arXiv subjects

Leonid P. Yatsenko

Publications and source records attributed to Leonid P. Yatsenko.

6 recordsLinked to original sources

arXiv2022

Ultrabright and narrowband intra-fiber biphoton source at ultralow pump power

Nonclassical photon sources of high brightness are key components of quantum communication technologies. We here demonstrate the generation of narrowband, nonclassical photon pairs by employing spontaneous four-wave mixing in an optically-dense ensemble of cold atoms within a hollow-core fiber. The brightness of our source approaches the limit of achievable generated spectral brightness at which successive photon pairs start to overlap in time. For a generated spectral brightness per pump power of up to $2\times 10^{9} \ \textrm{pairs/(s MHz mW)}$ we observe nonclassical correlations at pump powers below $100 \textrm{nW}$ and a narrow bandwidth of $2π\times 6.5 \ \textrm{MHz}$. In this regime we demonstrate that our source can be used as a heralded single-photon source. By further increasing the brightness we enter the regime where successive photon pairs start to overlap in time and the cross-correlation approaches a limit corresponding to thermal statistics. Our approach of combining the advantages of atomic ensembles and waveguide environments is an important step towards photonic quantum networks of ensemble based elements.

quant-ph↗

arXiv2022

Observation of oscillatory Raman gain associated with two-photon Rabi oscillations of nanofiber-coupled atoms

Quantum emitters with a $Λ$-type level structure enable numerous protocols and applications in quantum science and technology. Understanding and controlling their dynamics is, therefore, one of the central research topics in quantum optics. Here, we drive two-photon Rabi oscillations between the two ground states of cesium atoms and observe the associated oscillatory Raman gain and absorption that stems from the atom-mediated coherent photon exchange between the two drive fields. The atoms are efficiently and homogeneously coupled with the probe field by means of a nanofiber-based optical interface. We study the dependence of the two-photon Rabi frequency on the system parameters and observe Autler-Townes splitting in the probe transmission spectrum. Beyond shedding light on the fundamental processes underlying two-photon Rabi oscillations, our method could also be used to investigate (quantum) correlations between the two drive fields as well as the dynamical establishment of electromagnetically induced transparency.

physics.atom-ph↗

arXiv2021

Loading and spatially-resolved characterization of a cold atomic ensemble inside a hollow-core fiber

We present a thorough experimental investigation of the loading process of laser-cooled atoms from a magneto-optical trap into an optical dipole trap located inside a hollow-core photonic bandgap fiber, followed by propagation of the atoms therein. This, e.g., serves to identify limits to the loading efficiency and thus optical depth which is a key parameter for applications in quantum information technology. Although only limited access in 1D is available to probe atoms inside such a fiber, we demonstrate that a detailed spatially-resolved characterization of the loading and trapping process along the fiber axis is possible by appropriate modification of probing techniques combined with theoretical analysis. Specifically, we demonstrate the loading of up to $2.1 \times 10^5$ atoms with a transfer efficiency of 2.1 % during the course of 50 ms and a peak loading rate of $4.7 \times 10^3$ atoms ms$^{-1}$ resulting in a peak atomic number density on the order of $10^{12}$ cm$^{-3}$. Furthermore, we determine the evolution of the spatial density (profile) and ensemble temperature as it approaches its steady-state value of $T=1400$ $μ$K, as well as loss rates, axial velocity and acceleration. The spatial resolution along the fiber axis reaches a few millimeters, which is much smaller than the typical fiber length in experiments. We compare our results to other fiber-based as well as free-space optical dipole traps and discuss the potential for further improvements.

physics.atom-ph↗

arXiv2018

Spatial distribution of atoms in the field of the criss-cross standing bichromatic light waves

We show that properly detuning the carrier frequency of each of the criss-cross bichromatic waves from the transition frequency of the atom, it is possible to form a two-dimensional trap for atoms if the intensity of the waves is sufficiently large. For zero and near zero initial phases of waves, and also for $π$ and near $π$ phase shift between criss-cross waves a dynamic spatial structure of square cells with the side $λ/\sqrt{2}$ is formed. Numerical simulations are carried out for sodium atoms.

physics.atom-ph↗

arXiv2017

Trapping of Atoms by the Counter-Propagating Stochastic Light Waves

We calculate the temperature of the atoms in the field of counter-propagating stochastic light waves (the chaotic-field model). We show that the temperature of the atomic ensemble depends on the autocorrelation time of the waves, their intensity and the detuning of the carrier frequency of the waves from the atomic transition frequency. The field can form a one-dimensional trap for atoms, as is readily seen from our previous investigation of light-pressure force on an atom in counter-propagating stochastic light waves [V. I. Romanenko, B. W. Shore, L. P. Yatsenko, Opt. Commun. 268 (2006) 121-132]. We carry out a numerical simulation of the atomic ensemble using parameters appropriate for sodium atoms. Analyzing the known investigation of the light-pressure force on atoms and their motion in the counter-propagating polychromatic waves, we suggest an hypothesis that any polychromatic counter-propagating waves that have a discrete spectrum, or waves described by a stationary stochastic process, one of which repeats the other, can form a trap for atoms.

physics.atom-ph↗

arXiv2012

Capture of atoms and small particles in an optical trap formed by sequences of counter-propagating light pulses with a large area

A new trap for atoms and small particles based on the interaction between an atom and the field of counter-propagating light pulses that are partially superposed in time has been proposed. A substantial difference from the known analogs consists in that the atom-field interaction is close to the adiabatic one, which allows a considerably higher momentum to be transferred to the atom within the same time interval and makes the trap smaller in size. It has been shown that, owing to the dependence of the light pressure force on the atom velocity, the atomic ensemble is cooled at its interaction with the field.

physics.optics↗