Information cloning of harmonic oscillator coherent states

G. Dattoli, A. Torre, S. Lorenzutta +1 more

Rainer Dick

N. D. Hari Dass

We give an alternative formulation of the no-cloning theorem that applies to harmonic oscillator coherent states. It says that {\em unknown} single harmonic oscillator coherent states can not be {\em amplified}. Conversely it says that {\em known} harmonic oscillator coherent states can be directly amplified through an universal unitary process. It is also shown that such a formulation is needed for the consistency of {\em information cloning} proposed by us long ago.

N. D. Hari Dass, Pradeep Ganesh

We show that in the case of unknown {\em harmonic oscillator coherent states} it is possible to achieve what we call {\it perfect information cloning}. By this we mean that it is still possible to make arbitrary number of copies of a state which has {\it exactly} the same information content as the original unknown coherent state. By making use of this {\it perfect information cloning} it would be possible to estimate the original state through measurements and make arbitrary number of copies of the estimator. We define the notion of a {\em Measurement Fidelity}. We show that this information cloning gives rise, in the case of $1\to N$, to a {\em distribution} of {\em measurement fidelities} whose average value is ${1\over 2}$ irrespective of the number of copies originally made. Generalisations of this to the $M\to MN$ case as well as the measurement fidelities for Gaussian cloners are also given.

Rainer Dick

Ardeshir Rabeie, Ardalan Fatahizadeh

In this paper, we reproduce the harmonic oscillator bipartite coherent states with imperfect cloning of coherent states. We show that if these entangled coherent states are embedded in a vacuum environment, their entanglement is degraded but not totally lost . Also, the optimal fidelity of these states is worked out for investigating their teleportation