Investigations of Quantum Coherence in Josephson Junctions and Superconducting Circuits

* 非技术摘要 * 近年来，在低温下显示出显著量子力学特性的超导电路的开发方面取得了相当大的进展。这些电路可以被认为是“人造原子”。像原子一样，它们可以以不同的量子力学状态存在;然而，与真实的原子不同的是，这些人造原子的性质可以通过转动各种控制旋钮来调整。这些系统是探索量子力学基本概念的迷人试验台;此外，它们有朝一日可能会被用作量子计算机中的比特。量子计算机有望比传统的经典计算机强大得多。最近的研究表明，超导电路材料中的缺陷会导致破坏电路量子态的噪声。这个个人研究者奖支持研究，以了解管理超导电路中量子态破坏的基本材料物理学。电学测量将与材料表征工具相结合，以将量子行为与材料特性相关联。这项工作将有助于改进固态量子技术的发展，并可能为更精确地探测纳米尺度上广泛的量子现象打开大门。本科生和研究生将参与这项研究的各个方面，他们将接受各种最先进的纳米纤维和测量技术的宝贵培训。该项目得到了材料研究和物理部门的支持。基于约瑟夫森结的超导量子电路为探索纠缠、退相干和量子测量等基本量子力学概念提供了一个迷人的试验平台。超导量子电路作为量子比特和探测凝聚态系统中量子纠缠的工具的持续发展将需要对控制能量弛豫和退相的基础物理学有新的见解。这个个人研究奖支持一个项目，以了解微波损耗和低频噪声的微观起源从缺陷状态在非晶材料。微波传输测量将与红外和隧道光谱相结合，将介电损耗与微观材料特性相关联。基于SQUID的噪声测量将与交流自旋磁化率的测量相结合，以探测超导薄膜中表面磁态引起的退相的微观物理。这些研究将为开发可扩展、可调的量子位架构铺平道路。此外，这些实验将教育学生在各种国家的最先进的纳米制造和测量技术。 该项目得到了材料研究和物理部门的支持。

****NON-TECHNICAL ABSTRACT****Recent years have seen considerable progress in the development of superconducting circuits that display remarkable quantum mechanical properties at low temperature. These circuits can be thought of as "artificial atoms". Like atoms, they can exist in different quantum mechanical states; unlike real atoms, however, the properties of these artificial atoms can be adjusted by turning various control knobs. These systems are a fascinating test bed for the exploration of fundamental concepts in quantum mechanics; in addition, they might one day be used as bits in a quantum computer. A quantum computer promises to be vastly more powerful than a conventional classical computer. Recent work has shown that defects in the materials of the superconducting circuit cause noise that destroys the quantum state of the circuit. This individual investigator award supports research to understand the underlying materials physics that governs disruption of quantum states in superconducting circuits. Electrical measurements will be combined with materials characterization tools to correlate quantum behavior with materials properties. This work will contribute to the development of improved solid-state quantum technologies, and could open the door to more accurate probes of a broad range of quantum phenomena at the nanoscale. Undergraduates and graduate students will be involved in all aspects of this research, and they will receive invaluable training in a variety of state-of-the-art nanofabrication and measurement techniques. This project receives support from the Divisions of Materials Research and Physics.****TECHNICAL ABSTRACT****Superconducting quantum circuits based on Josephson junctions form a fascinating test bed for the exploration of fundamental quantum mechanics concepts such as entanglement, decoherence, and quantum measurement. The continued development of superconducting quantum circuits as qubits and as tools to probe quantum entanglement in condensed matter systems will require new insights into the fundamental physics that governs energy relaxation and dephasing. This individual investigator award supports a project to understand the microscopic origin of microwave loss and low-frequency noise from defect states in amorphous materials. Microwave transport measurements will be combined with infrared and tunneling spectroscopy to correlate dielectric loss with microscopic materials properties. SQUID-based noise measurements will be combined with measurements of ac spin susceptibility to probe the microscopic physics of dephasing due to surface magnetic states in superconducting thin films. These investigations will pave the way to the development of scalable, tunable qubit architectures. Additionally, these experiments will educate students in a variety of state-of-the-art nanofabrication and measurement techniques. The project receives support from the Divisions of Materials Research and Physics.