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  • Open Access

Implementation of a Quantum Addressable Router Using Superconducting Qubits

Connie Miao1,*,†, Sébastien Léger1,*,‡, Ziqian Li1, Gideon Lee2, Liang Jiang2, and David I. Schuster1

  • 1Departments of Physics and Applied Physics, Stanford University, Stanford, California 94305, USA
  • 2Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA

  • *These authors contributed equally to this work.
  • †Contact author: cmiao@stanford.edu
  • ‡Contact author: sebleger@stanford.edu
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PRX Quantum 6, 040335 – Published 13 November, 2025

DOI: https://doi.org/10.1103/pq3x-cmw9

Abstract

The implementation of a quantum router capable of performing both quantum signal routing and quantum addressing (a Q2-router) represents a key step toward building quantum networks and quantum random access memories. We realize a Q2-router that uses fixed-frequency transmon qubits to implement a routing protocol based on two native controlled-iswap gates. These gates leverage a large ZZ interaction to selectively route information according to a quantum address. We find an estimated average routing fidelity of 95.3%, with errors arising primarily from decoherence or state preparation and measurement. We present a comprehensive calibration and characterization of both the c-iswap gates and the overall routing protocol through randomized benchmarking techniques and state tomography.

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Physics Subject Headings (PhySH)

Popular Summary

Recent advances in quantum information are bringing us closer to operational quantum computers, which can exponentially outperform certain classical algorithms. To enable this speedup, we need to effectively manage how quantum information is moved around. Our focus is on a new router, called a Q2-router, that can route information in two different quantum ways. It can send data to two places at once, and it can also route quantum data itself. However, a router that does both of these tasks has yet to be implemented.

In our study, we use superconducting quantum bits called transmon qubits to implement the Q2-router. By employing a straightforward scheme that takes advantage of our design, we are able to control the flow of quantum information. Our comprehensive measurements reveal that the router operates with a high average fidelity (95%).

Given the performance and simplicity of our Q2-router, this research lays the groundwork for a quantum router scalable for larger quantum networks, including a component of high interest for a full-scale quantum computer, the quantum random access memory. In addition, our architecture provides a toolset that can be adapted more broadly for other quantum information applications and quantum platforms.

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Outline

Information

PRX Quantum 6, 040335– Published 13 November, 2025
  • Received 7 April 2025
  • Revised 14 August 2025
  • Accepted 20 August 2025
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