Quantum teleportation and nonlocality: the puzzling predictions of entanglement are coming of age

TL;DR

This paper discusses the fundamental and practical aspects of quantum entanglement, focusing on recent experiments with photons that demonstrate quantum teleportation and nonlocality, advancing quantum communication and network development.

Contribution

It reviews recent photon-based experiments on quantum teleportation and nonlocality, highlighting their significance for quantum networks and information security.

Findings

Entanglement enables secure quantum key distribution without trusting measurement devices.

Recent experiments demonstrate successful quantum teleportation over large distances.

Photon-based systems are promising for future quantum network implementations.

Abstract

The academic research into entanglement nicely illustrates the interplay between fundamental science and applications, and the need to foster both aspects to advance either one. For instance, the possibility to distribute entangled photons over tens or even hundreds of kilometers is fascinating because it confirms the quantum predictions over large distances, while quantum theory is often presented to apply to the very small (see Figure 1). On the other hand, entanglement enables quantum key distribution (QKD) [1]. This most advanced application of quantum information processing allows one to distribute cryptographic keys in a provably secure manner. For this, one merely has to measure the two halves of an entangled pair of photons. Surprisingly, and being of both fundamental and practical interest, the use of entanglement removes even the necessity for trusting most equipment used for the measurements [5]. Furthermore, entanglement serves as a resource for quantum teleportation (see Figure 2) [1]. In turn, this provides a tool for extending quantum key distribution to arbitrarily large distances and building large-scale networks that connect future quantum computers and atomic clocks [6]. In the following, we describe the counter-intuitive properties of entangled particles as well as a few recent experiments that address fundamental and applied aspects of quantum teleportation. While a lot of work is being done using different quantum systems, including trapped ions, color centers in diamond, quantum dots, and superconducting circuits, we will restrict ourselves to experiments involving photons due to their suitability for building future quantum networks.