Distinguishing Coherent and Thermal Photon Noise in a Circuit Quantum Electrodynamical System
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PhysRevLett.120.260504.pdf
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Author(s)
Yan, Fei
Campbell, Daniel Lawrence
Krantz, Philip Johan Erik
Kjaergaard, Morten
Kim, David M.
Yoder, Jonilyn Longenecker
Hover, David J.
Sears, Adam P.
Kerman, Andrew J
Orlando, Terry Philip
Date Issued
June 2018
Journal
Physical Review Letters
Publisher
American Physical Society
Citation
Yan, Fei et al. "Distinguishing Coherent and Thermal Photon Noise in a Circuit Quantum Electrodynamical System." Physical Review Letters 120, 26 (June 2018): 260504 © 2018 American Physical Society
Version
Final published version
Abstract
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.
MIT Department
Lincoln Laboratory
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering
Massachusetts Institute of Technology. Department of Physics
Massachusetts Institute of Technology. Research Laboratory of Electronics
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DOI of Published Version
https://doi.org/10.1103/PhysRevLett.120.260504
