Going Beyond Basic Noiseless Linear Amplifiers

Entanglement distribution is essential in quantum communications, underpinning secure quantum key distribution, quantum networks, and computing protocols. However, losses in optical channels, such as fiber attenuation and detector inefficiencies, significantly degrade entanglement quality and limit communication distances. Methods like quantum repeaters or advanced encoding schemes are needed to address these issues. Entanglement distillation via noiseless linear amplification (NLA) enhances entanglement quality by probabilistically amplifying quantum states without adding noise, improving the signal-to-noise ratio. By selectively amplifying successful quantum events, NLA increases entanglement fidelity and extends communication distances.   We demonstrate a pioneering experimental protocol, strategically crafted to improve the probability of success of existing NLA protocols. We show that employing a distributed NLA protocol with a relay point positioned equidistantly between two parties (Alice and Bob) yields a better probability of success compared to employing NLA solely at Bob's end or using a recently suggested purification protocol in the majority of scenarios. We also realise an NLA protocol that goes beyond single-photon amplifiers, which has been a bottleneck for going beyond low-energy states.


Dr. Farzad Ghafari is a Postdoctoral Research Fellow at Queensland Quantum and Advanced Technologies Research Institute, Griffith University, specialising in experimental quantum optics and photonic quantum information processing. His work focuses on developing scalable quantum technologies by leveraging single photons.