Quantum entanglement is one of the most counter-intuitive and
perplexing effects in modern physics. Two objects can be separated
by great distances, yet they share the same quantum states. Famed
physicist Albert Einstein once described the process of affecting an
object in this way as “spooky action at a distance,” and a team of
Chinese scientists just took spooky into space. For the first time,
quantum “teleportation” has been
demonstrated between Earth and an object in space.
China launched its Micius research satellite last year to study
the limits of quantum entanglement. The Long March 2D rocket
deposited its payload in Sun-synchronous orbit, meaning it passes
over the same point on Earth at the same time each day. This allows
the team to plan this carefully timed research, which relies upon
the highly sensitive photon receiver on the Micius satellite. It’s
able to detect the quantum states of single photons projected from
the ground.
Researchers have announced the successful communication of
quantum information between the ground station and Micius, which is
anywhere from 500 and 1,400 kilometers (310-870 miles) above the
surface, breaking the distance record for quantum entanglement. This
is
not teleportation in the Star Trek sense, but
quantum teleportation is often cited as a potential basis for
high-speed communication and uncrackable cryptography. Basically,
when two objects become entangled, they share the same quantum
state. From a physics perspective, they’re the same object. The
entanglement remains even when the objects are separated by great
distances. Thus, changes to one object are immediately replicated by
the other.
This sort of teleportation has been accomplished in laboratories
on Earth, but the record for distance was around 100 km (62 miles).
The problem is that two objects (photons in this case) will only
remain entangled if they don’t interact too much with other objects.
The atmosphere and fiber optic cables used in experiments will
eventually break the bond between two entangled objects. However,
it’s easier to control for that in space.
Most of the transmission distance is in a vacuum, where the
photos don’t interact with anything that could break the link. The
team worked to lessen the chance photos would be disrupted by
building the ground station at an altitude of 4,000 feet in Tibet.
The team created entangled pairs of photos at a rate of 4,000 per
second, then beamed then beamed half of the pair to Micius.
Measurements carried out on the ground and orbiting photos shows
that some of them were indeed still entangled.
This process is far from perfect, though. Out of millions of
photons sent up to Micius, only 911 of them remained entangled with
the ones on the ground. That’s still an impressive result, and one
that could help us better understand this spooky action.