Bounding the Classical Capacity of Multilevel Damping Quantum Channels

Resonant Multilevel Amplitude Damping Channels

We introduce a new set of quantum channels: resonant multilevel amplitude damping (ReMAD) channels. Among other instances, they can describe energy dissipation effects in multilevel atomic systems induced by the interaction with a zero-temperature bosonic environment. At variance with the already known class of multilevel amplitude damping (MAD) channels, this new class of maps allows the presence of an environment unable to discriminate transitions with identical energy gaps. After characterizing the algebra of their composition rules, by analyzing the qutrit case, we show that this new set o…

广义多级振幅阻尼通道及其热力学性能

Generalized multilevel amplitude damping channels and their thermodynamic performances

本文引入广义多级振幅阻尼（GMAD）通道来模拟与热环境耦合的qudit中的噪声和退相干效应，通过评估功泛函和ergotropic电容研究GMAD下能量资源的退化，揭示了ergotropic电容随环境温度非单调变化以及马尔可夫Mpemba效应等反直觉现象。

Combining $T_1$ and $T_2$ estimation with randomized benchmarking and bounding the diamond distance

The characterization of errors in a quantum system is a fundamental step for two important goals. First, learning about specific sources of error is essential for optimizing experimental design and error correction methods. Second, verifying that the error is below some threshold value is required to meet the criteria of threshold theorems. We consider the case where errors are dominated by the generalized damping channel (encompassing the common intrinsic processes of amplitude damping and dephasing) but may also contain additional unknown error sources. We demonstrate the robustness of stand…

多能级弛豫下量子传感的极限信息率

Ultimate Information Rate for Quantum Sensing under Multilevel Relaxation

本研究确定了多能级弛豫量子传感器在自适应控制下的极限信息率，证明其等于亮态平均布居寿命，并给出达到该极限的显式协议，同时表明独立监测即可实现最优渐近速率。

Quantum Error-Correcting Codes for Qudit Amplitude Damping

Traditional quantum error-correcting codes are designed for the depolarizing channel modeled by generalized Pauli errors occurring with equal probability. Amplitude damping channels model, in general, the decay process of a multilevel atom or energy dissipation of a bosonic system at zero temperature. We discuss quantum error-correcting codes adapted to amplitude damping channels for higher dimensional systems (qudits). For multi-level atoms, we consider a natural kind of decay process, and for bosonic systems,we consider the qudit amplitude damping channel obtained by truncating the Fock basi…

Bounding the quantum capacity with flagged extensions

In this article we consider flagged extensions of convex combination of quantum channels, and find general sufficient conditions for the degradability of the flagged extension. An immediate application is a bound on the quantum $Q$ and private $P$ capacities of any channel being a mixture of a unitary map and another channel, with the probability associated to the unitary component being larger than $1/2$. We then specialize our sufficient conditions to flagged Pauli channels, obtaining a family of upper bounds on quantum and private capacities of Pauli channels. In particular, we establish ne…