Friday, October 18, 2002
4:00 PM
Physics Building, Room 204
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"Superconducting Schrodingers Cat and its Application to Quantum Computing"

Siyuan Han , Department of Physics and Astronomy, University of Kansas
[Host: B. Shivaram]
Since the beginning days of quantum mechanics the possibility of having coherent superposition of macroscopic quantum states, e.g., Schrodingers Cat, has stimulated much theoretical debates. The idea can actually be tested out experimentally in superconducting electronic devices called Josephson junctions (JJs) and SQUIDs. Ill show that when sufficiently isolated from environments a current biased JJ is a very well characterized and controllable macroscopic quantum system and that Rabi oscillations can be utilized to create coherent superposition of macroscopic quantum states. In a recent experiment, we have succeeded in placing a JJ in the superposition of its ground (alive) and excited (dead) states and observing its time evolution as it oscillates coherently between the alive and dead states of the junction [Y. Yu et al., Science 296, p889 (May 2002)]. The coherence time, estimated from the exponentially decaying amplitude of the oscillations, is about 5 s which is very promising for quantum computing using the phase qubits (JJs) or flux qubits (SQUIDs).

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