Intrinsic error floor of Rydberg-blockade entangling gates
In plain words
Neutral-atom computers entangle two atoms by briefly lifting them to giant, strongly interacting Rydberg states (highly excited atomic states), which decay and are disturbed by room-temperature heat radiation. How small the gate error can be made, given these limits, is not known.
Precise statement
For controlled-Z gates between alkali or alkaline-earth atoms in optical tweezers using the Rydberg blockade, the error has contributions from radiative and blackbody-induced decay of the Rydberg state (lifetime $\tau_R$ of order $10^{-4}\,\mathrm{s}$ at 300 K for principal quantum number $n \sim 50-70$, approximate), finite blockade shift $B$ relative to the Rabi frequency, laser phase and intensity noise, and atomic motion. Determine the lowest achievable two-qubit error once all intrinsic contributions are minimized jointly over pulse shape and gate time, and decide whether errors $\le 10^{-4}$ are reachable at room temperature or require cryogenic environments or conversion of errors into detectable erasures.
What would settle it
A complete error budget, validated against measured gate errors, that gives the minimum CZ error versus $\tau_R$, $B$ and noise spectra, with an experiment approaching it.
Status in the literature
Evered et al. reported 99.5% two-qubit gate fidelity on up to 60 atoms in parallel (Nature 622, 268, 2023, arXiv:2304.05420); later records were not checked for this entry.