Waveguide-QED-based measurement of a reservoir spectral density

Abstract

The spectral density (SD) function has a central role in the study of open quantum systems (OQSs). We discover a method allowing for a "static" measurement of the SD -i.e., it requires neither the OQS to be initially excited nor its time evolution tracked in time -which is not limited to the weak-coupling regime. This is achieved through one-dimensional photon scattering for a zero-temperature reservoir coupled to a two-level OQS via the rotating wave approximation. We find that the SD profile is a universal simple function of the photon's reflectance and transmittance. As such, it can be straightforwardly inferred from photon's reflection and transmission spectra.

Dressed emitters as impurities

“…A quantum emitter coupled to a homogeneous photonic reservoir has interesting analogies with the textbook impurity problem in condensed matter [16]. For instance, the reflection and transmission coefficients of a photon scattering off an atom in a waveguide are formally the same as those for an impurity described by an effective, energy-dependent, scattering potential [17,18]. Moreover, as first suggested in Ref.…”

“…Notice that, for z / ∈ R, generally F 12 = F * 21 , and that |Ψ i (z) and F ii (z) coincide with Eqs. ( 17) and (18), respectively, when |0 is replaced by |x i .…”

Optomechanical force sensor in a non-Markovian regime

“…In figure 2(b), we plot the maximal ratio xm x0 c w c ( )/ of the susceptibility with a different environment as a function of the equivalent damping rate eff g . Here, eff g is a spectrum-dependent parameter which describes the dissipation strength of the structured bath; through the inverse Laplace transform of w S( ), we have eff m  g p w » ( ) [38]. Under this condition, eff g is proportional to the system-bath coupling strength η.…”

Remote weak signal measurement via bound states in optomechanical system

“…Theoretically, the waveguide can be treated as structured reservoirs [35][36][37][38][39], and the theory of non-Markovian quantum open system is an effective method to study the dynamics of the objects coupling to the reservoir. In cavity quantum electrodynamics regime, the structured reservoir can be photonic crystals or waveguides [37,[40][41][42][43][44]. It has been shown that the bound states without dissipation can be formed when system coupled to band gaps or finite band spectrum [36,45] which is easily satisfied in photonic crystals or waveguides [35,36,41,46,47].…”