Quantum Critical Detector : Amplifying Weak Signals Using First-Order Dynamical Quantum Phase Transitions

TL;DR

This paper introduces a quantum critical detector leveraging first-order dynamical quantum phase transitions to amplify weak signals with high sensitivity, demonstrating potential for quantum metrology and single-photon detection.

Contribution

It proposes a novel quantum critical detector based on dynamical quantum phase transitions, showing linear scaling of gain and noise ratio with system size.

Findings

Giant sensitivity proportional to N^2 at the critical point.

Time-dependent quantum gain demonstrated through numerical simulations.

Linear scaling of gain and noise ratio with the number of spins.

Abstract

We introduce a first-order quantum-phase-transition model, which exhibits giant sensitivity $\chi \propto N^2$ at the critical point. Exploiting this effect, we propose a quantum critical detector (QCD) to amplify weak input signals. The time-dynamic QCD functions by triggering a first-order dynamical quantum phase transition in a system of spins with long-range interactions coupled to a bosonic mode. We numerically demonstrate features of the dynamical quantum phase transition, which leads to a time-dependent quantum gain. We also show the linear scaling with the spin number $N$ in both the quantum gain and the corresponding signal-to-quantum noise ratio of this QCD. Our QCD can be a resource for metrology, weak signal amplification, and single photon detection.