Physics is fascinating because of the intellectual excitement it provides and because of the applications it offers. In the Group of Applied Physics (GAP) at Geneva University we get our inspiration from both of these motivations. Optics, in this respect, has a privileged place. Indeed, in modern optics, experiments and theory progress hand-in-hand, and practical applications are close behind. Consequently, we can work both on conceptual issues and on applications. Moreover, it is a very good time for optics! The fascinating new insight about quantum mechanics brought about by recent quantum optics experiments on one side, and the tremendous development of optical communications on the other, illustrates our privileged position!
The American Research Council has recently declared optics as the technology of the 21st century. In contrast, a famous physicist, Michael Berry, has declared that the 21st century will be shaped by quantum physics, in a way similar to electrodynamics, which shaped the 20th century. Our position in GAP-Quantique, at the crossroads between optics and quantum physics, ensures our participation to both challenges.
Long-lived quantum memories are essential components of a long-standing goal of remote distribution of entanglement in quantum networks. In our letter published in Physical Review Letters, we experimentally demonstrate a quantum level manipulation with the spin excitation in a large solid-state ensemble, generated through storage of a weak optical pulse. After a storage time of about 1 ms we optically read-out the spin excitation with a high signal-to-noise ratio. Our results pave the way for long-duration optical quantum storage using spin-echo techniques for any ensemble-based memory.
Nicolas Gisin has been awarded the Marcel Benoist Prize 2014 - the Swiss science award - for his outstanding work on the theoretical foundations and possible applications of quantum mechanics and quantum cryptography.
In an interview at Radio Télévision Suisse professor Nicolas Gisin, discusses the influence of the chance to the whole world and our future from scientific point of view.
“Nicolas Gisin, professeur de physique quantique à l’UNIGE. On ouvre un chapitre qui anime de nombreux débats: le déterminisme. Est-ce que l'entier du monde et de son futur est écrit d'une seule manière ou le hasard peut-il l'influencer?”
Listen to the interview in two parts here:
Harnessing nonlinearities strong enough to allow single photons to interact with one another is not only a fascinating challenge but also central to numerous advanced applications in quantum information science. We recently realised the first nonlinear interaction between two single photons. Each photon is generated in independent parametric down-conversion sources. They are subsequently combined in a nonlinear waveguide where they are converted into a single photon of higher energy by the process of sum-frequency generation. Our approach results in the direct generation of photon triplets. More generally, it highlights the potential for quantum nonlinear optics with integrated devices and, as the photons are at telecom wavelengths, it opens the way towards novel applications in quantum communication such as device-independent quantum key distribution.
We are very pleased that this work has been published in the Physical Review Letters. The letter can be found on our website. It was also highlighted by the Editors and received a Viewpoint article, Two Photons into One.
Entanglement in our experiment is established between a rare-earth-ion doped crystals storing a single photon that is polarization-entangled with a flying telecom-wavelength photon. The latter is jointly measured with another flying qubit carrying the polarization state to be teleported, which heralds the teleportation.
We also performed teleportation in a configuration where the combined distance travelled by both telecom-wavelength photons is 25 km in standard optical fibre while still outperforming the classical benchmark, demonstrating the long-distance capability of our approach.
Our experiment demonstrates the feasibility of long-distance teleportation of a single quanta of light onto a solid-state quantum memory. The fundamentals of our experiment could be used to demonstrate a small-scale network of remote quantum memories, or a real-world quantum repeater based on an optical-fibre architecture.