  A novel two-qubit entangling gate for RF-controlled trapped-ion quantum
processors is proposed theoretically and demonstrated experimentally. The speed
of this gate is an order of magnitude higher than that of previously
demonstrated two-qubit entangling gates in static magnetic field gradients. At
the same time, the phase-modulated field driving the gate, dynamically
decouples the qubits from amplitude and frequency noise, increasing the qubits'
coherence time by two orders of magnitude. The gate requires only a single
continuous RF field per qubit, making it well suited for scaling a quantum
processor to large numbers of qubits. Implementing this entangling gate, we
generate the Bell states $|\Phi^+\rangle$ and $|\Psi^+\rangle$ in $\leq 313$
$\mathrm{\mathrm{\mu}}$s with fidelities up to $98^{+2}_{-3}$ % in a static
magnetic gradient of only 19.09 T/m. At higher magnetic field gradients, the
entangling gate speed can be further improved to match that of laser-based
counterparts.
