Decoherence in dc SQUID phase qubits

Abstract

We report measurements of Rabi oscillations and spectroscopic coherence times in an Al/AlOx/Al and three Nb/AlOx/Nb dc SQUID phase qubits. One junction of the SQUID acts as a phase qubit and the other junction acts as a current-controlled nonlinear isolating inductor, allowing us to change the coupling to the current bias leads in situ by an order of magnitude. We found that for the Al qubit a spectroscopic coherence time T2* varied from 3 to 7 ns and the decay envelope of Rabi oscillations had a time constant T' = 25 ns on average at 80 mK. The three Nb devices also showed T2* in the range of 4 to 6 ns, but T' was 9 to 15 ns, just about 1/2 the value we found in the Al device. For all the devices, the time constants were roughly independent of the isolation from the bias lines, implying that noise and dissipation from the bias leads were not the principal sources of dephasing and inhomogeneous broadening.

5 figures. Accepted to Physical Review B

References in corpus (7)

• Quantum state engineering with Josephson-junction devices
• Superconducting Circuits and Quantum Information
• Decoherence in Josephson Qubits from Dielectric Loss
• Coherent quantum state storage and transfer between two phase qubits via a resonant cavity
• Decoherence in Josephson Qubits from Junction Resonances
• Decoherence in Josephson-junction qubits due to critical current fluctuations
• Comparison of coherence times in three dc SQUID phase qubits

Cited by in corpus (12)

• Multi-level Spectroscopy of Two-Level Systems Coupled to a dc SQUID Phase Qubit
• Towards a feasible implementation of quantum neural networks using quantum dots
• Deep-well ultrafast manipulation of a SQUID flux qubit
• Aluminum Hard Mask Technique for the Fabrication of High-Quality Submicron Nb/Al-AlOx/Nb Josephson Junctions
• Entanglement in a quantum neural network based on quantum dots
• Spin-Weyl quantum unit: theoretical proposal
• Realistic quantum manipulation of two-level system fluctuators
• Damping of local Rabi oscillations in the presence of thermal motion
• Protecting Superconducting Qubits with Universal Quantum Degeneracy Point
• Universal Quantum Degeneracy Point for Superconducting Qubits
• A Controllable Interaction between Two-Level Systems inside a Josephson Junction
• Floquet Dynamical Decoupling at Zero Bias