In general, generation of entangled photon pairs and also the random choice of measurement basis can be implemented with passive optical devices in entanglement based quantum key distribution (QKD) system. However, auxiliary random numbers are still mandatory for conducting the privacy amplification procedure. In this paper, we propose a fully passive entanglement based QKD scheme in which certified random bits for privacy amplification are extracted from detection events of measurement-basis-mismatched entangled photon pairs. The privacy of these random bits can be certified by estimating the phase error rate in the sifted key. The idea of extracting certified random numbers from measurement-basis-mismatched photons, can be extended to all practical QKD schemes.
Security of passive entanglement-based key distribution protocols
Network Innovation Laboratories, NTT, Inc.（NTT网络创新实验室）；NTT Research Center for Theoretical Quantum Information, NTT, Inc.（NTT理论量子信息研究中心）；Basic Research Laboratories, NTT, Inc.（NTT基础研究所）
We quantify the maximum amount of entanglement of formation (EoF) that can be achieved by continuous-variable states under passive operations, which we refer to as EoF-potential. Focusing, in particular, on two-mode Gaussian states we derive analytical expressions for the EoF-potential for specific classes of states. For more general states, we demonstrate that this quantity can be upper-bounded by the minimum amount of squeezing needed to synthesize the Gaussian modes, a quantity called squeezing of formation. Our work, thus, provides a new link between non-classicality of quantum states and …
Although entropy is a necessary and sufficient quantity to characterize the order of work content for equal energetic (EE) states in the asymptotic limit, for the finite quantum systems, the relation is not so linear and requires detail investigation. Toward this, we have considered a resource theoretic framework taking the energy preserving operations (EPO) as free, to compare the amount of extractable work from two different quantum states. Under EPO, majorization becomes a necessary criterion for state transformation. It is also shown that the passive state energy is a concave function and …
University of Calgary（卡尔加里大学）；University of Hong Kong（香港大学）；University of Toronto（多伦多大学）；Centre for Quantum Information and Quantum Control (CQIQC)（量子信息与量子控制中心）
High-Performance Fully Passive Discrete-State Continuous-Variable Quantum Key Distribution With Local Local Oscillator
Shanxi University（山西大学）；Hefei National Laboratory（合肥国家实验室）；Hong Kong Applied Science and Technology Research Institute（香港应用科技研究院）；Beijing Academy of Quantum Information Sciences（北京量子信息科学研究院）
On the equivalence between squeezing and entanglement potential for two-mode Gaussian states
Australian National University（澳大利亚国立大学）；University of California, Los Angeles (UCLA)（加利福尼亚大学洛杉矶分校）；Agency for Science, Technology and Research (A*STAR)（科学技术研究局）；Nanyang Technological University（南洋理工大学）
Quantum communication is developed owing to the theoretically proven security of quantum mechanics, which may become the main technique in future information security. However, most studies and implementations are limited to two or several parties. Herein, we propose a fully connected quantum communication network without a trusted node for a large number of users. Using flexible wavelength demultiplex/multiplex and space multiplex technologies, 40 users are fully connected simultaneously without a trusted node by a broadband energy-time entangled photon pair source. This network architecture …
我们研究了连通图对应的图态中不同纠缠度的性质。结合图态的操作定义和纠缠测度的假设，证明了在N>3个量子比特的连通图态中不存在真正的三量子比特纠缠。对于某些类的图状态，所有真正的k量子比特纠缠，2 \leq k \leq N-1，在每k量子比特之间消失。这些关于连通图态的结果自然引出了完全多比特纠缠态的定义。我们还发现四量子比特的连通图态是一类但不是唯一的四量子比特完全纠缠态。
