Ion trap-integrated optical cavities for fast networked quantum computation

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The QCS vision of quantum computing using distributed modular processors (networked 'nodes') depends upon the rapid production of remote entanglement between nodes. The current state-of-the-art rate is our NQIT result of 182 Hz [Phys. Rev. Lett. 124, 110501 (2020)]; any further performance increases will be modest and hard-won, due to the limited photon collection efficiency achievable via refractive optics. Meanwhile, a useful networked processor will require much higher remote entanglement rates. Critically, it will also need simpler and more reliable nodes, with a design amenable to large-scale fabrication and requiring minimal maintenance and calibration.It has long been recognised that optical cavities provide an elegant route to photon collection with near-unit efficiency. This presents the possibility of high-fidelity remote entangling operations at MHz rates, comparable to that of the fastest local two-qubit ion gates. However, experiments combining ion traps and cavities have historically struggled with a series of technical challenges. These have ranged from the difficulty of maintaining mirror alignment, to perturbations of the trapping potential due to the proximity of the dielectric mirror surfaces