Scalable Entanglement Certification via Quantum Communication

Harnessing the advantages of shared entanglement for sending quantum messages often requires the implementation of complex two-particle entangled measurements. We investigate entanglement advantages in protocols that use only the simplest two-particle measurements, namely, product measurements. For experiments in which only the dimension of the message is known, we show that robust entanglement advantages are possible but that they are fundamentally limited by Einstein-Podolsky-Rosen steering. Subsequently, we propose a natural extension of the standard scenario for these experiments and show that it circumvents this limitation. This leads us to prove entanglement advantages from every entangled two-qubit Werner state, evidence its generalization to high-dimensional systems, and establish a connection to quantum teleportation. Our results reveal the power of product measurements for generating quantum correlations in entanglement-assisted communication and they pave the way for practical semi-device-independent entanglement certification well beyond the constraints of Einstein-Podolsky-Rosen steering.

Popular Summary

A pair of quantum particles can be linked to each other in way that has no counterpart in classical physics. While this link, called entanglement, cannot be used to communicate, it can be used to boost communication abilities between two parties who hold these particles and use them to send messages. A major practical difficulty is that once the message is received, extracting information from it requires challenging quantum operations, especially when the message grows larger than a bit.

Here, we show that the simplest two-particle operations in quantum theory might already suffice to extract useful information from even the weakest forms of entanglement. This way, the implementation bottleneck may be circumvented, and basic building blocks can be used to probe the truly nonclassical effects of entanglement in quantum communication well beyond current limitations.

Figure 1

The EAPM scenario between a sender (Alice) and a receiver (Charlie). The information, $x$, is encoded into one share of the entangled state.

Figure 2

The symmetric EAPM scenario between the senders (Alice and Bob) and the receiver (Charlie). The information, ($x$,$y$), is encoded into the shares of the entangled state.