15 research outputs found
Probing the quantum vacuum with an artificial atom in front of a mirror
Quantum fluctuations of the vacuum are both a surprising and fundamental
phenomenon of nature. Understood as virtual photons flitting in and out of
existence, they still have a very real impact, \emph{e.g.}, in the Casimir
effects and the lifetimes of atoms. Engineering vacuum fluctuations is
therefore becoming increasingly important to emerging technologies. Here, we
shape vacuum fluctuations using a "mirror", creating regions in space where
they are suppressed. As we then effectively move an artificial atom in and out
of these regions, measuring the atomic lifetime tells us the strength of the
fluctuations. The weakest fluctuation strength we observe is 0.02 quanta, a
factor of 50 below what would be expected without the mirror, demonstrating
that we can hide the atom from the vacuum
Enhancement of Rydberg-mediated single-photon nonlinearities by electrically tuned Förster resonances
We demonstrate experimentally that Stark-tuned Förster resonances can be used to substantially increase the interaction between individual photons mediated by Rydberg interaction inside an optical medium. This technique is employed to boost the gain of a Rydberg-mediated single-photon transistor and to enhance the non-destructive detection of single Rydberg atoms. Furthermore, our all-optical detection scheme enables high-resolution spectroscopy of two-state Förster resonances, revealing the fine structure splitting of high-n Rydberg states and the non-degeneracy of Rydberg Zeeman substates in finite fields. We show that the ∣50S1/2,48S1/2⟩↔∣49P1/2,48P1/2⟩ pair state resonance in 87Rb enables simultaneously a transistor gain G>100 and all-optical detection fidelity of single Rydberg atoms F>0.8. We demonstrate for the first time the coherent operation of the Rydberg transistor with G>2 by reading out the gate photon after scattering source photons. Comparison of the observed readout efficiency to a theoretical model for the projection of the stored spin wave yields excellent agreement and thus successfully identifies the main decoherence mechanism of the Rydberg transistor
Gauge Theories with Ultracold Atoms
We discuss and review in this chapter the developing field of research of
quantum simulation of gauge theories with ultracold atoms.Comment: Contribution for the proceedings of the Advanced School and Workshop
on "Strongly Coupled Field Theories for Condensed Matter and Quantum
Information Theory" held in Natal from 2-21/8 of 2015. Published in "Springer
Proceedings in Physics" (ISBN 978-3-030-35473-2), with material from the PhD
Thesis of Jo\~ao C. Pinto Barros, available at
https://iris.sissa.it/handle/20.500.11767/57731#.XcQtPk6YWh
Mesoscopic Rydberg-blockaded ensembles in the superatom regime and beyond
International audienceThe control of strongly interacting many-body systems enables the creation of tailored quantum matter with complex properties. Atomic ensembles that are optically driven to a Rydberg state provide many examples for this: atom-atom entanglement, many-body Rabi oscillations, strong photon-photon interaction and spatial pair correlations. In its most basic form Rydberg quantum matter consists of an isolated ensemble of strongly interacting atoms spatially confined to the blockade volume--a superatom. Here we demonstrate the controlled creation and characterization of an isolated mesoscopic superatom by means of accurate density engineering and excitation to Rydberg p-states. Its variable size allows the investigation of the transition from effective two-level physics to many-body phenomena. By monitoring continuous laser-induced ionization we observe a strongly anti-bunched ion emission under blockade conditions and extremely bunched ion emission under off-resonant excitation. Our measurements provide insights into both excitation statistics and dynamics. We anticipate applications in quantum optics and quantum information as well as many-body physics experiments
Effects of light intensity on motility three species of copepods: Acartia tonsa, Calanus finmarchicus and Temora longicornis
Certain wave functions of non-interacting quantum chaotic systems can exhibit
"scars" in the fabric of their real-space density profile. Quantum scarred wave
functions concentrate in the vicinity of unstable periodic classical
trajectories. We introduce the notion of many-body quantum scars which reflect
the existence of a subset of special many-body eigenstates concentrated in
certain parts of the Hilbert space. We demonstrate the existence of scars in
the Fibonacci chain -- the one- dimensional model with a constrained local
Hilbert space realized in the 51 Rydberg atom quantum simulator [H. Bernien et
al., arXiv:1707.04344]. The quantum scarred eigenstates are embedded throughout
the thermalizing many-body spectrum, but surprisingly lead to direct
experimental signatures such as robust oscillations following a quench from a
charge-density wave state found in experiment. We develop a model based on a
single particle hopping on the Hilbert space graph, which quantitatively
captures the scarred wave functions up to large systems of L = 32 atoms. Our
results suggest that scarred many-body bands give rise to a new universality
class of quantum dynamics, which opens up opportunities for creating and
manipulating novel states with long-lived coherence in systems that are now
amenable to experimental study.Comment: 8 pages, 4 figures; updated reference