Techniques for microwave near-field quantum control of trapped ions
Ulrich Warring, C. Ospelkaus, Yves Colombe, Kenneth R. Brown, Jason Amini, Martina Carsjens, Dietrich G. Leibfried, D. J. Wineland · Physical Review A · 2013
Microwave near-field quantum control of spin and motional degrees of freedom of ${}^{25}$Mg${}^{+}$ ions can be used to generate two-ion entanglement, as recently demonstrated in Ospelkaus et al. [Nature 476, 181 (2011)]. Here, we describe additional details of the setup and calibration procedures for these experiments. We discuss the design and characteristics of the surface-electrode trap and the microwave system and compare experimental measurements of the microwave near fields with numerical simulations. Additionally, we present a method that utilizes oscillating magnetic-field gradients to detect micromotion induced by the ponderomotive radio-frequency potential in linear traps. Finally, we discuss the present limitations of microwave-driven two-ion entangling gates in our system.