Crosstalk Dispersion and Spatial Scaling in Superconducting Quantum Arrays
ORAL
Abstract
Residual crosstalk between non-adjacent qubits introduces correlated errors that violate the independence assumptions underlying quantum error correction, presenting a critical barrier to fault-tolerant quantum computation. We present a theoretical framework and experimental results for understanding and suppressing crosstalk in fixed-frequency transmon arrays. The model captures three mechanisms: (i) exponential spatial localization arising from the inverse of banded capacitance matrices, (ii) suppression from virtual multi-hop paths that scales with detuning to intermediate modes, and (iii) enclosure-mediated coupling in a below-cutoff environment that decays with distance. Measurements on a 4×4 device with inductive shunt pillars reveal a strong separation dependence and show that treating exchange couplings as distance-independent causes standard dispersive estimates to overpredict non-nearest-neighbor interactions. Incorporating the spatial and spectral dependencies yields quantitative agreement and provides design rules for multi-band frequency allocation and geometry-aware layout that reduce long-range interactions while preserving intended nearest-neighbor coupling, offering a practical path to crosstalk-aware scaling of superconducting quantum processors.
*M.B. acknowledges support from EPSRC QT Fellowship grant EP/W027992/1, and EP/Z53318X/1. P.L. acknowledges support from EP/N015118/1, and EP/T001062/1. We would like to acknowledge the Superfab Nanofabrication facility at Royal Holloway, University of London, and Optoelectronics Research Centre at University of Southampton where part of device fabrication was performed, and thank Anuj Aggarwal for useful discussions.
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Presenters
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Mustafa Bakr
- University of Oxford