The device bridges the significant energy gap between microwave and optical photons, enabling qubit control using a light signal transmitted from miles away.

Researchers at the Harvard School of Engineering and Applied Sciences (SEAS), in collaboration with Rigetti Computing, the University of Chicago, and the Massachusetts Institute of Technology, have developed a photon router designed to integrate with quantum networks and establish interfaces for noise-sensitive microwave quantum computers, according to a press release.

Figure1. Photon Router.

As startups and tech giants compete to advance quantum computing—the next frontier of technology—building quantum-compatible networks is also essential for real-world deployment [1]. Figure1 represents Photon Router.

Quantum computers exploit the unique properties of quantum materials to perform computations at unprecedented speeds. However, these quantum states require ultra-low temperatures, which are feasible within specialized computing facilities but impractical for large-scale quantum networks.

To bridge this gap, researchers are exploring ways to transmit quantum information using existing communication infrastructure. Since photons can travel efficiently through fiber-optic cables worldwide, they are the ideal candidates for this task.

What is a Photon Router?

Researchers at Harvard SEAS have developed a microwave-optical quantum transducer capable of interfacing with superconducting microwave qubits, a fundamental information storage unit in quantum computing [2]. The device bridges the significant energy gap between microwave and optical photons, enabling qubit control through a light signal transmitted from miles away. It is the first device to achieve control of a superconducting qubit using only optical signals.

“The realization of these systems is still a long way off, but to get there, we must develop practical methods to scale and integrate the different components,” said Hana Warner, a graduate student at SEAS involved in the research.

How Was It Built?

The photon router developed by the Harvard team resembles a small paper clip and measures just two millimeters. Mounted on a chip approximately two centimeters long, the device features two optical resonators connected to a microwave resonator, enabling energy transfer between them without requiring bulky microwave cables.

Constructed from lithium niobate, the device enables qubit state readout and the conversion of quantum information into light packets for transmission between quantum computing nodes.

Reference:

1. https://wis-wander.weizmann.ac.il/space-physics/world%E2%80%99s-first-photonic-router
2. https://interestingengineering.com/innovation/harvard-photon-router-quantum-network

Cite this article:

Keerthana S (2025), World-First: US-Designed Photon Router to Connect Qubits in Quantum Networks,AnaTechMaz, pp. 214