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arXiv · 2609.26429

Photonic CZ gates based on few-photon scattering from emitter-cavity systems

Mateusz Duda·Pieter Kok
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Abstract

In this paper we analyze the performance of photonic CZ gates based on N waveguide-coupled cavities containing two-level emitters. We derive single- and two-photon scattering matrices for one cavity using the input-output formalism of quantum optics and for N>1 cavities using the SLH formalism, allowing us to compute the CZ gate fidelity. We consider two input Gaussian wave packets that are centered on a two-photon transition of the emitter-cavity system, and find a trade-off between optimizing the single-photon and two-photon wave packet shape. While the single-photon wave packet is preserved for large emitter-cavity coupling rates, where there is little overlap with the single-photon transitions, the two-photon wave packet acquires the necessary $π$ phase shift for smaller coupling rates, comparable to the cavity decay rate multiplied by the number of cavities. We find that this trade-off limits the CZ gate fidelity to approximately 60% when averaging over all input states.

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Mateusz Duda, Pieter Kok. 2026-09-22. Photonic CZ gates based on few-photon scattering from emitter-cavity systems. https://arxiv.org/abs/2609.26429

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