Interference at a beam splitter reveals both classical and quantum properties of electromagnetic radiation. When two indistinguishable single photons impinge at the two inputs of a beam splitter they coalesce into a pair of photons appearing in either one of its two outputs. This effect is due to the bosonic nature of photons and was first experimentally observed by Hong, Ou, and Mandel (HOM) [1]. Here, we present the observation of the HOM effect with two independent single-photon sources in the microwave frequency domain. We probe the indistinguishability of single photons, created with a controllable delay, in time-resolved second-order cross- and auto-correlation function measurements. Using quadrature amplitude detection we are able to resolve different photon numbers and detect coherence in and between the output arms. This measurement scheme allows us to observe the HOM effect and, in addition, to fully characterize the two-mode entanglement of the spatially separated beam splitter output modes. Our experiments constitute a first step towards using two-photon interference at microwave frequencies for quantum communication and information processing, e.g. for distributing entanglement between nodes of a quantum network [2, 3] and for linear optics quantum computation [4, 5].
Probing the Quantum Capacitance of Rydberg Transitions of Surface Electrons on Liquid Helium via Microwave Frequency Modulation
RIKEN Center for Quantum Computing（理化学研究所量子计算中心）；Institute of Physics, Kazan Federal University（喀山联邦大学物理研究所）；B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine（乌克兰国家科学院B.维尔金低温物理与工程研究所）；McGill University（麦吉尔大学）；RIKEN Cluster for Pioneering Research（理化学所前沿研究集群）
Probing an electron spin ensemble with squeezed microwave signals
Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften（瓦尔特·迈斯纳研究所，巴伐利亚科学院）；Technical University of Munich, TUM School of Natural Sciences, Physics Department（慕尼黑工业大学，自然科学学院，物理系）；Munich Center for Quantum Science and Technology (MCQST)（慕尼黑量子科学与技术中心）
Probing Quantum Anomalous Hall Transport Under Microwave Irradiation Using a Topological Circulator
Institute for Quantum Computing and Department of Physics and Astronomy, University of Waterloo（滑铁卢大学量子计算研究所与物理天文学系）；Lawrence Livermore National Laboratory（劳伦斯利弗莫尔国家实验室）；Department of Electrical and Computer Engineering, University of Minnesota（明尼苏达大学电气与计算机工程系）；Department of Electrical and Computer Engineering, University of California, Los Angeles（加州大学洛杉矶分校电气与计算机工程系）
Detecting induced $p \pm ip$ pairing at the Al-InAs interface with a quantum microwave circuit
超导体-半导体混合器件是量子信息处理的几种方法的核心，但它们的基本性质仍有待了解。我们将二维Al-InAs混合系统嵌入谐振微波电路中，研究了外加磁场对超导性的破坏。我们发现一个强大的指纹从两个组件的混合系统的性质，并定量比较的理论，其中包括带内$p \pm i p$配对的InAs中的贡献，以及由于磁场的Bogoliubov费米表面的出现。分别解决Al和InAs的贡献，使我们能够确定的载流子密度和迁移率的InAs。
Probing the quantum coherence of a nanomechanical resonator using a superconducting qubit II: Implementation
我们描述了一种可能的实现方式的纳米力学量子叠加生成和检测方案中描述的前面，同伴论文[Armour AD和Blencowe M P 2008新。J. Phys.该实施方案是基于电路量子电动力学（QED）的设置，与额外的机械自由度形成了一个悬浮的，双钳位段的超导回路的直流SQUID位于直接相对的中心导体的共面波导（CPW）。讨论了两种基于SQUID的量子比特实现的相对优点，特别是电容耦合电荷量子比特和电感耦合通量量子比特。结果发现，这两种实现是同样有前途的，具有可比的量子位机械谐振器模式以及量子位微波谐振器模式耦合强度。
