All-photonic quantum repeaters could pave the way for faster, more secure quantum internet

All-photonic repeaters require only photons in place of expensive cryogenics or ion traps

An international team of researcher have demonstrated a proof-of-principle experiment on an important aspect of all-photonic quantum repeaters that could, they claim, serve as the backbone for a faster, more secure, long-distance quantum internet.

Led by University of Toronto professor Hoi-Kwong Lo, the researchers say that their all-photonic repeaters "allow time-reversed adaptive (TRA) Bell measurement" and require only photons in place of expensive cryogenics or ion traps. These devices are also capable of eliminating many shortcomings of traditional quantum repeaters.

The internet, as we see it today, comes with a variety of security challenges. Due to its security weaknesses, hackers sometimes get a chance to poke holes in the layers of defence created by institutions and government agencies.

Researchers therefore propose using quantum communication techniques to provide unbreakable encryption during data transmission.

One promising quantum communication technique, which can be used to transmit data securely, is quantum key distribution (QKD). This technique exploits the fact that any attempt to snoop on a quantum system would disturb the system, leaving behind a clearly noticeable trace. In this way, data transmission can be aborted before any sensitive information is lost.

So far, QKD security has only been demonstrated in some small-scale systems. Lo and his colleagues (and many other scientists across the world) are currently working to demonstrate quantum communication over larger distances, using optical fibres.

One issue they face concerns the use of repeaters. The repeaters currently used in quantum communication systems are highly problematic. They are difficult to build, expensive and prone to errors.

Lo claims that an all-photonic quantum repeater developed by his team would reduce many of these shortcomings.

"Because these repeaters are all-optical, they offer advantages that traditional - quantum-memory-based matter - repeaters do not. For example, this method could work at room temperature," says Professor Lo.

"An all-optical network is a promising form of infrastructure for fast and energy-efficient communication that is required for a future quantum internet."

Professor Lo carried out the study in collaboration with researchers from the Japanese Universities of Osaka and Toyama and NTT Corporation in Japan.

The findings of the study are published in journal Nature Communications.