The first successful demonstration of quantum teleportation over a fiber optic cable has been achieved, according to groundbreaking new research.
The breakthrough, made by engineers at Northwestern University and funded by the U.S. Department of Energy (DoE), presents new potentials in the realm of quantum communication by allowing it to be combined with existing cables used for providing Internet. This innovative approach reduces the requirement for additional infrastructure needed for quantum computing or quantum sensing technologies.
Previously thought to be impossible, the Northwestern team responsible for the breakthrough says their work showcases the next stage in leveraging a single fiber optic infrastructure that can unite both quantum and classical networks.
“Our work shows a path towards next-generation quantum and classical networks sharing a unified fiber optic infrastructure,” said Prem Kumar, a Northwestern researcher who led the recent research.
“Basically, it opens the door to pushing quantum communications to the next level,” Kumar said.
A Quantum Teleportation Breakthrough
Quantum teleportation works by leveraging the unique properties of quantum entanglement, or what Einstein called “spooky action at a distance.” Because particles remain entangled even when they are separated by significant amounts of space, they can transfer information without having to physically carry it.
The Northwestern team’s achievement is significant since these unique properties that enable quantum teleportation allow for an extremely fast new means of transferring information over great distances without requiring direct transmission.
Kumar says that all signals become converted into light in optical communications systems, and that although millions of light particles are required in classical communications, quantum information relies on single photons.
By conducting a destructive measurement of a pair of photons where one carries a quantum state, and one is entangled with another photon, the research team says that the quantum state can be carried over to the remaining photon, regardless of the distance involved.
“The photon itself does not have to be sent over long distances, but its state still ends up encoded onto the distant photon,” said Jordan Thomas, a Ph.D. candidate studying with Kumar’s laboratory and lead author of a new paper describing the team’s achievement.
“Teleportation allows the exchange of information over great distances without requiring the information itself to travel that distance,” Thomas said in a statement.
Achieving the Impossible
It was previously thought that using standard optical communications cables that already carry classical communications would present limitations with regard to quantum teleportation, since it was believed that entangled photons would “drown” amid the millions of other light particles present.
To overcome this, Kumar and the Northwestern engineering team discovered a means of allowing the delicate photons to avoid this issue by utilizing a certain wavelength of light as a pathway for their photons. Additionally, the team developed special filters they could use to help reduce the amount of noise caused by generated by normal Internet traffic sent through optical cables.
“We carefully studied how light is scattered and placed our photons at a judicial point where that scattering mechanism is minimized,” Kumar said, which allowed he and his fellow researchers to achieve quantum communication without interference from the classical information being sent through the same cables.
The team then tested their method using a 30-kilometer fiber optic cable with photons located at either end. After sending quantum information and high high-speed Internet traffic through the cable, the team executed a teleportation protocol by gauging the quality of the quantum information that was transferred to the receiving end, while taking measurements at the mid-point. This allowed the team to confirm that the quantum information was transmitted successfully, despite the simultaneous transfer of classical information.
A Quantum Teleportation First
Thomas said the team’s achievement represents “the first to show quantum teleportation in this new scenario,” adding that sending information without direct transmission in such a way “opens the door for even more advanced quantum applications being performed without dedicated fiber.”
“Quantum teleportation has the ability to provide quantum connectivity securely between geographically distant nodes,” Kumar said of the team’s research, though adding that “many people have long assumed that nobody would build specialized infrastructure to send particles of light.”
Going forward, the team plans to conduct their experiments over even longer distances while using two pairs of entangled photons, which will allow them to demonstrate another potential milestone in quantum applications known as entanglement swapping.
Additionally, the team hopes to conduct experiments using optical cables in real-world settings outside the lab.
“If we choose the wavelengths properly, we won’t have to build new infrastructure. Classical communications and quantum communications can coexist,” Kumar says.
The team’s new study, “Quantum teleportation coexisting with classical communications in optical fiber,” was published this month in the journal Optica.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. He can be reached by email at micah@thedebrief.org. Follow his work at micahhanks.com and on X: @MicahHanks.