发表机构
School of Science, STEM College, RMIT University; Quantum Systems, Technology, CSIRO; School of Mathematics and Physical Sciences, the University of Sheffield; School of Electrical and Computer Engineering, Cornell University（斯威本科技大学理学院STEM学院; 澳大利亚联邦科学与工业研究组织量子系统与技术部; 谢菲尔德大学数学与物理科学学院; 康奈尔大学电气与计算机工程学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究将分子吸收光谱学的基本极限建模为量子信道判别问题，通过半定规划优化探针态，证明非经典探针在随机损耗下仍显著优于传统激光光谱，并为多频率光子分配提供额外优势。
AI 中文摘要
吸收光谱学通过检测频率相关的光学损耗来识别分子，其基本极限是一个量子信道判别问题。在本工作中，我们发展了一个通用框架来刻画无集体测量的分子吸收光谱学的终极量子极限：我们将其表述为不同吸收信道之间的非对称量子假设检验任务。利用半定规划公式，我们构造了最优探针态，并将其与相干态光子计数、福克态和双模压缩真空探针进行比较。我们引入了一个随机损耗信道模型来描述不完美已知的背景透射，这反映了空白实验不一定因散射、溶剂吸收或收集损耗而返回所有入射光子的事实。我们的结果表明，优化的非经典探针可以显著优于传统激光光谱学，并且该优势对现实的基线随机损耗具有鲁棒性。在多频率光谱学中，优化还决定了光子应如何在吸收线之间分配，揭示了超越单模态工程之外的额外资源分配优势。我们利用4-硝基苯酚的红外检测及其化学相关的比较分子来说明我们的框架，展示了量子信道判别方法如何在现实光子约束下为分子光谱学提供建设性的性能极限。
英文摘要
Absorption spectroscopy identifies molecules by detecting frequency-dependent optical loss, and its fundamental limit is a quantum channel-discrimination problem. In this work, we develop a general framework for characterizing the ultimate quantum limit of molecular absorption spectroscopy without collective measurements: we formulate it as an asymmetric quantum hypothesis testing task between different absorption channels. Using a semidefinite-programming formulation, we construct optimal probe states and compare them with coherent-state photon counting, Fock states, and two-mode squeezed vacuum probes. We introduce a random-loss channel model for imperfectly known background transmission, reflecting the fact that a blank experiment need not return all incident photons due to scattering, solvent absorption, or collection losses. Our results show that optimized non-classical probes can substantially outperform conventional laser spectroscopy, and that the advantage is robust to realistic baseline random loss. % In multi-frequency spectroscopy, the optimization also determines how photons should be allocated across absorption lines, revealing an additional resource-allocation advantage beyond single-mode state engineering. We illustrate our framework using infrared detection of 4-nitrophenol against chemically relevant comparison molecules, showing how quantum channel-discrimination methods provide constructive performance limits for molecular spectroscopy under realistic photon constraints.
Comments9 pages, 7 figures, 13 pages of appendices. Comments are welcome
