Curator's Take
AI Commentary
This article demonstrates the first steady‑state, mid‑circuit sympathetic cooling of every computationally relevant mode in a 23‑ion chain, showing that long ion strings can be kept near their motional ground state without interrupting qubit operations or sacrificing coherence. By using a second isotope as a coolant and preserving gate‑mode occupations over a 56 ms circuit, the work directly tackles the heating bottleneck that has limited trapped‑ion scalability beyond ten ions, complementing recent advances in fast entangling gates and modular architectures. The parallel reset protocol and demonstrated compatibility with high‑fidelity single‑ and two‑qubit gates suggest a practical path toward deeper algorithms and more realistic open‑system simulations on near‑term ion‑based quantum processors.
— Mark Eatherly
Summary
Owing to their high controllability and connectivity, one-dimensional ion chains are attractive building blocks for near-term quantum computers. However, long ion chains are susceptible to motional heating caused by fluctuating external electric fields. To enable deep computations, this source of noise must be suppressed without inducing qubit decoherence or degrading qubit connectivity. We demonstrate steady-state mid-circuit sympathetic cooling of all computationally-relevant motional modes of a 23-ion chain consisting of \qubit qubit and \coolant coolant ions without using any qubit operations. In a room-temperature system, our cooling scheme preserves the mean phonon occupations of the long-wavelength axial and radial modes near their values following state preparation, while keeping the modes used to implement entangling gates near their ground states throughout a 56-ms circuit. Crucially, we show that our cooling sequence preserves qubit coherence, and evaluate its impact on single- and two-qubit gate operations. Additionally, we demonstrate a parallel qubit reset protocol leveraging the shared radial mode coupling between species. Our sympathetic cooling scheme represents a critical step toward reducing gate errors in individually-addressed long ion chains and establishes a versatile platform for simulating open quantum systems.