David Paredes

Postdoctoral Researcher

Research Areas:
Quantum Optics

Research Topics:
Quantum Non-Linear Optics at the single photon level with Cold Rydberg Atoms

Academic Background

University Degree:
PhD in Atomic and Molecular Physics, Durham University (UK)


Office: 013
Office Telephone:  +34 935534123
Laboratory Telephone: +34 935542206,   +34 935542203
Fax:   +34 935534000

e-Mail:  david.paredes@icfo.es

A story of deception

At the age of 11 or 12, during a hot summer, I started throwing stones into the air and timing them as they hit the ground to try and find out if I could somehow describe their motion. Obviously, I failed: I did not understand the importance of repeatability in experiments.

…thus I decided that I would become a Physicist.

Later, when I was studying Theoretical Physics in the Universidad Complutense de Madrid (Spain), I really loved Differential Geometry and Relativity, but had to take some modules on Quantum Physics, and Atomic and Molecular Physics… and failed them (once): I did not understand the non-intuitive ways in which matter and light interact at the fundamental level!
That’s why I decided to do research on Quantum and Atomic Optics.

And after spending a summer at the Catalonian Institute of Photonic Sciences (ICFO) working in Morgan Mitchell’s group, I landed in Durham. There, under the supervision of Charles Adams we studied the (highly) nonlinear properties of cold Rydberg gases and their interactions with light. Most of my work in Durham consisted in a proposal of a novel way to make photons interact in a way that is useful for quantum processing technologies [1].

Since there are a lot of things that I do not understand, I decided to go back to Barcelona and join Hugues de Riedmatten’s group to  continue researching the strong photon-photon interactions induced by their propagation and storage in a cloud of cold Rydberg atoms, and their applications to quantum information, processing and communication technologies.

Can we make two photons interact?

We want to make photons interact (for several reasons), but that can only happen if we provide a very nonlinear medium that can provide interactions even between single photons.

The idea is to store quanta of light (photons) in a tightly-confined ensemble of atoms that are excited to a high principal quantum number state (also called Rydberg atoms) [1]. To do that, we use electromagnetically induced transparency [2], which “converts” these photons into excitations in the medium. These atoms interact very strongly with each other, and we can map that interaction to an effective interaction between the photons that have been stored (called polaritons). Then, when we retrieve the photons, we check the effect of the interactions in the photons.

Food for thought (just a couple of links)

[1] D. Paredes-Barato and C. S. Adams. Phys. Rev. Lett. 112, 040501 (2014) (Open access)
[2] D. Maxwell et al. Phys. Rev. Lett. 110, 103001 (2013)[free version here]
[3] M. Fleischhauer, A. Imamoglu, and J. P. Marangos (2005), “Electromagnetically induced transparency: Optics in Coherent Media”, Reviews Modern Physics, 77, 633 [free version here]