Physicists have teleported quantum information from one
ensemble of atoms to another 150 metres away, a demonstration that paves the
way towards quantum routers and a quantum Internet
One of the enabling technologies behind a quantum internet
will be quantum routers capable of transmitting quantum information from one
location to another without destroying it.
That's no easy task. Quantum bits or qubits are famously
fragile—a single measurement destroys them. So it's not all obvious how
macroscopic objects such as routers in a fibre optics network can handle qubits
without demolishing them.
However, physicists have a trick up their sleeve to help
send qubits safely. This trick is teleportation, a standard tool in any decent
quantum optics lab.
It relies on the strange phenomenon of entanglement in which
two quantum objects share the same existence. That link ensures that no matter
how far apart they are, a measurement on one particle instantly influences the
other.
It is this 'influence' that allows physicists to transmit
quantum information from one point in space to another without it passing
through the space in between.
Of course, teleportation is tricky, but physicists are
getting better at it. They've teleported quantum information from one photon to
another, from ions to photons and even from a macroscopic ensemble of atoms to
a photon.
Today, Xiao-Hui Bao at the University of Science and
Technology of China in Hefei and a few buddies say they've added a new and
important technique to this box of tricks.
These guys have teleported quantum information from ensemble
of rubidium atoms to another ensemble of rubidium atoms over a distance of 150
metres using entangled photons. That's the first time that anybody has
performed teleportation from one macroscopic object to another.
“This is interesting as the first teleportation between two
macroscopic-sized objects at a distance of macroscopic scale,” say Xiao-Hui and
co.
Quite right. The goal in a quantum internet is that
ensembles of atoms will sit at the heart of quantum routers, receiving quantum
information from incoming photons and then generating photons that pass this
information on to the next router.
So clearly the first teleportation from one of these hearts
to another is an important advance.
Of course, there are hurdles ahead. Xiao-Hui and co want to
increase the probability of success for each instance of teleportation, to
increase the amount of time that the atomic ensemble can store quantum
information before it leaks away (currently just over 100 microseconds) and to
create a chain of atomic ensembles that will better demonstrate the potential
of the technique for quantum routing.
None of those challenges seem like showstoppers. Which means
that practical quantum routers and the quantum internet that relies on them are
just around the corner.
