Entanglement is the strangest and most powerful phenomenon in quantum physics. When two particles become entangled, measuring one instantly reveals the state of the other, no matter how far apart they are. This effect is the foundation of quantum computing, quantum cryptography, and quantum networks. But creating entanglement between distant qubits usually requires careful manipulation, precise timing, and active control — until now.
Physicists at the Institute of Science and Technology Austria (ISTA), led by PhD student Alejandro Andrés-Juanes and Professor Johannes Fink, have experimentally demonstrated a fully autonomous method for generating distributed entanglement. Their work, published in Physical Review X, confirms a theoretical prediction first made more than 20 years ago: that two physically separated qubits can spontaneously become entangled when they share a common "quantum bath" — a reservoir of correlated light particles.
The team built a proof-of-concept prototype using superconducting circuits. Two qubits, placed several millimeters apart on a microchip, were connected to a shared quantum bath — an engineered electromagnetic environment that acts as a source of entangled photon pairs. Without any external control or measurement, the qubits gradually synchronized their quantum states through the bath, eventually becoming entangled. The process is analogous to two pendulums hung from the same beam gradually falling into synchronized motion, except that here the synchronization happens at the quantum level.
The current prototype transfers about 10 percent of the bath's available entanglement to the qubits — a modest but unambiguous confirmation that the principle works. The team believes that with better engineering, the efficiency can be improved significantly. The implications are far-reaching: future quantum computers could be built as networks of smaller, independently operated modules that become entangled through shared baths, without needing complex active connections between them. This "distributed entanglement" approach could solve one of the hardest engineering challenges in scaling up quantum computing.