Tunability of Excited-State Energy Levels of Four-Josephson-Junction Circuit in Crossover from Double-Well to Single-Well Potential
arXiv:1105.0263 · doi:10.1143/JPSJ.80.054701
Abstract
A double-loop four-Josephson-junction (4-JJ) flux qubit is a tunable qubit wherein the potential profile can be varied in situ via two applied magnetic fluxes. This provides a high level of control over state transitions. Here, we report the results of spectroscopic measurements on this system. We observed microwave resonances associated with the first and second excited states. A branch of resonances that is most likely attributable to the third excited state was also observed. The excitation energy spectra for these levels were in qualitative agreement with the results of simplified calculations performed using an effective Hamiltonian with two phases. The three lowest levels characterized in this study may allow novel applications, including those proposed theoretically in the past. Our analysis showed that the potential exhibited a crossover from the commonly used double-well regime to the novel single-well regime. This indicates the possibility of manipulation and readout of a 3-JJ (and 4-JJ) qubit in the single-well regime using a simple technique.
11 pages, 6 figures
References in corpus (8)
- Superconducting Circuits and Quantum Information
- Low-decoherence flux qubit
- Tuning the Gap of a Superconducting Flux Qubit
- Strong Coupling of a Quantum Oscillator to a Flux Qubit at its Symmetry Point
- Simultaneous cooling of an artificial atom and its neighboring quantum system
- Coherent oscillations in a superconducting tunable flux qubit manipulated without microwaves
- Hamiltonian for coupled flux qubits
- Optimal effective current operator for flux qubit accounting for inductive effects