Coulomb anti-blockade in a Rydberg gas

Abstract

We perform a comprehensive investigation of the coupling between a Rydberg-dressed atomic gas and an ultra-cold plasma (UCP). Using simultaneous time-resolved measurements of both neutral atoms and ions, we show that plasma formation occurs via a Coulomb anti-blockade mechanism, in which background ions DC Stark shift nearby atoms into resonance at specific distances. The result is a highly correlated growth of the Rydberg population that shares some similarities with that previously observed for van der Waals interactions. We show that a rate equation model that couples the laserdriven Rydberg gas to the UCP via a Coulomb anti-blockade mechanism accurately reproduces both the plasma formation and its subsequent decay. Using long-lived high angular momentum states as a probe, we also find evidence of a crossover from Coulomb anti-blockade to Coulomb blockade at high density. As well as shedding light on loss mechanisms in Rydberg-dressed gases, our results open new ways to create low-entropy states in UCPs. Introduction/motivationHybrid quantum systems of ultracold atoms and ions are emerging as a platform for fundamental research in quantum physics [1]. Recently, Rydberg states have received attention as a way to control the coupling between ionic and atomic systems [2-5], for example, using Coulomb blockade from a single ion to suppress Rydberg excitation [6]. Ultracold mixtures of Rydberg atoms and ions have also been studied in the context of cold Rydberg gases, where it was generally found that ions are almost always present due to processes such as collisions between nearby Rydberg atoms and blackbody photoionization. Indeed, studies using resonant laser excitation of Rydberg states have shown an ultra-cold plasma (UCP) under conditions of strong excitation, both in the pulsed [7-9] and continuously driven [10, 11] regimes.In this paper, we demonstrate that an off-resonant excitation of the Rydberg state can be used to tailor the the interaction between Rydberg atoms and ions in an ultracold gas. We show that plasma formation occurs via a Coulomb anti-blockade mechanism, illustrated in figure 1(b), where background ions DC Stark shift nearby atoms into resonance at specific distances. The result is a highly correlated 'facilitated growth' of the Rydberg population that shares some similarities with that previously observed using van der Waals anti-blockade [12]. A rate equation model that couples the driven Rydberg gas to an UCP via this correlated excitation model accurately reproduces both the initial creation and subsequent decay of the observed ion signal. At longer times, the ionization of long-lived high angular momentum Rydberg states produced in the plasma provides evidence for the interplay between Coulomb blockade [6] and Coulomb anti-blockade in the plasma. In future experiments, controlling this process could provide a route to creating an UCP with a strongly correlated ionic state [13].Our results also provide a strategy for minimising losses due to ionization in cold Rydberg gas experiments, p...

Implementation of the Rydberg double anti-blockade regime and the quantum logic gate based on resonant dipole-dipole interactions

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One-Step Implementation of Collective Anti-Blockade in a Rydberg Ring

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The role of Coulomb anti-blockade in the photoassociation of long-range Rydberg molecules

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