Tailoring Tunable Interactions in Superconducting Circuits Mediated by Bosonic Modes

Gihwan Kim

California Institute of Technology, Pasadena, CA

Institute for Quantum Information and Matter, Pasadena, CA

Superconducting quantum circuits are a promising platform for fault-tolerant quantum computing and for exploring broader topics in quantum information science. Central to their flexibility is the ability to dynamically control coherent and dissipative interactions among qubits, resonators, and waveguides. This enables switching between distinct operational regimes required for crucial operations, such as idling, entangling operations, readout, and reset, within a single device.

Tunable coherent and dissipative interactions mediated by a single bosonic mode or a qubit have been highly successful. Representative examples include tunable couplers for nearest-neighbor two-qubit gates and single-pole Purcell filters for flux-controlled reset. However, emerging applications place demands that exceed what single-mode mediation can provide, such as achieving larger on/off ratios in interaction rates, and supporting increased or long-range connectivity.

In this talk, we explore richer schemes for tunable interactions that leverage either a small number or a continuum of bosonic modes. We show how multi-mode mediation enables new capabilities and performance regimes, and we discuss representative applications that illustrate advantages of these approaches. These include demonstrations of fast on-demand photon emission, rapid unconditional qubit reset, and dedicated leakage-reduction operations, as well as ongoing efforts toward simultaneous long-range connectivity in superconducting quantum circuits.