Surpassing the no-cloning limit with a heralded hybrid linear amplifier for coherent states

TL;DR

This paper experimentally demonstrates a probabilistic hybrid linear amplifier that surpasses the quantum no-cloning limit for coherent states, enabling higher fidelity cloning with potential applications in quantum communication.

Contribution

The authors introduce a hybrid linear amplifier scheme combining deterministic and heralded noiseless amplification to surpass the no-cloning limit for coherent states.

Findings

Successfully produced up to five clones with fidelity exceeding the no-cloning limit.

Demonstrated the scheme's potential for quantum repeater and teleportation applications.

Achieved probabilistic cloning that outperforms deterministic limits.

Abstract

The no-cloning theorem states that an unknown quantum state cannot be cloned exactly and deterministically due to the linearity of quantum mechanics. Associated with this theorem is the quantitative no-cloning limit that sets an upper bound to the quality of the generated clones. However, this limit can be circumvented by abandoning determinism and using probabilistic methods. Here, we report an experimental demonstration of probabilistic cloning of arbitrary coherent states that clearly surpasses the no-cloning limit. Our scheme is based on a hybrid linear amplifier that combines an ideal deterministic linear amplifier with a heralded measurement-based noiseless amplifier. We demonstrate the production of up to five clones with the fidelity of each clone clearly exceeding the corresponding no-cloning limit. Moreover, since successful cloning events are heralded, our scheme has the potential to be adopted in quantum repeater, teleportation and computing applications.