2026-10-30 理化学研究所,東京大学
本研究での推定対象である光共振器
＜関連情報＞
- https://www.riken.jp/press/2026/20261030_2/index.html
- https://www.nature.com/articles/s41534-026-01390-0
光量子ダイナミクスの追跡と純度およびスクイージングの回復のための量子状態平滑化 Quantum state smoothing for tracking optical quantum dynamics and recovering purity and squeezing
Shota Yokoyama, Kiarn T. Laverick, David McManus, Qi Yu, Areeya Chantasri, Warit Asavanant, Daoyi Dong, Howard M. Wiseman & Hidehiro Yonezawa
npj Quantum Information Published:21 October 2026
DOI:https://doi.org/10.1038/s41534-026-01390-0 Early provide
Abstract
Tracking the dynamics of a quantum system is conventionally achieved by monitoring the system continuously in time and filtering the information contained in measurement records via the causal quantum trajectory approach. However, in practical scenarios, there is often loss of information to the environment, leading to filtered states that are impure because of decoherence. If real-time tracking is not required, the lost information can be maximally extracted via acausal quantum state smoothing, which has been theoretically proven to better restore the system’s coherence (purity) than causal filtering. Interestingly, quantum state smoothing requires assumptions about how any lost quantum information (unobserved by the experimenter) was turned into classical information by the environment. In this work, we experimentally demonstrate smoothing scenarios, using an optical parametric oscillator and introducing ‘observed’ and ‘unobserved’ channels by splitting the output beam into two independent homodyne detectors. We achieve improvement in state purification of 10.3% ± 1.6%, squeezing restoration of 7.6% ± 2.6%, and show that smoothed states are better estimates of hidden true states than those from conventional filtering. The estimation techniques used in this paper are promising for many applications in quantum information that incorporate post-processing.
