Longitudinally Coupled Three-Qubit Circuits as Building Blocks for a Quantum Processor*

Efficient implementation of quantum algorithms requires precise control over single and multi-qubit gates in addition to maximum inter-qubit connectivity. We recently demonstrated a new three-qubit device called trimon [1], with all-to-all longitudinal coupling. Trimon has an eight-dimensional Hilbert space which can be controlled with high fidelity by manipulating twelve transitions. A π pulse on any of these transitions implements a generalized Toffoli gate which makes this processor fully programmable. We propose to use the trimon device as the building block for a quantum processor. As a first step, we will present preliminary experimental data demonstrating the conventional cross-resonance gate [2] between a trimon and a transmon. We will conclude by discussing the implementation of inter-trimon gates to realize a 3N-qubit quantum processor.
[1] Phys. Rev. Applied 7, 054025
[2] Phys. Rev. B 81, 134507