The work, carried out by physicists at the University of Illinois Urbana-Champaign and the University of Chicago, realizes a theoretical proposal for generating entanglement in an externally driven quantum system. The researchers used two superconducting qubits connected by a unidirectional waveguide, a device that allows electromagnetic signals to travel from one qubit toward the other in a controlled direction. By combining this cascaded architecture with a technique known as synthetic squeezing, they were able to stabilize high-quality entanglement despite the imperfections present in a real laboratory system.

Entanglement occurs when two quantum objects share correlations that cannot be explained by classical physics. Measuring one object can reveal information about the other, even when they are physically separated. These correlations are essential for quantum computing, quantum communication and quantum sensing, but they are also extremely fragile. Interactions with the surrounding environment typically cause decoherence, rapidly erasing the delicate quantum relationships that make entanglement useful.

Conventional approaches usually create entanglement through a sequence of operations and then attempt to distribute the entangled particles or quantum states to separate locations. That transport stage is particularly vulnerable because noise, loss and uncontrolled interactions can degrade the quantum state. The new approach seeks to eliminate the need to move fragile quantum information. Instead, the qubits remain in place and continuously exchange signals, allowing entanglement to emerge as the stable outcome of their interaction with a driven and dissipative environment.

The key idea is based on cascaded quantum systems. In such a system, quantum objects continuously absorb and emit light or microwave photons. Some of that radiation escapes into the environment, creating dissipation. When an external drive is introduced with the correct phase, amplitude and direction, it can balance the dissipated field. The combined system then evolves toward a nonequilibrium steady state rather than simply losing its quantum properties. If the interactions are engineered correctly, that steady state contains entanglement between the separated qubits.

“This idea has attracted theoretical attention for a long time because it runs counter to our experience with quantum entanglement,” said Aashish Clerk, a professor of molecular engineering at the University of Chicago’s Pritzker School of Molecular Engineering. Rather than preparing entanglement once and watching it decay, he explained, the system naturally relaxes toward a state in which entanglement is continuously maintained. The researchers compare the effect to a refrigerator that uses an ongoing energy flow to preserve a desired condition, except that here the protected resource is quantum correlation rather than low temperature.

In idealized theoretical models, cascaded systems can generate strong steady-state entanglement. Real hardware, however, introduces unwanted loss, imperfect components and additional noise channels. These effects normally weaken the correlations and can prevent the system from reaching the predicted performance. Synthetic squeezing addresses this problem by modifying the effective quantum environment seen by the qubits. Through carefully selected drive settings, the researchers reproduce key features of an ideal squeezed reservoir without requiring a physically perfect source of squeezed radiation.

Squeezing is a distinctly quantum process that reduces uncertainty in one property of a field while increasing uncertainty in another. In the experiment, synthetic squeezing does not simply amplify the qubits’ interaction; it reshapes the noise and fluctuations entering the system. This allows the researchers to compensate for imperfections and tune the qubits toward an entangled steady state. Because the qubits are superconducting circuits, their quantum behavior can be controlled using microwave pulses, while the waveguide provides the directional channel needed for the cascaded interaction.

The experiment represents an important step toward quantum networks in which separated processors can share entanglement without transmitting delicate quantum states through long, noisy channels. The researchers are now exploring how the method can be extended from two qubits to larger systems. One possible application is entanglement distillation, a process in which many weakly entangled pairs are combined to produce a smaller number of pairs with stronger correlations. If such protocols can be integrated with the new architecture, the system could eventually support more demanding quantum operations and help connect remote quantum computers.

The researchers emphasize that the technique is not yet a complete quantum networking solution. The entanglement achieved remains below the theoretical maximum, and future work must determine which computational and communication protocols can benefit most from autonomous stabilization. Nevertheless, the result challenges a central assumption in quantum engineering: that environmental coupling is always destructive. By controlling the flow of energy, photons and information through a quantum system, dissipation can instead become the mechanism that repeatedly restores and protects entanglement.

Subject of Research: Dissipation-enabled generation and stabilization of entanglement between superconducting qubits in a cascaded quantum network

Article Title: Autonomous Stabilization of Remote Entanglement in a Cascaded Quantum Network

News Publication Date: 13-Jul-2026

Web References: Physical Review X: https://journals.aps.org/prx/abstract/10.1103/z6zz-vw5q ; Physics viewpoint: https://physics.aps.org/articles/v19/91

References: DOI: 10.1103/z6zz-vw5q

Image Credits: Wolfgang Pfaff

Keywords

Quantum entanglement, superconducting qubits, quantum networks, cascaded quantum systems, synthetic squeezing, dissipation, quantum computing, decoherence, quantum communication, quantum physics

Quantum teleportation, an extraordinary protocol that transfers quantum states from one location to another without moving the physical carriers themselves, lies at the heart of advancing quantum networks. Historically, achieving reliable quantum teleportation across disparate platforms without substantial losses or decoherence has been an immense challenge. Overcoming these constraints by integrating quantum photonic chips via optical fibers not only optimizes the distance and fidelity of state transfer but also paves the way for expandable and robust quantum networks.

This study capitalized on a star-topology network architecture, where multiple nodes are connected centrally through a hub node, facilitating efficient routing and distribution of quantum information. Such a structure is vital for practical quantum networks given its flexibility, resilience, and ease of scalability compared to linear topologies. The researchers engineered a system wherein quantum states generated and processed on photonic chips could be teleported through fiber optic channels to other remote photonic chips, effectively demonstrating a viable path toward distributed quantum computation and communication.

At the core of their experimental setup is an integrated photonic chip capable of generating entangled photon pairs with high purity and indistinguishability. The entangled states serve as the backbone for teleporting quantum information, utilizing standard telecom wavelengths suitable for low-loss transmission over optical fibers. The integration of on-chip sources and detectors reduces coupling losses which have historically hindered performance in quantum communication systems.

To achieve quantum teleportation, the team implemented Bell-state measurements — a quintessential quantum operation that projects pairs of entangled photons to a joint quantum state — on the intermediate chip while ensuring coherence preservation for the teleported state. The precision and stability necessary for these delicate operations were realized through sophisticated photonic circuitry combined with active stabilization techniques, optimizing fidelity of teleportation to levels compatible with practical use.

An intriguing feature of their demonstration was the seamless interfacing between disparate physical platforms: the photonic chips and the optical fiber network. This hybrid approach leverages the compactness and scalability of integrated photonics with the long-haul transmission capabilities of optical fibers, addressing a critical bottleneck in current quantum communication efforts. The use of low-loss single-mode fibers allowed the teleportation protocol to maintain quantum coherence over distances exceeding several kilometers.

The star topology used in the experiment enables multiple quantum nodes to connect to a central node, opening avenues for multi-user quantum communication systems and networked quantum computing architectures. This configuration also simplifies resource sharing—such as entanglement distribution—among various users, improving overall network efficiency and security. By demonstrating quantum teleportation in such a topology, the authors lay a foundational framework for future quantum networks capable of converting theoretical constructs into operational realities.

Beyond the immediate technical triumph, this research carries profound implications for quantum information science and technology. The ability to teleport quantum states between chips interconnected by fiber indicates a scalable route toward building complex networks capable of performing distributed quantum computations, quantum cryptography, and entanglement-based sensing applications. These networks could one day constitute the backbone of a technologically transformative quantum internet.

Crucially, the approach utilizes photonic integration — a technology compatible with existing semiconductor foundry processes — affording an immensely practical advantage. This suggests that quantum network components can be manufactured en masse with high precision, reducing costs and facilitating broader adoption. Integration also provides robustness against environmental disturbances, which are a perennial challenge for quantum systems operating in real-world environments.

The demonstration’s success is a testament to advances in nonlinear optics, ultra-low-loss photonic components, and quantum state manipulation, all meticulously orchestrated to perform a functionality once confined to theoretical physics or laboratory curiosities. The synchronization of chip-based entangled photon sources, fiber-based transmission, and on-chip Bell-state measurements are indicative of the multidisciplinary ingenuity driving quantum technologies forward.

Furthermore, the experimental platform accommodates future enhancements such as the incorporation of quantum memories and error-correcting codes, enhancing network reliability and performance. This makes the demonstrated star-topology quantum network not just a proof-of-concept but a versatile testbed for further innovations in quantum communication protocols and hardware designs.

The researchers highlight that while challenges remain—such as increasing teleportation distances to metropolitan or even global scales and integrating additional quantum nodes—the current achievement sets a critical benchmark. The work firmly establishes the potential of chip-fiber-chip networks in realizing the dream of a fully connected quantum internet, where quantum information can be securely and reliably transmitted across vast distances instantaneously.

In essence, the marriage of integrated photonics and fiber optics within a star-topology quantum network manifests what can be viewed as the dawn of practical quantum telecommunication networks. The prospects of such systems are vast, promising secure communication channels impervious to eavesdropping, enhanced computational frameworks, and groundbreaking sensing capabilities leveraging quantum entanglement.

The robustness, scalability, and compatibility with existing telecommunications infrastructure underscored in this study signal a paradigm shift. Instead of isolated quantum devices, the future envisions fully interconnected quantum networks where chip-based nodes communicate flawlessly across fiber-optic channels, amplifying the reach and applicability of quantum technologies.

Ultimately, this pioneering work by Kashi and Kues represents not only a foundational advance in quantum teleportation but also an inspiring blueprint for global quantum networking. The fusion of photonic integration and network architecture design showcased here lays the groundwork for a quantum internet poised to revolutionize technology and communication.

As quantum technologies rapidly evolve, the significance of demonstrating chip-fiber-chip quantum teleportation in star-topology networks promises to reverberate widely—from academic research and industry development to strategic technological investments—bringing the once-elusive quantum internet tantalizingly close to reality.

Subject of Research: Chip-based quantum teleportation and integrated quantum networks
Article Title: Chip-fiber-chip quantum teleportation in a star-topology quantum network
Article References:

Khodadad Kashi, A., Kues, M. Chip-fiber-chip quantum teleportation in a star-topology quantum network.
Light Sci Appl 14, 349 (2025). https://doi.org/10.1038/s41377-025-02034-2