2023-11-30 マサチューセッツ工科大学(MIT)
◆この理論を実証する実験を進め、超量子精度の時計やレーザーが実現すれば、量子コンピュータ内のキュビットの揺らぎや検出器間を舞い踊る暗黒物質粒子など、微小な時間差を追跡するのに利用できるかもしれません。
＜関連情報＞
- https://news.mit.edu/2023/quantum-squeeze-clocks-more-precise-time-1130
- https://www.nature.com/articles/s41467-023-42739-9
フィードバック発振器における量子ノイズとその回避 Quantum noise and its evasion in feedback oscillators
Hudson A. Loughlin & Vivishek Sudhir
Nature Communications Published:04 November 2023
DOI:https://doi.org/10.1038/s41467-023-42739-9
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.
