A quantum state of light was successfully teleported through more than 30 kilometers (around 18 miles) of fiber optic cable amid a torrent of internet traffic – a feat of engineering once considered impossible.
The impressive demonstration by researchers in the US in 2024 may not help you beam to work to beat the morning traffic, or download your favourite cat videos faster.
However, the ability to teleport quantum states through existing infrastructure represents a monumental step towards achieving a quantum-connected computing network, enhanced encryption, or powerful new methods of sensing.
“This is incredibly exciting because nobody thought it was possible,” says Prem Kumar, a Northwestern University computing engineer who led the study.
“Our work shows a path towards next-generation quantum and classical networks sharing a unified fiber optic infrastructure. Basically, it opens the door to pushing quantum communications to the next level.”
Bearing a passing resemblance to Star Trek transport systems that ghost passengers across time and space in the blink of an eye, teleportation takes the quantum possibilities of an object in one location and, by carefully destroying it, forces the same balance of possibilities onto a similar object in another location.
Though acts of measuring the two objects seal their fates in the same instant, the process of entangling their quantum identities still requires sending a single wave of information between points in space.
Like fairy floss in a spring shower, the quantum state of any object is a hazy smear of possibility at risk of melting into reality moments after creation. Electromagnetic waves of radiation and the thermal bumping-and-grinding of moving particles quickly reduces the quantum significance into decoherence if it isn’t protected in some way.
Shielding quantum states inside computers is one thing. Sending a single photon through optical fibers humming with bank transactions, cat videos, and text messages while protecting its quantum state is far more daunting. You might as well cast your quantum fairy floss into the Mississippi and hope it tastes as good at the end.
To preserve their lonely photon’s precious state against a 400 gigabit-per-second current of internet traffic, the team of researchers applied a variety of techniques that restricted the photon’s channel and reduced the chances it might scatter and mix with other waves.
“We carefully studied how light is scattered and placed our photons at a judicial point where that scattering mechanism is minimized,” says Kumar.
“We found we could perform quantum communication without interference from the classical channels that are simultaneously present.”
While other research groups have successfully transmitted quantum information alongside classical data streams in simulations of the internet, Kumar’s team is the first to teleport a quantum state alongside an actual internet stream.
Each test further suggests the quantum internet is inevitable, giving computing engineers a whole new toolkit for measuring, monitoring, encrypting, and calculating our world like never before, without needing to reinvent the internet to do it.
“Quantum teleportation has the ability to provide quantum connectivity securely between geographically distant nodes,” says Kumar.
“But many people have long assumed that nobody would build specialized infrastructure to send particles of light. If we choose the wavelengths properly, we won’t have to build new infrastructure. Classical communications and quantum communications can coexist.”
This research was published in Optica.
An earlier version of this article was published in December 2024.
