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We propose and demonstrate a quantum key distribution scheme in higher-order $d$-dimensional alphabets using spatial degrees of freedom of photons. Our implementation allows for the transmission of 4.56 bits per sifted photon, while…

Quantum Physics · Physics 2009-11-11 S. P. Walborn , D. S. Lemelle , M. P. Almeida , P. H. Souto Ribeiro

The decoy-state method is widely used in practical quantum key distribution systems to replace ideal single photon sources with realistic light sources by varying intensities. Instead of active modulation, the passive decoy-state method…

We analyse the distribution of secure keys using quantum cryptography based on the continuous variable degree of freedom of entangled photon pairs. We derive the information capacity of a scheme based on the spatial entanglement of photons…

Quantum Physics · Physics 2009-11-13 Lijian Zhang , Christine Silberhorn , Ian A. Walmsley

We analyze the performance of on-off keying (OOK) and its restricted version pulse position modulation (PPM) over a lossy narrowband optical channel under the constraint of a low average photon number, when direct detection is used at the…

Quantum Physics · Physics 2015-02-05 Marcin Jarzyna , Piotr Kuszaj , Konrad Banaszek

Quantum key distribution (QKD) is an important branch of quantum information science as it holds promise for unconditionally secure communication. For QKD research, a central issue is to improve the final secure key rate (SKR) and the…

Quantum Physics · Physics 2021-11-23 Hao-Kun Mao , Qiang Zhao , Yu-Cheng Qiao , Bing-Ze Yan , Bing-Jie Xu , Ahmed A. Abd EL-Latif , Qiong Li

We present and demonstrate a new protocol for practical quantum cryptography, tailored for an implementation with weak coherent pulses to obtain a high key generation rate. The key is obtained by a simple time-of-arrival measurement on the…

Quantum Physics · Physics 2009-11-11 Damien Stucki , Nicolas Brunner , Nicolas Gisin , Valerio Scarani , Hugo Zbinden

We present a practical method that can make quantum key distribution (QKD), for the first time, both ultra-long-distance and immune to all attacks in the detection system. This method is an important extension of the…

Quantum Physics · Physics 2013-08-22 Feihu Xu , Bing Qi , Zhongfa Liao , Hoi-Kwong Lo

To beat PNS attack, decoy state quantum key distribution (QKD) based on coherent state has been studied widely. We present a decoy state QKD protocol with modified coherent state (MCS). By destruction quantum interference, MCS with fewer…

Quantum Physics · Physics 2009-11-13 Zhen-Qiang Yin , Zheng-Fu Han , Fang-Wen Sun , Guang-Can Guo

We analyze theoretically the impact of background counts on the efficiency of optical communication in the photon-starved regime using the pulse position modulation (PPM) format with direct detection. Degradation of the photon information…

Quantum Physics · Physics 2018-05-25 Marcin Jarzyna , Konrad Banaszek

Quantum key distribution (QKD) has convincingly been proven compatible with real life applications. Its wide-scale deployment in optical networks will benefit from an optical platform that allows miniature devices capable of encoding the…

The ability to engineer the spatial wavefunction of photons has enabled a variety of quantum protocols for communication, sensing, and information processing. These protocols exploit the high dimensionality of structured light enabling the…

Quantum cryptography has attracted much recent attention due to its potential for providing secret communications that cannot be decrypted by any amount of computational effort. This is the first analysis of the secrecy of a practical…

Quantum Physics · Physics 2007-05-23 G. Gilbert , M. Hamrick

We report on the first real-time implementation of a quantum key distribution (QKD) system using entangled photon pairs that are sent over two free-space optical telescope links. The entangled photon pairs are produced with a type-II…

Quantum Physics · Physics 2012-10-25 C. Erven , C. Couteau , R. Laflamme , G. Weihs

In this Letter, we prove the unconditional security of single-photon differential phase shift quantum key distribution (DPS-QKD) protocol, based on the conversion to an equivalent entanglement-based protocol. We estimate the upper bound of…

Quantum Physics · Physics 2009-10-23 Kai Wen , Kiyoshi Tamaki , Yoshihisa Yamamoto

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

The original proposal of quantum key distribution (QKD) was based on ideal single photon sources, which 40 years later, are still challenging to develop. Therefore, the development of decoy state protocols using weak coherent states (WCS)…

In recent years, there has been a great effort to prove the security of quantum key distribution (QKD) with a minimum number of assumptions. Besides its intrinsic theoretical interest, this would allow for larger tolerance against device…

Quantum Physics · Physics 2018-03-28 Kiyoshi Tamaki , Marcos Curty , Marco Lucamarini

Decoy State Quantum Key Distribution (QKD), being capable of beating PNS attack and uncon- ditionally secure, have become an attractive one recently. But, in many QKD systems, disturbances of transmission channel make quantum bit error rate…

Quantum Physics · Physics 2009-11-13 Zhen-Qiang Yin , Zheng-Fu Han , Wei Chen , Fang-Xing Xu , Qing-Lin Wu , Guang-Can Guo

Single-photon sources are essential for quantum networks, enabling applications ranging from quantum key distribution (QKD) to the burgeoning quantum internet. Despite the remarkable advancements, the current reliance of QKD on attenuated…

Quantum light sources emitting triggered single photons or entangled photon pairs have the potential to boost the performance of quantum key distribution (QKD) systems. Proof-of-principle experiments affirmed these prospects, but further…