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Beam displacement measurements are widely used in optical sensing and communications; however, their performance is affected by numerous intrinsic and extrinsic factors including beam profile, propagation loss, and receiver architecture.…

Optics · Physics 2025-03-11 Wenhua He , Christos N. Gagatsos , Dalziel J. Wilson , Saikat Guha

We consider the effect of loss on quantum-optical communication channels. The channel based on direct detection of number states, which for a lossless transmission line would achieve the ultimate quantum channel capacity, is easily degraded…

Quantum Physics · Physics 2009-10-30 G. M. D'Ariano , M. F. Sacchi

Loss and decoherence are a major problem in the transmission of non-classical states of light over large distances. It was recently shown that the effects of decoherence can be reduced by applying a probabilistic noiseless attenuator before…

Quantum Physics · Physics 2018-09-19 R. A. Brewster , T. B. Pittman , J. D. Franson

In this paper we consider noisy index coding problem over AWGN channel. We give an algorithm to map the index coded bits to appropriate sized PSK symbols such that for the given index code, in general, the receiver with large amount of side…

Information Theory · Computer Science 2015-10-06 Anjana A. M. , B. Sundar Rajan

A scheme for the detection of low-intensity optical coherent signals was studied which uses a probabilistic amplifier operated in the non-heralded version, as the underlying non-linear operation to improve the detection efficiency. This…

Quantum Physics · Physics 2016-06-15 Matteo Rosati , Andrea Mari , Vittorio Giovannetti

A numerical security proof technique is used to analyse the security of continuous-variable quantum key distribution (CV-QKD) protocols with phase-shift keying modulation against collective attacks in the asymptotic limit. We argue why it…

Quantum Physics · Physics 2022-10-18 Florian Kanitschar , Christoph Pacher

We present a protocol in which sequential weak measurements of a quantum harmonic oscillator enable simultaneous estimation of both quadratures of a displacement channel. Calculations of the quantum Fisher information show that the…

Quantum Physics · Physics 2026-05-04 Koray Mentesoglu , Rahul Trivedi , Sara Mouradian

Post-processing is a significant step in quantum key distribution(QKD), which is used for correcting the quantum-channel noise errors and distilling identical corrected keys between two distant legitimate parties. Efficient error…

Quantum Physics · Physics 2019-05-09 Chaohui Gao , Dong Jiang , Liangliang Lu , Yu Guo , Lijun Chen

The performance of a wide range of quantum computing algorithms and protocols depends critically on the fidelity and speed of the employed qubit readout. Examples include gate sequences benefiting from mid-circuit, real-time,…

In this work, we consider optimal state discrimination for a quantum system that interacts with an environment, i.e., states evolve under a quantum channel. We show the conditions on a quantum channel and an ensemble of states such that a…

Quantum Physics · Physics 2019-06-12 Spiros Kechrimparis , Tanmay Singal , Chahan M. Kropf , Joonwoo Bae

Quantum control with restricted state access is central to near-term quantum devices, where full wave-function information is unavailable. We study this problem through multiqubit disentanglement scheduling from partial observations, where…

Quantum Physics · Physics 2026-05-01 Y. -X. Xiao , J. -Z. Han , Z. Zheng , Z. -H. Zhang , M. Xue , J. Li , X. Lv

In this paper, we study the sensitivity and robustness of Space Shift Keying (SSK) modulation to imperfect channel knowledge at the receiver. Unlike the common widespread belief, we show that SSK modulation is more robust to imperfect…

Performance · Computer Science 2016-11-18 Marco Di Renzo , Dario De Leonardis , Fabio Graziosi , Harald Haas

This paper presents a robust beam alignment technique for millimeter-wave communications in low signal-to-noise ratio (SNR) environments. The core strategy of our technique is to repeatedly transmit the most probable beam candidates to…

Information Theory · Computer Science 2023-12-05 Jihun Park , Yongjeong Oh , Jaewon Yun , Seonjung Kim , Yo-Seb Jeon

One of the most fascinating aspects of quantum mechanics is the principle impossibility of deterministic errorless discrimination of nonorthogonal signals, such as coherent states. On the one hand, it prevents perfect cloning of quantum…

Quantum Physics · Physics 2017-01-10 Denis Sych , Gerd Leuchs

Quantum state separation is a probabilistic map that transforms a given set of pure states into another set of more distinguishable ones. Here we investigate such a map acting onto uniparametric families of symmetric linearly dependent or…

Quantum Physics · Physics 2017-03-09 M. A. Solís-Prosser , A. Delgado , O. Jiménez , L. Neves

A key issue in physical-layer network coding (PNC) is how to deal with the asynchrony between signals transmitted by multiple transmitters. That is, symbols transmitted by different transmitters could arrive at the receiver with symbol…

Information Theory · Computer Science 2011-05-31 Lu Lu , Soung Chang Liew , Shengli Zhang

For space-based laser communications, when the mean photon number per received optical pulse is much smaller than one, there is a large gap between communications capacity achievable with a receiver that performs individual pulse-by-pulse…

Quantum Physics · Physics 2021-08-20 Narayanan Rengaswamy , Kaushik P. Seshadreesan , Saikat Guha , Henry D. Pfister

Index coded PSK modulation over an AWGN broadcast channel, for a given index coding problem (ICP) is studied. For a chosen index code and an arbitrary mapping (of broadcast vectors to PSK signal points), we have derived a decision rule for…

Information Theory · Computer Science 2017-03-10 Divya U. S. , B. Sundar Rajan

Current implementations of quantum key distribution (QKD) typically rely on prepare-and-measure (P&M) schemes. Unfortunately, these implementations are not completely secure, unless security proofs fully incorporate all imperfections of…

This paper studies noisy index coding problems over single-input single-output broadcast channels. The codewords from a chosen index code of length $N$ are transmitted after $2^N$-PSK modulation over an AWGN channel. In "Index Coded PSK…

Information Theory · Computer Science 2023-05-23 Navya Saxena , Anjana A. Mahesh , B. Sundar Rajan