2026-05-19 スウェーデン王立工科大学（KTH）
＜関連情報＞
- https://www.kth.se/en/om/nyheter/centrala-nyheter/new-chip-offers-way-to-make-use-of-quantum-system-imperfections-1.1476233
- https://www.nature.com/articles/s41467-026-72850-6
プログラム可能な線形フォトニック回路におけるフォック状態量子光のコヒーレント吸収のエミュレーション Emulation of coherent absorption of Fock-state quantum light in a programmable linear photonic circuit
Govind Krishna,Jun Gao,Sam O’Brien,Rohan Yadgirkar,Venkatesh Deenadayalan,Stefan Preble,Val Zwiller & Ali W. Elshaari
Nature Communications Published:09 May 2026
DOI:https://doi.org/10.1038/s41467-026-72850-6
Abstract
Non-Hermitian quantum systems, governed by nonunitary evolution, offer powerful tools for manipulating quantum states through engineered loss. A prime example is coherent absorption, where quantum states undergo phase-dependent partial or complete absorption in a lossy medium. Here, we demonstrate a fully programmable implementation of nonunitary transformations that emulate coherent absorption of quantum light using a programmable integrated linear photonic circuit, with loss introduced via coupling to an ancilla mode. Probing the circuit with a single-photon dual-rail state reveals phase-controlled coherent tunability between perfect transmission and perfect absorption. A two-photon NOON-state input, by contrast, exhibits switching between deterministic single-photon absorption and probabilistic two-photon absorption. Across a broad range of input phases and circuit configurations, we observe nonclassical effects including anti-coalescence and bunching, together with continuous and coherent tuning of output Fock-state probability amplitudes. Classical Fisher information analysis reveals phase sensitivity peaks of 1 for single-photon states and 3.4 for NOON states, exceeding the shot-noise limit of 2 and approaching the Heisenberg limit of 4 for two-photon states. The experiment integrates quantum state generation, programmable photonic circuitry, and photon-number-resolving detection, establishing ancilla-assisted circuits as powerful platforms for programmable quantum state engineering, filtering, multiplexed sensing, and nonunitary quantum simulation.
