高持续电流能隙可调型磁通量子比特及其在量子杂化系统中的应用研究

Quantum computation has attracted significant attention recently as it can solve certain classes of problem much more efficiently than with their classical counterparts. There have been many physical systems investigated that show the potential to build a quantum computer, however each of them has some form of fundamental problems, so it seems almost impossible to build a viable quantum computer using only a single physical system. Recently, the conception of hybridization, where one integrates two or more different systems together and use the best parts of each, has been seen as a promising solution. Superconducting circuits and negatively charged nitrogen (NV−) centers in diamond are one such example where we can achieve both easy manipulation and long coherence times. Coherent coupling between a gap-tunable flux qubit and NV ensemble has been realized. But due to the high concentration of impurities in the NV system, the life time was only on the order of ten nanoseconds. We will develop a new generation of high persistent current gap-tunable flux qubit and coupled it to a much lower concentration NV ensemble (or other spin ensemble system). This way the coherent time of the NV ensemble is expected to be significantly longer (>ms), and so we should realize high fidelity memory operations.We will then couple two gap-tunable flux qubits together enabling us to store entangled states wth the memories in high fidelity way.

量子计算在某些领域相较于经典计算方式有着不可比拟的优势，是目前一个重要研究方向。在人们已经探索了的多种物理系统中，均有着其难以克服的问题，似乎用单一的系统来实现实用的量子计算依然很遥远。量子杂化系统，即相干耦合多个量子系统并充分扬长避短，这一新概念给这一方向带来了新的希望。超导量子比特与金刚石中的NV色心杂化系统因为其完美的互补性就是这样的一个典型的例子，目前超导量子比特与NV色心系统的相干耦合已经实现，但由于采用了浓度很高的NV色心样品，NV色心系综的退相干时间变得很短（~10ns）。本项目将着重于发展高持续电流能隙可调型磁通量子比特，这样就可以采用低浓度的NV色心样品（或其他自旋中心样品），以获得长退相干时间的NV色心系综（>ms）。然后，将开展单比特长寿命固态量子存储的研究。并尝试开展两比特甚至多比特高保真量子门研究，最终朝实用的量子计算努力。

量子计算在某些领域相较于经典计算方式有着不可比拟的优势，是目前一个重要研究方向。在人们已经探索了的多种物理系统中，均有着其难以克服的问题，似乎用单一的系统来实现实用的量子计算依然很遥远。量子杂化系统，即相干耦合多个量子系统并充分扬长避短，这一新概念给这一方向带来了新的希望。超导量子比特与金刚石中的NV色心杂化系统因为其完美的互补性就是这样的一个典型的例子，目前超导量子比特与NV色心系统的相干耦合已经实现，但由于采用了浓度很高的NV色心样品，NV色心系综的退相干时间变得很短（~10ns）。本项目着重于发展高持续电流能隙可调型磁通量子比特，这样就可以采用低浓度的NV色心样品（或其他自旋中心样品），以获得长退相干时间的NV色心系综（>ms）。本项目成功制备了集成比特数超过20个的量子芯片，获得了保真度达到99.5%的两比特门，并依托所研制的高质量超导量子多比特系统，进行了一系列原创的研究工作，为实用的量子计算奠定了基础。