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Measurements with photodetectors necessarily need to be described in the infinite dimensional Fock space of one or several modes. For some measurements a model has been postulated which describes the full mode measurement as a composition…

Quantum Physics · Physics 2008-09-17 Normand J. Beaudry , Tobias Moroder , Norbert Lütkenhaus

The squash operation, or the squashing model, is a useful mathematical tool for proving the security of quantum key distribution systems using practical (i.e., non-ideal) detectors. At the present, however, this method can only be applied…

Quantum Physics · Physics 2016-10-26 Toyohiro Tsurumaru , Tsubasa Ichikawa

Security analyses in quantum key distribution (QKD) and other adversarial quantum tasks often assume perfect device models. However, real-world implementations often deviate from these models. Thus, it is important to develop security…

Quantum Physics · Physics 2026-03-25 Shlok Nahar , Devashish Tupkary , Norbert Lütkenhaus

We work out a classification scheme for quantum modeling in Hilbert space of any kind of composite entity violating Bell's inequalities and exhibiting entanglement. Our theoretical framework includes situations with entangled states and…

Quantum Physics · Physics 2015-12-31 Diederik Aerts , Sandro Sozzo

Useful relations describing arbitrary parameters of given quantum systems can be derived from simple physical constraints imposed on the vectors in the corresponding Hilbert space. This is well known and it usually proceeds by partitioning…

Quantum Physics · Physics 2022-10-18 Chinonso Onah

Distributed computing seems to be a natural approach to overcome size limitations of quantum computers in terms of number of qubits. But one lacks an efficient distribution approach to deal systematically with potential algorithms. This…

Quantum Physics · Physics 2012-08-21 Iaakov Exman , Efrat Levy

Quantum key distribution (QKD) is a secure communication method that utilizes the principles of quantum mechanics to establish secret keys. The central task in the study of QKD is to prove security in the presence of an eavesdropper with…

Quantum Physics · Physics 2023-09-14 Sirui Peng , Xiaoming Sun , Hongyi Zhou

We imagine an experiment on an unknown quantum mechanical system in which the system is prepared in various ways and a range of measurements are performed. For each measurement M and preparation rho the experimenter can determine, given…

Quantum Physics · Physics 2009-01-20 Stephanie Wehner , Matthias Christandl , Andrew C. Doherty

Recent development in quantum information sciences and technologies, especially building programmable quantum computers, provide us new opportunities to study fundamental aspects of quantum mechanics. We propose qubit models to emulate the…

Quantum Physics · Physics 2022-06-29 Meng-Jun Hu , Yanbei Chen , Yiqiu Ma , Xiang Li , Yubao Liu , Yong-Sheng Zhang , Haixing Miao

A Hilbert space embedding of a distribution---in short, a kernel mean embedding---has recently emerged as a powerful tool for machine learning and inference. The basic idea behind this framework is to map distributions into a reproducing…

Machine Learning · Statistics 2020-12-15 Krikamol Muandet , Kenji Fukumizu , Bharath Sriperumbudur , Bernhard Schölkopf

Many protocols and experiments in quantum information science are described in terms of simple measurements on qubits. However, in a real implementation, the exact description is more difficult, and more complicated observables are used.…

Quantum Physics · Physics 2010-09-28 Tobias Moroder , Otfried Gühne , Normand J. Beaudry , Marco Piani , Norbert Lütkenhaus

A quantum key distribution and identification protocol is proposed, which is based on entanglement swapping. Through choosing particles by twos from the sequence and performing Bell measurements, two communicators can detect eavesdropping,…

Quantum Physics · Physics 2007-05-23 Fei Gao , Fenzhuo Guo , Qiaoyan Wen , Fuchen Zhu

Quantum classifiers are trainable quantum circuits used as machine learning models. The first part of the circuit implements a quantum feature map that encodes classical inputs into quantum states, embedding the data in a high-dimensional…

Quantum Physics · Physics 2022-07-03 Seth Lloyd , Maria Schuld , Aroosa Ijaz , Josh Izaac , Nathan Killoran

The squashed entanglement is a fundamental entanglement measure in quantum information theory, finding application as an upper bound on the distillable secret key or distillable entanglement of a quantum state or a quantum channel. This…

Quantum Physics · Physics 2018-01-09 Mark M. Wilde

The transmission of photons through open-air or an optical fiber is an important primitive in quantum information processing. Theoretical description of such a transmission process often considers only a single photon as the information…

Quantum Physics · Physics 2011-09-06 Chi-Hang Fred Fung , H. F. Chau , Hoi-Kwong Lo

We present a detailed description of a widely applicable mathematical model for quantum key distribution (QKD) systems implementing the measurement-device-independent (MDI) protocol. The model is tested by comparing its predictions with…

Quantum Physics · Physics 2014-05-22 Philip Chan , Joshua A. Slater , Itzel Lucio-Martinez , Allison Rubenok , Wolfgang Tittel

In this project we examine several different quantum key distribution protocols which we divide into ones utilizing qubits whose Hilbert spaces are two dimensional and ones whose Hilbert space dimension is greater than two, these units of…

Quantum Physics · Physics 2024-02-05 Yuval Idan , Avihai Didi

The security of device-independent (DI) quantum key distribution (QKD) protocols relies on the violation of Bell inequalities. As such, their security can be established based on minimal assumptions about the devices, but their…

Quantum Physics · Physics 2015-10-08 Erik Woodhead , Stefano Pironio

Many quantum key distribution (QKD) schemes are based on sending and measuring qubits -- two-dimensional quantum systems. Yet, in practical realizations and experiments, the measuring devices at the receiver's (Bob) site commonly do not…

Quantum Physics · Physics 2016-05-23 Ran Gelles , Tal Mor

Theoretical quantum key distribution (QKD) protocols commonly rely on the use of qubits (quantum bits). In reality, however, due to practical limitations, the legitimate users are forced to employ a larger quantum (Hilbert) space, say a…

Quantum Physics · Physics 2007-11-25 Ran Gelles , Tal Mor
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