Engineers at the University of Pennsylvania have made a remarkable scientific breakthrough. Their successful transmission of quantum signals via ordinary Internet Protocol (IP) brought us a step closer to the ultimate goal of a functional quantum internet. The team created a system that maintains transmission fidelities above 97%, overcoming one of the most significant barriers in quantum communication: the variability of real-world transmission lines.
Quantum entanglement was first described by the physicist Erwin Schrödinger. This strange phenomenon entangles particles in such a way that what’s happening to one immediately determines what’s happening to another, regardless of distance. Schrödinger notoriously explained this idea with a thought experiment involving a cat in a box. In this imagined world, the cat has the potential to be both alive and dead simultaneously, contingent on an unobserved quantum occurrence.
The Penn engineers created the “Q-Chip,” or Quantum-Classical Hybrid Internet by Photonics, that would time and place classical signals in parallel to quantum particles. Such a chip allows quantum signals to be transmitted through the same chip as classical headers measured, all while preserving the delicate quantum information.
Yichi Zhang, one of the lead engineers on the project, described how their system works.
“The classical signal travels just ahead of the quantum signal,” – Yichi Zhang.
With traditional networks, you only monitor the bits to make sure they got where they were supposed to go. Even so, Robert Broberg, another team member, mentioned a key limitation. He reasoned that in fully quantum networks, since measuring particles destroys their quantum state, this approach simply wouldn’t work.
“That allows us to measure the classical signal for routing, while leaving the quantum signal intact,” – Yichi Zhang.
This simple innovation brings promising new opportunities and potential! It uses the principles of quantum entanglement to link multiple quantum computers together, and unite their processing power, which could lead to breakthroughs in artificial intelligence and drug design. Broberg compared their success to the first days of the classical internet.
“Normal networks measure data to guide it towards the ultimate destination,” – Robert Broberg.
The Q-Chip packs quantum and classical data together in conventional internet-style packets. It then processes these packets through currently used infrastructures. Zhang likened their system to a train. In this analogy, the classical header is the engine that drives these sealed cargo containers of quantum information.
“This feels like the early days of the classical internet in the 1990s, when universities first connected their networks,” – Robert Broberg.
Liang Feng, another major contributor to this line of research, took issue with the compatibility between classical and quantum systems.
“That opened the door to transformations no one could have predicted. A quantum internet has the same potential,” – Robert Broberg.
Their small private network so far only links the two buildings across nearly one kilometer of fiber-optic cable no longer used by Verizon.
“You can’t open the containers without destroying what’s inside, but the engine ensures the whole train gets where it needs to go,” – Yichi Zhang.
Liang Feng, another key contributor to this research, emphasized the importance of compatibility between classical and quantum systems.
“By embedding quantum information in the familiar IP framework, we showed that a quantum internet could literally speak the same language as the classical one,” – Yichi Zhang.
The team’s small network currently connects two buildings over approximately one kilometer of fiber-optic cable installed by Verizon.
“By showing an integrated chip can manage quantum signals on a live commercial network like Verizon’s, and do so using the same protocols that run the classical internet, we’ve taken a key step toward larger-scale experiments and a practical quantum internet,” – Liang Feng.