New world record for quantum teleportation distance
Researchers at the National
Institute of Standards and Technology (NIST) have “teleported” or
transferred quantum information carried in light particles over 100
kilometres (km) of optical fibre, four times farther than the previous
record.
Researchers at NIST have “teleported” or
transferred quantum information carried in light particles over 100 km
(62 miles) of optical fibre – four times farther than the previous
record. The experiment confirmed that quantum communication is feasible
over long distances in fibre. Other research groups have teleported
quantum information over longer distances in free space, but the ability to do so over conventional fibre-optic lines offers more flexibility for network design.
Not to be confused with Star Trek‘s fictional “beaming up”
of people, quantum teleportation involves the transfer, or remote
reconstruction, of information encoded in quantum states of matter or
light. Teleportation is useful in both quantum communications and
quantum computing, which offer prospects for novel capabilities such as
unbreakable encryption. The basic method for quantum teleportation was
first proposed more than 20 years ago and has been performed by a number
of research groups, including one at NIST using atoms in 2004.
The new record, described in Optica,
involved transferring quantum information contained in one photon – its
specific time slot in a sequence – to another photon transmitted over
102 km of spooled fibre in a laboratory in Colorado. The achievement was
made possible by advanced single-photon detectors designed and made at
NIST.
“Only about 1 percent of photons make it all the way through 100 km of
fibre,” says NIST’s Marty Stevens. “We never could have done this
experiment without these new detectors, which can measure this
incredibly weak signal.”
Until now, so much quantum data was lost
in fibre that transmission rates and distances were low. This new
teleportation technique could be used to make devices called quantum
repeaters that could resend data periodically, in order to extend
network reach, perhaps enough to eventually build a “quantum internet.”
Previously, researchers thought quantum repeaters might need to rely on
atoms or other matter, instead of light – a difficult engineering
challenge that would also slow down transmission.
Various quantum states can be used to
carry information; the NIST experiment used quantum states that indicate
when in a sequence of time slots a single photon arrives. This method
is novel, in that four of NIST’s photon detectors were positioned to
filter out specific quantum states. The detectors rely on
superconducting nanowires made of molybdenum silicide. They can record
over 80 percent of arriving photons, revealing whether they are in the
same or different time slots, each just 1 nanosecond long. The
experiments were performed at wavelengths commonly used in
telecommunications. Below is an infographic with more details.
