Noiseless Loss Suppression in Quantum Optical Communication

M Mičuda,I Straka,M Dušek,M Ježek,J Fiurášek,M Miková,N J Cerf

doi:10.1103/physrevlett.109.180503

Abstract

We propose a protocol for conditional suppression of losses in direct quantum state transmission over a lossy quantum channel. The method works by noiselessly attenuating the input state prior to transmission through a lossy channel followed by noiseless amplification of the output state. The procedure does not add any noise; hence, it keeps quantum coherence. We experimentally demonstrate it in the subspace spanned by vacuum and single-photon states, and consider its general applicability.

Highlights

We propose a protocol for conditional suppression of losses in direct quantum state transmission over a lossy quantum channel
This cannot be done perfectly because gn is unbounded, faithful noiseless amplification is possible in any finite subspace spanned by the Fock states jni with n N, albeit with a correspondingly low probability scaling as gÀ2N in the worst case of input vacuum state
The noiseless amplifier can improve the performance of quantum key distribution protocols [20,21,22,23] and it can be used to distribute high-quality entanglement over a lossy channel [13,24]

Summary

Introduction

We propose a protocol for conditional suppression of losses in direct quantum state transmission over a lossy quantum channel. The noiseless amplifier is not useful to suppress losses in direct transmission of arbitrary quantum states because it is not the inverse map of a lossy channel L. In this Letter, we prove that a suitable combination of noiseless attenuation and amplification provides a powerful tool to conditionally suppress losses in channel L to an arbitrary extent without adding noise.

Results

Conclusion