Eternally non-Markovian dynamics of a qubit interacting with a single-photon wavepacket

Entanglement negativity as a universal non-Markovianity witness

In order to engineer an open quantum system and its evolution, it is essential to identify and control the memory effects. These are formally attributed to the non-Markovianity of dynamics that manifests itself by the evolution being indivisible in time, a property which can be witnessed by a non-monotonic behavior of contractive functions or correlation measures. We show that by monitoring directly the entanglement behavior of a system in a tripartite setting it is possible to witness all invertible non-Markovian dynamics, as well as all (also non-invertible) qubit evolutions. This is achieve…

A class of quasi-eternal non-Markovian Pauli channels and their measure

We study a class of qubit non-Markovian general Pauli dynamical maps with multiple singularities in the generator. We discuss a few easy examples involving trigonometric or other non-monotonic time dependence of the map, and discuss in detail the structure of channels which don't have any trigonometric functional dependence. We demystify the concept of a singularity here, showing that it corresponds to a point where the dynamics can be regular but the map is momentarily non-invertible, and this gives a basic guideline to construct such non-invertible non-Markovian channels. Most members of the…

在d级系统中正、Schwarz和完全正演化之间的插值

Interpolating between positive, Schwarz, and completely positive evolution for d-level systems

研究d级系统中插值量子动态映射的类，通过参数空间几何分析揭示不同正性类区域及其边界结构，展示动态轨迹在正性类间过渡的几何解释，以及演化最终变为纠缠破缺的特性。

Quantum evolution with a large number of negative decoherence rates

Non-Markovian effects in quantum evolution appear when the system is strongly coupled to the environment and interacts with it for long periods of time. To include memory effects in the master equations, one usually incorporates time-local generators or memory kernels. However, it turns out that non-Markovian evolution with eternally negative decoherence rates arises from a simple mixture of Markovian semigroups. Moreover, one can have as many as $(d-1)^2$ always negative rates out of $d^2-1$ total, and the quantum evolution is still legitimate.

超导量子比特非马尔可夫性的确凿特征

Smoking-gun signatures of non-Markovianity of a superconducting qubit

本文研究了超导transmon量子比特闲置演化的时间相关噪声，利用量子电路理论构建了时间局域主方程，揭示了相干性周期性恢复和额外频率等非马尔可夫特征。

加速度保护的量子输运：免受非绝热性与耗散影响

Quantum Transport Protected by Acceleration From Nonadiabaticity and Dissipation

提出加速度操控策略，通过最大化传输保真度，实现不稳定量子波包在浴诱导耗散下的高保真快速输运，优于反绝热场方法，适用于多种量子系统的耗散与非耗散输运。

Non-Markovian Dynamics of a Qubit Due to Single-Photon Scattering in a Waveguide

We investigate the open dynamics of a qubit due to scattering of a single photon in an infinite or semi-infinite waveguide. Through an exact solution of the time-dependent multi-photon scattering problem, we find the qubit's dynamical map. Tools of open quantum systems theory allow us then to discuss the general features of this map, find the corresponding non-Linbladian master equation, and assess in a rigorous way its non-Markovian nature. The qubit dynamics has distinctive features that, in particular, do not occur in emission processes. Two fundamental sources of non-Markovianity are prese…

Analyzing photon-count heralded entanglement generation between solid-state spin qubits by decomposing the master equation dynamics

We analyze and compare three different schemes that can be used to generate entanglement between spin qubits in optically-active single solid-state quantum systems. Each scheme is based on first generating entanglement between the spin degree of freedom and either the photon number, the time bin, or the polarization degree of freedom of photons emitted by the systems. We compute the time evolution of the entanglement generation process by decomposing the dynamics of a Markovian master equation into a set of propagation superoperators conditioned on the cumulative detector photon count. We then…