Key Findings
Researchers from RIKEN and the University of Tokyo have achieved the first experimental demonstration of quantum state smoothing. By utilizing observation records from both the “past” and the “future” relative to a specific point in time, the team successfully estimated the dynamics of light’s quantum state with greater accuracy than is possible using only past records. The experiment confirmed that this approach brings the estimated state closer to the true quantum state and improves the purity and squeezing of the estimated state.
Technical Details
The research team, including Shoryu Yokoyama and Hidehiro Yonezawa from RIKEN and Assistant Professor Warit Asavanant from the University of Tokyo, overcame previous experimental hurdles by simulating a specific theoretical condition: a scenario where a “hidden observer” measures information that remains invisible to the observer performing the estimation. To ensure accuracy, the group precisely calibrated the experimental apparatus and employed an analytical model that accounted for detection efficiency and light loss.
Background and Context
Standard quantum state estimation typically relies solely on observation records available up to the moment of estimation. While incorporating future data theoretically increases accuracy, applying classical calculation methods directly to quantum systems can lead to results that contradict the principles of quantum mechanics. Quantum state smoothing was proposed as a theoretical solution to avoid these contradictions, but it remained unverified until this demonstration.
Significance and Outlook
High-precision estimation of quantum states is essential for maximizing the performance of quantum technologies. This breakthrough is expected to be applied to quantum information processing where measurement records can be processed post-hoc, specifically in the development and evaluation of measurement-induced quantum computers. The findings were published in the October 21 online edition of the scientific journal npj Quantum Information.
Source: https://www.nikkei.com/article/DGXZRSP714661_Q6A031C2000000/
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