WHY THIS MATTERS IN BRIEF

The era of secure quantum communications just took a step closer to becoming reality but a long road remains.

Physicists have set a new record for quantum teleportation – the science of moving information from one place to another without physically sending anything between the locations. And while it’s not quite the same as the Star Trek teleporters that you’ll probably be more familiar with it’s not too dissimilar either – expect rather than teleporting objects from one place to the other, without them actually having to travel there, this time it’s information.

This week two separate teams managed to teleport information across several kilometres of a fibre optic network in two cities and it’s this type of teleportation over long distances and – more specifically –  across optical fibre that’s an important step towards bringing to life the ultra-secure communications promised by quantum cryptography.

The setup the teams used is described in Nature Photonics Journal and could be the building blocks for a future “Quantum Internet”, something that has long been heralded by National Security agencies around the world as the gold standard of security – far beyond today’s meagre 1,024 and 2,048 bit encryption.

In one of the papers, Dr Wolfgang Tittel and colleagues describe how they teleported the quantum state of a photon, or light particle, over 8.2km in the Canadian city of Calgary.

The process by which information – the quantum state of a photon – is teleported involved creating two photons at the University of Calgary (Site B in the aerial photo below).

A map of the area where the experiment took place

One of these photons was sent in a “classical” way – in other words it traveled along the optical fibre cable in the same way you and I take the tube to get from A to B – to a building 11.1km away near Calgary City Hall (C), while the other photon remained behind at the university.

Meanwhile, another photon was sent to City Hall (C) from site A. This resulted in the quantum state of the photon from site A being transferred to the photon which remained behind at the university (B) via quantum teleportation.

Teleportation occurs via a phenomenon known as entanglement, which describes how sub-atomic particles can be linked even if they are separated by a very large distance. The details of entanglement are not well understood though – it even befuddled Einstein, who famously described it as “spooky action at a distance”.

While there is still someway to go before we can realise a truly secure, dare we say, unbreakable quantum internet – whether those are private networks buried at the NSA or public ones we can all use Dr Tittel said at the time that the configuration for his study could serve as the benchmark for useful city wide quantum network. And that in future  repeaters could help amplify signals, enabling communications over much bigger distances.

In the same issue of Nature Photonics, quantum information researcher Frédéric Grosshans from the Université Paris-Sud in Orsay, France, said: “Undoubtedly many interesting quantum information experiments in the future will be built on this work and for the longer term, the paper demonstrates that the possibility of quantum networks that span a city are a realistic proposition, which is an exciting vision for the future.”