Entropy dynamics for a harmonic propeller-shaped planar molecular quantum Brownian rotator

Dynamic stability is vital for the operation and control of molecular nanodevices, particularly molecular cogwheels in an external harmonic field. We used the relative change in rotator entropy as a measure of dynamical stability. This rotator dynamic is described by the Caldeira–Leggett quantum master equation: the main challenge is the absence of a general solution for this equation. As an alternative, we look for the initial states (pure or mixed) of the rotator that result in low entropy change. In order to create candidate initial states, we use an ansatz that align with the maximum entropy principle. We then find conditions for state preparation and system/bath parameters to achieve a small relative change in both linear and differential entropy in underdamped and non-underdamped regimes. We identify cases with relatively small entropy change and discuss their practical feasibility.