Recent years, quantum computers have been actively studied for their potential to solve combinatorial optimization problems and other computational tasks that are intractable for classical computers within a feasible time. However, scalability remains a critical challenge, particularly due to the wiring overhead required for control and readout in cryogenic environments.
In this work, we investigate a readout scheme for transmon qubits by coupling them to a nonlinear resonator known as a Josephson Parametric Oscillator (JPO). We propose that the internal state of the qubit can be
inferred from the oscillation phase of the JPO. To enhance system scalability, we convert the phase of the JPO oscillation current into digital signals using an Adiabatic Quantum-Flux-Parametron (AQFP) circuit, enabling in-situ digital signal processing at cryogenic temperatures.
In this presentation, we report our recent progress in reading out the oscillation phase of the JPO using an AQFP circuit and discuss the implications of this approach for scalable quantum computing architectures.