Cooperative robustness to dephasing: Single-exciton superradiance in a nanoscale ring to model natural light-harvesting systems

Abstract

We analyze a 1-d ring structure composed of many two-levels systems, in the limit where only one excitation is present. The two-levels systems are coupled to a common environment, where the excitation can be lost, which induces super and subradiant behavior. Moreover, each two-levels system is coupled to another independent environment, modeled by a classical white noise, simulating a dephasing bath and described by the Haken-Strobl master equation. Single exciton Superradiance, an example of cooperative quantum coherent effect, is destroyed at a critical dephasing strength proportional to the system size, showing robustness of cooperativity to the action of the dephasing environment. We also show that the coupling to a common decay channel contrasts the action of dephasing, driving the entanglement decay to slow down on increasing the system size. Moreover, after a projective measurement which finds the excitation in the system, the entanglement reaches a stationary value, independent of the initial conditions.

Cooperative robustness to static disorder: Superradiance and localization in a nanoscale ring to model light-harvesting systems found in nature

“…This is in agreement with the results recently found in Ref. [16], where the same ring structure has been analyzed in presence of dephasing (dynamical disorder) and the strength necessary to destroy Superradiance was found to be proportional to both γ and N .…”

“…• in the strong opening regime, Superradiance is quenched at a critical disorder proportional to N γ, as in the case of time-dependent disorder [16], thus showing its cooperative robusteness to disorder;…”

“…It is interesting to observe that also in the case of dynamical disorder it was found [16] that the critical dephasing necessary to destroy the cooperative superradiant effects is proportional to both N and γ. Note that this regime was not analyzed in Ref.…”

“…By static disorder we mean position dependent, but time-independent, fluctuations of the site energies. The case of time-dependent fluctuations of site energies has been considered in a separate paper [16].…”

Water Bridging Dynamics of Polymerase Chain Reaction in the Gauge Theory Paradigm of Quantum Fields

“…These remarks may account for the stability and efficiency of the PCR process against the high temperatures (up to 95 • C) of the various thermal cycles, otherwise inexplicable in a purely statistical approach based on molecular kinematics. These kinds of enhancement phenomena for the coupling constants are well known to occur in superradiance and cooperative two-level systems [33,34]. As a result, the macroscopic stability of the system follows since it is protected against quantum fluctuations in the microscopic short-range dynamics, and, for sufficiently large N, against thermal fluctuations, unless k B T is of the same order or larger than the height of the protective energy gap.…”