Copper waveguide cavities with reduced surface loss for coupling to superconducting qubits

Abstract

Significant improvements in superconducting qubit coherence times have been achieved recently with three-dimensional microwave waveguide cavities coupled to transmon qubits. While many of the measurements in this direction have utilized superconducting aluminum cavities, other recent work has involved qubits coupled to copper cavities with coherence times approaching 0.1 ms. The copper provides a good path for thermalizing the cavity walls and qubit chip, although the substantial cavity loss makes conventional dispersive qubit measurements challenging. We are exploring various approaches for improving the quality factor of three-dimensional copper cavities, including electropolishing and coating with superconducting layers of tin. We have characterized these cavities on multiple cooldowns and found the tin-plating to be robust. In addition, we have performed coherence measurements on transmon qubits in these cavities and observed promising performance.

7 pages, 6 figures; published in ISEC 2013 Special Issue of IEEE Transactions on Applied Superconductivity

References in corpus (10)

• Charge insensitive qubit design derived from the Cooper pair box
• Surface codes: Towards practical large-scale quantum computation
• Coupling Superconducting Qubits via a Cavity Bus
• Superconducting qubit in waveguide cavity with coherence time approaching 0.1ms
• Controlling the spontaneous emission of a superconducting transmon qubit
• High-Fidelity Readout in Circuit Quantum Electrodynamics Using the Jaynes-Cummings Nonlinearity
• Microwave Dielectric Loss at Single Photon Energies and milliKelvin Temperatures
• Ultrahigh finesse Fabry-Perot superconducting resonator
• Demonstrating a Driven Reset Protocol of a Superconducting Qubit
• Photon Shot Noise Dephasing in the Strong-Dispersive Limit of Circuit QED