Rydberg Blockade
The effect that gives neutral atoms their two-qubit gates: excite one to a giant orbit and within a blockade radius only a single atom can be excited at a time.
Neutral atoms normally ignore each other, which is what makes them quiet, well-behaved qubits, and also what makes two-qubit gates a puzzle. The solution is the Rydberg blockade. Excite an atom's outer electron to a huge, loosely bound orbit (a Rydberg state) and the atom balloons by a factor of thousands, suddenly interacting strongly with neighbors. Within a 'blockade radius,' only one atom can be excited at a time, and that conditional behavior is exactly the logic of an entangling gate.
The blockade is the engine of every neutral-atom quantum computer, including Atom Computing's machines in Boulder and the gate-fidelity records Infleqtion has been chasing with inter-species Rydberg gates. The atoms stay neutral and aloof until the laser asks them to interact, interaction on demand.