Telecloning of Continuous Quantum Variables

Abstract

We propose entangled $(M+1\mathrm{})$-mode quantum states as a multiuser quantum channel for continuous-variable communication. Arbitrary quantum states can be sent via this channel simultaneously to $M$ remote and separated locations with equal minimum excess noise in each output mode. For a set of coherent-state inputs, the channel realizes optimal symmetric $1\to M$ cloning at a distance (“telecloning”). It also provides the optimal cloning of coherent states without the need of amplifying the state of interest. The generation of the multiuser quantum channel requires no more than two $10{log}_{10}\{(\sqrt{M}-1\mathrm{})/(\sqrt{M}+1\mathrm{})\}\mathrm{dB}$ squeezed states and $M$ beam splitters.