固体媒質におけるコヒーレンス及び干渉効果に基づいた量子情報

在2013财政年度，我们主要研究混合量子电路中的量子操纵及其在量子信息科学中的应用。（1）提出了利用磁通量子比特、氮空位中心系综（NVE）和传输线谐振腔的混合量子结构实现强自旋-谐振腔耦合和高保真量子存储的方法。首先，我们提出了一个实验上可实现的混合量子电路，通过超导磁通量子比特作为数据总线，实现自旋系综和传输线谐振器之间的强耦合。我们的结果表明，基于我们的建议，自旋共振器耦合强度可以提高两个数量级。此外，我们提出了如何实现高保真的量子存储使用的混合量子体系结构，包括两个耦合通量量子比特和氮空位中心系综（NVE）。这种混合量子电路可以在自旋系综中存储信息时实现长时间量子存储。(2)我们研究了一个混合电光机械系统，使我们能够实现可控的强克尔非线性，即使在弱耦合制度。我们表明，当可控机电子系统接近其量子临界点，强光子-光子相互作用可以通过调节强度（或频率）的微波驱动场产生。非线性光学现象，例如光子阻塞的出现和非经典态的产生（例如，猫态），证明了在弱耦合制度，使目前可用的光机技术的观测强克尔非线性可行。

During FY2013, we mainly studied quantum manipulation in hybrid quantum circuits, and their application in quantum information science. The main results are :(1) We proposed the methods to realize strong spin-resonator coupling and high-fidelity quantum storage using the hybrid quantum architectures including flux qubits, nitrogen-vacancy center ensemble (NVE) and transmission-line resonator. Firstly, we proposed an experimentally realizable hybrid quantum circuit for achieving a strong coupling between a spin ensemble and a transmission-line resonator via a superconducting flux qubit used as a data bus. Our result show that the spin-resonator coupling strength can be enhanced two orders based on our proposal. Also, we proposed how to realize high-fidelity quantum storage using a hybrid quantum architecture including two coupled flux qubits and a nitrogen-vacancy center ensemble (NVE). This proposed hybrid quantum circuit could enable a long-time quantum memory when storing information in the spin ensemble.(2) We investigated a hybrid electro-optomechanical system that allows us to realize controllable strong Kerr nonlinearities even in the weak-coupling regime. We showed that when the controllable electromechanical subsystem is close to its quantum critical point, strong photon-photon interactions can be generated by adjusting the intensity (or frequency) of the microwave driving field. Nonlinear optical phenomena, such as the appearance of the photon blockade and the generation of nonclassical states (e.g., cat states), are demonstrated in the weak-coupling regime, making the observation of strong Kerr nonlinearities feasible with currently available optomechanical technology.