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We describe a general quantum receiver protocol that maps laser-light-modulated classical communications signals into quantum processors for decoding with quantum logic. The quantum logic enables joint quantum measurements over a codeword…

Quantum Physics · Physics 2026-03-16 Kelly Werker Smith , Don Boroson , Saikat Guha , Johannes Borregaard

We present an algorithm for calculation of the Gaussian classical capacity of a quantum bosonic memory channel with additive Gaussian noise. The algorithm, restricted to Gaussian input states, is applicable to all channels with noise…

Quantum Physics · Physics 2015-03-17 Joachim Schäfer , Evgueni Karpov , Nicolas J. Cerf

The quantum bits (qubits) on which superconducting quantum computers are based have energy scales corresponding to photons with GHz frequencies. The energy of photons in the gigahertz domain is too low to allow transmission through the…

We explore covert communication of qubits over the lossy thermal-noise bosonic channel, which is a quantum-mechanical model of many practical channels, including optical. Covert communication ensures that an adversary is unable to detect…

Is quantum communication possible over an optical fibre with transmissivity $\lambda\leq 1/2$ ? The answer is well known to be negative if the environment with which the incoming signal interacts is initialised in a thermal state. However,…

Quantum Physics · Physics 2025-12-29 Francesco Anna Mele , Ludovico Lami , Vittorio Giovannetti

The optimal rate of reliable communication over a quantum channel can be enhanced by pre-shared entanglement. Whereas the enhancement may be unbounded in infinite-dimensional settings even when the input power is constrained, a…

Noise is often regarded as anathema to quantum computation, but in some settings it can be an unlikely ally. We consider the problem of learning the class of $n$-bit parity functions by making queries to a quantum example oracle. In the…

Quantum Physics · Physics 2015-08-05 Andrew W. Cross , Graeme Smith , John A. Smolin

Quantum machine learning models have the potential to offer speedups and better predictive accuracy compared to their classical counterparts. However, these quantum algorithms, like their classical counterparts, have been shown to also be…

Quantum Physics · Physics 2021-05-27 Maurice Weber , Nana Liu , Bo Li , Ce Zhang , Zhikuan Zhao

A simple method to enhance the quality of communication is to send a carrier with its copies. Classical information theory says that information behaves quantitatively under copying. In other words, if a carrier is more informatic than…

Quantum Physics · Physics 2020-09-04 Jisho Miyazaki

The mechanism of extraction of information stored in a quantum memory is studied here in detail. We consider memories containing a single excitation of a collective atomic state, which is mapped into a single photon during the reading…

Quantum Physics · Physics 2013-09-16 Milrian S. Mendes , Pablo L. Saldanha , José W. R. Tabosa , Daniel Felinto

Recently, increased computational power and data availability, as well as algorithmic advances, have led machine learning techniques to impressive results in regression, classification, data-generation and reinforcement learning tasks.…

We show that the amount of coherent quantum information that can be reliably transmitted down a dephasing channel with memory is maximized by separable input states. In particular, we model the channel as a Markov chain or a multimode…

Quantum Physics · Physics 2007-09-09 Antonio D'Arrigo , Giuliano Benenti , Giuseppe Falci

Quantum capacity gives the fundamental limit of information transmission through a channel. However, evaluating the quantum capacities of a continuous-variable bosonic quantum channel, as well as finding an optimal code to achieve the…

Quantum Physics · Physics 2025-10-03 Adam Taylor , Michael Hanks , Hyukjoon Kwon , M. S. Kim

Quantum batteries are anticipated to achieve significant advancements in energy storage capacity. In classical batteries, the energy density at each subsystem reaches its maximum value, denoted as $E_C$, which is determined by dividing the…

Quantum Physics · Physics 2025-06-25 Masahiro Hotta , Kazuki Ikeda

Nonclassical correlations between the quadrature-phase amplitudes of two spatially separated optical beams are exploited to realize a two-channel quantum communication experiment with a high degree of immunity to interception. For this…

Quantum Physics · Physics 2009-11-06 S. F. Pereira , Z. Y. Ou , H. J. Kimble

Shannon's channel coding theorem describes the maximum possible rate of reliable information transfer through a classical noisy communication channel. It, together with the source coding theorem, characterizes lossless channel communication…

Quantum Physics · Physics 2021-05-17 Sristy Agrawal , Rajashik Tarafder , Graeme Smith , Arup Roy , Manik Banik

Recent years have seen significant activity on the problem of using data for the purpose of learning properties of quantum systems or of processing classical or quantum data via quantum computing. As in classical learning, quantum learning…

Quantum Physics · Physics 2024-04-17 Leonardo Banchi , Jason Luke Pereira , Sharu Theresa Jose , Osvaldo Simeone

We calculate the entanglement-assisted classical capacity of symmetric and asymmetric Pauli channels where two consecutive uses of the channels are correlated. It is evident from our study that in the presence of memory, a higher amount of…

Quantum Physics · Physics 2009-11-13 Nigum Arshed , A. H. Toor

Quantum sensing is an important application of emerging quantum technologies. We explore whether a hybrid system of quantum sensors and quantum circuits can surpass the classical limit of sensing. In particular, we use optimization…

Transmitting data reliably over noisy communication channels is one of the most important applications of information theory, and well understood when the channel is accurately modelled by classical physics. However, when quantum effects…

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