  A global race towards developing a gate-based, universal quantum computer
that one day promises to unlock the never before seen computational power has
begun and the biggest challenge in achieving this goal arguably is the quality
implementation of a two-qubit gate. In a trapped-ion quantum computer, one of
the leading quantum computational platforms, a two-qubit gate is typically
implemented by modulating the individual addressing beams that illuminate the
two target ions, which, together with others, form a linear chain. The required
modulation, expectedly so, becomes increasingly more complex, especially as the
quantum computer becomes larger and runs faster, complicating the control
hardware design. Here, we develop a simple method to essentially remove the
pulse-modulation complexity at the cost of engineering the normal modes of the
ion chain. We demonstrate that the required mode engineering is possible for a
three ion chain, even with a trapped-ion quantum computational system built and
optimized for a completely different mode of operations. This indicates that a
system, if manufactured to target specifically for the mode-engineering based
two-qubit gates, would readily be able to implement the gates without
significant additional effort.
