Tightening the eavesdropping accessible information for continuous variable quantum key distribution protocols that involve non-maximally entanglement

This paper has been withdrawn.Comment: This paper has been withdraw

Phase coherent states for enhancing the performance of continuous variable quantum key distribution

In this paper, we present three continuous variable quantum key distribution protocols (named two-, four-, and eightstate protocols) based on the discrete modulation of phase coherent states. We investigate the security of these protocols against the collective eavesdropping attacks and show their performance in a realistic setup by taking into consideration the realistic lossy noisy quantum channels, and the imperfection of detection. We show that the use of phase coherent states gives better performance in terms of noise tolerance, key rate, and achievable distance than that of common linear coherent states

Continuous-variable quantum key distribution protocols with eight-state discrete modulation

We propose a continuous variable quantum key distribution protocol based on discrete modulation of eight-state coherent states. We present a rigorous security proof against the collective attacks by taking into consideration the realistic lossy and noisy quantum channel,the imperfect detector efficiency, and the detector electronic noise. This protocol shows high tolerance against excess noise and promises to achieve over 100km distance of optical fiber

Optical Gaussian Notch Filter Based on Periodic Microbent Fiber Bragg Grating

In this paper, we demonstrated an optical notch filter constructed from a periodic microbent fiber Bragg grating attained by using two copper-wire-wound slabs. In the reflection spectrum, sideband peaks are created as a result of mechanically induced modulation on the grating period, and a higher number of peaks are observed when greater modulation is applied. The peak wavelength spacing depends upon the period of microbending, which can be varied by changing the diameter of the winding wire or the angle of placement of fiber Bragg grating placed in between the two wound slabs. Moreover, the trend of Bragg transmission loss (BTL) for the transmission spectrum changes with the changing of modulation period and amplitude. The proposed technique is very stable, and it can be used as an optical Gaussian notch filter

Spectral analysis of bent fiber Bragg gratings: theory and experiment

This Letter presents a simple mathematical model developed from coupled-mode theory to describe the relationship between Bragg transmission loss (BTL), grating length, coupling coefficients, and bending loss in a bent fiber Bragg grating. In our investigation, the finding indicates that the decrement of BTL can be attributed to the increasing bending loss and degradation of both dc and ac coupling coefficients as the bending radius decreases. Besides, the center wavelength shifts as a result of coupling coefficients degradation. The validity of the proposed model is supported by experimental result