Coherence and decay of higher energy levels of a superconducting transmon qubit

Michael J Peterer; Samuel J Bader; Xiaoyue Jin; Fei Yan; Archana Kamal; Theodore J Gudmundsen; Peter J Leek; Terry P Orlando; William D Oliver; Simon Gustavsson

doi:10.1103/PhysRevLett.114.010501

Coherence and decay of higher energy levels of a superconducting transmon qubit

Phys Rev Lett. 2015 Jan 9;114(1):010501. doi: 10.1103/PhysRevLett.114.010501. Epub 2015 Jan 6.

Authors

Affiliations

¹ Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA and Clarendon Laboratory, Department of Physics, University of Oxford, OX1 3PU Oxford, United Kingdom.
² Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
³ MIT Lincoln Laboratory, 244 Wood Street, Lexington, Massachusetts 02420, USA.
⁴ Clarendon Laboratory, Department of Physics, University of Oxford, OX1 3PU Oxford, United Kingdom.
⁵ Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA and MIT Lincoln Laboratory, 244 Wood Street, Lexington, Massachusetts 02420, USA.

PMID: 25615454
DOI: 10.1103/PhysRevLett.114.010501

Abstract

We present measurements of coherence and successive decay dynamics of higher energy levels of a superconducting transmon qubit. By applying consecutive π pulses for each sequential transition frequency, we excite the qubit from the ground state up to its fourth excited level and characterize the decay and coherence of each state. We find the decay to proceed mainly sequentially, with relaxation times in excess of 20 μs for all transitions. We also provide a direct measurement of the charge dispersion of these levels by analyzing beating patterns in Ramsey fringes. The results demonstrate the feasibility of using higher levels in transmon qubits for encoding quantum information.