Entanglement can completely defeat quantum noise

TL;DR

This paper demonstrates that entanglement can enable perfect quantum communication over channels that individually cannot transmit any information, revealing a novel form of superactivation and noise resistance.

Contribution

It introduces the concept that entanglement can completely overcome quantum noise in channels with zero capacity, including zero-error quantum communication.

Findings

Superactivation of zero-error classical capacity.

Entanglement enables perfect quantum communication over noisy channels.

New form of superactivation with shared entanglement between sender and receiver.

Abstract

We describe two quantum channels that individually cannot send any information, even classical, without some chance of decoding error. But together a single use of each channel can send quantum information perfectly reliably. This proves that the zero-error classical capacity exhibits superactivation, the extreme form of the superadditivity phenomenon in which entangled inputs allow communication over zero capacity channels. But our result is stronger still, as it even allows zero-error quantum communication when the two channels are combined. Thus our result shows a new remarkable way in which entanglement across two systems can be used to resist noise, in this case perfectly. We also show a new form of superactivation by entanglement shared between sender and receiver.