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Quantum key distribution (QKD) enables unconditionally secure communication ensured by the laws of physics, opening a promising route to security infrastructure for the coming age of quantum computers. QKD's demonstrated secret-key rates…

Quantum Physics · Physics 2017-12-15 Zheshen Zhang , Changchen Chen , Quntao Zhuang , Franco N. C. Wong , Jeffrey H. Shapiro

We assess the overall performance of our quantum key distribution (QKD) system implementing the measurement-device-independent (MDI) protocol using components with varying capabilities such as different single photon detectors and qubit…

The single photon detection efficiency of the detector unit is crucial for the security of common quantum key distribution protocols like Bennett-Brassard 1984 (BB84). A low value for the efficiency indicates a possible eavesdropping attack…

Quantum Physics · Physics 2018-06-20 Øystein Marøy , Vadim Makarov , Johannes Skaar

The quantum bit error rate is a key quantity in quantum communications. If the quantum channel is the atmosphere, the information is usually encoded in the polarization of a photon. A link budget is required, which takes into account the…

We have demonstrated quantum key distribution (QKD) over a 10-km, 1-airmass atmospheric range during daylight and at night. Secret random bit sequences of the quality required for the cryptographic keys used to initialize secure…

Quantum Physics · Physics 2009-11-07 Richard J. Hughes , Jane E. Nordholt , Derek Derkacs , Charles G. Peterson

Employing the fundamental laws of quantum physics, Quantum Key Distribution (QKD) promises the unconditionally secure distribution of cryptographic keys. However, in practical realisations, a QKD protocol is only secure, when the quantum…

Quantum Physics · Physics 2011-12-07 Muhammad Mubashir Khan , Jie Xu , Almut Beige

We address a continuous-variable quantum key distribution (CV-QKD) protocol employing quaternary phase-shift-keying (QPSK) of coherent states and a non-Gaussian measurement inspired by quantum receivers minimizing the error probability in a…

Quantum Physics · Physics 2023-10-13 Michele N. Notarnicola , Marcin Jarzyna , Stefano Olivares , Konrad Banaszek

The decoy state protocol has been considered to be one of the most important methods to protect the security of quantum key distribution (QKD) with a weak coherent source. Here we test two experimental approaches to generating the decoy…

Quantum Physics · Physics 2018-09-18 Anqi Huang , Shi-Hai Sun , Zhihong Liu , Vadim Makarov

Coherent one photon pulses are sent with four possible time delays with respect to a reference. Ambiguity of the photon time detection resulting from pulses overlap combined with interferometric measurement allows for secure key exchange.

Quantum Physics · Physics 2007-05-23 Thierry Debuisschert , William Boucher

We present a scalable star-shaped quantum key distribution (QKD) optical fiber network. We use wavelength-division demultiplexing (WDM) of broadband photon pairs to establish key exchange between multiple pairs of participants…

We present two new schemes for quantum key distribution (QKD) that neither require entanglement nor an ideal single-photon source, making them implementable with commercially available single-photon sources. These protocols are shown to be…

Quantum Physics · Physics 2025-05-13 Arindam Dutta , Anirban Pathak

In this paper, we present a Quantum Key Distribution (QKD) protocol that accounts for fundamental practical challenges, including chromatic dispersion, time measurement uncertainty, and dark counts. Our analysis provides a comprehensive…

Quantum Physics · Physics 2024-10-16 Artur Czerwinski , Saeed Haddadi

We propose and experimentally demonstrate a new scheme for measuring high-dimensional phase states using a two-photon interference technique, which we refer to as quantum-controlled measurement. Using this scheme, we implement a…

We implement an InGaAs/InP single-photon avalanche diode (SPAD) for single-photon detection with the fastest gating frequency reported so far, of 2.23 GHz, which approaches the limit given by the bandwidth of the SPAD - 2.5 GHz. We propose…

Quantum Physics · Physics 2010-04-29 Jun Zhang , Patrick Eraerds , Nino Walenta , Claudio Barreiro , Rob Thew , Hugo Zbinden

A key goal of quantum communication is to determine the maximum number of bits shared between two quantum systems. An important example of this is in entanglement based quantum key distribution (QKD) schemes. A realistic treatment of this…

Quantum Physics · Physics 2015-06-04 Thomas Brougham , Stephen M. Barnett

Quantum key distribution (QKD) promises information theoretic secure key as long as the device performs as assumed in the theoretical model. One of the assumptions is an absence of information leakage about individual photon detection…

We propose an efficient quantum key distribution scheme based on entanglement. The sender chooses pairs of photons in one of the two equivalent nonmaximally entangled states randomly, and sends a sequence of photons from each pair to the…

Quantum Physics · Physics 2009-11-07 Peng Xue , Chuan-Feng Li , Guang-Can Guo

In this article, we experimentally demonstrate an eavesdropper's (Eve's) information gain by exploiting the breakdown flash generated by the single photon avalanche detector (SPAD) used in coherent one-way quantum key distribution (COW-QKD)…

Quantum Physics · Physics 2025-05-07 Ashutosh Kumar Singh , Nilesh Sharma , Vaibhav Pratap Singh , Anil Prabhakar

A typical implementation of BB84 protocol for quantum communication uses four laser diodes for transmitting weak coherent pulses, which may not have the same characteristics. We have characterized these lasers for mismatch in various…

Quantum Physics · Physics 2021-10-11 Ayan Biswas , Anindya Banerji , Pooja Chandravashi , Rupesh Kumar , Ravindra P. Singh

Quantum key distribution (QKD) is nowadays a well established method for generating secret keys at a distance in an information-theoretic secure way, as the secrecy of QKD relies on the laws of quantum physics and not computational…