Quantum noise and its evasion in feedback oscillators
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s41467-023-42739-9.pdf
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952.05 KB
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Adobe PDF
Checksum (MD5)
07e3a126f0b38088082f5d8344bb6f6d
Author(s)
Loughlin, Hudson A.
Sudhir, Vivishek
Date Issued
November 4, 2023
Publisher
Springer Science and Business Media LLC
Citation
Loughlin, H.A., Sudhir, V. Quantum noise and its evasion in feedback oscillators. Nat Commun 14, 7083 (2023).
Version
Final published version
Abstract
Feedback oscillators, consisting of an amplifier whose output is partially fed back to its input, provide stable references for standardization and synchronization. Notably, the laser is such an oscillator whose performance can be limited by quantum fluctuations. The resulting frequency instability, quantified by the Schawlow-Townes formula, sets a limit to laser linewidth. Here, we show that the Schawlow-Townes formula applies universally to feedback oscillators beyond lasers. This is because it arises from quantum noise added by the amplifier and out-coupler in the feedback loop. Tracing the precise origin of quantum noise in an oscillator informs techniques to systematically evade it: we show how squeezing and entanglement can enable sub-Schawlow-Townes linewidth feedback oscillators. Our analysis clarifies the quantum limits to the stability of feedback oscillators in general, derives a standard quantum limit (SQL) for all such devices, and quantifies the efficacy of quantum strategies in realizing sub-SQL oscillators.
Subjects
General Physics and Astronomy
General Biochemistry, Genetics and Molecular Biology
General Chemistry
Multidisciplinary
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
LIGO (Observatory : Massachusetts Institute of Technology)
Terms of Use
Creative Commons Attribution
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DOI of Published Version
https://doi.org/10.1038/s41467-023-42739-9
