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Thermalization of Quantum Superconducting Devices
Palmer, Ben - Laboratory for Physical Sciences, College Park, MD
Presentation on Thursday, Nov. 29, 2018, 7 a.m.
Location: MIT Room 26-214
Since the seminal results by Nakamura, Pashkin, and Tsai [Y. Nakamura, Yu. A. Pashkin & J. S. Tsai, Nature 398, 786-788 (1999)], coherence times for quantum superconducting devices have increased from a few nanoseconds up to 100 microseconds [W. Oliver & P. Welander, MRS Bulletin 36, 813 (2013)]. With recent improvements in the energy relaxation times of circuit quantum electrodynamic (c-QED) devices, the tunneling of thermal or non-equilibrium resonant microwave photons into and out of the read-out cavity used to measure the state of the qubit has been shown to be a source of qubit dephasing and hence decoherence [A. Sears, et al., Physical Review B 86, 180504 (2012)]. I’ll describe some work we have conducted to improve upon the thermalization of the signals going to our c-QED devices. In particular, by designing and fabricating some microwave attenuators for ultra-low temperatures, where it is easy to heat the electrons out of equilibrium with the 10 mK phonon bath, we have decreased the effective noise temperature of the signals going to the c-QED device by as much as a factor of two to approximately 50 mK [Jen-Hao Yeh, et al., Journal of Applied Physics 121, 224501 (2017)].