Demonstrating a high-fidelity bosonic control architecture with a dynamic dispersive shift (part 2 of 2)

Encoding quantum information in bosonic modes provides a promising route toward fault-tolerant quantum computing within circuit-QED architectures. Traditionally, control over these harmonic oscillators is achieved through a direct coupling to auxiliary nonlinear elements, which can, however, introduce unwanted oscillator nonlinearity and dephasing. In this pair of talks, we experimentally demonstrate a multi-oscillator architecture that interrupts the always-on oscillator-transmon connection with a LINC[1] coupler that exhibits near-zero static nonlinearity. Using parametric drives, the LINC mediates resonant exchange interactions, including both oscillator–oscillator and oscillator–transmon couplings, at will. Further, by turning on a detuned exchange interaction, we can dynamically hybridize the oscillator with the nonlinearity, activating a parametric dispersive interaction for bosonic control. With its unique combination of static isolation and high-fidelity parametric operations, this architecture provides a versatile platform for exploring bosonic error correction that is no longer limited by auxiliary elements.

In part 2, we showcase some of the applications available with these tools, including a joint parity measurement of the oscillators' state, and chart a path towards fault-tolerant entangling operations with the auxiliary transmon qubit

[1] A. Maiti et al. "A linear quantum coupler for clean bosonic control" Arxiv:2501.18025