Speaker
Description
Conventional two-qubit gate mechanisms feature high connectivity between spatially-separated qubits, mediated by collective vibrations of ions within a single trap. However, controlling off-resonant excitation of spectator modes becomes increasingly challenging as the length of the chain increases, reducing gate speeds and fidelities. Modern architectures circumvent this challenge by separating ions into small chains connected via ion shuttling or photonic interconnects. However, these approaches introduce significant resource overheads, making them the primary bottlenecks when scaling trapped-ion processors.
An alternative pathway to increasing quantum logic rates in trapped-ion systems is to employ ‘fast gate’ protocols, where the ions are subject to sequences of spin-dependent kicks (SDKs) driven by broadband laser pulses. Previous studies suggest fast gates can enable MHz quantum logic rates in current trapped-ion processors without reduction of gate speed in scaled ion crystals, while also supporting more flexible trap geometries. However, while fast gates have been widely studied in the context of nearest-neighbour operations, their potential for enabling scalable, high-connectivity architectures remains an open question.
We present a theoretical study of fast all-to-all entangling gates in trapped-ion processors [1]. We explore how fast gate protocols operating in different regimes of the ion dynamics can be exploited to achieve high-fidelity, non-local entangling operations in scalable trapped-ion crystals. In particular, we identify a regime of phonon-mediated entanglement in which gates between arbitrary ion pairs can be performed in approximately 1.3-2 center-of-mass oscillation periods. We further assess the experimental feasibility of the proposed gate schemes, showing that the required SDK resources are independent of both chain length and qubit separation [2].
These results suggest that entangling gates based on impulsive spin-dependent excitation can overcome key scaling bottlenecks in trapped-ion platforms, and outline pathways toward combining fast operation, high connectivity, and modular scalability in future quantum processors.
[1] I. Savill-Brown, J. J. Hope, A. K. Ratcliffe, V. D. Vaidya, H. Liu, et al. High-Speed and High-Connectivity Two-Qubit Gates in Long Chains of Trapped Ions. 2025. arXiv: 2506.11385 [quant-ph].
[2] I. Savill-Brown, Z. Mehdi, A. K. Ratcliffe, V. D. Vaidya, H. Liu, et al. Error-Resilient Fast Entangling Gates for Scalable Ion-Trap Quantum Processors. 2025. arXiv: 2508.07593 [quant-ph].
| Academic level | PhD student |
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