference device (SQUID) can be put into a superposition of two macroscopic magnetic-flux states. The first state |0⟩ corresponds to a few micro-amperes of current flowing clockwise, the other state |1⟩ corresponds to the same amount of current flowing anti-clockwise.

In the parameter regime of this experiment the SQUID is a realization of a dissipative two level system coupled to an environment. It therefore represents an excellent model system which provides the basis for a quantum computer. The relevant property is the coherence time of the superposition. Therefore the understanding of quantum decoherence mechanisms is important.

We have developed a description beyond the Markovian limit using the time-convolution-less (TCL) projection operator technique in order to derive an equation of motion for the system density operator. I solved this equation of motion in second and fourth order of TCL. Further I developed a criterion to estimate the border between coherent and decohernt motion of the system, the critical damping rate of the bath.