Enhanced qubit readout using locally-generated squeezing and inbuilt Purcell-decay suppression

TL;DR

This paper proposes a novel dispersive qubit readout method that generates two-mode squeezing directly in measurement cavities, enhancing fidelity and protecting qubits from decoherence without external squeezed state injection.

Contribution

It introduces a self-contained squeezing-based readout scheme that suppresses noise and Purcell decay, improving qubit measurement fidelity and robustness in circuit QED systems.

Findings

Achieves high-fidelity qubit readout with noise suppression.

Automatically suppresses Purcell decay through interference.

Compatible with current circuit QED technology.

Abstract

We introduce and analyze a dispersive qubit readout scheme where two-mode squeezing is generated directly in the measurement cavities. The resulting suppression of noise enables fast, high- fidelity readout of naturally weakly coupled qubits, and the possibility to protect strongly coupled qubits from decoherence by weakening their coupling. Unlike other approaches exploiting squeezing, our setup avoids the difficult task of transporting and injecting with high fidelity an externally-generated squeezed state. Our setup is also surprisingly robust against unwanted non-QND backaction effects, as interference naturally suppresses Purcell decay: the system acts as its own Purcell filter. Our setup is compatible with the experimental state-of-the-art in circuit QED systems, but the basic idea could also be realized in other systems.