Abstract

Realizing large-scale superconducting quantum circuits containing individually addressable, high-coherence qubits remains a significant hardware challenge toward utility-scale quantum computing. Current scalability challenges include spurious microwave modes, Josephson-junction fabrication yield, design frequency targeting and decoherence from materials-related loss mechanisms. Scalable two-dimensional (2D) lattice architectures enable the implementation of logical operations using quantum error-correction codes, and the simulation of 2D lattice Hamiltonians in condensed matter physics. In this talk, we present the full characterization of a 4x4 square lattice of 16 fixed-frequency transmon qubits, demonstrating low crosstalk and single-qubit gate errors across the device. The lattice is implemented in a tileable 3D-integrated circuit architecture which is shown to maintain performance at larger scales through the use of off-chip inductive shunting to suppress enclosure modes. We discuss the design and fabrication process, and show measurements of qubit coherence, single- and two-qubit gates, and inter-qubit couplings. To investigate materials-induced decoherence, we complement this system-level characterization with atomic-scale analysis of circuit elements using high-resolution materials scanning and spectroscopy techniques. Our findings highlight the importance of interface quality in maintaining coherence and emphasize the need for an improved fabrication process as we scale up superconducting quantum circuits.

Biography

Mohammed is a Rhodes scholar and Ibn Rushd fellow, conducted his PhD research in superconducting quantum computing and condensed matter physics at the University of Oxford. His primary research interests lie in the development of quantum devices for quantum information processing and simulation. Mohammed completed his undergraduate studies in both physics and electrical engineering at King Fahd University (KFUPM) and has since gained valuable research experience at various prestigious institutions. He worked at King Abdullah University (KAUST) and developed novel surface treatments to reduce coherent losses in quantum devices. In addition, Mohammed worked at the Quantum Nanoelectronics Laboratory at the University of California, Berkeley, and at Lawrence Berkeley National Laboratory, investigating defects in quantum processors that limit their efficiency and controllability. Beyond these efforts, his other research interests include computational materials and machine learning.