Efficient universal quantum channel simulation in IBM＇s cloud quantum computer  

作　　者：Shi-Jie Wei Tao Xin Gui-Lu Long 

机构地区：[1]State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, China [2]Tsinghua National Laboratory of Information Science and Technology, Beijing 100084, China [3]Collaborative Innovation Center of Quantum Matter, Beijing 100084, China

出　　处：《Science China(Physics,Mechanics & Astronomy)》2018年第7期44-53,共10页中国科学：物理学、力学、天文学（英文版）

基　　金：supported by the National Basic Research Program of China (Grant No. 2015CB921002);the National Natural Science Foundation of China (Grant Nos. 11175094, and 91221205);the Fund of Key Laboratory (Grant No. 9140C75010215ZK65001)

摘　　要：The study of quantum channels is an important field and promises a wide range of applications, because any physical process can be represented as a quantum channel that transforms an initial state into a final state. Inspired by the method of performing non-unitary operators by the linear combination of unitary operations, we proposed a quantum algorithm for the simulation of the universal single-qubit channel, described by a convex combination of ＂quasi-extreme＂ channels corresponding to four Kraus operators, and is scalable to arbitrary higher dimension. We demonstrated the whole algorithm experimentally using the universal IBM cloud-based quantum computer and studied the properties of different qubit quantum channels. We illustrated the quantum capacity of the general qubit quantum channels, which quantifies the amount of quantum information that can be protected. The behavior of quantum capacity in different channels revealed which types of noise processes can support information transmission, and which types are too destructive to protect information. There was a general agreement between the theoretical predictions and the experiments, which strongly supports our method. By realizing the arbitrary quhit channel, this work provides a universally- accepted way to explore various properties of quantum channels and novel prospect for quantum communication.The study of quantum channels is an important field and promises a wide range of applications, because any physical process can be represented as a quantum channel that transforms an initial state into a final state. Inspired by the method of performing non-unitary operators by the linear combination of unitary operations, we proposed a quantum algorithm for the simulation of the universal single-qubit channel, described by a convex combination of "quasi-extreme" channels corresponding to four Kraus operators, and is scalable to arbitrary higher dimension. We demonstrated the whole algorithm experimentally using the universal IBM cloud-based quantum computer and studied the properties of different qubit quantum channels. We illustrated the quantum capacity of the general qubit quantum channels, which quantifies the amount of quantum information that can be protected. The behavior of quantum capacity in different channels revealed which types of noise processes can support information transmission,and which types are too destructive to protect information. There was a general agreement between the theoretical predictions and the experiments, which strongly supports our method. By realizing the arbitrary qubit channel, this work provides a universallyaccepted way to explore various properties of quantum channels and novel prospect for quantum communication.

关 键 词：quantum channel quantum algorithm quantum capacity IBM quantum cloud 

分 类 号：TP38[自动化与计算机技术—计算机系统结构]