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State-of-the-art quantum key distribution systems are based on the BB84 protocol and single photons generated by lasers. These implementations suffer from range limitations and security loopholes, which require expensive adaptation. The use…

Quantum cryptography is reviewed, first using entanglement both for the intuition and for the experimental realizations. Next, the implementation is simplified in several steps until it becomes practical. At this point entanglement has…

Quantum Physics · Physics 2007-05-23 Nicolas Gisin , Nicolas Brunner

Particle entanglement is a fundamental resource upon which are based many quantum technologies. However, the up-to-now best sources of entangled photons rely on parametric down-conversion processes, which are optimal only at certain…

A source of entangled photons that emits one, and only one, pair of photons on demand has now been realized in a semiconductor chip. The solid-state source will be a useful resource for experiments in optical quantum information.

Popular Physics · Physics 2015-06-23 Chao-Yang Lu , Jian-Wei Pan

We present a source of polarization entangled photon pairs based on spontaneous parametric downconversion engineered for frequency uncorrelated telecom photon generation. Our source provides photon pairs that display, simultaneously, the…

Entangled photon-pairs are a critical resource in quantum communication protocols ranging from quantum key distribution to teleportation. The current workhorse technique for producing photon-pairs is via spontaneous parametric down…

Quantum entanglement has become an essential resource in quantum information processing. Existing works employ entangled quantum states to perform various tasks, while little attention is paid to the control of the resource. In this work,…

Quantum Physics · Physics 2023-05-23 Qiang Zeng , Haoyang Wang , Huihong Yuan , Yuanbin Fan , Lai Zhou , Yuanfei Gao , Haiqiang Ma , Zhiliang Yuan

We propose an experimentally feasible scheme for generating a two $2\times4\times4$ dimensional photons hyperentangled state, entangled in polarization, frequency and spatial mode. This scheme is mainly based on a parametric down-conversion…

Quantum Physics · Physics 2013-04-30 Hong-Bo Xu , Kun Du , Cong-Feng Qiao

With the advancement of non-classical light sources such as single-photon and entangled-photon sources, innovative microscopy based on the quantum principles has been proposed over traditional microscopy. This paper introduces the…

Quantum Physics · Physics 2025-01-08 Mousume Samad , Maki Shimizu , Yasuto Hijikata

We demonstrate two key components for optical quantum information processing: a bright source of heralded single photons; and a bright source of entangled photon pairs. A pair of pump photons produces a correlated pair of photons at widely…

Quantum key distribution (QKD) is a crucial technology for information security in the future. Developing simple and efficient ways to establish QKD among multiple users are important to extend the applications of QKD in communication…

Quantum Physics · Physics 2020-01-15 Xu Liu , Xin Yao , Rong Xue , Heqing Wang , Hao Li , Zhen Wang , Lixing You , Xue Feng , Fang Liu , Kaiyu Cui , Yidong Huang , Wei Zhang

Real sources of entangled photon pairs (like parametric down conversion) are not perfect. They produce quantum states that contain more than only one photon pair with some probability. In this paper it is discussed what happens if such…

Quantum Physics · Physics 2007-05-23 Miloslav Dusek , Kamil Bradler

Entangled photons are crucial resources for quantum information processing. Here, we present an ultrabright polarization-entangled photon source based on a periodically poled lithium niobate waveguide designed for practical quantum…

This paper presents a multi-stage, multi-photon quantum key distribution protocol based on the double-lock cryptography. It exploits the asymmetry in the detection strategies between the legitimate users and the eavesdropper. The security…

Quantum Physics · Physics 2016-07-14 Kam Wai Clifford Chan , Mayssaa El Rifai , Pramode K. Verma , Subhash Kak , Yuhua Chen

A two-step quantum key distribution protocol using frequency and polarization doubly entangled photons is proposed. In this protocol, information is encoded by a unitary operation on each of the two doubly entangled photons and sent from…

Quantum Physics · Physics 2007-10-09 Chuan Wang , Wan-Ying Wang , Li Xiao , Gui Lu Long

We report the generation of polarization-entangled photons, using a quantum dot single photon source, linear optics and photodetectors. Two photons created independently are observed to violate Bell's inequality. The density matrix…

Practical implementations of quantum cryptography use attenuated laser pulses as the signal source rather than single photons. The channels used to transmit are also lossy. Here we give a simple derivation of two beam-splitting attacks on…

Quantum Physics · Physics 2015-06-26 Mark Williamson , Vlatko Vedral

A pulsed source of energy-time entangled photon pairs pumped by a standard laser diode is proposed and demonstrated. The basic states can be distinguished by their time of arrival. This greatly simplifies the realization of 2-photon quantum…

Quantum Physics · Physics 2016-09-08 J. Brendel , N. Gisin , W. Tittel , H. Zbinden

We present a scheme for quantum secure direct communication with quantum encryption. The two authorized users use repeatedly a sequence of the pure entangled pairs (quantum key) shared for encrypting and decrypting the secret message…

Quantum Physics · Physics 2007-07-31 Xi-Han Li , Chun-Yan Li , Fu-Guo Deng , Ping Zhou , Yu-Jie Liang , Hong-Yu Zhou

In state-of-the-art quantum key distribution (QKD) systems, the main limiting factor in increasing the key generation rate is the timing resolution in detecting photons. Here, we present and experimentally demonstrate a strategy to overcome…

Quantum Physics · Physics 2021-07-29 Johannes Pseiner , Lukas Achatz , Lukas Bulla , Martin Bohmann , Rupert Ursin