Fig. 1. Erasure conversion for high-fidelity entanglement.

a, Level structure used in this work. We distinguish two subspaces: a qubit subspace in which the atoms interact via their Rydberg states and a measurement subspace used to detect leakage errors from the qubit subspace with single-site resolution, realizing erasure conversion. b, Sketch of the erasure-conversion scheme, as applied to Bell pair generation. After arranging atoms into pairs (top) we prepare them in $∣g⟩$, and entangle them via the Rydberg blockade mechanism (right), denoted by a unitary operation $\widehat{U}\left(t\right)$. Immediately afterwards, we auto-ionize atoms in $∣r⟩$, effectively projecting the populations of the Bell states, and follow with a fast erasure-conversion image to detect leakage out of the qubit subspace during the preparation or evolution periods. This is followed by the final detection of atoms in $∣g⟩$, yielding two separate, independent images. We can discard data from pairs where atoms are detected in the erasure-error image, termed erasure excision in the following. Atom fluorescence images are single shot, with post-processing applied to improve detection fidelity³⁰ (Methods). c, Lower bounds for Bell state fidelities with (blue) and without (pink) the erasure excision, and using incoherent repumping to reduce preparation errors instead of erasure excision (green; Methods). We present the results for the raw data, corrected for measurement errors and corrected for SPAM errors. All data are averaged over eight pairs of atoms that are excited in parallel. Error bars represent a 68% confidence interval (Extended Data Fig. 5 and Methods).