Transport signatures of phase fluctuations in superconducting qubits

Abstract

Josephson junctions supply the nonlinear inductance element in superconducting qubits. In the widely used transmon configuration, where the junction is shunted by a large capacitor, the low charging energy minimizes the sensitivity of the qubit to charge noise while maintaining the necessary anharmonicity to qubit states. We report here low-frequency transport measurements on small standalone junctions and identically fabricated capacitively-shunted junctions that show two distinct features normally attributed to small capacitance junctions near zero bias: reduced switching currents and prominent finite resistance associated with phase diffusion in the current-voltage characteristic. Our transport data reveals the existence of phase fluctuations in transmons arising from intrinsic junction capacitance.

References in corpus (5)

• Experimental realization of an intrinsically error-protected superconducting qubit
• Merged-Element Transmons: Design and Qubit Performance
• Quantum Effects in Small-Capacitance Single Josephson Junctions
• Phase Diffusion in Low-$E_J$ Josephson Junctions at milli-Kelvin Temperatures
• Current dependence of the low bias resistance of small capacitance Josephson junctions

Cited by in corpus (1)

• Submicrometer tunnel ferromagnetic Josephson junctions with transmon energy scale