The team generated and transmitted secret quantum keys over 184.6 kilometers (km) of fiber-optic cable, the longest distance ever recorded for quantum key distribution (QKD). The previous record was 122 km. Secret quantum key is a code for encrypting data that not only have been transmitted and detected successfully, but also processed to correct for errors and enhance privacy, steps considered essential for practical applications. The keys are then used to encrypt ordinary digital data for transmission over conventional communications channels.
A weakness in typical QKD systems is the current lack of reliable commercial single-photon sources. Very weak laser pulses are used instead, and they often produce more than one photon per pulse, all with the same orientation and bit value (0 or 1). This introduces vulnerability: An eavesdropper could intercept a photon and “read” it accurately without its loss being detected by the intended receiver, because the same laser pulse may still contain another photon.
The LANL/NIST absolute distance record of 184.6 km is secure against reasonable attacks, that is, the laser adjustments used in this case have only a moderate probability of generating more than one photon per pulse. The team also used slightly different adjustments to set other QKD distance records, including absolutely secure transmission of secret keys over 67.5 km, surpassing the previous record of 50.6 km. This method generated so few multi-photon pulses that some of the photons detected at the receiver must have originated in single-photon pulses, enabling the creation of secret key.
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
Known for identifying cutting edge technologies, he is currently a Co-Founder of a startup and fundraiser for high potential early-stage companies. He is the Head of Research for Allocations for deep technology investments and an Angel Investor at Space Angels.
A frequent speaker at corporations, he has been a TEDx speaker, a Singularity University speaker and guest at numerous interviews for radio and podcasts. He is open to public speaking and advising engagements.