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Whether noisy quantum devices without error correction can provide quantum advantage over classical computers is a critical issue of current quantum computation. In this work, the random quantum circuits, which are used as the paradigm…

Quantum Physics · Physics 2022-12-07 Meng Zhang , Chao Wang , Shaojun Dong , Hao Zhang , Yongjian Han , Lixin He

Entanglement properties of Gaussian states of light as well as the security of continuous variable quantum key distribution with Gaussian states in free-space fading channels are studied. These qualities are shown to be sensitive to the…

Certifying quantum behavior from classically accessible data is essential for secure communication and scalable quantum technologies. While powerful certification methods such as Bell nonlocality and quantum steering exist, their…

Quantum superdense coding protocols enhance channel capacity by using shared quantum entanglement between two users. The channel capacity can be as high as 2 when one uses entangled qubits. However, this limit can be surpassed by using…

Quantum Physics · Physics 2019-05-09 Xiao-Min Hu , Yu Guo , Bi-Heng Liu , Yun-Feng Huang , Chuan-Feng Li , Guang-Can Guo

Transmission of quantum entanglement will play a crucial role in future networks and long-distance quantum communications. Quantum Key Distribution, the working mechanism of quantum repeaters and the various quantum communication protocols…

Quantum Physics · Physics 2013-10-08 Laszlo Gyongyosi

The emergence of quantum computing has introduced unprecedented security challenges to conventional cryptographic systems, particularly in the domain of optical communications. This research addresses these challenges by innovatively…

The exploitation of quantum coherence at the level of propagation represents a powerful paradigm for quantum communication networks. In this work, we show that the coherent superposition of spatially distinct communication links enables…

Quantum Physics · Physics 2026-05-14 Claudio Pellitteri , Rajiuddin Sk , Marcello Caleffi , Angela Sara Cacciapuoti

Generating multiple entangled qubit pairs between distributed nodes is a prerequisite for a future quantum internet. To achieve a practicable generation rate, standard protocols based on photonic qubits require multiple long-term quantum…

Quantum Physics · Physics 2022-11-17 Yunzhe Zheng , Hemant Sharma , Johannes Borregaard

In this paper, we show that there are instances where eavesdropping causes noise reduction for a quantum key distribution (QKD) protocol. To witness these phenomena, we investigate a fault-tolerant six-state QKD protocol over a collective…

Quantum Physics · Physics 2023-07-18 Hiroo Azuma

Fiber-based quantum communication networks are currently limited without quantum repeaters. Satellite-based quantum links have been proposed to extend the network domain. We have developed a quantum communication system, suitable for…

Quantum Physics · Physics 2022-10-27 Joseph C. Chapman , Charles C. W. Lim , Paul G. Kwiat

An energy-time entanglement-based dispersive optics quantum key distribution (DO-QKD) is demonstrated experimentally over optical fibers of 20 km. In the experiment, the telecom band energy-time entangled photon pairs are generated through…

Quantum Physics · Physics 2019-04-30 Xu Liu , Xin Yao , Heqing Wang , Hao Li , Zhen Wang , Lixing You , Yidong Huang , Wei Zhang

We develop a theory for long-distance quantum key distribution based on concatenated entanglement swapping using parametric down-conversion sources and show numerical results of our model. The model incorporates practical resources…

Quantum Physics · Physics 2016-02-09 Aeysha Khalique , Barry C. Sanders

We introduce a new relativistic orthogonal states quantum key distribution protocol which leverages the properties of both quantum mechanics and special relativity to securely encode multiple bits onto the spatio-temporal modes of a single…

Quantum Physics · Physics 2014-06-12 Jordan S. Cotler , Peter W. Shor

High-dimensional entanglement offers promising perspectives in quantum information science. In practice, however, the main challenge is to devise efficient methods to characterize high-dimensional entanglement, based on the available…

Addition of single photons to two-mode-squeezed-vacuum states has the effect of distilling quantum entanglement, and, when deployed in quantum key distribution, should lead also to an increase in the secret key rate. However, the extraction…

Quantum Physics · Physics 2025-07-25 Hao Jeng , Ping Koy Lam , Syed M. Assad

Quantum key distribution (QKD) refers to specific quantum strategies which permit the secure distribution of a secret key between two parties that wish to communicate secretly. Quantum cryptography has proven unconditionally secure in ideal…

Quantum Physics · Physics 2008-10-14 C. Rodó , O. Romero-Isart , K. Eckert , A. Sanpera

Free-space quantum cryptography plays an integral role in realizing a global-scale quantum internet system. Compared to fiber-based communication networks, free-space networks experience significantly less decoherence and photon loss due to…

Quantum Physics · Physics 2023-05-03 Md Mehdi Hassan , Kazi Reaz , Adrien Green , Noah Crum , George Siopsis

We present a complete protocol for BB84 quantum key distribution for a realistic setting (noise, loss, multi-photon signals of the source) that covers many of todays experimental implementations. The security of this protocol is shown…

Quantum Physics · Physics 2007-07-10 Hitoshi Inamori , Norbert Lütkenhaus , Dominic Mayers

Quantum networks have been shown to connect users with full-mesh topologies without trusted nodes. We present advancements on our scalable polarisation entanglement-based quantum network testbed, which has the ability to perform protocols…

Standard quantum key distribution (QKD) protocols typically assume that the distant parties share a common reference frame. In practice, however, establishing and maintaining a good alignment between distant observers is rarely a trivial…

Quantum Physics · Physics 2014-04-04 Joshua A. Slater , Cyril Branciard , Nicolas Brunner , Wolfgang Tittel