Geometry of Generalized Depolarizing Channels

Geometry of depolarizing channels

Depolarizing maps acting on an N dimensional system are completely positive maps resulting into compression of the Bloch ball along the different polarization directions. In the qubit case these maps are a convex sum of four extremal maps and form a simplex in the space of compression coefficients along the three polarization directions. We calculate the compression domain for three and four level systems. For a three level system the region has curved surfaces, but it is a simplex for a four level system. We conjecture that it is a simplex in the case of 2^n level systems.

Generalized Kraus operators for the one-qubit depolarizing quantum channel

Microscopic Hamiltonian models of the composite system "open system + environment" typically do not provide the operator-sum Kraus form of the open system's dynamical map. With the use of a recently de- veloped method [16], we derive the Kraus operators starting from the mi- croscopic Hamiltonian model, i.e. from the proper master equation, of the one-qubit depolarizing channel. Those Kraus operators generalize the stan- dard counterparts, which are widely used in the literature. Comparison of the standard and the here obtained Kraus operators is performed via inves- tigating dynamical change …

Teleportation as a Depolarizing Quantum Channel, Relative Entropy and Classical Capacity

We show that standard teleportation with an arbitrary mixed state resource is equivalent to a generalized depolarizing channel with probabilities given by the maximally entangled components of the resource. This enables the usage of any quantum channel as a generalized depolarizing channel without additional twirling operations. It also provides a nontrivial upper bound on the entanglement of a class of mixed states. Our result allows a consistent and statistically motivated quantification of teleportation success in terms of the relative entropy and this quantification can be related to a cla…

退极化噪声在引发纠缠突然死亡中的有效性

Effectiveness of Depolarizing noise in causing sudden death of entanglement

研究证明退极化噪声比广义振幅阻尼噪声更有效地引发双部量子系统纠缠突然死亡，且作用更快。

Effect of Decoherence in Ekert-Protocol

We have examined the effect of the decoherence in the Ekert91 quantum cryptographic protocol. In order to explore this issue we have introduced two major decoherences, the depolarizing channel and the generalized amplitude damping, between the singlet source and one of the legitimate users. It is shown that the depolarizing channel disentangles the quantum channel more easily than the generalized amplitude damping. This fact indicates that the Ekert protocol is more robust to the generalized amplitude damping. We also have computed the Bell inequality to check the robustness or weakness of the…

广义概率理论中的去极化参考装置

Depolarizing Reference Devices in Generalized Probabilistic Theories

本文在GPT框架下刻画使Born规则对LTP的变形呈逐项仿射形式的参考装置，证明任意参考测量均可通过选择测量后态与去极化测量—制备信道实现，并揭示其中常数的规范性意义。