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Quantum dynamics in a camelback potential of a dc SQUID
E Hoskinson1, F Lecocq, N Didier
1Institut Néel, C.N.R.S.-Université Joseph Fourier, BP 166, 38042 Grenoble-cedex 9, France.
Physical Review Letters
|April 28, 2009
Summary
We studied a novel quantum oscillator and found an optimal operating condition. This condition makes the phase qubit insensitive to noise, improving its stability.
Area of Science:
- Quantum mechanics
- Solid-state physics
- Superconducting circuits
Background:
- Anharmonic oscillators are crucial in quantum mechanics.
- Macroscopic quantum tunneling describes escape from potential wells.
- Superconducting Quantum Interference Devices (SQUIDs) are sensitive magnetic flux detectors.
Purpose of the Study:
- To investigate a quadratic-quartic anharmonic oscillator.
- To realize this potential using a dc SQUID.
- To explore macroscopic quantum tunneling and qubit decoherence.
Main Methods:
- Fabricated a dc SQUID biased near zero current and half flux quantum.
- Measured escape rates from the potential well.
- Applied generalized double-path macroscopic quantum tunneling theory.
- Identified an optimal bias line for qubit operation.
Main Results:
- Observed escape via tunneling through two potential barriers.
- Achieved good agreement with theoretical predictions for tunneling.
- Demonstrated an "optimal line" in bias parameters.
- Showed qubit insensitivity to low-frequency current fluctuations along this line.
Conclusions:
- The dc SQUID successfully realizes a quadratic-quartic anharmonic oscillator.
- Macroscopic quantum tunneling theory accurately describes the system's escape dynamics.
- An optimal bias line offers a path towards robust quantum computing with phase qubits.
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