Quantum entanglement — the phenomenon where two particles become linked such that measuring one instantly reveals the state of the other, regardless of distance — is the foundation of quantum computing and quantum networks. But keeping entanglement alive across separate devices has traditionally required carefully orchestrated pulse sequences, repeated measurements, and post-selection, making it fragile and intermittent.
Two research teams changed that equation in July 2026, showing that remote qubits can remain entangled in a steady state without active pulse control. The results were published simultaneously by the University of Illinois Urbana-Champaign and the Institute of Science and Technology Austria (ISTA).
Three key facts about the breakthrough:
1. The Illinois approach: cascaded microwave network. The University of Illinois team, led by Abdullah Irfan and published in Physical Review X, used a directed microwave network connecting two superconducting-qubit devices. By arranging nonreciprocal waveguide coupling and local drives, they created what they call a "coherent quantum absorber" — a configuration where unwanted emissions cancel each other out instead of leaking quantum information away. The system naturally falls into a remote entangled state rather than visiting it briefly between rounds of control. Their protocol achieved concurrence approaching 0.5, with local loss setting the remaining ceiling.
2. The ISTA approach: quantum-correlated photonic reservoir. The ISTA team took a different hardware route, using a Josephson parametric converter to generate entangled microwave fields that were sent to two distant transmon qubits. The qubits were driven into a stationary entangled state by a two-mode squeezed reservoir — a "quantum bath" of correlated photons. The experiment transferred about 10% of the bath's available entanglement to the qubits and verified the state using tomography over 20 to 80 nanoseconds.
3. This matters for modular quantum computers. A practical quantum computer will likely be built from multiple modules connected by quantum links. Until now, those links required precisely timed control sequences that worked only in brief windows. The new results demonstrate that researchers now have more than one serious path toward an "always-on" quantum connection — a persistent entanglement that is available whenever the machine needs it, without waiting for a perfect control sequence.
Neither group has solved the problem completely. The Illinois team's entanglement was limited by local loss, and the ISTA team transferred only a fraction of the bath's entanglement to the qubits. But the fact that two independent groups reached the same broad milestone through different hardware routes suggests that steady-state remote entanglement is becoming an engineering reality rather than a theoretical curiosity.
As quantum networks grow from single-chip demonstrations to multi-module architectures, the ability to maintain entanglement without active intervention will be essential. The July 2026 results mark a concrete step toward that future.