Noise powered amplification in CV quantum key distribution

TL;DR

This paper investigates noise powered amplifiers in continuous-variable quantum key distribution, demonstrating that their added noise, while incoherent, can be acceptable or even advantageous for secure quantum communication.

Contribution

It shows that noise powered amplifiers, despite their incoherence, are viable in quantum key distribution and can sometimes improve performance.

Findings

Added noise is not detrimental in QKD tasks

Noise powered amplification can be beneficial in certain scenarios

Incoherent amplification is suitable for QKD despite limitations

Abstract

Amplification plays a key role in classical communication protocols, where it compensates the unavoidable loss of the signal. However, when we enter the quantum domain this approach starts being problematic as the standard kinds of amplifiers are usually accompanied by excess noise which detrimentally affects the quantum features of used states. Recently, several kinds of "noiseless" amplifiers that do not suffer from this feature have been proposed. Among these amplifiers, one that stands out is the noise powered amplifier, which acts incoherently, amplifying the signal by adding the "right" kind of noise. Here we show that despite the incoherence, which makes the amplifier unsuitable for protocols such as entanglement distillation, the added noise is not a big problem in quantum key distribution tasks and can be in some situations beneficial.