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تسجيل مستخدم جديدInformation cloning of harmonic oscillator coherent states and its fidelity
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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 $1to N$, to a {em distribution} of {em measurement fidelities} whose average value is ${1over 2}$ irrespective of the number of copies originally made. Generalisations of this to the $Mto MN$ case as well as the measurement fidelities for Gaussian cloners are also given.
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We have withdrawn this paper due to a fatal flaw in eqn(38).
We present a new scheme for controlling the quantum state of a harmonic oscillator by coupling it to an anharmonic multilevel system (MLS) with first to second excited state transition frequency on-resonance with the oscillator. In this scheme that w
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lying Hilbert space of coherent states is infinite-dimensional and the states are typically represented in phase space. For the particular case of binary coherent state alphabets these otherwise distinct formalisms can equally be applied. We capitalize this formal connection to analyse the properties of optimally cloned binary coherent states. Several practical and near-optimal cloning schemes are discussed and the associated fidelities are compared to the performance of the optimal cloner.
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