In this paper, we report on experimental demonstration of the propagation and self-healing property of Bessel-Gaussian (BG) beam carrying orbital angular momentum (OAM) in an underwater environment. Especially, the effects of topological charge, temperature gradient, and salinity on the transmission and self-reconstruction of BG beam in underwater turbulence are analyzed. The results show that the detection probabilities both for propagation and self-healing greatly decrease with temperature gradient, and gradually decrease with salinity. BG beam has a self-healing property in the underwater environment when the obstruction is quite small. The detection probability greatly decreases with obstruction size, while it gradually decreases with salinity fluctuations for different obstruction sizes. For the same blockage ratio, the smaller topological charge of BG beam is, the better self-healing characteristics the BG beam has.
he entanglement-assisted stabilizer formalism provides a useful framework for constructing quantum error-correcting codes (QECC), which can transform arbitrary classical linear codes into entanglement-assisted quantum error correcting codes (EAQECCs) by using pre-shared entanglement between the sender and the receiver. In this paper, we construct five classes of entanglement-assisted quantum MDS (EAQMDS) codes based on classical MDS codes by exploiting one or more pre-shared maximally entangled states. We show that these EAQMDS codes have much larger minimum distance than the standard quantum MDS (QMDS) codes of the same length, and three classes of these EAQMDS codes consume only one pair of maximally entangled states.
Abstract. Recently, Liu et al. [Commun. Theor. Phys. 57, 583, 2012] proposed a quantum private comparison protocol based on entanglement swapping of Bell states, which aims to securely compare the equality of two participants' information with the help of a semi-honest third party (TP). However, this study points out there is a fatal loophole in this protocol, i.e., TP can obtain all of the two participants secret inputs without being detected through making a specific Bell-basis measurement. To fix the problem, a simple solution, which uses one-time eavesdropper checking with decoy photons instead of twice eavesdropper checking with Bell states, is demonstrated. Compared with the original protocol, it also reduces the Bell states consumption and simplifies the steps in the protocol.PACS numbers: 03.65. Ta, 03.67.Dd, 03.67.Lx Keywords: Quantum private comparison, Bell states, Entanglement swapping, TP's measurement attack, ImprovementCryptanalysis and improvement of the quantum private comparison protocol based on Bell entangled states2
The problem of definite information leakage existing in the controlled bidirectional quantum direct communication protocol using GHZ states [Chin. Phys. Lett. 23 (2006) 1680] was pointed out by Ye and Jiang [Chin. Phys. Lett. 30 (2013) 040305]. Then, they proposed two strategies to improve this security bug. However, if the revised versions are analyzed from the viewpoint of information theory, it can be found that they still have the problem of information leakage. That is, three quarters and one half of the information interchanged by the communication parties are leaked out unknowingly in the first and second revised protocols, respectively.
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