Researchers have developed Plaquette, a theoretical and software platform designed to evaluate the logical performance of fault-tolerant quantum computing (FTQC) architectures based on the physical imperfections of devices. This tool addresses a critical need in the development of quantum computers, where error suppression is fundamental. Plaquette enables hardware teams to make informed decisions about which imperfections to mitigate, offering a precise view of how actual hardware noise affects the logical performance of an FTQC.

Unlike stochastic Pauli models used by scalable stabilizer simulators, Plaquette considers a broader range of noise sources common in physical qubits. This includes leakage out of the computational subspace in superconducting qubits, scattering through intermediate states in neutral atoms, heating in trapped ions due to phonon absorption, and coherent errors from miscalibrated controls. The platform allows hardware error models to be specified using Kraus operators, Hamiltonian-Lindblad dynamics, or experimentally reconstructed quantum channels, automatically compiling them for different classes of samplers.

Plaquette incorporates samplers such as stabilizer sampling for Pauli noise, the new XPauli sampler for leakage and environment sectors, near-Clifford samplers for coherent errors, and full-state simulation for exact reference calculations. Validation of the XPauli and near-Clifford samplers against full-state simulation has demonstrated their accuracy, matching within statistical uncertainty, while Pauli twirling can fall short depending on the error model. The tool has been demonstrated on three specific error models: leakage in superconducting qubits, intermediate-state scattering in neutral atoms, and heating in trapped ions.

The discrepancy between Plaquette simulations and Clifford-only simulations varies with platform and noise process. This highlights the importance of using the most accurate simulation available to obtain reliable thresholds, error budgets, and overhead estimates. Plaquette provides a direct path from the open-system physics of a device to the evaluation of the logical performance of the FTQC built upon it, facilitating progress towards robust and functional quantum computers.