Non-Markovianity of Quantum Brownian Motion

Ancillary Gaussian modes activate the potential to witness non-Markovianity

We study how the number of employed modes impacts the ability to witness non-Markovian evolutions via correlation backflows in continuous-variable quantum dynamics. We first prove the existence of non-Markovian Gaussian evolutions that do not show any revivals in the correlations between the mode evolving through the dynamics and a single ancillary mode. We then demonstrate how this scenario radically changes when two ancillary modes are considered. Indeed, we show that the same evolutions can show correlation backflows along a specific bipartition when three-mode states are employed, and wher…

Gaussian interferometric power as a measure of continuous variable non-Markovianity

We investigate the non-Markovianity of continuous variable Gaussian quantum channels through the evolution of an operational metrological quantifier, namely the Gaussian interferometric power, which captures the minimal precision that can be achieved using bipartite Gaussian probes in a black-box phase estimation setup, where the phase shift generator is \emph{a priori} unknown. We observe that the monotonicity of the Gaussian interferometric power under the action of local Gaussian quantum channels on the ancillary arm of the bipartite probes is a natural indicator of Markovian dynamics; cons…

Non-Markovianity-assisted optimal continuous variable quantum teleportation

We study the continuous-variable (CV) quantum teleportation protocol in the case that one of the two modes of the shared entangled resource is sent to the receiver through a Gaussian Quantum Brownian Motion noisy channel. We show that if the channel is engineered in a non-Markovian regime, the information backflow from the environment induces an extra dependance of the phase of the two-mode squeezing of the shared Gaussian entangled resource on the transit time along the channel of the shared mode sent to the receiver. Optimizing over the non-Markovianity dependent phase of the squeezing yield…

Effects of counter-rotating-wave terms on the non-Markovianity in quantum open systems

We investigate the effect of counter-rotating-wave terms on the non-Markovianity in quantum open systems by employing the hierarchical equations of motion in the framework of the non-Markovian quantum state diffusion approach. As illustrative examples, the non-Markovian memory effect of a qubit embedded in a bosonic and a fermionic environment at zero temperature are analyzed. It is found that the counter-rotating-wave terms are able to enhance the observed non-Markovianity no matter the environment is composed of bosons or fermions. This result suggests that the rotating-wave approximation ma…

Non-Markovianity in the optimal control of an open quantum system described by hierarchical equations of motion

Optimal control theory is implemented with fully converged hierarchical equations of motion (HEOM) describing the time evolution of an open system density matrix strongly coupled to the bath in a spin-boson model. The populations of the two-level sub-system are taken as control objectives; namely, their revivals or exchange when switching off the field. We, in parallel, analyze how the optimal electric field consequently modifies the information back flow from the environment through different non-Markovian witnesses. Although the control field has a dipole interaction with the central sub-sys…

开放系统中信息流的相空间测度：非马尔可夫性的量子与经典视角

Phase space measures of information flow in open systems: A quantum and classical perspective of non-Markovianity

本研究建立了开放系统中量子迹距离与相空间准概率分布Kolmogorov距离的对应关系，通过Caldeira-Legget模型验证了Wigner函数距离在经典极限下快速收敛于迹距离，为半经典信息回流与连续变量系统非马尔可夫性量化提供了最优工具。

Brownian Motion and Quantum Mechanics

A theoretical parallel between the classical Brownian motion and quantum mechanics is explored. It is shown that, in contrast to the classical Langevin force, quantum mechanics is driven by turbulent velocity fluctuations with diffusive behavior. In the case of simultaneous action of the two stochastic sources, the quantum Brownian motion takes place, which is theoretically described as well.

Momentum coupling in non-Markovian Quantum Brownian motion

We consider a model of non-Markovian Quantum Brownian motion that consists of an harmonic oscillator bilinearly coupled to a thermal bath, both via its position and momentum operators. We derive the master equation for such a model and we solve the equations of motion for a generic Gaussian system state. We then investigate the resulting evolution of the first and second moments for both an Ohmic and a super-Ohmic spectral density. In particular, we show that, irrespective of the specific form of the spectral density, the coupling with the momentum enhances the dissipation experienced by the s…

强场区域及非马尔可夫性下的囚禁离子动力学实现

Realization of Trapped Ion Dynamics in the Strong-Field Regime and Non-Markovianity

该研究实验探究了强驱动区域下囚禁离子的动力学，利用量子比特约化动力学表征物理现象，观测到遵循广义共振条件的结构化非马尔可夫响应，揭示了强自旋-运动杂化特性。

耗散驱动量子比特中非马尔可夫性的动力学特征

Dynamical signatures of non-Markovianity in a dissipative-driven qubit

本文研究了耗散玻色子环境中周期性驱动量子比特的非马尔可夫动力学特征，通过数值精确的HEOM方法量化了多种非马尔可夫指标，发现外部驱动可增强非马尔可夫效应并抵消各态历经弛豫，在弱耦合下观察到永恒非马尔可夫性现象。

Brownian Motion: The Quantum Perspective

We briefly go through the problem of the quantum description of Brownian motion, concentrating on recent results about the connection between dynamics of the particle and dynamic structure factor of the medium.

Exact non-Markovian dynamics of Gaussian quantum channels: Finite-time and asymptotic regimes

We investigate the Markovian and non-Markovian dynamics of Gaussian quantum channels, exploiting a recently introduced necessary and sufficient criterion and the ensuing measure of non-Markovianity based on the violation of the divisibility property of the dynamical map. We compare the paradigmatic instances of Quantum Brownian motion (QBM) and Pure Damping (PD) channels, and for the former we find that the exact dynamical evolution is always non-Markovian in the finite-time as well as in the asymptotic regimes, for any nonvanishing value of the non-Markovianity parameter. If one resorts to th…

Overview: Brownian Motion and Dephasing due to Dynamical Disorder

The motion of a particle under the influence of a dynamical disorder is described by the DLD model. One motivation is to understand the motion of an electron inside a metal; Another is to understand quantal Brownian motion. The overview is based on a research report for 1996-1998.