Towards time-domain directional amplification with an embedded amplifier - Part I

To improve readout fidelity for quantum circuits, parametric amplification schemes must be able to scale efficiently in parallel with the number of output channels. Typical quantum parametric amplifiers lack directionality, and so use a circulator to separate the input and output fields, but microwave circulators are bulky and contribute to signal loss. In the first part of this two-talk series, we present a directional, multiplexed amplification design for three readout resonators coupled to transmons. A single, voltage-pumped SNAIL coupler implements a parametrically-controlled photon conversion between the readout resonators, SNAIL mode, and a single, short-lived output resonator. By sequentially applying photon conversion and gain processes among the SNAIL and resonator modes, we can transmit amplified light from the output mode with minimal loss and without amplifying in the qubit-adjacent readout resonators. We will present experimental progress towards the implementation of the full directional amplifier via characterization of the rate of photon conversion between the SNAIL and readout resonator modes, gain and isolation of the amplifier, and the amplifier's effect on coherence times on the transmon qubits.