Quantum noise and its evasion in feedback oscillators
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 ins...
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| Format: | Article |
| Language: | English |
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Nature Portfolio
2023-11-01
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| Series: | Nature Communications |
| Online Access: | https://doi.org/10.1038/s41467-023-42739-9 |
| _version_ | 1797636758132752384 |
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| author | Hudson A. Loughlin Vivishek Sudhir |
| author_facet | Hudson A. Loughlin Vivishek Sudhir |
| author_sort | Hudson A. Loughlin |
| collection | DOAJ |
| description | 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. |
| first_indexed | 2024-03-11T12:39:42Z |
| format | Article |
| id | doaj.art-795a7cda7bd641338d77d7d6dbf54e94 |
| institution | Directory Open Access Journal |
| issn | 2041-1723 |
| language | English |
| last_indexed | 2024-03-11T12:39:42Z |
| publishDate | 2023-11-01 |
| publisher | Nature Portfolio |
| record_format | Article |
| series | Nature Communications |
| spelling | doaj.art-795a7cda7bd641338d77d7d6dbf54e942023-11-05T12:24:07ZengNature PortfolioNature Communications2041-17232023-11-011411910.1038/s41467-023-42739-9Quantum noise and its evasion in feedback oscillatorsHudson A. Loughlin0Vivishek Sudhir1LIGO Laboratory, Massachusetts Institute of TechnologyLIGO Laboratory, Massachusetts Institute of TechnologyAbstract 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.https://doi.org/10.1038/s41467-023-42739-9 |
| spellingShingle | Hudson A. Loughlin Vivishek Sudhir Quantum noise and its evasion in feedback oscillators Nature Communications |
| title | Quantum noise and its evasion in feedback oscillators |
| title_full | Quantum noise and its evasion in feedback oscillators |
| title_fullStr | Quantum noise and its evasion in feedback oscillators |
| title_full_unstemmed | Quantum noise and its evasion in feedback oscillators |
| title_short | Quantum noise and its evasion in feedback oscillators |
| title_sort | quantum noise and its evasion in feedback oscillators |
| url | https://doi.org/10.1038/s41467-023-42739-9 |
| work_keys_str_mv | AT hudsonaloughlin quantumnoiseanditsevasioninfeedbackoscillators AT vivisheksudhir quantumnoiseanditsevasioninfeedbackoscillators |