2019/11/18 by Mike Reppert, Deborah Reppert, Leonardo A. Pachón +2
Computer Science · Physics and Astronomy · #Advanced Thermodynamics and Statistical Mechanics #Boson #Classical mechanics #Coherence (philosophical gambling strategy) #Density matrix #Harmonic oscillator #Physics #Quantum #Quantum Information and Cryptography #Quantum mechanics #Quantum system #Semiclassical physics #Spectroscopy and Quantum Chemical Studies #Stationary state #Statistical physics #quant-ph
paper · pdf · doi:10.1103/physreva.102.012211
published as Phys. Rev. A 102, 012211 (2020) · 14 pages, 2 figures
arxiv created 2019/11/18 · openalex created_date 2019/11/22 · openalex publication_date 2020/07/09 · arxiv updated 2020/07/15 · openalex updated_date 2026/08/05
Interaction between a quantum system and its environment can induce stationary coherences---off-diagonal elements in the reduced system density matrix in the energy eigenstate basis---even at equilibrium. This work investigates the ``quantumness'' of such phenomena by examining the ability of classical and semiclassical models to describe equilibrium stationary coherence in the multilevel spin boson model, a common model for light-harvesting systems. A well justified classical harmonic-oscillator model is found to fail to capture equilibrium coherence. This failure is attributed to the effective weakness of classical system-bath interactions due to the absence of a discrete system energy spectrum and, consequently, of quantized shifts in oscillator coordinates. Semiclassical coherences also vanish for a dimeric model with parameters typical of biological light harvesting, i.e., where both system sites couple to the bath with the same reorganization energy. In contrast, equilibrium coherence persists in a fully quantum description of the same system, suggesting a uniquely quantum-mechanical origin for equilibrium stationary coherence in, e.g., photosynthetic systems. Finally, as a computational tool, a perturbative expansion is introduced that, at third order in \ensuremathℏ, gives qualitatively correct behavior at ambient temperatures for all configurations examined.