"Causal limit on quantum communication" co-authored by Zhikuan Zhao published in Physical Review Letters

The paper "Causal limit on quantum communication" by Robert Pisarczyk, Zhikuan Zhao, Yingkai Ouyang, Vlatko Vedral, and Joseph F. Fitzsimons has been published in Physical Review Letters.

Popular summary by Zhikuan Zhao: 

We exploit the causal structure of quantum mechanics to study the rates of communication over noisy quantum channels. As a technical framework, we introduce a measure for quantum causality that quantifies temporal correlations between ends of a communication channel. We then prove it to be a general upper bound on the capacity of the channel to transmit quantum information.

Our result illuminates an example of harnessing quantum causality in practice. Just as the discovery of quantum entanglement-based protocols over the decades have furnished our comprehension of locality and realism, this revelation in the operational meaning of causal structure on information processing tasks will inspire insight into the nature of time in quantum mechanics.

From an applicational point of view, the newly discovered general bound for quantum channel capacity has the advantage of being efficiently computable comparing to many previously known approaches. As the need for efficient estimates of information transmission over more prevalent and complex networks of quantum channels is ever-growing, we believe our result will provide invaluable additional toolkits to study realistic noisy quantum channels and hence contribute to the design and future realization of a large-scale quantum internet.