This research focuses on advanced noise suppression technologies for high-precision measurement systems, particularly addressing the limitations of classical noise reducing approaches. The noise level of laser sources is a crucial factor that directly affects the measurement sensitivity in applications such as gravitational wave detection and biomedical imaging. Classical feedback control technologies are effective but often encounter a bottleneck resulting from the classical noise suppression limits. To cope with these challenges, a novel method integrating quantum squeezed light with classical feedback control systems to reduce intensity noise is proposed in this work. By employing an amplitude-squeezed light field, a quantum-enhanced feedback control model is developed, thereby theoretically examining the influence of both the feedback loop gain and the degree of squeezing on the noise suppression performance. The results show that the injection of squeezed light significantly reduces the intensity noise, approaching the shot noise limit (SNL), thereby improving the system sensitivity beyond the classical noise reduction boundaries. Specifically, –10 dB squeezed state injection into the feedback system yields an additional noise suppression of approximately 8.97 dB, exceeding what is achievable using classical feedback alone. This demonstrates that the potential of the proposed method can enhance measurement precision close to the quantum noise limits without increasing the laser power. The analysis highlights the asymmetric noise suppression effects between the inner feedback loop and outer feedback loop. Although the outer loop benefits significantly from the squeezed light injection and achieves noise levels that are unattainable by classical feedback methods, the inner loop shows relatively minor improvements. This asymmetry is attributed to the inherent characteristics of quantum squeezing and the limitations of the feedback loop design. Further investigation into the individual noise components reveals that the primary contributors to the intensity noise include input noise, photodetector noise, and beam splitter-induced vacuum fluctuations. The injection of squeezed light effectively mitigates these vacuum fluctuations, which are typically a major noise source in high-precision laser systems. Theoretical research results show that the use of squeezed light in feedback control systems can effectively enhance noise suppression, equivalent to a nine fold increase in detected optical power, without the physical drawbacks of increasing laser power such as thermal noise. In conclusion, this study provides a theoretical validation of combining quantum squeezed states with classical feedback control to exceed classical noise suppression limits. The integration of a –10 dB squeezed state demonstrates a significant noise reduction, showing that this hybrid approach could revolutionize noise management in precision measurement applications. The results pave the way for further exploring quantum-enhanced control technologies in fields such as gravitational wave detection, quantum communication, and advanced optical sensing, providing a pathway for improving sensitivity and noise suppression without increasing additional power requirements.
The direct realization of a quantum-enhanced phase noise filter has remained a major challenge. Conventional techniques are not only plagued by substantial technical noise but also fundamentally constrained by inherent quantum penalty, precluding their direct application in quantum-enhanced noise filtering. This work has realized a practical approach to the first, to our knowledge, quantum-enhanced laser phase noise filter by confronting the key challenges that degrade phase noise extraction and quantum enhancement, specifically the technical noises in the laser’s amplitude and phase. Our strategy employs a detuned cavity to direct optical readout of phase noise combined with a hybrid stabilization scheme to suppress both amplitude and phase noises simultaneously. This allows us to circumvent the limitations imposed by quantum noise penalty and effectively enable quantum enhancement via squeezed vacuum injection. Experimentally, we have achieved up to 5 dB of quantum-enhanced phase noise suppression across Fourier frequencies ranging from 5 to 60 kHz. This scheme represents more than just a proof-of-principle—it unlocks the potential of squeezed-enhanced laser phase noise suppression for a broad spectrum of applications.
불확정성관계에 있는 두 변량이 불확정성 원리를 만족하며 각 변량의 uncertainty를 최소로 만든 것 중의 하나인 Coherent state와 두 변량의 uncertainty의 곱은 coherent state와 같은 채로 한 변량의 uncertainty를 크게하여 다른 변량의 uncertainty를 작게 만드는 squeezed state에 대한 이론적 고찰을 했고, 이 squeezed state는 양자역학적 noise 보다 적은 noise를 갖는 파속을 만들 때 사용됨을 알 수 있었다.
Quantum-enhanced optical phase tracking is a quantum optical technique for tracking and measuring optical phases with high accuracy. It has important applications in laser interferometry, spectral analysis, and optical measurements. In this study, we propose a quantum-enhanced optical phase tracking protocol based on squeezed state optical fields. By using a continuous solid-state laser source with a central wavelength of 1064 nm, combing second harmonic generation, optical parametric oscillator, and PDH (Pound-Drever-Hall) locking technology, we prepare an initial squeezed state with a squeezing level of (8.0±0.2) dB. Through signal modulation technique and demodulation technique, we control the phase of the squeezed state optical field, thereby realizing the quantum-enhanced tracking of optical phases within the range of 0－2π. Compared with classical protocols, this protocol can suppress the noise fluctuations of phase tracking to at least 6.27 dB below the shot noise limit, improving the phase tracking accuracy by more than 76.4%. Because of the high requirements for phase measurement accuracy in applications such as angle estimation, phased array radar, and phased array sonar, this protocol is expected to improve the phase estimation accuracy beyond the shot noise limit. It provides compressed light sources for relevant fields, laying a theoretical and experimental foundation for higher-precision spatial positioning and quantum ranging techniques. The probe is made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues. The sequence of amino acids in a protein is determined by a gene and encoded in the genetic code. This can happen either before the protein is used in the cell, or as part of control mechanism.