基于弱场零差结构的量子探测器的响应机制和量子功能研究

项目名称： 基于弱场零差结构的量子探测器的响应机制和量子功能研究

项目编号： No.11474159

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 数理科学和化学

项目作者： 张利剑

作者单位： 南京大学

项目金额： 90万元

中文摘要： 弱场零差探测器（weak-field homodyne detector）可以同时探测入射信号的粒子行为和波动行为，因而逐渐开始在各种量子技术和量子力学基本理论的研究中发挥重要作用。全面理解其响应机制和量子功能，不但对于设计更为复杂和强大的量子探测器有着重要意义，对于我们理解量子力学核心问题之一的测量问题也有着启发意义。申请人在国际上首次通过探测器层析的方法对弱场零差探测器的基本结构进行了实验研究，对其响应机制和非经典特性有了初步理解。本项目将建立关于该探测器工作原理的完备理论模型，进一步拓展探测器结构；改进现有的探测器层析方案，对新的探测器结构进行实验研究；开发新的理论和实验工具来定量地研究不同结构的测量精度和分辨率，以及在各种量子技术中的应用。本项目在开发新的探测系统结构以及基于这些结构的量子技术的同时，还将完善现有的量子探测器研究的理论体系，建立探测器量子功能的研究基准。

中文关键词： 量子光学；量子信息；量子通信；量子相干

英文摘要： Weak-field homodyne detector as a new quantum detector structure provides simultaneous sensitivity to both the particle behavior and wave behavior of light field. Such kind of hybrid quantum detectors are beginning to play key roles in investigating fundamental quantum phenomena, generating exotic quantum states, and form essential resources for quantum-enhanced applications, e.g. entanglement distillation and quantum computation, as well as highly efficient optical telecommunications. Therefore a complete study of the response and quantum utility of weak-field homodyne detectors will not only help us to design more powerful quantum detector structures to improve the performance of quantum-optical applications, but also shed new light on the study of one of the fundamental theories of quantum mechanics, the measurement theory. We have for the first time experimentally characterized the fundamental structure of the weak-field homodyne detector through quantum detector tomography. Compared to the classical characterization of photodetectors using parameters such as detectivity, spectral sensitivity and noise equivalent power, detector tomography provides a direct, complete, and assumption-free specification of quantum detectors via its operator (called Positive-Operator-Valued Measure, or POVM), which links the quantum input states to the classical detector output. As an example, our experiment reveals the non-classical nature within the weak-field homodyne detector. Being the first tomography of phase-sensitive quantum detectors, these results provide a universal, device-independent understanding of the role of quantum coherence in a measurement process. Therefore our scheme underpins the study of the quantum utility of a quantum-optical detector. In this project, we will establish a complete theoretical model based on the previous experimental results to describe the behavior of the weak-field homodyne detector. The model will take into account the coupling to the external degrees of freedom to highlight the effect of decoherence on the quantum utility of the detector. We will extend this model to more complicated structures, e.g. with multiple receiving ports, multiple local oscillators and even with feedbacks. To test and complement the theoretical study, we will improve the current detector tomography scheme for the experimental investigation of extended structures of the weak-field homodyne detector. We will further develop novel tools to quantify the 'quantum detectivity', e.g. the precision of measuring certain parameters, the capability of distinguishing certain states, of weak-field homodyne detectors through their POVM operators, and study the applications of such detectors in quantum metrology, quantum and classical communications. The proposed work will not only design and develop novel quantum-optical detector structures and applications, but also try to build a toolbox for benchmarking the quantum utility of detectors.

英文关键词： quantum optics;quantum information;quantum communication;quantum coherence