Multi-level effects in the Rabi oscillations of a Josephson phase qubit

Published

September 15, 2008

Author(s)

S. K. Dutta, H. Paik, T. A. Palomaki, J. R. Anderson, A. J. Dragt, C. J. Lobb, F. C. Wellstood, Frederick Strauch, Kaushik Mitra, Eite Tiesinga

Abstract

We present Rabi oscillation measurements of an Nb/AlOx/Nb dc SQUID phase qubit with a 100 ¿m2 area junction acquired at 25 mK over a range of microwave power and frequency detuning. Given the slightly anharmonic level structure of the qubit, several excited states play an important role in the device dynamics, particularly at high microwave power. These states, which lie outside of the desired qubit space, can become populated through multi-photon transitions and cause shifts in the resonance properties of the oscillations. All of these effects were monitored by measuring the tunneling escape rate of the device to the voltage state, which is particularly sensitive to excited state population. We compare the observed oscillation frequencies with a simplified model constructed from the full phase qubit Hamiltonian and also compare time-dependent escape rate measurements with a more complete density matrix simulation. Good agreement is found for a relaxation time T1 = 17 ns and pure dephasing time Tphi = 16 ns, allowing us to identify multi-level features in the oscillations.

Citation

Physical Review B (Condensed Matter and Materials Physics)

Volume

78

Issue

No 10

Pub Type

Journals

Keywords

dc SQUID, quantum information, Joshepson junctions, decoherence

Citation

Dutta, S. , Paik, H. , Palomaki, T. , Anderson, J. , Dragt, A. , Lobb, C. , Wellstood, F. , Strauch, F. , Mitra, K. and Tiesinga, E. (2008), Multi-level effects in the Rabi oscillations of a Josephson phase qubit, Physical Review B (Condensed Matter and Materials Physics) (Accessed October 28, 2025)