We demonstrate the coherent excitation of a mesoscopic ensemble of about 100 ultracold atoms to Rydberg states by driving Rabi oscillations from the atomic ground state. We employ a dedicated beam shaping and optical pumping scheme to compensate for the small transition matrix element. We study the excitation in a weakly interacting regime and in the regime of strong interactions. When increasing the interaction strength by pair state resonances, we observe an increased excitation rate through coupling to high angular momentum states. This effect is in contrast to the proposed and previously observed interaction-induced suppression of excitation, the so-called dipole blockade.
For a two-level system, it is believed that a far-off-resonant driving cannot help coherent population transfer between two states. In this work, we propose a scheme to implement the coherent transfer with far-off-resonant driving. The scheme works well with both constant driving and Gaussian driving. The total time to finish population transfer is also minimized by optimizing the detuning and coupling constants. We find that the scheme is sensitive to spontaneous emission much more than dephasing. It might find potential applications in X-ray quantum optics and population transfer in Rydberg atoms as well.
The performance of many control tasks with Rydberg atoms can be improved via suppression of the motion-induced dephasing between the ground state and Rydberg states of neutral atoms. This dephasing often occurs during the gap time when the atom is shelved in a Rydberg state before its deexcitation. This paper presents two theories about how to suppress this dephasing. First, by using laser fields to induce a specific extra phase change in the Rydberg state during the gap time, it is possible to faithfully transfer the Rydberg state back to the ground state after the gap. Although the Rydberg state transitions back and forth between different eigenstates during the gap time, it preserves the blockade interaction between the atom of interest and a nearby Rydberg excitation. This simple method of suppressing the motional dephasing of a flying Rydberg atom can be used in a broad range of methods of quantum control of neutral atoms. Second, we find that the motional dephasing can also be suppressed by using a transition in a ``V''-type dual-rail configuration. The left (right) arm of this ``V'' represents a transition to a Rydberg state
∣r1(2)⟩ with a Rabi frequency $\mathrm{\ensuremath{\Omega}}{e}^{ikz}\phantom{\rule{0.2em}{0ex}}(\mathrm{\ensuremath{\Omega}}{e}^{\ensuremath{-}ikz})$, where
z is frozen without atomic drift, but changes linearly in each experimental cycle. Such a configuration is equivalent to a transition between the ground state and a hybrid time-dependent Rydberg state with a Rabi frequency $\sqrt{2}\mathrm{\ensuremath{\Omega}}$, such that there is no phase error whenever the state returns to the ground state. We study two applications of the second theory: (i) it is possible to faithfully transfer the atomic state between a hyperfine ground state and Rydberg states
∣r1(2)⟩ with no gap time between the excitation and deexcitation; and (ii) if infrared laser fields are added to induce a transition between
∣r1(2)⟩ and a nearby Rydberg state
∣r3⟩ via a greatly detuned low-lying intermediate state during the gap time, the atom can keep its internal state in the Rydberg level as well as adjust the population branching in
∣r1(2)⟩ during the gap time. This allows an almost perfect Rydberg deexcitation after the gap time, making it possible to recover a high fidelity in a Rydberg blockade gate. These theories pave the way for high-fidelity quantum control over neutral Rydberg atoms without cooling qubits to motional ground states in optical traps.
We propose a paradigm for macroscopic control of high-order harmonic generation by modulating the bound-state population of the medium atoms. A unique result of this scheme is that apart from regular spatial quasi-phase-matching (QPM), also purely temporal QPM of the emitted radiation can be established. Our simulations demonstrate temporal QPM by inducing homogenous Rabi oscillations in the medium and also spatial QPM by creating a grating of population inversion using the process of rapid adiabatic passage. In the simulations a scaled version of high-order harmonic generation is used: a far off-resonance 2.6 μm source generates UV-visible high-order harmonics from alkali-metal-atom vapor, while a resonant near IR source is used to coherently control the medium.
Abstract The photonic spin Hall effect (SHE) is explored in a highly tunable Rydberg‐based atomic system by leveraging the distinctive properties of Rydberg superatoms. These superatoms arise from strong dipole–dipole interactions and extended radiative lifetimes, resulting in collective excitations governed by the dipole blockade mechanism. An ensemble of three‐level atoms in a cascade configuration models a medium in which each superatom acts as a coherent quantum entity. The photonic SHE shows strong dependence on the probe field Rabi frequency and atomic number density. At high Rabi frequencies, the blockade effect suppresses the photonic SHE, confining its occurrence to specific resonant conditions. In contrast, under weak probe excitation, the blockade influence diminishes, enabling an amplified photonic SHE response at resonant detuning due to increased light‐matter interaction sensitivity. Reducing atomic number density further broadens the detuning range over which the photonic SHE occurs, indicating a transition toward a more sensitive, less resonance‐constrained optical behavior. The effect of van der Waals interactions on the photonic SHE shift is also characterized. This expanded operational bandwidth demonstrates the potential of Rydberg‐based systems for robust spin‐optical control, particularly in scenarios where precise stabilization of the probe field frequency is experimentally challenging.