利用Cluster State实现远程态制备

量子态是量子信息的载体，因此，从某种意义上说，量子信息过程就是量子态的传递和操作的过程。量子态的远程制备包括量子隐形传态（Telepotation）和远程态制备（Remote State Preparation（RSP））。远程态制备是一种利用纠缠和经典通讯传输量子态的简单方法，相比较量子态telepotation耗费的资源更少（1 ebit and 1 cbit）。Cluster State是一种特殊的量子态，在量子计算方案中有着广泛的应用。我们实验上利用SPDC产生的偏振纠缠双光子，加入时间比特，构造出Cluster State，并利用Cluster State实现了量子态的远程制备。     

Quantum metrology

The statistical error is ineluctable in any measurement. Quantum techniques, especially with the development of quantum information, can help us squeeze the statistical error and enhance the precision of measurement. In a quantum system, there are some quantum parameters, such as the quantum state, quantum operator, and quantum dimension, which have no classical counterparts. So quantum metrology deals with not only the traditional parameters, but also the quantum parameters. Quantum metrology includes two important parts： measuring the physical parameters with a precision beating the classical physics limit and measuring the quantum parameters precisely. In this review, we will introduce how quantum characters （e.g., squeezed state and quantum entanglement） yield a higher precision, what the research areas are scientists most interesting in, and what the development status of quantum metrology and its perspectives are.     

实现光子的远程量子操作

量子纠缠的非局域性质为量子信息应用提供了强有力的工具,利用量子纠缠态可以实现量子隐形传态、量子密集编码、量子密码、远程量子态制备、远程量子态测量.这里,我们将给出一个基于两粒子纠缠态的利用局域操作和经典通信的远程量子操作的实验方案.该方案可以实现对单光子偏振态在Bloch球空间中绕固定方向进行任意旋转操作,或者绕任意方向进行180度旋转操作.     

量子信道干涉

单个信道的性质可以用量子测量和量子层析技术等方法描述，但是仅仅单个信道的性质还不足以描述两个信道同时作用时的情况。J．Aberg告诉我们仅仅知道单个信道的信息并不足以帮助我们说明两个映射（一个信道的作用可以用一个映射来描述）同时作用时的情况。但是两个信道之间的干涉可以提供给我们单个信道描述中所没有的附加信息，即两个信道间的相干性质。因此，干涉测量可以用来提取量子层析技术所不能获得的信息。     

Compressed Sensing Quantum State Tomography Assisted by Adaptive Design

The recently proposed compressed sensing(CS) method sheds light on quantum state tomography of multi-qubit systems with low rank, which greatly reduces the complexity of measurement and computation. However, the restricted isometry property requirement of CS is difficult to be promised or verified in practice, which makes this method probably assign unreasonable results. In regard to this problem, we adopt a two-step procedure and implement an adaptive strategy to update measurement operators based on the measurement results of the first step for CS, which not only serves as a way to verify the estimate but also improves the accuracy of tomography.Our numerical simulations manifest that our adaptive protocol can reduce about half of the infidelity of nonadaptive protocol and is still efficient even when the rank of the state is slightly high, which would greatly benefit multi-qubit state tomography in future experiments.     

噪声信道下的远程混态制备

量子信息过程实际上也就是量子态的制备,操作,传输的过程.量子隐形传态(quantum teleporation)给我们提供了一种远程制备量子态的方法.近来,远程态制备(remote state preparation)的研究越来越受到人们的关注.它给我们提供了一种新的远程制备量子态的方法.与量子隐形传态不同的是:传送方(Alice)知道要传送的态,并且接收方知道要传送态所处在的系综.     

集体测量估计量子相干性的性能研究

量子相干性作为资源理论提出后，对它的量化和实验测量的研究一直受到大家广泛的关注。目前已有研究证明集体测量可以提高相干性的测量精度，但在具体实验中实验条件对集体测量估计量子相干性的性能影响还尚不清晰。分别数值模拟了在不同探测效率和资源数条件下集体测量估计相干性的误差，并与其他方法进行了比较。分析发现存在一定参数范围使集体测量的方法在探测效率为60%的情况下比探测效率为90%的态层析的方法更优；此外，随着资源数的增多，集体测量的性能几乎不依赖于量子态和相干性的度量方式，误差均以相同尺度在减小。     

Ⅱ型晶体的厚度对纠缠双光子对的四阶干涉可见度的影响

在自发参量下转换(SPDC)的非线性光学过程中,一束激光作用在非线性晶体上,产生处于纠缠态的双光子对.近几年人们对自发参量下转换(SPDC)产生双光子纠缠性质及应用做了许多研究.     

Transporting Cold Atoms towards a GaN-on-Sapphire Chip via an Optical Conveyor Belt

Trapped atoms on photonic structures inspire many novel quantum devices for quantum information processing and quantum sensing. Here, we demonstrate a hybrid photonic-atom chip platform based on a Ga N-onsapphire chip and the transport of an ensemble of atoms from free space towards the chip with an optical conveyor belts. Due to our platform’s complete optical accessibility and careful control of atomic motion near the chip with a conveyor belt, successful atomic transport towards the chip is m...