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arXiv:2606.07797

Floquet Entanglement Generation in Parametrically Driven Coupled Superconducting Qubits

Gustavo M. Meneses A., Daniel Dominguez, María José Sánchez

quant-phcond-mat.supr-conSubmitted Jun 5, 2026• Announced Jun 9, 2026• 0 citations

Abstract

We investigate the dynamical generation of entanglement in a system of two superconducting qubits coupled through a parametrically driven longitudinal interaction. Using Floquet theory and exact numerical simulations, we analyze the time evolution of the system initialized in a separable ground state. Our results reveal a nontrivial mechanism for entanglement generation, fundamentally distinct from the conventional resonant excitation to an entangled eigenstate. We show that this mechanism emerges when two initially separable eigenstates are mixed by the periodic driving under multiphoton resonance conditions. Since the effect cannot be captured within a standard rotating-wave approximation, we employ generalized Van Vleck near-degenerate perturbation theory to derive an effective analytical description. Within this framework, we demonstrate that the sustained entanglement originates from the hybridization of the dominant Floquet states, namely those with the largest overlap with the initial ground state. Furthermore, the degree of entanglement can be efficiently controlled through the driving amplitude. In particular, for specific amplitudes, the entanglement is fully suppressed. We term this phenomenon as coherent destruction of entanglement.

Comments: 15 pages, 7 figures

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Coupling qubits to a superconducting resonator provides a mechanism to enable long-distance entangling operations in a quantum computer based on spins in semiconducting materials. Here, we demonstrate a controllable spin-photon coupling based on a longitudinal interaction between a spin qubit and a resonator. We show that coupling a singlet-triplet qubit to a high-impedance superconducting resonator can produce the desired longitudinal coupling when the qubit is driven near the resonator's frequency. We measure the energy splitting of the qubit as a function of the drive amplitude and frequency of a microwave signal applied near the resonator antinode, revealing pronounced effects close to the resonator frequency due to longitudinal coupling. By tuning the amplitude of the drive, we reach a regime with longitudinal coupling exceeding 1 MHz. This mechanism for qubit-resonator coupling represents a stepping stone towards producing high-fidelity two-qubit gates mediated by a superconducting resonator.