Experimental System for Quantum Cryptography Based on Two Nonorthogonal Photon Polarization States

Abstract

Quantum cryptography allows the establishing o f a highly confidential sequence of random bits between two parties who share no secret information in advance. Its security is guaranteed by the basic laws o f quantum mechanics rather than mathematical difficulty. A n experimental system based on a novel protocol for quantum cryptography using only two nonorthogonal photon polarization states is implemented. The photon sources are two semiconductor laser diodes operated at 680 n m , their light pulses which are heavily attenuated to far below one photon per pulse are employed t o encode the key. Gated single photon detection technique is used t o minimize the dark count effect o f the photon multiplier tube. Key establishing rate of 40 b/s and error rate o f 2.1 % are obtained. Compared with other systems, our system has the simplest experimental setup.

Several teleportation schemes of an arbitrary unknown multi-particle state via different quantum channels

“…After Bennett et al [1] proposed the teleportation theory, quantum teleportation has been playing an important role in the rapidly evolving fields of quantum information and quantum communications. It may have applications in quantum cryptography, [2][3][4] quantum computing, [5,6] and quantum dense coding. [7] Moving beyond the teleportation of one-particle or two-particle unknown states, some previous studies have focused on the teleportation of a multi-particle state, [8][9][10][11] probabilistic teleportation, [12,13] and controlled teleportation.…”

Quantum logical networks for probabilistic teleportation of many particle state of general form

“…It can be used to transmit information reliably in noisy situations where a message would otherwise be degraded, and to transfer information from fleeting or hard-to-control carriers to particles more suitably for permanent storage. Moreover, it has application in quantum cryptography and quantum dense coding [4][5][6][7][8].…”