Research on Quantum Memory using Superconducting Artificial Atoms

我们已经证明了固态量子处理单元（超导人造原子：通量量子比特）和专用量子存储器（金刚石中的氮空位（NV）中心）之间的强耦合。这些结果表明，在通量量子比特中操纵的量子信息可以存储到NV中心的系综中并从NV中心的系综中检索。量子存储器是量子通信和信息处理的重要组成部分。我们的工作表明，金刚石是未来量子存储器的一个有希望的候选者。这是量子计算机发展的重要一步，也是微波和光学世界之间的接口。这一结果也证明了两种不同的宏观物质之间纠缠的产生，即，数千万（阿托摩尔）NV中心的自旋状态和在微米大小的电子电路中循环的持续电流，通量量子比特。我们分析了NV中心系综和单个NV中心与超导量子位强耦合的动力学。我们还研究了用Wigner函数和其他准分布函数来表示这些量子态的数学工具。该物理系统可以用于构建新型量子信息器件，如存储器和接口。我们研究了几种可能性，并展示了这种器件在量子信息网络中的优势

We have demonstrated strong coupling between a solid-state quantum processing unit (a superconducting artificial atom : a flux-qubit) and a dedicated quantum memory (nitrogen-vacancy (NV) centers in diamond). These results indicate that quantum information manipulated in flux qubits can be stored to and retrieved from an ensemble of NV centers. A quantum memory is an essential component for quantum communication and information processing. Our work demonstrated that diamond is a promising candidate for a future quantum memory. This is a significant step forward in the development of a quantum computer and additionally to an interface between the microwave and optical worlds. This result also demonstrated generation of entanglement between two distinct macroscopic matter i.e., the spin state of a few tens of million (attomol) NV centers and the persistent current circulating in a micro-meter sized electronic circuit, a flux-qubit. We have analysed the dynamics of the NV center ensemble and a single NV center strongly coupled with the superconducting qubit. We also investigated mathematical tools to represent these quantum states with a generalization of Wigner function as well as other quasi-distribution functions. This physical system can be applied to construct novel quantum information devices, such as memory and interface. We investigated several possibilities and showed advantages of such devices in quantum information network