The interference between a giant atom and an internal resonator

The Jaynes–Cummings model plays an important role in quantum entanglement and state measurements. Here, we discuss how to realize it in a waveguide-mediated interaction system, which comprises a giant atom and a resonator. We show the vacuum Rabi splitting and discuss how to achieve a unidirectional transport. We extend the Purcell effect in cQED to this waveguide QED system, showing how to control the giant atom decay rate. Our design can further be built experimentally and has application in quantum manipulation.     

Examining Supervised Machine Learning Methods for Integer Link Weight Prediction Using Node Metadata

With the goal of understanding if the information contained in node metadata can help in the task of link weight prediction, we investigate herein whether incorporating it as a similarity feature (referred to as metadata similarity) between end nodes of a link improves the prediction accuracy of common supervised machine learning methods. In contrast with previous works, instead of normalizing the link weights, we treat them as count variables representing the number of interactions between end nodes, as this is a natural representation for many datasets in the literature. In this preliminary study, we find no significant evidence that metadata similarity improved the prediction accuracy of the four empirical datasets studied. To further explore the role of node metadata in weight prediction, we synthesized weights to analyze the extreme case where the weights depend solely on the metadata of the end nodes, while encoding different relationships between them using logical operators in the generation process. Under these conditions, the random forest method performed significantly better than other methods in 99.07% of cases, though the prediction accuracy was significantly degraded for the methods analyzed in comparison to the experiments with the original weights.     

Nonreciprocal two-photon transmission and statistics in a chiral waveguide QED system

We study the nonreciprocal properties of transmitted photons in a chiral waveguide quantum electrodynamics (QED) system, including single- and two-photon transmissions and second-order correlations. For the single-photon transmission, the nonreciprocity is induced by the effects of chiral coupling and atomic dissipation in the weak coupling region. It vanishes in the strong coupling regime when the effect of atomic dissipation becomes ignorable. In the case of two-photon transmission, there exist two ways of going through the emitter: independently as plane waves and formation of bound state. Besides the nonreciprocal behavior of plane waves, the bound state that differs in two directions also alters transmission probabilities. In addition, the second-order correlation of transmitted photons depends on the interference between plane wave and bound state. The destructive interference leads to the strong antibunching in the weak coupling region, while the effective formation of bound state leads to the strong bunching in the intermediate coupling region. However, the negligible interactions for left-propagating photons hardly change the statistics of the input coherent state.     

Non-Markovian Master Equation for Distant Resonators Embedded in a One-Dimensional Waveguide

We develop a master equation approach to describe the dynamics of distant resonators coupled through a one-dimensional waveguide. Our method takes into account the back-actions of the reservoirs, and enables us to calculate the exact dynamics of the complete system at all times. We show that such system can cause nonexponential and long-lived photon decay due to the existence of a relaxation effect. The physical origin of non-Markovianity in our model system is the finite propagation speed resulting in time delays in communication between the nodes, and strong decay rate of the emitters into the waveguide. When the distance satisfies the standing wave condition, we find that when the time delay is increased, the dark modes formation is no longer perfect, and the average photon number of dark mode decreases in steady time limit.     

利用纠缠交换制备原子-原子最大纠缠态

基于腔量子电动力学(QED)提出一种利用两对纠缠的级联型三能级原子与单模腔场系统制备原子-原子最大纠缠态的简单方案,最初两原子之间、两腔场之间互不纠缠,使其中一个原子与一个腔场发生作用,即纠缠交换,该过程仅需对单个腔场态测量就可实现从未有直接作用的两个原子之间的纠缠,精确控制原子与腔场的相互作用时间可获得具有最大保真度的纠缠态.该方案可以延长腔的有效泄漏时间,从而能有效克服光腔的消相干的影响,这样大大降低了系统对腔的品质的要求.     

On‐chip single photon sources using planar photonic crystals and single quantum dots

We review the basic light‐matter interactions and optical properties of chip‐based single photon sources, that are enabled by integrating single quantum dots with planar photonic crystals. A theoretical framework is presented that allows one to connect to a wide range of quantum light propagation effects in a physically intuitive and straightforward way. We focus on the important mechanisms of enhanced spontaneous emission, and efficient photon extraction, using all‐integrated photonic crystal components including waveguides, cavities, quantum dots and output couplers. The limitations, challenges, and exciting prospects of developing on‐chip quantum light sources using integrated photonic crystal structures are discussed.     

铌酸锂基光量子器件与集成技术：机遇与挑战

铌酸锂材料具有宽的透光范围和高的非线性光学、电光、声光、热光系数,且化学性能稳定,是理想的光子集成芯片的衬底材料。在量子光学领域,人们已经发展出一系列铌酸锂基集成器件,能够实现光子态的高效率产生、调控、频率转换、存储和异质集成的单光子探测,有望实现全集成的频率态操控、确定性多光子态制备和单光子间相互作用,最终形成全功能集成的有源光量子芯片,推动量子物理基础研究和光量子信息应用发展。文章回顾了基于铌酸锂基量子集成的研究进展,并对其在未来光量子信息时代的机遇与挑战进行探讨。     

An Efficient Supervised Deep Hashing Method for Image Retrieval

In recent years, searching and retrieving relevant images from large databases has become an emerging challenge for the researcher. Hashing methods that mapped raw data into a short binary code have attracted increasing attention from the researcher. Most existing hashing approaches map samples to a binary vector via a single linear projection, which restricts the flexibility of those methods and leads to optimization problems. We introduce a CNN-based hashing method that uses multiple nonlinear projections to produce additional short-bit binary code to tackle this issue. Further, an end-to-end hashing system is accomplished using a convolutional neural network. Also, we design a loss function that aims to maintain the similarity between images and minimize the quantization error by providing a uniform distribution of the hash bits to illustrate the proposed technique’s effectiveness and significance. Extensive experiments conducted on various datasets demonstrate the superiority of the proposed method in comparison with state-of-the-art deep hashing methods.     

新型超导量子比特及量子物理问题的研究

近年来,超导量子计算的研究有了很大的进展.本文首先介绍了nSQUID新型超导量子比特的制备和研究进展,包括器件的平面多层膜制备工艺和量子相干性的研究.这类器件在量子态的传输速度和二维势系统的基础物理问题研究方面有着很大的优越性.其次,国际上新近发展的平面形式的transmon和Xmon超导量子比特具有更长的量子相干时间,在器件的设计和耦合方面也有相当的灵活性.本文介绍了我们和浙江大学与中国科学技术大学等单位合作逐步完善的这种形式的Xmon器件的制备工艺、制备出的多种耦合量子比特芯片,以及参与合作,在国际上首次完成的多达10个超导量子比特的量子态纠缠、线性方程组量子算法的实现和多体局域态等固体物理问题的量子模拟.最后介绍了基于这些超导量子比特器件开展的大量的量子物理、非线性物理和量子光学方面的研究,包括在Autler-Townes劈裂、电磁诱导透明、受激拉曼绝热通道、循环跃迁和关联激光等方面形成的一整套系统和独特的研究成果.     

Weakly Supervised Building Semantic Segmentation Based on Spot-Seeds and Refinement Process

Automatic building semantic segmentation is the most critical and relevant task in several geospatial applications. Methods based on convolutional neural networks (CNNs) are mainly used in current building segmentation. The requirement of huge pixel-level labels is a significant obstacle to achieve the semantic segmentation of building by CNNs. In this paper, we propose a novel weakly supervised framework for building segmentation, which generates high-quality pixel-level annotations and optimizes the segmentation network. A superpixel segmentation algorithm can predict a boundary map for training images. Then, Superpixels-CRF built on the superpixel regions is guided by spot seeds to propagate information from spot seeds to unlabeled regions, resulting in high-quality pixel-level annotations. Using these high-quality pixel-level annotations, we can train a more robust segmentation network and predict segmentation maps. To iteratively optimize the segmentation network, the predicted segmentation maps are refined, and the segmentation network are retrained. Comparative experiments demonstrate that the proposed segmentation framework achieves a marked improvement in the building’s segmentation quality while reducing human labeling efforts.     

单原子脉塞和单原子激光——腔量子电动力学的实验平台

单原子脉塞和单原子激光是腔量子电动力学研究的重要实验平台。本文综述关于几类单原子脉塞和单原子激光的研究工作,包括德国Walther小组的单原子脉塞、超冷原子注入的单原子脉塞,法国Haroche小组的腔量子电动力学系统、注入原子的单原子激光、以及囚禁原子和囚禁离子的单原子激光。我们介绍相关的理论工作、实验系统、以及主要结果。     

Discrete Infomax Codes for Supervised Representation Learning

For high-dimensional data such as images, learning an encoder that can output a compact yet informative representation is a key task on its own, in addition to facilitating subsequent processing of data. We present a model that produces discrete infomax codes (DIMCO); we train a probabilistic encoder that yields k-way d-dimensional codes associated with input data. Our model maximizes the mutual information between codes and ground-truth class labels, with a regularization which encourages entries of a codeword to be statistically independent. In this context, we show that the infomax principle also justifies existing loss functions, such as cross-entropy as its special cases. Our analysis also shows that using shorter codes reduces overfitting in the context of few-shot classification, and our various experiments show this implicit task-level regularization effect of DIMCO. Furthermore, we show that the codes learned by DIMCO are efficient in terms of both memory and retrieval time compared to prior methods.     

堆叠监督自动编码器的近红外光谱建模

近红外光谱中包含了物质中有机分子含氢基团的特征信息,具有维度高、冗余大等特点.传统的基于浅层校正模型,比如主成分回归、偏最小二乘回归、人工神经网络、支持向量回归等,无法提取近红外光谱数据深层的信息.提出一种基于堆叠监督自动编码器的近红外光谱建模方法,不仅可以拟合光谱数据与理化值之间复杂的非线性关系,还可以提取数据深层的...     

玻璃基集成光量子芯片：从二维到三维

玻璃基集成光量子芯片已经应用于量子计算、量子模拟、量子通信、量子精密测量等光量子信息处理领域,显示出强大的功能。文章从量子计算和量子模拟两个方面介绍利用飞秒激光三维高精度直写技术在玻璃中制备集成光量子芯片的重要进展。量子计算芯片包括面向通用量子计算的单比特到多比特光量子逻辑门以及用于解决特定问题的芯片,可实现玻色采样、量子快速傅里叶变换、量子快速到达等功能。在量子模拟方面,玻璃基光量子芯片成为研究关联粒子量子行走动力学和拓扑量子光子学的极佳平台,揭示了一维、二维和合成维度的离散以及连续时间量子行走的演化规律,展示了光子拓扑绝缘体的鲁棒性拓扑模式对量子态传输的保护作用等。     

基于腔QED制备四粒子supersinglets

在双光子跃迁下,本文基于腔量子电动力学(QED)系统提出了一种制备4粒子supersinglets的方案.方案要求腔场最初处于真空态,依次与四个腔场发生共振作用的三能级原子最初处于激发态.分析和讨论了该方案的可行性以及原子-腔场的耦合常数对保真度的影响.结果表明：1)该态保真度的值随原子与腔场相互作用时间的不同而不同,选择合适的原子-腔场相互作用过程以及对原子态的探测,可获得具有最大保真度的纠缠态;2)失谐量等于零时,耦合常数越大,保真度对原子与腔场相互作用的时间越敏感.     

周期不对称度对光子晶体透射谱特性的影响研究

利用传输矩阵法,研究周期不对称度对光子晶体透射谱的影响,结果表明:当周期不对称度为零时,光子晶体透射峰随着周期数的增大而变得越精细,但其透射率均为100%不变;当周期不对称度为不等于零的恒定值时,光子晶体透射峰的透射率低于100%,但随着周期数的增大,透射峰仅变得精细而透射率不变;光子晶体透射峰的透射率随着周期不对称度增大而下降,而且不对称度越大,透射率下降越快,同时透射峰变窄的速度也越快。周期不对称度对光子晶体透射谱的影响规律,为光子晶体模型的构造和设计制备等提供方法依据。     

Supervised Contrastive Learning and Intra-Dataset Adversarial Adaptation for Iris Segmentation

Precise iris segmentation is a very important part of accurate iris recognition. Traditional iris segmentation methods require complex prior knowledge and pre- and post-processing and have limited accuracy under non-ideal conditions. Deep learning approaches outperform traditional methods. However, the limitation of a small number of labeled datasets degrades their performance drastically because of the difficulty in collecting and labeling irises. Furthermore, previous approaches ignore the large distribution gap within the non-ideal iris dataset due to illumination, motion blur, squinting eyes, etc. To address these issues, we propose a three-stage training strategy. Firstly, supervised contrastive pretraining is proposed to increase intra-class compactness and inter-class separability to obtain a good pixel classifier under a limited amount of data. Secondly, the entire network is fine-tuned using cross-entropy loss. Thirdly, an intra-dataset adversarial adaptation is proposed, which reduces the intra-dataset gap in the non-ideal situation by aligning the distribution of the hard and easy samples at the pixel class level. Our experiments show that our method improved the segmentation performance and achieved the following encouraging results: 0.44%, 1.03%, 0.66%, 0.41%, and 0.37% in the Nice1 and 96.66%, 98.72%, 93.21%, 94.28%, and 97.41% in the F1 for UBIRIS.V2, IITD, MICHE-I, CASIA-D, and CASIA-T.     

Micro-scale Fabry–Perot interferometer with high spectral resolution and tunable transmission frequency via chiral waveguide-emitter coupling

A micro-scale Fabry–Perot interferometer with high spectral resolution and tunable transmission frequency is proposed. In this scheme, two partially reflecting mirrors with a separation of several wavelengths is fabricated in a waveguide, and a two-level emitter is located between the mirrors and coupled to the waveguide with chiral interaction. We analytically show that the single emitter plays the role of a strongly dispersive medium and the full width at half maximum (FWHM) of the transmission fringes around the resonance frequency of the emitter can be narrowed by 5 orders of magnitude. The proposed micro-scale interferometer can have the same spectral resolution as meter-scale traditional interferometers. We also show that the central frequency of the narrowed transmission fringe can be tuned by adjusting the asymmetry of the emitter-waveguide coupling. Our scheme has potential applications in the fields of integrated optical circuit and quantum information processing.     

连续变量六组份和八组份星型Cluster纠缠态光场产生系统

Cluster纠缠态是执行单向量子计算的基本资源.星型Cluster态可用于构建量子信息网络.以非简并光学参变放大器产生的双模压缩态光场为基础,设计了产生连续变量六组份和八组份星型Cluster纠缠态光场的实验方案,并推导了相应的量子不可分判据.计算结果指出,当量子不可分判据中的增益因子取为1时,需要一定的初始压缩度才能制备星型Cluster纠缠态;但当选取最佳增益因子时,极低的压缩也能产生星型纠缠.计算为实验系统设计提供了直接参考.     

量子计算的进展和展望

该文主要介绍了量子计算机研究的历史和现状。强调发展大规模的量子计算和实现强关联多体系统的量子模拟,是当前量子计算研究的主流。文章主体部分主要介绍了量子计算机硬件研究方面的进展,主要聚焦于几个具有qubit可集成性的量子系统:量子点系统、超导约瑟夫森结系统、离子阱系统、腔量子电动力学系统,作为实现量子计算机的最主要的候选系统,上述方向的研究吸引了国际上研究量子计算的最主要的力量。我们调研了在这些系统中,在qubit表征、操控方面最具代表性的进展,以及在实现大规模量子计算道路上的困难,和可能的解决办法。