  Trapped ions are a promising tool for building a large-scale quantum
computer. However, the number of required radiation fields for the realisation
of quantum gates in any proposed ion-based architecture scales with the number
of ions within the quantum computer, posing a major obstacle when imagining a
device with millions of ions. Here we present a fundamentally different concept
for trapped-ion quantum computing where this detrimental scaling entirely
vanishes, replacing millions of radiation fields with only a handful of fields.
The method is based on individually controlled voltages applied to each logic
gate location to facilitate the actual gate operation analogous to a
traditional transistor architecture within a classical computer processor. To
demonstrate the key principle of this approach we implement a versatile quantum
gate method based on long-wavelength radiation and use this method to generate
a maximally entangled state of two quantum engineered clock-qubits with
fidelity 0.985(12). This quantum gate also constitutes a simple-to-implement
tool for quantum metrology, sensing and simulation.
