Designing optimised quantum architectures requires understanding the leading sources of noise and imperfections in a given hardware platform, and identifying techniques, codes and decoders that best suppress the impact of these sources.

Plaquette v2024.11 introduces upgrades that expand the flexibility to explore various architectures on different hardware platforms:

• Complete support for transmon superconducting qubit simulations: The Plaquette library now provides comprehensive support for superconducting qubits. Users can now study the performance of superconducting-based architectures under realistic noise models including leakage and investigate the impact of leakage reduction techniques on the fault-tolerance performance.

• New qLDPC codes and decoders: The built-in code library has been expanded to include the recently developed lifted-product codes and the XZZX variant of the hypergraph product codes. Additionally, a new belief-propagation-based BP-LSD decoder has been introduced. These upgrades further enhance Plaquette’s utility towards studying fault-tolerance techniques that are tailored to the specific noise characteristics and properties of the quantum hardware.

• Simplified interface to model imperfect gate operations: This release introduces a streamlined interface for simulating the physical processes governing quantum hardware. Customers can now efficiently generate Plaquette-compatible error models that integrate seamlessly into the threshold calculation pipeline. This simplifies the evaluation of fault-tolerance performance for any hardware imperfection across all hardware platforms, enabling exploration of the most promising designs.

As an example of the enhanced functionality offered by Plaquette v2024.11, we consider fault-tolerance thresholds for rotated planar codes implemented on transmon superconducting qubit hardware. The simulations account for dephasing noise and additional heating and cooling noise sources. Observe that in the presence of this type of noise, no fault-tolerance threshold is found. This changed under the application of leakage reduction techniques, making it possible to recover a threshold. This numerical experiment, performed with a few lines of code in Plaquette emphasizes the importance of leakage reduction techniques for fault-tolerant quantum computing with superconducting qubits.