Quantum networks could one day connect quantum computers into more powerful systems and enable new forms of secure communication. But a fundamental obstacle stands in the way: Quantum information is extraordinarily fragile, and the entanglement between particles of light on which such networks would depend is easily disrupted.

Now, in a new paper in Nature Physics, engineers at the University of Pennsylvania have demonstrated a potential workaround using topology, the branch of mathematics that famously considers a doughnut and a coffee mug equivalent because they both have a single hole that remains unchanged even when their shapes are distorted.

To explore whether topology’s focus on properties that persist under deformation could lend resilience to quantum systems, the researchers built a chip that generates a pair of entangled photons, then gives one of them a distinctive pattern, known as a skyrmion, by polarizing its light in a particular way.