Polarization basis tracking scheme for quantum key distribution with revealed sifted key bits

Fundamental Insecurity of Multi-Photon Sources Under Photon-Number Splitting Attacks in Quantum Key Distribution

A simple photon-number splitting attack is described which works on any lossy quantum key distribution system with a multi-photon source independently of the mean source photon number, and with no induced error rate. In particular, it cannot be detected by decoy states. The quantitative loss of security is similar when the user employs photon-number resolving detectors or threshold detectors. Numerical values indicate that existing implementations of concrete QKD systems are fundamentally insecure against this attack because a large portion of leaked sifted key bits is not accounted for. The p…

High-dimensional quantum cryptography with twisted light

Quantum key distributions (QKD) systems often rely on polarization of light for encoding, thus limiting the amount of information that can be sent per photon and placing tight bounds on the error that such a system can tolerate. Here we describe a proof-of-principle experiment that indicates the feasibility of high-dimensional QKD based on the transverse structure of the light field, allowing for the transfer of more than 1 bit per photon. Our implementation uses the orbital angular momentum (OAM) of photons and the corresponding mutually unbiased basis of angular position (ANG). Our experimen…

High Throughput and Low Cost LDPC Reconciliation for Quantum Key Distribution

Reconciliation is a crucial procedure in post-processing of Quantum Key Distribution (QKD), which is used for correcting the error bits in sifted key strings. Although most studies about reconciliation of QKD focus on how to improve the efficiency, throughput optimizations have become the highlight in high-speed QKD systems. Many researchers adpot high cost GPU implementations to improve the throughput. In this paper, an alternative high throughput and efficiency solution implemented in low cost CPU is proposed. The main contribution of the research is the design of a quantized LDPC decoder in…

面向量子互联网的纠缠交换系统

Entanglement swapping systems toward a quantum internet

本研究展示了一种可部署的纠缠交换系统，在电信波长下实现高保真度纠缠隐形传态，并支持量子网络协议，为量子互联网奠定基础。

对 BB84 协议纠缠探针攻击的完整物理模拟

Complete physical simulation of the entangling-probe attack on the BB84 protocol

本研究利用确定性单光子双量子比特量子逻辑，实现了针对 BB84 协议的最强单光子攻击，物理模拟了 Eve 访问 Bob 接收模块的真实攻击，实验结果与理论预测高度一致，证明了确定性量子逻辑在量子信息处理模拟中的实用性。

Characterizing high-quality high-dimensional quantum key distribution by state mapping between different degree of freedoms

Quantum key distribution (QKD) guarantees the secure communication between legitimate parties with quantum mechanics. High-dimensional QKD (HDQKD) not only increases the secret key rate but also tolerates higher quantum bit error rate (QBER). Many HDQKD experiments have been realized by utilizing orbital-angular-momentum (OAM) photons as the degree of freedom (DOF) of OAM of the photon is a prospective resource for HD quantum information. In this work we proposed and characterized that a high-quality HDQKD based on polarization-OAM hybrid states can be realized by utilizing state mapping betwe…

On conclusive eavesdropping and measures of mutual information in quantum key distribution

We address the question of quantifying eavesdropper's information gain in an individual attack on systems of quantum key distribution. It is connected with the concept of conclusive eavesdropping introduced by Brandt. Using the BB84 protocol, we examine the problem of estimating a performance of conclusive entangling probe. The question of interest depends on the choice of a quantitative measure of eavesdropper's information about the error-free sifted bits. The Fuchs--Peres--Brandt probe realizes a very powerful individual attack on the BB84 scheme. In the usual formulation, Eve utilizes the …

一个隐私保护的公开可验证量子随机数生成器

A privacy-preserving publicly verifiable quantum random number generator

本文提出并实现了一种基于纠缠的协议，允许第三方在不泄露随机位隐私的情况下公开验证量子随机数生成器的质量，解决了用户计算能力受限及需公开证明随机性而不暴露随机位的问题。

揭秘隐形传态

Teleportation Revealed

针对量子隐形传态的定域解释难题，本文重新梳理并发展了Deutsch和Hayden基于海森堡绘景的完全定域分析，揭示了隐形传态的作用机制，彰显了该绘景的解释力。

Towards $\textit{ab initio}$ identification of paramagnetic substitutional carbon defects in hexagonal boron nitride acting as quantum bits

Paramagnetic substitutional carbon (C$_\text{B}$, C$_\text{N}$) defects in hexagonal boron nitride (hBN) are discussed as candidates for quantum bits. Their identification and suitability are approached by means of photoluminescence (PL), charge transitions, electron paramagnetic resonance, and optically detected magnetic resonance (ODMR) spectra. Several clear trends in these are revealed by means of an efficient plane wave periodic supercell \textit{ab initio} density functional theory approach. In particular, this yields insight into the role of the separation between C$_\text{B}$ and C$_\t…

Resolving the positions of defects in superconducting quantum bits

Solid-state quantum coherent devices are quickly progressing. Superconducting circuits, for instance, have already been used to demonstrate prototype quantum processors comprising a few tens of quantum bits. This development also revealed that a major part of decoherence and energy loss in such devices originates from a bath of parasitic material defects. However, neither the microscopic structure of defects nor the mechanisms by which they emerge during sample fabrication are understood. Here, we present a technique to obtain information on locations of defects relative to the thin film edge …

NuQKD：面向工程应用的模块化量子密钥分发仿真框架

NuQKD: A Modular Quantum Key Distribution Simulation Framework for Engineering Applications

本文提出了开源模块化QKD仿真框架NuQKD，支持信道衰减建模、设备缺陷建模及真随机序列等功能，以解决现有仿真器功能不足的问题，实现便捷准确的实验条件表征。

Cryptographic encryption scheme for solving the trusted courier problem based on metastable excited nuclei

Quantum cryptography makes it possible to expand a short shared key (of e.g. 256 bits[1]) into an arbitrary long shared key. The novelty of quantum cryptography is that whenever a spy tries to eavesdrop the communication he causes disturbances in the transmission of the message. Ultimately this unavoidable disturbance is a consequence of Heisenberg's uncertainty principle that limits the joint knowledge of complementary observables. Now, a problem remains: in order to initialize quantum key distribution, Alice and Bob need to share a short shared key in order to be able to identify each other …