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Tuned transition from quantum to classical for macroscopic quantum states.
A Fedorov1, P Macha, A K Feofanov
1Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands. fedoroar@phys.ethz.ch
Physical Review Letters
|June 4, 2011
Summary
Researchers explored the quantum-classical boundary using a tunable flux qubit. They observed a transition from quantum to classical behavior by adjusting the tunnel barrier, noting changes in oscillations and state lifetimes.
Area of Science:
- Quantum physics
- Condensed matter physics
- Superconductivity
Background:
- The classical-quantum boundary is a fundamental area of research.
- Understanding quantum phenomena in macroscopic systems is crucial.
- Flux qubits offer a platform to study quantum effects in superconducting circuits.
Purpose of the Study:
- To investigate the transition from quantum to classical behavior in a tunable flux qubit.
- To explore the influence of a tunable tunnel barrier on quantum dynamics.
- To characterize the behavior of persistent currents and coherent oscillations.
Main Methods:
- Fabrication of a tunable flux qubit.
- Utilizing basis states with persistent currents of 1 μA.
- Tuning the tunnel barrier to observe system dynamics.
- Measuring state lifetimes and tunneling periods.
Main Results:
- Observed a crossover from quantum to classical behavior by tuning the tunnel barrier.
- Demonstrated spontaneous coherent oscillations when released from nonequilibrium.
- Found that increased barrier height dramatically increases state lifetime.
- Noted tunneling period approaching phase coherence time as oscillations fade.
Conclusions:
- The tunable flux qubit provides a controllable system to study the quantum-classical transition.
- Barrier properties significantly influence the quantum coherence and classical characteristics of the system.
- The observed phenomena offer insights into decoherence mechanisms and macroscopic quantum effects.
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