Dressed-state electromagnetically induced transparency for light storage in uniform-phase spin waves

We present, experimentally and theoretically, a scheme for dressed-state electromagnetically induced transparency (EIT) in a three-step cascade system in which a four-level system is mapped into an effective three-level system. Theoretical analysis reveals that the scheme provides coherent-state control via adiabatic following and a generalized protocol for light storage in uniform phase spin-waves that are insensitive to motional dephasing. The three-step driving enables a number of other features, including spatial selectivity of the excitation region within the atomic medium, and kick-free and Doppler-free excitation that produces narrow resonances in thermal vapor. As a proof of concept, we present an experimental demonstration of the generalized EIT scheme using the 6S1/2→6P3/2→7S1/2→8P1/2 excitation path in thermal cesium vapor. This technique could be applied to cold and thermal ensembles to enable longer storage times for Rydberg polaritons

Probing an Excited-State Atomic Transition Using Hyperfine Quantum Beat Spectroscopy

We describe a method to observe the dynamics of an excited-state transition in a room-temperature atomic vapor using hyperfine quantum beats. Our experiment using cesium atoms consists of a pulsed excitation of the D2 transition and continuous-wave driving of an excited-state transition from the 6P3/2 state to the 7S1/2 state. We observe quantum beats in the fluorescence from the 6P3/2 state which are modified by the driving of the excited-state transition. The Fourier spectrum of the beat signal yields evidence of Autler-Townes splitting of the 6P3/2, F=5 hyperfine level and Rabi oscillations on the excited-state transition. A detailed model provides qualitative agreement with the data, giving insight to the physical processes involved

A terahertz-driven non-equilibrium phase transition in a room temperature atomic vapour

There are few demonstrated examples of phase transitions that may be driven directly by terahertz-frequency electric fields, and those that are known require field strengths exceeding 1 MVcm−1. Here we report a non-equilibrium phase transition driven by a weak ( 1 Vcm−1), continuous-wave terahertz electric field. The system consists of room-temperature caesium vapour under continuous optical excitation to a high-lying Rydberg state, which is resonantly coupled to a nearby level by the terahertz electric field. We use a simple model to understand the underlying physical behaviour, and we demonstrate two protocols to exploit the phase transition as a narrow-band terahertz detector: the first with a fast (20μs) nonlinear response to nano-Watts of incident radiation, and the second with a linearised response and effective noise equivalent power (NEP) ≤1 pWHz−1/2. The work opens the door to a new class of terahertz devices controlled with low field intensities and operating in a room-temperature environment

Polarization spectroscopy of an excited state transition

We demonstrate polarization spectroscopy of an excited state transition in room-temperature cesium vapor. An anisotropy induced by a circularly polarized pump beam on the D2 transition is observed using a weak probe on the 6P3/2→7S1/2 transition. At high pump power, a subfeature due to Autler-Townes splitting is observed that theoretical modeling shows is enhanced by Doppler averaging. Polarization spectroscopy provides a simple modulation–free signal suitable for laser frequency stabilization to excited state transitions

Nonlinear optics using cold Rydberg atoms

The implementation of electromagnetically induced transparency (EIT) in a cold Rydberg gas provides an attractive route towards strong photon–photon interactions and fully deterministic all-optical quantum information processing. In this brief review we discuss the underlying principles of how large single photon nonlinearities are achieved in this system and describe experimental progress to date

Fast switching of alkali atom dispensers using laser induced heating

We show that by using an intense laser source to locally heat an alkali atom dispenser, one can generate a high flux of atoms followed by fast recovery (<100 ms) of the background pressure when the laser is extinguished. For repeated heating pulses a switch-on time for the atomic flux of 200 ms is readily attainable. This technique is suited to ultracold atom experiments using simple ultrahigh vacuum (UHV) chambers. Laser-induced heating provides a fast repetition of the experimental cycle, which, combined with low atom loss due to background gas collisions, is particularly useful for experiments involving far-off resonance optical traps, where sufficient laser power (0.5–4 W) is readily availabl

Subnatural linewidths in two-photon excited-state spectroscopy

We investigate, theoretically and experimentally, absorption on an excited-state atomic transition in a thermal vapor where the lower state is coherently pumped. We find that the transition linewidth can be sub-natural, i.e. less than the combined linewidth of the lower and upper state. For the specific case of the 6P_{3/2} -> 7S_{1/2} transition in room temperature cesium vapor, we measure a minimum linewidth of 6.6 MHz compared with the natural width of 8.5 MHz. Using perturbation techniques, an expression for the complex susceptibility is obtained which provides excellent agreement with the measured spectra.Comment: 9 pages, 5 figure

Fast and quasideterministic single ion source from a dipole-blockaded atomic ensemble

We present a fast and quasideterministic protocol for the production of single ions and electrons from a cloud of laser-cooled atoms. The approach is based on a two-step process where first a single Rydberg atom is photoexcited from a dipole-blockade configuration and subsequently ionized by an electric field pulse. We theoretically describe these excitation-ionization cycles via dynamical quantum maps and observe a rich behavior of the ionization dynamics as a function of laser Rabi frequency, pulse duration, and particle number. Our results show that a fast sequential heralded production of single charged particles is achievable even from an unstructured and fluctuating atomic ensemble