  A major obstacle in the way of practical quantum computing is achieving
scalable and robust high-fidelity entangling gates. To this end, quantum
control has become an essential tool, as it can make the entangling interaction
resilient to sources of noise. Nevertheless, it may be difficult to identify an
appropriate quantum control technique for a particular need given the breadth
of work pertaining to robust entanglement. To this end, we attempt to
consolidate the literature by providing a non-exhaustive summary and critical
analysis. The quantum control methods are separated into two categories:
schemes which extend the robustness to (i) spin or (ii) motional decoherence.
We choose to focus on extensions of the $\sigma_x\otimes\sigma_x$
Molmer-Sorensen interaction using microwaves and a static magnetic field
gradient. Nevertheless, some of the techniques discussed here can be relevant
to other trapped ion architectures or physical qubit implementations. Finally,
we experimentally realize a proof-of-concept interaction with simultaneous
robustness to spin and motional decoherence by combining several quantum
control methods presented in this manuscript.
