Capacity of non-Markovianity to boost the efficiency of molecular switches

Non-Markovian thermal operations boosting the performance of quantum heat engines

It is investigated whether non-Markovianity, i.e., the memory effects resulting from the coupling of the system to its environment, can be beneficial for the performance of quantum heat engines. Specifically, two physical models are considered. The first one is a well known single-qubit Otto engine; the non-Markovian behaviour is there implemented by replacing standard thermalization strokes with so-called extremal thermal operations which cannot be realized without the memory effects. The second one is a three-stroke engine in which the cycle consists of two extremal thermal operations and a …

利用弱测量实现通用量子隐形传态的研究

Towards realization of universal quantum teleportation using weak measurements

本文研究了在记忆或非马尔可夫动力学下，利用部分塌缩测量算符实现通用量子隐形传态（UQT），发现记忆效应与弱测量结合能显著提升UQT的实现并最小化保真度偏差。

Quantum parameter estimation in a dissipative environment

We investigate the performance of quantum parameter estimation based on a qubit probe in a dissipative bosonic environment beyond the traditional paradigm of weak-coupling and rotating-wave approximations. By making use of an exactly numerical hierarchical equations of motion method, we analyze the influences of the non-Markovian memory effect induced by the environment and the form of probe-environment interaction on the estimation precision. It is found that (i) the non-Markovianity can effectively boost the estimation performance and (ii) the estimation precision can be improved by introduc…

Local quantum uncertainty guarantees the measurement precision for two coupled two-level systems in non-Markovian environment

Quantum Fisher information (QFI) is an important feature for the precision of quantum parameter estimation based on the quantum Cramér-Rao inequality. When the quantum state satisfies the von Neumann-Landau equation, the local quantum uncertainty (LQU), as a kind of quantum correlation, present in a bipartite mixed state guarantees a lower bound on QFI in the optimal phase estimation protocol [Phys. Rev. Lett. 110 (2013) 240402]. However, in the open quantum systems, there is not an explicit relation between LQU and QFI generally. In this paper, we study the relation between LQU and QFI in ope…

Subexponential rate versus distance with time-multiplexed quantum repeaters

Quantum communications capacity using direct transmission over length-$L$ optical fiber scales as $R \sim e^{-αL}$, where $α$ is the fiber's loss coefficient. The rate achieved using a linear chain of quantum repeaters equipped with quantum memories, probabilistic Bell state measurements (BSMs) and switches used for spatial multiplexing, but no quantum error correction, was shown to surpass the direct-transmission capacity. However, this rate still decays exponentially with the end-to-end distance, viz., $R \sim e^{-s{αL}}$, with $s < 1$. We show that the introduction of temporal multiplexing …

非马尔可夫量子系统中的量子近似优化算法

Quantum Approximate Optimization Algorithm in Non-Markovian Quantum Systems

本文提出在非马尔可夫量子系统中运行QAOA的框架，通过增广系统模型模拟色噪声，并利用量子轨迹增强模拟，证明非马尔可夫性可作为量子资源提升算法性能。