Regensburg 2007 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 28: Transport - Poster Session

TT 28.32: Poster

Thursday, March 29, 2007, 14:00–17:45, Poster A

Measuring the many-body size of a Schrödinger cat state — Florian Marquardt, Benjamin Abel, and •Jan von Delft — Physics Department, Arnold Sommerfeld Center for Theoretical Physics, and Center for NanoScience, Ludwig-Maximilians Universität Munich

We propose a measure for the "many-body size" of a Schrödinger cat state, i.e. a quantum superposition of two many-body states with (supposedly) macroscopically distinct properties, by counting how many single-particle operations are needed to map one state onto the other. This definition gives sensible results for simple, analytically tractable cases and is consistent with a previous definition restricted to Greenberger-Horne-Zeilinger-like states. We apply our measure to the experimentally relevant, nontrivial example of a superconducting three-junction flux qubit put into a superposition of left- and right-circulating supercurrent states and find this Schrödinger cat to be surprisingly small.

Reference: quant-ph/0609007