Quantum Teleportation over 100km

Experimental setup. (a) Setup for generating time-bin entangled photon pairs. ATT, attenuator; EDFA, erbium-doped fiber amplifier; PPLN, periodically poled lithium niobate waveguide; SHG, second-harmonic generation; SPDC, spontaneous parametric downconversion. (b) Quantum teleportation setup. Yellow and gray solid lines indicate the optical fibers and electrical lines, respectively. SNSPD, superconducting nanowire single-photon detector; MZI, unbalanced Mach–Zehnder interferometer; DSF, dispersion-shifted fiber; TIA, time interval analyzer. Credit: NTT Basic Research Laboratories and NIST Colorado

This graphic describes how 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. Credit: K. Irvine/NIST

With Quantum Teleportation we mean the transport of unknown quantum information from two points. Notice that because of the "strangeness" of quantum physics you cannot "read" the quantum properties of an entity, like a photon, and then transmit them since by reading them you alter them... 

The very fact that by reading quantum properties you alter them comes handy for encryption and protection of communications transmission. 

Quantum teleportation has been proved by many experiments and distances exceeding 100km have already been achieved using wireless communications. However using optical fibres, and photons, has proved more tricky in terms of distance and so far quantum teleportation was possible over shorter span, in the order of 25km. It is more than just experiment: actual products are available and are being used especially by banks to provide secure link and secure transmission.

Now a team of researchers at NTT basic research laboratories collaborating with a team at NIST working in Boulder, Colorado, has published a paper describing a successful experiment in quantum teleportation over a 100km span.

This was possible by using single photon detectors made of superconducting nanowires made of molybdenum silicide. They can detect photons spaced by one nanosecond. Notice that over a length span of 100km only 1 photon out of 100 makes it through...

The experiment was run using photons at the wavelength used in telecommunications so the result is actually viable in today's networks.

Author - Roberto Saracco

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