Multi-mode superconducting circuits for realizing strongly coupled multi-qubit processor units

  1. Tanay Roy,
  2. Madhavi Chand,
  3. Sumeru Hazra,
  4. Suman Kundu,
  5. Kedar Damle,
  6. and R. Vijay
Inter-qubit coupling and qubit connectivity in a processor are crucial for achieving high fidelity multi-qubit gates and efficient implementation of quantum algorithms. Typical superconducting processors employ relatively weak transverse inter-qubit coupling which are activated via frequency tuning or microwave drives. Here, we propose a class of multi-mode superconducting circuits which realize multiple transmon qubits with all-to-all longitudinal coupling. These „artificial molecules“ directly implement a multi-dimensional Hilbert space that can be easily manipulated due to the always-on longitudinal coupling. We describe the basic technique to analyze such circuits, compute the relevant properties and discuss how to optimize them to create efficient small-scale quantum processors with universal programmability.

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