Just a couple of weeks ago, we discussed a Chinese experiment in which physicists teleported photons over a distance of almost 100 kilometres. That’s almost an order of magnitude more than previous records.
Today, European physicists say they’ve broken the record again, this time by teleporting photons between the two Canary Islands of La Palma and Tenerife off the Atlantic coast of north Africa, a distance of almost 150 kilometres.
That’s sets the scene for a fascinating prize. Both teams say the next step is to teleport to an orbiting satellite and that the technology is ripe to make this happen.
The Canary islands experiment was no easy ride. In ordinary circumstances, the quantum information that photons carry cannot survive the battering it gets in passing through the atmosphere. It simply leaks away.
Indeed, the European team say that unusually bad weather including wind, rain, rapid temperature changes and even sand storms all badly affected the experiment. “These severe conditions delayed our experimental realizations of quantum teleportation for nearly one year,” say Anton Zeilinger at the Institute for Quantum Optics and Quantum Information in Vienna and a few pals.
(However, they are quick to point out that satellite-based quantum communication shouldn’t be as susceptible since there is less weather to pass through if you fire photons straight up.)
To perform this experiment, Zeilinger and co had to perfect a number of new techniques to dramatically reduce noise, which would otherwise overwhelm the quantum signal.
Perhaps the most significant of these is a way of using entangled photons to synchronise clocks on both islands. That’s important because it allows the team to send photons and then look for them at the receiver at the exact instant they are due to arrive.
This significantly reduces the number of extraneous photons that could swamp the signal. The GPS system allows clocks to be synchronised in a way that allows a 10 nanosecond coincidence window. But entanglement-enhanced synchronisation allowed Zeilinger and co to use coincidence windows just 3 nanoseconds long.
The results sets up an interesting race between east and west. These experiments are proof-of-principle runs for a much more ambitious idea–quantum teleportation to orbiting satellites.
Since teleportation is the basis of more-or-less perfectly secure communication, the prize here is a global communications network that cannot be hacked, even in principle.
“The technology implemented in our experiment thus certainly reached the required maturity both for satellite and for long-distance ground communication,” say Zeilinger and co.
The questions, of course, is who will be first to orbit. The Europeans have a space agency that could be persuaded to test this idea but they won’t be in a hurry. China is currently showing great ambition in space and will want to show off its technological prowess. Both have the wherewithall to pull off this next step.
The contrast with the US couldn’t be clearer.
Ref: arxiv.org/abs/1205.3909: Quantum Teleportation Using Active Feed-Forward Between Two Canary Islands