The Rx Gate

The Rx(theta) gate is a continuous X-axis rotation - the tunable knob a drive pulse physically implements in the circuits Kronos runs.

What it does

Rx(theta) = cos(theta/2) I - i sin(theta/2) X. It is generated by the Pauli-X Hamiltonian, so a resonant microwave drive of controlled duration is an Rx.

Where it appears at Kronos

Continuous rotations are the trainable parameters in the variational circuits Kronos uses for materials chemistry and control optimization; the optimizer literally searches over angles like this theta.

Honest note

Variational methods run today but are noise-limited; the durable advantage is expected ~mid-2030s.