TETRIS-Q: Tiling-based Effective Transient-fault Reduction and Parallelism Optimizations for Quantum Circuit Mapping
Rowan Brad Quni-Gudzinas
Abstract
Quantum circuit mapping on Noisy Intermediate-Scale Quantum (NISQ) devices must satisfy physical connectivity constraints while minimizing both SWAP overhead and exposure to transient faults like decoherence. Existing compilers typically optimize qubit routing and noise-aware placement independently, failing to jointly exploit spatial structure to reduce both SWAP depth and idle-time-induced decoherence. We introduce TETRIS-Q, a mapping framework that partitions the physical qubit topology into local rectangular tiles. This tiling abstraction enables a unified strategy: tile-local mapping minimizes idle qubit lifetimes, while cross-tile parallel scheduling maximizes concurrent two-qubit gate execution. By treating transient-fault probability as a function of idle duration and gate ordering, rather than just circuit depth, TETRIS-Q jointly penalizes SWAP count and cumulative idle time. On grid-heavy architectures, we project a 10–30% reduction in SWAP count [to verify] and measurable fidelity improvements over routing-only baselines [to verify]. This approach demonstrates that spatial tiling offers a robust paradigm for high-fidelity NISQ compilation. ## 1. Introduction Compiling quantum algorithms for Noisy Intermediate-Scale Quantum (NISQ) hardware requires mapping logical qubits onto physical qubits with limited connectivity. To execute gates between non-adjacent physical qubits, compilers insert SWAP gates—operations that exchange qubit states—to route interacting qubits into adjacency. While SWAP gates introduce additional circuit depth and gate errors, they also indirectly increase exposure to transient faults (decoherence and relaxation, characterized by T1 and T2 timescales) by extending the duration that idle qubits wait for dependent operations. Existing quantum compilers generally treat routing minimization and noise-aware placement as separate optimization passes. However, this independent optimization misses opportunities to exploit the spatial locali