All communication channels are at bottom quantum mechanical. Quantum mechanics contributes both obstacles to communication in the form of noise, and opportunities in the use of intrinsically quantum representations for information. This paper investigates the trade-off between power and communication rate for coupled quantum channels. By exploiting quantum correlations such as entanglement, cou...

The communication complexity of a quantum channel is the minimal amount of classical communication required for classically simulating the process of preparation, transmission through the channel, and subsequent measurement of a quantum state. At present, only little is known about this quantity. In this Letter, we present a procedure for systematically evaluating the communication complexity o...

The possibility of totally secure communication through the application of quantum mechanical properties was introduced in 1984 by Bennett and Brassard in their paper, “Quantum Cryptography: Public Key Distribution and Coin Tossing”. As Bennett and Brassard outlined, quantum communication makes it impossible for an eavesdropper to intercept a message without detection by the desired parties. Th...

The crucial issue of quantum communication protocol is its security. A quantum communication scheme must be based on the existing or nearly existing technology, but its security must be guaranteed against an eavesdropper whose technology is limited only by the laws of quantum mechanics. In this paper, we show that all the deterministic and direct two-way quantum communication protocols, sometim...