Hakob Avetisyan

Improvement in secure transmission of information is an urgent practical need for governments, corporations and individuals. Quantum key distribution (QKD) promises security based on the laws of physics and has rapidly grown from proof-of-concept to robust demonstrations and even deployment of commercial systems. Despite these advances, QKD has not been widely adopted, and practical large-scale deployment will likely require integrated chip-based devices for improved performance, miniaturisation and enhanced functionality, fully integrated into classical communication networks. Here we report low error rate, GHz clocked QKD operation of an InP transmitter chip and a SiO$_x$N$_y$ receiver chip --- monolithically integrated devices that use state-of-the-art components and manufacturing processes from the telecom industry. We use the reconfigurability of these devices to demonstrate three important QKD protocols --- BB84, Coherent One Way (COW) and Differential Phase Shift (DPS) --- with performance comparable to state-of-the-art. These devices, when combined with integrated single photon detectors, satisfy the requirements at each of the levels of future QKD networks --- from point-of-use through to backbone --- and open the way to operation in existing and emerging classical communication networks.

Author(s): Scott Roger Shepard

The complementarity between time and energy, as well as between an angle and a component of angular momentum, is described at three different layers of understanding. The phenomena of super-resolution are readily apparent in the quantum phase representation which also reveals that entanglement is no...

[Phys. Rev. A 90, 062117] Published Fri Dec 12, 2014

A. Sanchez-Castillo, S. Eslami, F. Giesselmann, P. Fischer
We describe a novel polarization interferometer which permits the determination of the refractive indices for circularly-polarized light. It is based on a Jamin-Lebedeff interferometer, modified with waveplates, and permits us to experimentally determine the refractive indices nL and nR of the ... [Opt. Express 22, 31227-31236 (2014)]

Author(s): Filippo Caruso, Vittorio Giovannetti, Cosmo Lupo, and Stefano Mancini

Any physical process can be represented as a quantum channel mapping an initial state to a final state. Hence it can be characterized from the point of view of communication theory, i.e., in terms of its ability to transfer information. Quantum information provides a theoretical framework and the pr…

[Rev. Mod. Phys. 86, 1203] Published Wed Dec 10, 2014

Author(s): Colin R. Greenshields, Robert L. Stamps, Sonja Franke-Arnold, and Stephen M. Barnett

We show that an electron moving in a uniform magnetic field possesses a time-varying “diamagnetic” angular momentum. Surprisingly this means that the kinetic angular momentum of the electron may vary with time, despite the rotational symmetry of the system. This apparent violation of angular momentu...

[Phys. Rev. Lett. 113, 240404] Published Tue Dec 09, 2014

Author(s): H. D. Liu and L. B. Fu

The Majorana’s stellar representation, which represents the evolution of a quantum state with the trajectories of the Majorana stars on a Bloch sphere, provides an intuitive way to study a physical system with a high dimensional projective Hilbert space. In this Letter, we study the Berry phase by t...

[Phys. Rev. Lett. 113, 240403] Published Tue Dec 09, 2014

It is pointed out that there exists an unambiguous definition of locality that enables one to distinguish local and nonlocal quantities. Observables of both types coexist in quantum optics, but one must be very careful when attempting to measure them. A nonlocal observable that formally depends on the spatial position ##IMG## [http://ej.iop.org/images/1367-2630/16/11/113056/njp503750ieqn1.gif] {${\boldsymbol{r}} $} cannot be locally measured without disturbing the measurements of this observable at all other positions.

Hyunseok Jeong, Changsuk Noh, Seunglee Bae, Dimitris G. Angelakis, Timothy C. Ralph
We investigate how to experimentally detect a recently proposed measure to quantify macroscopic quantum superpositions [Phys. Rev. Lett.106, 220401 (2011)10.1103/PhysRevLett.106.220401PRLTAO0031-9007], namely, “macroscopic quantumness” I. Schemes based on overlap measurements for ... [J. Opt. Soc. Am. B 31, 3057-3066 (2014)]