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Quantum Networks
Published in Jonathan P. Dowling, Schrödinger’s Web, 2020
Alice then uses two quantum gates to entangle her two quantum-encoded bits with her half of the ebit. She then sends her half of the ebit, thus modified, to Bob. Bob then performs two more quantum gates and – hey presto! – out pops Alice’s two classical bits. If the ebits are free and the gates are free, then they transmit two classical bits for the price of one, thus doubling the classical transmission rate. Here’s where it gets weird. Bob can’t extract the classical bits unless he has both of qubits in the ebit. An eavesdropper cannot tap this classical communication channel unless she has access to both Alice and Bob’s labs. In addition to doubling the transmission rate, super-dense coding is a type of quantum cryptosystem. Alice’s two bits are the plaintext, and the encoding into the ebit is the cyphertext.
Quantum Theory
Published in Paul L. Goethals, Natalie M. Scala, Daniel T. Bennett, Mathematics in Cyber Research, 2022
We now consider the problem of using quantum technology to transmit classical information. The protocol we will follow is called superdense coding. It is dual to quantum teleportation in the following sense: while quantum teleportation allows us to transmit a single qubit using only entanglement and the transmission of two classical bits, superdense coding allows us to transmit two classical bits using only entanglement and the transmission of a single qubit.
Quantum Computer
Published in Shabnam Siddiqui, Quantum Mechanics, 2018
Superdense coding is an example of the use of quantum properties where quantum information can be transmitted in a way that classical information cannot. The idea is to transmit a maximum amount of information by employing a minimum number of qubits.
Quantifying quantumness of correlations using Gaussian Rényi-2 entropy in optomechanical interfaces
Published in Journal of Modern Optics, 2018
J. El Qars, M. Daoud, R. Ahl Laamara
It is well believed that entanglement is a very important ingredient for quantum information processing and quantum communication tasks that cannot be done efficiently classically [1]. It plays a central role in several tasks such as, quantum teleportation, quantum key distribution and superdense coding [2,3]. Previously, any correlation without entanglement was thought to be purely classical as they can be produced with local operations and classical communications [4]. However, it has been shown in many theoretical [5] and experimental [6] works that separable(unentangled) states, traditionally referred to as classically correlated, might retain some signatures of quantumness with potential operational applications for quantum tasks [4,7]. For example, quantum correlations without entanglement were shown to be useful to characterize resources in [8]: a quantum computational model; quantum state merging; remote state preparation; encoding information onto a quantum state; quantum phase estimation; and quantum key distribution. In general, entanglement is difficult to generate, more fragile and rapidly decays to zero in dissipative-noisy systems [9]. Conversely, it has been pointed out that quantum correlations without entanglement are robust, exhibiting some peculiar features against Markovian decoherence [4]. We can cite for instance [10]: they can never suffer the sudden death; within a dissipative-noisy systems, they can reach an asymptotic nonzero value (i.e. freezing behaviour) even for high temperatures; they can exhibit a sudden change from the classical decoherence regime to the quantum decoherence regime. Such interesting properties make, therefore, this kind of quantum correlations more desirable resource in quantum information processing, opening new avenues for theoretical exploration and practical applications [4].