基于金刚石NV色芯与光学微腔相互作用的量子信息处理

Quantum information, including quantum communication and quantum computer, provides some secure ways for the transmission of information between legal users and the powerful capability for parallel computation. It is useful in some important fields, such as scientific research, data processing, and information security. The proposals for quantum information processing (QIP) based on some a single physical system cannot overcome the two bottlenecks in their physical implementation, i.e., the scalability and the long coherence time. However, the hybrid quantum system by combining a diamond nitrogen-vacancy center and an optical microcavity is a good platform for QIP as it is in possession of the advantages coming from both photonic systems and solid-state quantum systems, but not their defects. Moreover, NV centers have a long coherence time even at the room temperature. The previous proposals for QIP with this hybrid system are almost based on the fields with a single wave length and those for universal quantum gates are based on the ideal input-output relation of the single photon from the cavity. There are some differences between these proposals and the outcomes from experimental implementations. In this project, we will investigate the effective methods for manipulating the hybrid system with the multichannel fields and the cavities with some special structures, the ways for the state transfer between several degrees of quantum systems, some practical quantum repeater protocols in which quantum states can be stored in a long time and the flying qubits are robust, and the optimal universal quantum gates with shorter operation time. We hope our work can give some contribution to the development of QIP.

以量子通信与量子计算为主要内容的量子信息，能提供安全的通信模式和快速的并行计算能力，在科学研究、数据处理和信息安全等领域有重要的应用价值。基于单一物理体系的量子信息处理方案很难同时克服可扩展性和消相干性这两大物理实现中的瓶颈。然而，金刚石NV色芯和光学微腔耦合体系结合了光子和固态量子系统的优点，避免了彼此的缺点，是一个很好的量子信息处理平台，且NV色芯在室温下就具有比较长的相干时间。基于这一杂化体系，已有的模型主要是针对单一波段甚至单一中心波长的光场对耦合系统的操控，构造的普适量子门大都基于比较理想的单光子输入输出关系和两比特系统，与实验发现有一定的偏差。我们将重点研究可见光和微波等多波段光场对几种光学微腔中的NV色芯耦合系统的有效操控方法，研究各自由度量子态之间的转化和基于这一模型下的既能长时间存储又能方便传输的量子中继器，设计紧跟实验进展的优化普适量子门，为量子信息的发展做出贡献。

基于单一物理体系的量子信息处理方案很难同时克服可扩展性和消相干性这两大物理实现中的瓶颈。金刚石NV色芯和光学微腔耦合体系可以结合光子和固态量子系统的优点，避免各自缺点，是一个很好的量子信息处理平台。本项目重点研究微波和可见光等多波段光场与金刚石色芯和光学微腔耦合系统的相互作用机制。我们采用核自旋态实现量子态的长时间储存，利用电子态和光场的相互作用实现电子态的高速量子操控。通过微波操控完成电子态和核自旋态之间的转换，从而达到两种量子自由度优点的集成，实现以光场为量子数据总线、以微结构量子态作为量子比特、以多种波长光场与微结构不同自由度的耦合和作用为操控手段的可拓展的量子信息处理物理系统。同时，我们研究基于不同耦合系统下的量子信息处理，包括各种实用纠缠量子态的制备和分析，量子计算机的核心元件――普适量子门的构造。本项目取得的成果和进展包括：1. 建立了利用微波和可见光波段对光学微腔中的金刚石NV色芯微结构体系进行有效操控的物理模型；2. 提出了NV色芯电子自旋与核自旋量子态、可见光与微波光子态之间的快速转换方法；3. 设计出了多种纠缠态产生方案，构建出优化的普适量子门模型；4. 初步探索了了以退相干时间长的NV色芯原子核自旋或原子系综为静态存储量子比特、光子为传输量子比特的实用量子中继器模型。这些重要结果可以应用于远程量子计算，为量子信息的发展做出贡献。