Phase diagram and observables of many-body localization in transmon circuit arrays

Sasu Tuohino

Matti Silveri, Richard Brierley, Xiongjie Yu +1 more

Alexander Nico-Katz, Gulzat Jaliel, Madhumita Sarkar +5 more

We investigate the feasibility of identifying many-body localization in semiconductor quantum dot arrays within current experimental capabilities. Using an extended Fermi-Hubbard model parameterized by realistic device conditions, we analyze the phase diagram through a set of observables with varying experimental accessibility. Our results demonstrate that signatures of MBL can, in principle, be accessed in present-day quantum dot platforms. Crucially, we show that the widely used imbalance fails to distinguish between interaction-induced freezing and genuine localization, highlighting the importance of carefully selecting and interpreting experimental probes. We identify observables that can reliably distinguish genuine MBL from interaction-induced effects, thereby establishing practical criteria for detecting localization in realistic quantum dot arrays.

William Morong, Fangli Liu, Patrick Becker +7 more

Thiago R. Girão Souza, Andreia Saguia, Alan C. Santos +1 more

The failure of quantum thermalization due to Many-Body Localization (MBL) has evolved from a theoretical concept in spin chains to an experimental reality in synthetic quantum platforms, most notably superconducting circuits based on transmon qubits. Despite its significance, the MBL transition has been studied primarily under purely random disorder and local couplings, leaving more complex and realistic configurations largely unexplored. Here, we investigate the quantum dynamics of transmon networks subject to the unavoidable competing effects of correlated disorder and network-mediated non-local interactions. First, we show how to engineer the physical parameters of the quantum hardware to systematically control the correlated disorder patterns emerging in the system. Then, we demonstrate that the MBL phase transition is robust against such correlations, which is essential for tuning localization properties in realistic transmon devices. This robustness is established through the analysis of the block entanglement entropy variance across disorder realizations, which precisely locates the MBL critical point. Independently, we introduce a local memory parameter, whose dynamics at long evolution times reveals memory retention in the localized phase and yields a critical point consistent with the entropy analysis. These results provide a framework for understanding localization in complex quantum network topologies, with potential implications for multi-qubit processor design.

Evangelos Varvelis, David Peter Divincenzo

To be useful for quantum computation, qubits in an array must remain localized -- that is, not ``dressed'' too much by nearby degrees of freedom. This localization has been previously achieved using disorder. But the authors observe here that a more effective route to localization is with a quasiperiodic patterning of the qubit array Hamiltonian. This paper develops two different perturbation approaches to calculate diagnostics for many-body localization in quasiperiodic superconducting transmon arrays. Perturbing in anharmonicity versus perturbing in hopping strength give complementary information.