The Entanglement-Assisted Communication Capacity Over Quantum Trajectories

Abstract

The unique and often-weird properties of quantum mechanics allow an information carrier to propagate through multiple trajectories of quantum channels simultaneously. This ultimately leads us to quantum trajectories with an indefinite causal order of quantum channels. It has been shown that indefinite causal order enables the violation of bottleneck capacity, which bounds the amount of the transferable classical and quantum information through a classical trajectory with a well-defined causal order of quantum channels. In this treatise, we investigate this beneficial property in the realm of both entanglementassisted classical and quantum communications. To this aim, we derive closed-form capacity expressions of entanglement-assisted classical and quantum communication for arbitrary quantum Pauli channels over classical and quantum trajectories. We show that by exploiting the indefinite causal order of quantum channels, we obtain capacity gains over classical trajectory as well as the violation of bottleneck capacity for various practical scenarios. Furthermore, we determine the operating region where entanglement-assisted communication over quantum trajectory obtains capacity gain against classical trajectory and where the entanglement-assisted communication over quantum trajectory violates the bottleneck capacity.

Quantum Internet Protocol Stack: a Comprehensive Survey

“…But this assumption can be generalized such as, not only the information or the channels, but also the placement of the channels -i.e., the paths along with the carriers propagate -can be quantum [30,100,101]. This unconventional placement of channels has been theoretically and experimentally verified, and it has been proven to be able to describe powerful setups for the transmission of both classical and quantum information [31,32,33,34,35,102]. This genuine quantum phenomenon, preliminary investigated in [33,83,102], plays a paramount role for achieving unprecedented information transfer capacities, and it must be fully understood and harnessed for the Quantum Internet design.…”

“…Any node sharing entanglement resources can act either as source or as destination, as long as it coordinates with the other entangled nodes. Even more astonishing, recently it has been discovered that the order among the communication channels traversed by a quantum information carrier can be indefinite, giving raise to unparalleled and powerful setups for the transmission of information [30,31,32,33,34,35]. This has tremendous effects on the Quantum Internet protocol stack as discussed in Section 7.7.…”