The sudden death of quantum advantage in correlation generations

Abstract

As quantum error corrections still cannot be realized physically, quantum noise is the most profound obstacle to the implementations of large-scale quantum algorithms or quantum schemes. It has been well-known that if a quantum computer suffers from too strong quantum noise, its running can be easily simulated by a classical computer, making the quantum advantage impossible. Generally speaking, however, the dynamical process that how quantum noise of varying strengths from 0 to a fatal level impacts and destroys quantum advantage has not been understood well. Undoubtedly, achieving this will be extremely valuable for us to understand the power of noisy intermediate-scale quantum computers. Meanwhile, correlation generation is a precious theoretical model of information processing tasks in which the quantum advantage can be precisely quantified. Here we show that this model also provides us a valuable insight into understanding the impact of noise on quantum advantage. Particularly, we will rigorously prove that when the strength of quantum noise continuously goes up from 0, the quantum advantage gradually declines, and eventually fades away completely. Surprisingly, in some cases we observe an unexpected phenomenon we call the sudden death of the quantum advantage, i.e., when the strength of quantum noise exceeds a certain point, the quantum advantage disappears suddenly from a non-negligible level. This interesting phenomenon reveals the tremendous harm of noise to quantum information processing tasks from a new viewpoint.