Hangxi Li, Avdelningen för kvantteknologi

Sammanfattning: Superconducting quantum processors are promising platforms to achieve quantum computational advantage and implement useful quantum algorithms. In this seminar, we will present our successful design and demonstration of superconducting quantum devices in a flip-chip architecture with qubit coherence (>90 µs), gate fidelities (single-qubit gate >99.9%, two-qubit gate >98.6%) and readout fidelity (99.5%) that are near the state of art in the community [1,2]. In addition, since future large-scale quantum processors require repeating designs of a large number of coplanar-waveguide resonators and qubits within one module, to reduce the computational resources of the design process, we will also present an analytic method to predict the resonators’ parameters directly from their 2-D cross-sections, avoiding computationally heavy and time-consuming 3-D simulations. We verify this method by measuring 15 resonators within a multi-qubit flip-chip-integrated superconducting quantum processor, achieving a discrepancy of less than 2% between designed and measured resonator frequencies [3].
References:
[1] Sandoko Kosen, Hang-Xi Li, Marcus Rommel, Daryoush Shiri, Christopher Warren, Leif Grönberg, Jaakko Salonen, Tahereh Abad, Janka Biznárová, Marco Caputo, Liangyu Chen, Kestutis Grigoras, Göran Johansson, Anton Frisk Kockum, Christian Križan, Daniel Pérez Lozano, Graham J. Norris, Amr Osman, Jorge Fernández-Pendás, Alberto Ronzani, Anita Fadavi Roudsari, Slawomir Simbierowicz, Giovanna Tancredi, Andreas Wallraff, Christopher Eichler, Joonas Govenius, and Jonas Bylander (2022). “Building Blocks of a Flip-Chip Integrated Superconducting Quantum Processor.” Quantum Science and Technology 7(3):035018. doi: 10.1088/2058-9565/ac734b

[2] Liangyu Chen, Hang-Xi Li, Yong Lu, Christopher W. Warren, Christian J. Križan, Sandoko Kosen, Marcus Rommel, Shahnawaz Ahmed, Amr Osman, Janka Biznárová, Anita Fadavi Roudsari, Benjamin Lienhard, Marco Caputo, Kestutis Grigoras, Leif Grönberg, Joonas Govenius, Anton Frisk Kockum, Per Delsing, Jonas Bylander, and Giovanna Tancredi (2023). “Transmon Qubit Readout Fidelity at the Threshold for Quantum Error Correction without a Quantum-Limited Amplifier.” Npj Quantum Information 9(1):26. doi: 10.1038/s41534-023-00689-6
[3] Hang-Xi Li, Daryoush Shiri, Sandoko Kosen, Marcus Rommel, Lert Chayanun, Andreas Nylander, Robert Rehammar, Giovanna Tancredi, Marco Caputo, Kestutis Grigoras, Leif Grönberg, Joonas Govenius, and Jonas Bylander (2023). “Experimentally Verified, Fast Analytic, and Numerical Design of Superconducting Resonators in Flip-Chip Architectures.” IEEE Transactions on Quantum Engineering 4:1–12. doi: 10.1109/TQE.2023.3302371

Supervisors: Jonas Bylander and Daryoush Shiri
Discussion leader: Prof. Philippe Tassin, Dept. of Physics