Researchers at the National Institute of Standards and
Technology (NIST) have "teleported" or transferred quantum
information carried in light particles over 100 kilometers (km) of optical
fiber, four times farther than the previous record.
The experiment confirmed that quantum communication is
feasible over long distances in fiber. Other research groups have teleported
quantum information over longer distances in free space, but the ability to do
so over conventional fiber-optic lines offers more flexibility for network
design.
Not to be confused in fictional movies like star trek,
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 and advanced
code-breaking, respectively. 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 the
transfer of quantum information contained in one photon--its specific time slot
in a sequence-- to another photon transmitted over 102 km of spooled fiber in a
NIST laboratory in Colorado.
The lead author, Hiroki Takesue, was a NIST guest researcher
from NTT Corp. in Japan. 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 fiber," NIST's Marty Stevens says. "We never could
have done this experiment without these new detectors, which can measure this
incredibly weak signal."
Credit: Content by Martin Stevens/NIST, design by Kelly Irvine/NIST
Until now, so much quantum data was lost in fiber that
transmission rates and distances were low. The new NTT/NIST 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
NTT/NIST experiment used quantum states that indicate when in a sequence of
time slots a single photon arrives. The teleportation 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 more than 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.
Because the experiment filtered out and focused on a limited
combination of quantum states, teleportation could be successful in only 25
percent of the transmissions at best. Thanks to the efficient detectors,
researchers successfully teleported the desired quantum state in 83 percent of
the maximum possible successful transmissions, on average. All experimental
runs with different starting properties exceeded the mathematically significant
66.7 percent threshold for proving the quantum nature of the teleportation
process.
Story Source:
The above post is reprinted from materials provided by National
Institute of Standards and Technology (NIST). Note: Materials
may be edited for content and length.
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