Underwater quantum links are possible across 30 meters (100 feet) of turbulent water, scientists have shown. Such findings could help to one day secure quantum communications for submarines.
Researchers have investigated establishing quantum communications links through water. Such work could lead to secure quantum communications between submarines and surface vessels, and with other subs, aircraft, or even satellites.
Although water absorbs many radio waves, it’s transparent to optical wavelengths between 400 to 500 nanometers, roughly corresponding to green, blue, and violet light.
Prior work suggested that quantum links through water had a maximum length of 300 meters with 418-nanometer-wavelength light under clear conditions. Previous research also successfully established quantum communication across 55 meters of sheltered water, such as that which is found in coves and bays. However, until now, scientists had only reported quantum communications across 5.5 meters of turbulent water.
In this new study, researchers achieved quantum communication at up to 72 kilobits per second across up to 30 meters of turbulent water, the longest distance yet reported for such links. Although turbulence did result in significant wandering and distortion of light signals, those error rates didn’t prevent quantum links from successfully being established with either communication protocol. (IEEE)
The scientists detailed their findings in a preprint article at Arxiv.