The coherent control of mesoscopic ensembles of atoms and Rydberg atom blockade are the basis for proposed quantum devices such as integrable gates and single photon sources. So far, experimental progress has been limited to complex experimental setups that use ultracold atoms. Here, we show that coherence times of ∼ 100 ns are achievable with coherent Rydberg atom spectroscopy in µm sized thermal vapor cells. We investigated states with principle quantum numbers between 30 and 50. Our results demonstrate that microcells with a size on the order of the blockade radius, ∼ 2 µm, at temperatures of 100 − 300 • C are robust, promising candidates to investigate low dimensional strongly interacting Rydberg gases, construct quantum gates and build single photon sources.Recently, the mutual interaction between highly excited Rydberg atoms in dense frozen samples has lead to the observation of Rydberg atom excitation blockade [1,2,3]. In Rydberg atom blockade, the excitation of more than one Rydberg atom within a blockade volume is suppressed as the mutual interaction between Rydberg atoms at internuclear separations on the order of micrometers shifts the atomic state out of resonance with a narrow band excitation laser. The corresponding blockade radius, a block , is on the order of several µm for Rydberg states in the range of n= 30 − 50. For example, the 32S state of Rb excited by a 1 MHz bandwidth laser has a block = 2 µm for an ensemble of atoms that do not move on the timescale of excitation [4]. As the huge interaction between individual Rydberg atoms can lead to controlled entanglement of atomic ensembles, Rydberg atom blockade is the basis for several proposals to realize photonic quantum devices, like single photon sources and quantum gates [5,6]. The first promising experimental steps toward this goal using individual well localized pairs of ultracold atoms have been reported [7,8]. Experiments on collective entanglement of ensembles of ultracold atoms have also been performed [1].A technologically interesting alternative approach to ultracold atoms would be to realize Rydberg atom quantum photonic devices in thermal Rb vapor microcells. For this idea, we envision arrays of small blockade sized vapor cells (cavities) etched in glass that can be connected by optical wave guides in a monolithic structure. In such a device, Rydberg atom quantum gates may be realized with mesoscopic ensembles of thermal atoms. Some of the advantages of this approach are the ability to exploit advances in microstructuring technology [9,10,11], the relative simplicity of maintaining and regenerating the sample, the collective enhancement of the laser matter dynamics, and the scalability. We also point out here that a block has a strong scaling with the atomic separation R, proportional to R 6 in the case of Van der Waals interactions. This means that its value for atoms frozen in place only decreases by approximately 2.7 for a thermal distribution of atoms at T = 300 • C, since a block ∝ 6 √ Doppler width.An important point for usin...

We report on the observation of Rabi oscillations to a Rydberg state on a time scale below 1 ns in thermal rubidium vapor. We use a bandwidth-limited pulsed excitation and observe up to 6 full Rabi cycles within a pulse duration of ∼4  ns. We find good agreement between the experiment and numerical simulations based on a surprisingly simple model. This result shows that fully coherent dynamics with Rydberg states can be achieved even in thermal atomic vapor, thus suggesting small vapor cells as a platform for room-temperature quantum devices. Furthermore, the result implies that previous coherent dynamics in single-atom Rydberg gates can be accelerated by 3 orders of magnitude.

We present evidence for Rydberg-Rydberg interaction in a gas of rubidium atoms above room temperature. Rabi oscillations on the nanosecond timescale to different Rydberg states are investigated in a vapor cell experiment. Analyzing the atomic time evolution and comparing to a dephasing model we find a scaling with the Rydberg quantum number n that is consistent with van der Waals interaction. Our results show that the interaction strength can be larger than the kinetic energy scale (Doppler width) which is the requirement for realization of thermal quantum devices in the GHz regime.PACS numbers: 32.80. Ee, 34.20.Cf, 42.50.Gy, 03.67.Lx Loosely bound electrons in highlying Rydberg states are giving rise to long range dipolar and van der Waals interactions [1,2]. The coherent control of this interaction allows for engineering of quantum correlated states [3,4]. In ultracold systems where an interaction strength on the order of several MHz is sufficient, the van der Waals interaction has lead to the observation of Rydberg blockade [5,6] and dephasing [7,8]. In such systems the interaction has been exploited for quantum logical operations [9,10] and the creation of non-classical light states [11]. So far the observation of this interaction has been limited to the ultracold domain. In very early related experiments density-dependent line broadening effects on Rydberg lines have been studied [12] and interaction effects in thermal vapor involving excited but non Rydberg states have been investigated [13,14].We present evidence for van der Waals-type interatomic interaction energies in the GHz regime between Rydberg-excited alkali atoms in thermal vapor. Using a pulsed laser excitation, we are able to drive Rabi oscillations on the nanosecond timescale to a Rydberg state [16] and are therefore faster than the coherence time limitation given by the Doppler width.We investigate the dephasing of these oscillations for different atomic densities and Rydberg states. For a fixed Rydberg state, we see a linear growth of the dephasing rate with density. Through a systematic study of various Rydberg states we have found that the scaling of this growth with the principal quantum number n is consistent with van der Waals-interaction.We excite 85 Rb atoms to a Rydberg S-state with an off-resonant two-photon excitation (Fig. 1a). The upper transition is addressed by a pulsed laser in order to provide sufficient intensity for driving GHz Rabi oscillations despite the small transition dipole matrix element. The peak Rabi frequencies of the pulse on the 5P − nS transition are in the range of Ω blue /2π ∼ 3.3 GHz to 3.7 GHz. The 780 nm laser addressing the ground state (Ω red /2π ∼ 750 MHz) is blue detuned by ∆/2π ∼ 2.3 GHz with respect to the intermediate state [15]. In this configuration a major part of the population oscillates directly between the ground and Rydberg state. In particular this means that changes in the absorption/emission of the 780 nm light are mainly caused by these population transfers and not due to excitation ...

A quantum network that consists of several components should ideally work on a single physical platform. Neutral alkali atoms have the potential to be very well suited for this purpose due to their electronic structure, which involves long-lived nuclear spins and very sensitive highly excited Rydberg states. In this Letter, we describe a fabrication method based on quartz glass to structure arbitrary shapes of microscopic vapor cells. We show that the usual spectroscopic properties known from macroscopic vapor cells are almost unaffected by the strong confinement.

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