QPlacer: Frequency-Aware Component Placement for Superconducting Quantum Computers

Abstract

Quantum Computers face a critical limitation in qubit numbers, hindering their progression towards large-scale and fault-tolerant quantum computing. A significant challenge impeding scaling is crosstalk, characterized by unwanted interactions among neighboring components on quantum chips, including qubits, resonators, and substrates. We motivate a general approach to systematically resolving multifaceted crosstalks in a limited substrate area. We propose QPlacer, a frequency-aware electrostatic-based placement framework tailored for superconducting quantum computers, to alleviate crosstalk by isolating these components in spatial and frequency domains alongside compact substrate design. QPlacer commences with a frequency assigner that ensures frequency domain isolation for qubits and resonators. It then incorporates a padding strategy and resonator partitioning for layout flexibility. Central to our approach is the conceptualization of quantum components as charged particles, enabling strategic spatial isolation through a ‘frequency repulsive force’ concept. Our results demonstrate that QPlacer carefully crafts the physical component layout in mitigating various crosstalk impacts while maintaining a compact substrate size. On various device topologies and NISQ benchmarks, QPlacer improves fidelity by an average of 37.5 × and reduces spatial violations (susceptible to crosstalk) by an average of 12.76 ×, compared to classical placement engines. Regarding area optimization, compared to manual designs, QPlacer can reduce the required layout area by 2.14 × on average.