Chip-based phonon router advances hybrid quantum networks

Chip-based phonon router advances hybrid quantum networks
by Riko Seibo
Tokyo, Japan (SPX) Oct 07, 2025

Researchers have demonstrated a silicon-based device capable of splitting and routing single phonons - quantized packets of mechanical vibration - marking a major step toward hybrid quantum networks that link diverse quantum systems through sound.

"Phonons can serve as on-chip quantum messages that connect very different quantum systems, enabling hybrid networks and new ways to process quantum information in a compact, scalable format," said research team leader Simon Groblacher from Delft University of Technology in the Netherlands. "To build practical phononic circuits requires a full set of chip-based components that can generate, guide, split and detect individual quanta of vibrations. While sources and waveguides already exist, a compact splitter was still missing."

In their study, published in the journal Optica Quantum, the researchers unveiled an integrated four-port directional coupler that performs controllable splitting of single phonons at quantum precision. The device could form the foundation for microscopic routers linking superconducting qubits, known for fast quantum operations, with spin-based systems suited for long-term information storage. It may also enable ultra-sensitive sensors and new quantum experiments.

Quantum technologies rely on different platforms that often cannot communicate directly. Previous efforts using surface acoustic waves faced high loss and large device sizes. The new chip-based coupler employs high-frequency phonons traveling in phononic-crystal waveguides, allowing compact circuits with minimal interference and longer phonon lifetimes for robust quantum routing.

"The coupler we made acts like a junction in a quantum 'postal route,'" Groblacher explained. "It can split, route or recombine single quantum vibrations so that an excitation created in one processor can be sent reliably to another processor on the same chip or to multiple recipients - enabling more flexible and compact quantum devices and networks."

The team fabricated nanoscale patterns on silicon to guide phonons through narrow channels, bringing them together to interact precisely. Initial tests with coherent phonon packets showed adjustable energy division between outputs, and further experiments using a phonon heralding scheme confirmed true single-phonon beam-splitting behavior.

Researchers now aim to integrate the coupler with other phononic components, reduce loss through refined fabrication, and link it with established quantum computing platforms. Groblacher noted, "The ability to route and manipulate single phonons on a chip is key to transferring quantum information between different types of quantum systems and unlocking the potential of hybrid quantum systems. We expect that the new device will be as important as the optical counterpart is in modern science."

Research Report:A single-phonon directional coupler