Distinguishing coherent and thermal photon noise in a circuit quantum electrodynamical system
Journal article, 2018

In the cavity-QED architecture, photon number fluctuations from residual cavity photons cause qubit dephasing due to the ac Stark effect. These unwanted photons originate from a variety of sources, such as thermal radiation, leftover measurement photons, and cross talk. Using a capacitively shunted flux qubit coupled to a transmission line cavity, we demonstrate a method that identifies and distinguishes coherent and thermal photons based on noise-spectral reconstruction from time-domain spin-locking relaxometry. Using these measurements, we attribute the limiting dephasing source in our system to thermal photons rather than coherent photons. By improving the cryogenic attenuation on lines leading to the cavity, we successfully suppress residual thermal photons and achieve T1-limited spin-echo decay time. The spin-locking noise-spectroscopy technique allows broad frequency access and readily applies to other qubit modalities for identifying general asymmetric nonclassical noise spectra.


Fei Yan

Massachusetts Institute of Technology (MIT)

Daniel L Campbell

Massachusetts Institute of Technology (MIT)

Philip Krantz

Administration MC2

Morten Kjaergaard

Massachusetts Institute of Technology (MIT)

David Kim

MIT Lincoln Laboratory

Jonilyn L Yoder

MIT Lincoln Laboratory

David Hover

MIT Lincoln Laboratory

Adam Sears

MIT Lincoln Laboratory

Andrew J Kerman

MIT Lincoln Laboratory

Terry P Orlando

Massachusetts Institute of Technology (MIT)

Simon Gustavsson

Massachusetts Institute of Technology (MIT)

William D Oliver

Massachusetts Institute of Technology (MIT)

Physical Review Letters

0031-9007 (ISSN) 1079-7114 (eISSN)

Vol. 120 26 260504

Subject Categories

Subatomic Physics

Nano Technology



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