We demonstrate a system for intensity stabilisation of optical pulse sequences used in laser-driven quantum control of trapped ions. Intensity instability is minimised by active stabilisation of the power (over a dynamic range of > 104 ) and position of the focused beam at the ion. The fractional Allan deviations in power were found to be < 2.2 × 10−4 for averaging times from 1 to 16,384 s. Over similar times, the absolute Allan deviation of the beam position is < 0.1 μm for a 45 μm beam diameter. Using these residual power and position instabilities, we estimate the associated contributions to infidelity in example qubit logic gates to be below 10−6 per gate.
- optical pulse
- laser-driven qubits