Robust and Resource-Efficient Microwave Near-Field Entangling 9Be+ Gate

Microwave trapped-ion quantum logic gates avoid spontaneous emission as a fundamental source of decoherence. However, microwave two-qubit gates are still slower than laser-induced gates and hence more sensitive to fluctuations and noise of the motional mode frequency. We propose and implement amplitude-shaped gate drives to obtain resilience to such frequency changes without increasing the pulse energy per gate operation. We demonstrate the resilience by noise injection during a two-qubit entangling gate with ⁹Be⁺ ion qubits. In the absence of injected noise, amplitude modulation gives an operation infidelity in the 10^-3 range.