  Strong and precisely-controlled interactions between quantum objects are
essential for quantum information processing, simulation, and sensing, and for
the formation of exotic quantum matter. A well-established paradigm for
coupling otherwise weakly-interacting quantum objects is to use auxiliary
bosonic quantum excitations to mediate the interactions. Important examples
include photon-mediated interactions between atoms, superconducting qubits, and
color centers in diamond, and phonon-mediated interactions between trapped ions
and between optical and microwave photons. Boson-mediated interactions can in
principle be amplified through parametric driving of the boson channel; the
drive need not couple directly to the interacting quantum objects. This
technique has been proposed for a variety of quantum platforms, but has not to
date been realized in the laboratory. Here we experimentally demonstrate the
amplification of a boson-mediated interaction between two trapped-ion qubits by
parametric modulation of the trapping potential. The amplification provides up
to a 3.25-fold increase in the interaction strength, validated by measuring the
speedup of two-qubit entangling gates. This amplification technique can be used
in any quantum platform where parametric modulation of the boson channel is
possible, enabling exploration of new parameter regimes and enhanced quantum
information processing.
