Photonics: from fundamental aspects to practical applications

Y. V. G. S. Murti, Cherianath Vijayan

Davıd L. Andrews

Zoran M. Ivić, Dalibor Čevizović, Željko Pržulj

We study quantum features of electromagnetic radiation propagating in a waveguide built of an infinite array of super-conducting qubits (SCQ) placed within a resonator comprised of two massive superconductors. Such engineered media, so-called superconducting quantum metamaterials (SCQMM), have a great potential for quantum information processing and communications and devise a comprehensive study of the nature of the “light”-matter interaction. We predict the emergence of novel in-terference effects with possible practical applications. For exam-ple, photons may exhibit a nontrivial dispersion relation such as band edges and band gaps. In this way, QMMs may be viewed as photonic crystals. This, in turn, enriches their potential for practi-cal applications and provides novel means for devising compre-hensive studies of both practical and fundamental aspects of the interaction of artificial atoms and the EM field.

Nicolas Gisin, Sébastien Tanzilli, Wolfgang Tittel

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.

Mustafa A. G. Abushagur