Duplicating classical bits with universal quantum cloning machine

摘要

It seems there is a large gap between quantum cloning and classical duplication since quantum mechanics forbid perfect copies of unknown quantum states.In this paper,we prove that a classical duplication process can be realized by using a universal quantum cloning machine(QCM).A classical bit is encoded not on a single quantum state,but on a large number of single identical quantum states.Errors are inevitable when copying these identical quantum states due to the quantum no-cloning theorem.When a small part of errors are ignored,i.e.,errors as the minority are automatically corrected by the majority,the fidelity of duplicated copies of classical information will approach unity infinitely.In this way,the classical bits can be duplicated precisely with a universal QCM,which presents a natural transition from quantum cloning to classical duplication.The implement of classical duplication by using QCM shines new lights on the universality of quantum mechanics.