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  • Open Access

Eigen-SNAP gate for photonic qubits in a cavity-transmon system

Marcus Meschede1,* and Ludwig Mathey1,2

  • *Contact author: marcus.meschede-2@uni-hamburg.de
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Phys. Rev. Research 8, 013252 – Published 6 March, 2026

DOI: https://doi.org/10.1103/2ks4-p82h

Abstract

In the pursuit of robust quantum computing, we put forth a platform based on photonic qubits in a circuit-QED environment. Specifically, we propose a versatile two-qubit gate based on two cavities coupled via a transmon, constituting a selective number-dependent phase gate operating on the in-phase eigenmodes of the two cavities, the Eigen-SNAP gate. This gate natively operates in the dispersive coupling regime of the cavities and the transmon, and operates by driving the transmon externally, to imprint desired phases on the number states. As an example for the utility of the Eigen-SNAP gate, we implement a SWAP gate on a system of two logical bosonic qubits encoded in the cavities. Further, we use numerical optimization to determine the optimal implementation of the SWAP. We find that the fidelities of these optimal protocols are only limited by the coherence times of the system's components. These findings pave the way to continuous-variable quantum computing in cavity-transmon systems.

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Phys. Rev. Research 8, 013252– Published 6 March, 2026
  • Received 24 March 2025
  • Accepted 4 February 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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