Physicists at the Institute of Science and Technology Austria (ISTA) have achieved a groundbreaking advancement in quantum computing by demonstrating a fully autonomous technique to distribute entanglement between distant qubits. This pioneering method leverages a “quantum bath” of correlated microwave photons to synchronize and stabilize entangled states without requiring active control or measurement—a feat that confirms a theoretical prediction made over two decades ago.
Entanglement, the quintessential quantum phenomenon where particle states exhibit correlations beyond classical explanation, is essential for scalable quantum computers and quantum networks. Traditionally, generating entanglement over distance involved either sending a single photon actively controlled from one qubit to another or matching photons emitted independently by two qubits. While these approaches, especially the latter recognized by the 2022 Nobel Prize in Physics, have propelled the field forward, they depend heavily on repeated measurements and post-selection, often limiting entanglement availability and reliability.
In contrast, the ISTA team engineered a new configuration in which the qubits interact with a common source of correlated photons forming a quantum bath. This environment autonomously “locks” the qubits into an entangled state continuously, maintaining coherence even beyond the qubits’ natural lifetimes. The non-local squeezed reservoir effectively creates a stable ground state that the qubits inhabit, ensuring entanglement is perpetually accessible, a critical feature for future quantum technologies.
Their prototype uses microwave photons, ideal for circuit-based superconducting qubits, to implement this novel scheme. Unlike optical photons commonly used in long-distance quantum communication, microwave photons suit the manipulation of stationary quantum bits and underpin many of today’s leading quantum processors. By bridging continuous-variable entanglement—described by smoothly varying properties—and discrete-variable entanglement—an all-or-nothing quantum correlation of qubits—the researchers have addressed a longstanding mismatch in quantum computing architectures.
To validate entanglement formation, the team employed quantum tomography, a sophisticated technique reconstructing qubit states from rapid, repeated measurements lasting mere nanoseconds. This analysis confirmed the synchronized states predicted by theory, definitively proving that the quantum bath can sustain distributed entanglement autonomously.
Although the current method captures about 10% of the quantum bath’s potential entanglement, it showcases a notably simple and scalable approach. The researchers suggest that their setup can be expanded to synchronize larger networks of qubits, promising a pathway toward fault-tolerant quantum computation.
This experimental realization not only closes a 20-year gap between theoretical proposal and laboratory demonstration but also opens new avenues for quantum optics experimentation and the scaling of quantum processors. By providing on-demand, long-lived entanglement without complex feedback, the ISTA breakthrough may redefine how quantum information technologies are built and operated.
Subject of Research: Not applicable
Article Title: Distributing stationary qubit entanglement through a non-local squeezed reservoir
News Publication Date: 13-Jul-2026
Web References: DOI: 10.1103/r4jt-j39w
Image Credits: © ISTA
Keywords: Qubits, Quantum computing, Quantum mechanics, Quantum entanglement, Photons
