Mitigation of frequency noise due to mechanical vibration in a cryogenic trapped-ion quantum processor

Trapped-ion systems equipped with closed-cycle cryocoolers confer several cost-efficient advantages over traditional room-temperature designs. For example, operation of ion traps at cryogenic temperatures has been shown to lower rates of anomalous motional heating, a limit to multi-qubit logic fidelity, by up to two orders of magnitude. This environment also permits the use of superconducting materials to shield the ion qubits from magnetic field fluctuations. Additionally, cryopumping quickly produces ultrahigh vacuum conditions without the need for extended high-temperature chamber bakeouts, greatly reducing the cycle time of ion trap prototyping. However, mechanical vibrations caused by the cryocooler compressor can degrade quantum gate performance. Specifically, we have identified uncompensated Doppler shifts due to the relative motion of the ion with respect to the laser driving our gates as a leading source of decoherence. Here we describe the recent implementation of an interferometric stabilization scheme that actively modulates the qubit laser frequency to compensate for the motion induced by the cryocooler vibration. We observe a significant increase in the laser-ion coherence time and investigate the effect of this frequency stabilization on two-qubit gate performance.