Overcoming the Limits: Quantum-Limited Amplification and Enhanced Measurement Efficiency for Quantum Information Processing

Amplifying weak microwave signals at the quantum limit is a cornerstone of quantum information processing, enabling high-fidelity readout of quantum states. Current amplifier technologies fall into two main categories: traveling-wave designs, which exploit nonlinearity in propagating media to achieve broadband amplification, and standing-wave designs, which enhance nonlinearity within a cavity to achieve quantum-limited performance. While traveling-wave amplifiers offer broader bandwidth, achieving the quantum limit remains challenging. Conversely, standing-wave amplifiers can operate at the quantum limit but suffer from narrow bandwidth. Neither implementation is perfectly nonreciprocal, necessitating additional nonreciprocal components in the signal chain, which degrade measurement efficiency through added noise. In this talk, we address these challenges by presenting strategies to overcome gain-bandwidth trade-offs, achieve intrinsic nonreciprocity, and improve measurement efficiency for dispersive qubit readout in embedded designs. Our findings are supported by experimental results across multiple platforms, demonstrating practical pathways to enhanced quantum measurement performance.