In what is being hailed as a breakthrough in demonstrating the feasibility of quantum teleportation, two independent teams of scientists have succeeded in transferring quantum information over several miles of commercial optical fiber networks. The experiments, carried out in the cities of Calgary, Canada and Hefei, China, are separately described in two studies published in the journal Nature Photonics.
First proposed by scientists nearly two decades ago, quantum teleportation relies on "entanglement" — a weird and counter-intuitive phenomenon once famously derided as “spooky action at a distance” by Albert Einstein. When two subatomic particles are entangled, changing the quantum state of one immediately changes the quantum state of the other, no matter how far apart they are.
By utilizing this property, researchers in Canada were able to send quantum information over 6.2 kilometers (3.9 miles) of Calgary's fiber optic network, while the Chinese team — using a slightly different configuration — was able to do so over a distance of 12.5 kilometers (7.8 miles).
Although greater distances have been achieved in laboratories before, this is the first time researchers were able to use existing telecommunications infrastructure to accomplish quantum teleportation — a key step in ensuring the viability and practicality of the process.
Here's how quantum teleportation works. Imagine, if you will, three people — Alice, Bob and Charlie. Alice wants to send information to Bob. In order to do so, she prepares a photon she wants to teleport and sends it to Charlie, while Bob entangles two photons and sends one of them to Charlie. When Charlie receives the two photons — one each from Alice and Bob — he carries out what's known as a Bell-state measurement, which actually forces the two to become entangled. This, in turn, causes the photon Bob has to collapse into the state of Alice's original photon, thereby teleporting quantum states between Alice and Bob, who can, in theory, be separated by a distance of miles.
Although the use of the word "teleportation" immediately conjures up images of Star Trek-like transporters — thanks to the theme being gratuitously exploited by science fiction books, shows and movies over the ages — quantum teleportation refers to the instantaneous transmission of information, rather than actual matter.
So, while the latest breakthrough is not going to lead the creation of transporters that seem straight out of science fiction, it does have several real-world implications. From the development of super fast quantum computers to quantum crypotography and the creation of extremely secure "quantum internet," feasible and reliable teleportation has the capability to revolutionize communications.
Quantum internet, for instance, would enable users to transfer information through quantum states instead of the currently used strings of 0s and 1s. Given that an eavesdropper cannot read the quantum state of a photon without disturbing it, a quantum network would be essentially unhackable.
"The two experiments can be seen as milestones on the path to a long-term goal, namely to build a fibre-based quantum internet connecting large cities," Johannes Kofler from the Max Planck Institute of Quantum Optics in Munich, who was not involved in the experiments, told New Scientist.