Markovian dynamics under weak periodic coupling

Non-Markovian noise that cannot be dynamically decoupled by periodic spin echo pulses

Dynamical decoupling is the leading technique to remove unwanted interactions in a vast range of quantum systems through fast rotations. But what determines the time-scale of such rotations in order to achieve good decoupling? By providing an explicit counterexample of a qubit coupled to a charged particle and magnetic monopole, we show that such time-scales cannot be decided by the decay profile induced by the noise: even though the system shows a quadratic decay (a Zeno region revealing non-Markovian noise), it cannot be decoupled by periodic spin echo pulses, no matter how fast the rotation…

On the Floquet analysis of commutative periodic Lindbladians in finite dimension

We consider the Markovian Master Equation over matrix algebra $\mathbb{M}_d$, governed by periodic Lindbladian $L_t$ in standard (Kossakowski-Lindblad-Gorini-Sudarshan) form. It is shown that under simplifying assumption of commutativity, i.e. if $L_t L_{t'} = L_{t'}L_t$ for any moments of time $t,t'\in\mathbb{R}_+$, the Floquet normal form of resulting completely positive dynamical map is not guaranteed to be given by simultaneously globally Markovian maps. In fact, the periodic part of the solution is even shown to be necessarily non-Markovian. Two examples in algebra $\mathbb{M}_2$ are expl…

马尔可夫量子主方程在弱耦合 regime 中的指数精度

Markovian quantum master equations are exponentially accurate in the weak coupling regime

本研究证明在弱耦合下，开放量子系统的非马尔可夫成分可通过马尔可夫量子主方程指数抑制，该方程通过广义Born-Markov近似获得并可迭代至任意阶次。