Towards an architecture for high-fidelity control of bosonic modes (Part 2 of 2)

Encoding quantum states in bosonic modes offers a promising pathway towards fault-tolerant quantum computing in circuit-QED systems. Conventionally, the control of such bosonic modes is realized via direct coupling to auxiliary nonlinear elements, which could introduce extraneous nonlinearity and dephasing to the memories. In this pair of talks, we propose and demonstrate a coupling architecture that interrupts the always-on resonator-qubit connection with a novel parametric coupling element, the Linear INductive Coupler (LINC), that exhibits near-zero static nonlinearity. With this arrangement, the resonators only see the nonlinearity that we desire, and only see it precisely when we activate it. Further, this same LINC can be used to mediate resonator-resonator interactions, allowing full control of multi-oscillator systems. With high-fidelity universal control that is no longer limited by auxiliary elements, this architecture can act as a fruitful testbed for novel quantum gate and readout schemes, bosonic error correction, and quantum simulation. In part 2, we present experimental results on driven behavior of the storage and ancilla modes in the system, as well as LINC-mediated parametric interactions between these modes.