Full Counting Statistics and Phase Diagram of a Dissipative Rydberg Gas

Abstract

Ultra-cold gases excited to strongly interacting Rydberg states are a promising system for quantum simulations of many-body systems [1,2]. For off-resonant excitation of such systems in the dissipative regime, highly correlated many-body states exhibiting, among other characteristics, intermittency and multi-modal counting distributions are expected to be created [3][4][5][6]. So far, experiments with Rydberg atoms have been carried out in the resonant, non-dissipative regime [7]. Here we realize a dissipative gas of rubidium Rydberg atoms and measure its full counting statistics for both resonant and off-resonant excitation. We find strongly bimodal counting distributions in the off-resonant regime that are compatible with intermittency due to the coexistence of dynamical phases. Moreover, we measure the phase diagram of the system and find good agreement with recent theoretical predictions [3,5,6]. Our results pave the way towards detailed studies of many-body effects in Rydberg gases. Ultra-cold atoms excited to high-lying Rydberg states have been shown in recent years to be promising candidates for experimental implementations of quantum computation and quantum simulation [8]. The strong and controllable interactions between Rydberg atoms mean that fast two-qubit quantum gates and models of many-body Hamiltonians can, in principle, be efficiently realized. As a further important ingredient, dissipation has been shown to lead to novel phases and to facilitate, under certain conditions, the creation of pure and coherent manybody states [9][10][11]. Also, a recent proposal for a quantum simulator based on Rydberg atoms relies on dissipation [1, 2].So far, Rydberg excitations in cold gases have been studied almost exclusively in the resonant, non-dissipative regime. In those experiments, the strong interactions between Rydberg atoms manifest themselves either as spatial correlations compatible with a radius of blockade around an excited atom [13,14] or through a reduction of fluctuations leading to sub-Poissonian statistics [15]. In this work we show that for off-resonant excitation, the behaviour of the system depends strongly on the detuning and the sign of the Rydberg-Rydberg interaction. We characterize the properties of our system through the full counting statistics of the excitation events, similarly to the methods recently used in condensed matter physics to unveil correlations in electronic transport processes [16,17]. When the detuning and the interaction have the same sign, excitation of pairs of Rydberg atoms can occur, leading to an asymmetry of the excitation lineshape as a function of detuning. In the dissipative regime, we observe strongly bimodal counting distributions in the full counting statistics [3,5,6], indicating phase coexistence and intermittency in the system [12]. Figure 1 summarizes the experimental method and typical results of the full counting statistics. Our experiments are performed using 87-rubidium atoms in magneto-optical traps (MOTs) that are excited to 70S Rydberg states us...

Dynamic formation of Rydberg aggregates at off-resonant excitation

“…Finally, we note that very recently, super-Poissonian excitation statistics have been observed in experiments operating at off-resonant driving in the strongly dissipative regime [40,41]. We expect that the mechanism of aggregate formation discussed here leading to a bimodal distribution of excitation numbers still applies in the presence of substantial decoherence.…”

Sub-Poissonian Statistics of Jamming Limits in Ultracold Rydberg Gases

“…This implies in particular that in the absence of blockade effects, the number of excited particles within the excitation volume, XðtÞ, will be Poisson distributed, as is the case in experiments [5][6][7][8][9][10]. It also implies that the particles are uniformly distributed at random over the excitation volume.…”

“…These atomic systems exhibit complicated spatial behavior due to strong van der Waals or dipolar interactions between neighboring atoms, which has been demonstrated through several experimental observations of reduced fluctuation in the number of excitations in ultracold gases of Rydberg atoms [5][6][7][8][9][10].…”

Monodisperse cluster crystals: Classical and quantum dynamics

“…The latter effect is at odds with results for systems such as He 4 or dipolar crystals [27], where bosonic statistics always favors a liquid behavior, while the former should be compared to recent findings for polydispersed hard spheres [23,28,31], where quantum fluctuations may help crystallization. Some of these effects may be relevant for systems as diverse as colloidal particles [22,32,33] as well as cold gases of Rydberg atoms [34], where light-dressing techniques can be used to tune effective inter particle interactions [35,36].…”