Tscherbul Timur V, Brumer Paul
Chemical Physics Theory Group, Department of Chemistry, and Center for Quantum Information and Quantum Control, University of Toronto, Toronto, Ontario M5S 3H6, Canada.
Phys Rev Lett. 2014 Sep 12;113(11):113601. doi: 10.1103/PhysRevLett.113.113601. Epub 2014 Sep 11.
We present a theoretical study of noise-induced quantum coherences in a model three-level V-type system interacting with incoherent radiation, an important prototype for a wide range of physical systems ranging from trapped ions to biomolecules and quantum dots. By solving the quantum optical equations of motion, we obtain analytic expressions for the noise-induced coherences and show that they exhibit an oscillating behavior in the limit of large excited level spacing Δ (Δ/γ≫1, where γ is the radiative decay width). Most remarkably, we find that in the opposite limit of small level spacing Δ/γ≪1, appropriate for large molecules, (a) the coherences can survive for an extremely long time τ=(2/γ)(Δ/γ)^{-2} before eventually decaying to zero, and (b) coherences at short times can be substantial. We further show that the long-lived coherences can survive environmental relaxation and decoherence, suggesting implications to the design of quantum heat engines and to incoherent light excitation of biological systems.
我们对一个与非相干辐射相互作用的三能级V型模型系统中的噪声诱导量子相干性进行了理论研究，该系统是从捕获离子到生物分子和量子点等广泛物理系统的重要原型。通过求解量子光学运动方程，我们得到了噪声诱导相干性的解析表达式，并表明在大激发能级间距Δ（Δ/γ≫1，其中γ是辐射衰变宽度）的极限情况下，它们呈现出振荡行为。最显著的是，我们发现在适合大分子的小能级间距Δ/γ≪1的相反极限情况下，（a）相干性可以在极长的时间τ=(2/γ)(Δ/γ)^{-2}内持续存在，最终才衰减到零，并且（b）短时间内的相干性可以相当可观。我们进一步表明，长寿命相干性可以经受环境弛豫和退相干，这对量子热机的设计以及生物系统的非相干光激发具有启示意义。
