Probabilistic Cloning of Coherent States without a Phase Reference

TL;DR

This paper introduces a probabilistic cloning method for coherent states that does not require a phase reference, using simple phase-randomized displacement and photon counting, outperforming previous deterministic schemes.

Contribution

It presents a novel phase-reference-free probabilistic cloning scheme for coherent states, demonstrating improved performance over existing deterministic methods.

Findings

Outperforms the best deterministic cloning schemes

Achieves asymptotically uncorrelated clones

Allows post-cloning optimization of success rate and fidelity

Abstract

We present a probabilistic cloning scheme operating independently of any phase reference. The scheme is based solely on a phase-randomized displacement and photon counting, omitting the need for non-classical resources and non-linear materials. In an experimental implementation, we employ the scheme to clone coherent states from a phase covariant alphabet and demonstrate that the cloner is capable of outperforming the hitherto best-performing deterministic scheme. An analysis of the covariances between the output states shows that uncorrelated clones can be approached asymptotically. An intriguing feature is that the trade-off between success rate and achieved fidelity can be optimized even after the cloning procedure.