Quantum amplification of boson-mediated interactions

Strong and precisely controlled interactions between quantum objects are essential for quantum information processing(1,2), simulation(3) and sensing(4,5), and for the formation of exotic quantum matter(6). 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(7), superconducting qubits(8), and colour centres in diamond(9), and phonon-mediated interactions between trapped ions(10-12) and between optical and microwave photons(13). 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(14-24), but has not, so far, 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(21). The amplification provides up to a 3.25-fold increase in the interaction strength, validated by measuring the speed-up 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.