Abstract
We propose a quantum critical detector (QCD) to amplify weak input signals. Our detector exploits a first-order discontinuous quantum-phase-transition and exhibits giant sensitivity (χ ∝ N2) when biased at the critical point. We propose a model consisting of spins with long-range interactions coupled to a bosonic mode to describe the time-dynamics in the QCD. We numerically demonstrate dynamical features of the first order (discontinuous) quantum phase transition such as time-dependent quantum gain in a system with 80 interacting spins. We also show the linear scaling with the spin number N in both the quantum gain and the corresponding signal-to-quantum noise ratio during the time evolution of the device. Our work shows that engineering first order discontinuous quantum phase transitions can lead to a device application for metrology, weak signal amplification, and single photon detection.
Highlights
We introduce a first-order quantum-phase-transition model, which exhibits giant sensitivity χ ∝ N 2 at the critical point
The goal of this paper is to propose a class of biased detectors with an amplification scheme that exploits quantum criticality in first-order dynamical quantum phase transitions (DQPT)
Most of the Quantum phase transition (QPT) discovered in physical systems are of second-order [11,12,13,14,15,16] and they have been proposed as a resource for metrology
Summary
During the time-evolution of our detector revealing high figures of merit. First-Order Quantum Phase Transition—The key element of a QCD is the first-order QPT based quantum amplification. To characterize the quantum phases and the corresponding QPTs in our Dicke-LMGy model, we introduce two new magnetic order parameters (OPs): ζM,x = Sx2 0/N 2 and ζM,y = Sy2 0/N 2 (Sα = j σjα/2 and · · · 0 means averaging on the ground state) characterizing the magnetic fluctuations in the spins along x and y axes, respectively. Once the spinspin coupling increases, there is no paramagnetic phase and there exists only a ferromagnetic phase for all spinboson coupling strengths This ferromagnetism is evident by studying the magnetic order parameter in Fig. 3 (b) (black, blue and gray curves). We predict that this type of first-order QPT should exist in the Ising XY-model [20] Another important characteristic is that the first-order phase transition point is sensitive to the spin-spin coupling (bias) while the second order ones in Fig. 2 (a) is not. This N 2 scaling, unique to our model arising from competing phases, may be used to en-
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
