量子フォトニック技術の進展（Advancing Quantum Photonic Technologies）

2025-10-10

2025-10-09 カリフォルニア大学サンディエゴ校 (UCSD)

カリフォルニア大学サンディエゴ校の研究チームは、光と物質が強く結合した準粒子「ポラリトン」の量子挙動を新たに解明し、量子フォトニクス分野の基礎理論を更新した。これまで光吸収や反射の解析では古典的な電磁波理論が主流だったが、研究チームは分子や半導体を微小光共振器内に閉じ込め、光スペクトルの揺らぎを高精度で測定。その結果、線形光応答の中に本来非線形領域でのみ現れるはずの「量子ゆらぎ由来の指紋」が観測された。この現象はポラリトン内で光子と励起子が量子力学的に干渉することで生じるものであり、従来理論では説明できない。成果は、量子光を利用した高感度センサーやフォトニックチップ上での化学反応制御、量子通信デバイスの実現につながる可能性を示す。論文は米国光学会誌『Optica』に掲載された。

Schematic illustrating the transmission, absorption and reflection of photons in a cavity.

＜関連情報＞

線形ポラリトンスペクトルに隠れた非線形光学感受率 Hidden nonlinear optical susceptibilities in linear polaritonic spectra

Arghadip Koner and Joel Yuen-Zho
Optica Published: October 7, 2025
DOI:https://doi.org/10.1364/OPTICA.568221

Abstract

Linear spectra of molecular polaritons, quasiparticles formed by the strong coupling of molecules to a confined photonic mode, are typically well described successfully by classical linear optics. This raises the fundamental question of where genuinely quantum and nonlinear optical effects arise in such systems. Here, we derive a general analytical expression for the polaritonic linear response and elucidate previously overlooked quantum corrections arising from cavity vacuum-induced molecular transitions. Using a systematic 1/N expansion, we show that finite-size quantum processes imprint nonlinear spectroscopic features, including Raman-like sidebands, onto the linear spectrum. We further demonstrate that while such effects are suppressed in conventional lossy cavities, they become manifest in regimes where the photon dissipation rate is commensurate with the single-molecule light–matter coupling strength. These findings establish clear theoretical criteria for identifying cavity-induced quantum electrodynamical effects in polaritonic spectra and delineate experimental regimes where they may be observed.