Quantum teleportation - the remote transfer from one location to another of quantum information encoded into particles of light - over several kilometres of optical fibre networks in the cities of Hefei, China and Calgary, Canada is reported in two papers published online in Nature Photonics this week. The two independent studies show that quantum teleportation across metropolitan networks is technologically feasible, and pave the way towards future city-scale quantum technologies and communications networks, such as a quantum internet.
Quantum teleportation over fibre optic networks has the potential to greatly improve the security and strength of internet connections. However, long-distance quantum teleportation using a fibre network requires independent light sources, and this presents a technological challenge: the light beam from one source needs to remain indistinguishable to the light beam from the other source after travelling through several kilometres of fibre that is laid through a changing environment.
To overcome this, the research groups independently developed several feedback and synchronization mechanisms to enable their teleportation experiments. Qiang Zhang, Jian-Wei Pan and colleagues implemented their field test in Hefei, China and used light at a telecommunication wavelength (as used in current telecommunications networks) to minimize the rate at which the signal light loses intensity in the fibre. Wolfgang Tittel and colleagues conducted their test in Calgary, Canada, but used photons at both a telecommunication wavelength and a wavelength of 795 nm, which allowed their quantum teleportation experiment to run faster than Zhang, Pan and colleagues’ experiment, but at a reduced fidelity.
In an accompanying News & Views article, Frederic Grosshans writes: “Combined, these two experiments clearly show that teleportation across metropolitan distances is technologically feasible, and undoubtedly many interesting quantum information experiments in the future will be built on this work.”