We present the wavelength attack on a practical continuous-variablequantum-key-distribution system with a heterodyne protocol, in which thetransmittance of beam splitters at Bob's station is wavelength-dependent. Ourstrategy is proposed independent of but analogous to that of Huang et al.[arXiv: 1206.6550v1 [quant-ph]], but in that paper the shot noise of the twobeams that Eve sends to Bob, transmitting after the homodyne detector, isunconsidered. However, shot noise is the main contribution to the deviation ofBob's measurements from Eve's when implementing the wavelength attack, so itmust be considered accurately. In this paper, we firstly analyze the solutionsof the equations specifically that must be satisfied in this attack, which isnot considered rigorously by Huang et al. Then we calculate the shot noise ofthe homodyne detector accurately and conclude that the wavelength attack can beimplemented successfully in some parameter regime.
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