Post-Selection Framework Controls Non-Classical States for Enhanced Quantum Metrology

The boundary between quantum and classical behaviour remains a fundamental question in physics, and recent research explores how to engineer this transition using light. Janarbek Yuanbek, Wen-Long Ma, and Yusuf Turek, from the Institute of Semiconductors, Chinese Academy of Sciences, and Liaoning University, investigate this boundary by manipulating states of light created through a process called squeezing. Their work establishes a method to control the non-classical properties of these squeezed light states during a specific type of measurement, revealing a critical point where quantum characteristics give way to classical behaviour. This discovery is significant because it identifies an optimal threshold for suppressing noise and enhancing signals, offering a tunable platform with potential applications in advanced sensing and the detection of weak signals.

Post-Selection Enhances Quantum Measurement Sensitivity

Researchers have developed a new method for improving the sensitivity of quantum measurements by manipulating squeezed states of light and employing a technique called post-selection. This work establishes a framework for precisely controlling the non-classical properties of these states, leading to enhanced performance in applications like sensing and detecting faint signals. The core of this advancement lies in amplifying subtle signals by carefully managing the interaction between the measured system and the measuring device. The team demonstrated that by using a specific measurement approach, they could guide a system from exhibiting non-classical behaviour towards characteristics more closely resembling classical physics.

This transition, controlled by adjusting the interaction strength, represents a crucial boundary for optimizing measurement precision, and the researchers identified the precise point at which this transition occurs, revealing it to be the ideal setting for minimizing noise and maximizing signal enhancement. The study introduces new ways to quantify this transition using concepts like Wigner-Yanase skew information, amplitude squared squeezing, and photon statistics. By comparing their method’s performance with standard approaches, the researchers demonstrated a significant improvement in measurement precision, opening possibilities for developing more sensitive sensors and detectors for a wide range of applications, including quantum information processing and advanced metrology. Furthermore, the research provides a theoretical foundation for understanding how measurement impacts quantum systems, offering insights into the fundamental principles of quantum mechanics.

Measurement Strength Controls Quantum to Classical Transition

This study establishes a framework for controlling the properties of squeezed states of light during measurement, demonstrating how weak value amplification can unify control mechanisms across different quantum states. Researchers investigated how the characteristics of single-photon subtracted squeezed vacuum and two-mode squeezed vacuum states change as the strength of measurement increases, revealing a transition from non-classical to classical behaviour and identifying a critical point where the system optimally suppresses noise and enhances signals. Analysis using the Husimi-Kano Q function confirmed that this transition aligns with theoretical predictions and demonstrates a clear degradation of quantum coherence as measurement strength increases, offering potential benefits for precision sensing and weak-signal detection technologies. The authors acknowledge that the study focuses on specific parameter regimes and that further investigation is needed to explore the full range of possible behaviours and potential applications.