arXiv subjects

A. S. Sheremet

Publications and source records attributed to A. S. Sheremet.

At least 19 recordsLinked to original sources

arXiv2021

Efficient reversible entanglement transfer between light and quantum memories

Reversible entanglement transfer between light and matter is a crucial requisite for the ongoing developments of quantum information technologies. Quantum networks and their envisioned applications, e.g., secure communications beyond direct transmission, distributed quantum computing or enhanced sensing, rely on entanglement distribution between nodes. Although entanglement transfer has been demonstrated, a current roadblock is the limited efficiency of this process that can compromise the scalability of multi-step architectures. Here we demonstrate the efficient transfer of heralded single-photon entanglement into and out-of two quantum memories based on large ensembles of cold cesium atoms. We achieve an overall storage-and-retrieval efficiency of 85% together with a preserved suppression of the two-photon component of about 10% of the value for a coherent state. Our work constitutes an important capability that is needed towards large scale networks and increased functionality.

quant-ph↗

arXiv2020

Extremely subradiant states in a periodic one-dimensional atomic array

We study the subradiant collective states of a periodic chain of two-level atoms with either transversal or longitudinal transition dipole moments with respect to the chain axis. We show that long-lived subradiant states can be obtained for the transversal polarization by properly choosing the chain period for a given number of atoms in the case of no open diffraction channels. These highly subradiant states have a linewidth that decreases with the number of atoms much faster than it was shown previously. In addition, our study shows that such states are present even if there are additional interaction channels between the atoms, i.e. they interact via waveguide mode of an optical nanofiber for instance. We develop a theoretical framework allowing to describe the spectral properties of the system in terms of contributions from each collective eigenstate and we show that subradiant states manifest themselves in the transmission and reflection spectra, allowing to observe interaction-induced transparency in a very narrow spectral range. Such long-lived collective states may find potential applications in nanophotonics and quantum optics.

quant-ph↗

arXiv2019

Waveguide-coupled single collective excitation of atomic arrays

Considerable efforts have been recently devoted to combining ultracold atoms and nanophotonic devices to obtain not only better scalability and figures of merit than in free-space implementations, but also new paradigms for atom-photon interactions. Dielectric waveguides offer a promising platform for such integration because they enable tight transverse confinement of the propagating light, strong photon-atom coupling in single-pass configurations and potentially long-range atom-atom interactions mediated by the guided photons. However, the preparation of non-classical quantum states in such atom-waveguide interfaces has not yet been realized. Here, by using arrays of individual caesium atoms trapped along an optical nanofibre, we observe a single collective atomic excitation coupled to a nanoscale waveguide. The stored collective entangled state can be efficiently read out with an external laser pulse, leading to on-demand emission of a single photon into the guided mode. We characterize the emitted single photon via the suppression of the two-photon component and confirm the single character of the atomic excitation, which can be retrieved with an efficiency of about 25%. Our results demonstrate a capability that is essential for the emerging field of waveguide quantum electrodynamics, with applications to quantum networking, quantum nonlinear optics and quantum many-body physics.

quant-ph↗

arXiv2018

The Design for a Nanoscale Single-Photon Spin Splitter

We propose using the effective spin-orbit interaction of light in Bragg-modulated cylindrical waveguides for the effcient separation of spin-up and spin-down photons emitted by a single photon emitter. Due to the spin and directional dependence of photonic stopbands in the waveguides, spin-up (down) photon propagation in the negative (positive) direction along the waveguide axis is blocked while the same photon freely propagates in the opposite direction.

physics.optics↗

arXiv2018

Highly-Efficient Quantum Memory for Polarization Qubits in a Spatially-Multiplexed Cold Atomic Ensemble

Quantum memory for flying optical qubits is a key enabler for a wide range of applications in quantum information science and technology. A critical figure of merit is the overall storage-and-retrieval efficiency. So far, despite the recent achievements of efficient memories for light pulses, the storage of qubits has suffered from limited efficiency. Here we report on a quantum memory for polarization qubits that combines an average conditional fidelity above 99% and an efficiency equal to (68$\pm$ 2)%, thereby demonstrating a reversible qubit mapping where more information is retrieved than lost. The qubits are encoded with weak coherent states at the single-photon level and the memory is based on electromagnetically-induced transparency in an elongated laser-cooled ensemble of cesium atoms, spatially multiplexed for dual-rail storage. This implementation preserves high optical depth on both rails, without compromise between multiplexing and storage efficiency. Our work provides an efficient node for future tests of quantum network functionalities and advanced photonic circuits.

quant-ph↗

arXiv2017

Light Scattering From an Atomic Array Trapped Near a One-Dimensional Nanoscale Waveguide: a Microscopic Approach

The coupling of atomic arrays and one-dimensional subwavelength waveguides gives rise to in- teresting photon transport properties, such as recent experimental demonstrations of large Bragg reflection and paves the way for a variety of potential applications in the field of quantum non-linear optics. Here, we present a theoretical analysis for the process of single-photon scattering in this configuration using a full microscopic approach. Based on this formalism, we analyze the spectral dependencies for different scattering channels from either ordered or disordered arrays. The de- veloped approach is entirely applicable for a single-photon scattering from a quasi-one-dimensional array of multilevel atoms with degenerate ground state energy structure. Our approach provides an important framework for including not only Rayleigh but also Raman channels in the microscopic description of the cooperative scattering process.

quant-ph↗

arXiv2016

Large Bragg Reflection from One-Dimensional Chains of Trapped Atoms Near a Nanoscale Waveguide

We report experimental observations of large Bragg reflection from arrays of cold atoms trapped near a one-dimensional nanoscale waveguide. By using an optical lattice in the evanescent field surrounding a nanofiber with a period nearly commensurate with the resonant wavelength, we observe a reflectance of up to 75% for the guided mode. Each atom behaves as a partially-reflecting mirror and an ordered chain of about 2000 atoms is sufficient to realize an efficient Bragg mirror. Measurements of the reflection spectra as a function of the lattice period and the probe polarization are reported. The latter shows the effect of the chiral character of nanoscale waveguides on this reflection. The ability to control photon transport in 1D waveguides coupled to spin systems would enable novel quantum network capabilities and the study of many-body effects emerging from long-range interactions.

quant-ph↗

arXiv2016

Collective polaritonic modes in an array of two-level quantum emitters coupled to optical nanofiber

In this paper we develop a microscopic analysis of the light scattering on a periodic two-level atomic array coupled to an optical nanofiber. We extend the scattering matrix approach for two-level system interaction with nanofiber fundamental waveguiding mode HE_{11}, that allows us modeling the scattering spectra. We support these results considering the dispersion of the polaritonic states formed by the superposition of the fundamental mode of light HE_{11} and the atomic chain states. To illustrate our approach we start with considering a simple model of light scattering over atomic array in the free space. We discuss the Bragg diffraction at the atomic array and show that the scattering spectrum is defined by the non-symmetric coupling of two-level system with nanofiber and vacuum modes. The proposed method allows considering two-level systems interaction with full account for dipole-dipole interaction both via near fields and long-range interaction owing to nanofiber mode coupling.

physics.optics↗

arXiv2016

Datta-and-Das spin transistor controlled by a high-frequency electromagnetic field

We developed the theory of spin dependent transport through a spin-modulator device (so-called Datta-and-Das spin transistor) in the presence of a high-frequency electromagnetic field (dressing field). Solving the Schrödinger problem for dressed electrons, we demonstrated that the field drastically modifies the spin transport. In particular, the dressing field leads to renormalization of spin-orbit coupling constants that varies conductivity of the spin transistor. The present effect paves the way for controlling the spin-polarized electron transport with light in prospective spin-optronic devices.

cond-mat.mes-hall↗

arXiv2016

Bunching of numbers in a non-ideal roulette: the key to winning strategies

Chances of a gambler are always lower than chances of a casino in the case of an ideal, mathematically perfect roulette, if the capital of the gambler is limited and the minimum and maximum allowed bets are limited by the casino. However, a realistic roulette is not ideal: the probabilities of realisation of different numbers slightly deviate. Describing this deviation by a statistical distribution with a width δ we find a critical δ that equalizes chances of gambler and casino in the case of a simple strategy of the game: the gambler always puts equal bets to the last N numbers. For up-critical δ the expected return of the roulette becomes positive. We show that the dramatic increase of gambler's chances is a manifestation of bunching of numbers in a non-ideal roulette. We also estimate the critical starting capital needed to ensure the low risk game for an indefinite time.

q-fin.GN↗

arXiv2015

Quantum statistics of bosonic cascades

Bosonic cascades formed by lattices of equidistant energy levels sustaining radiative transitions between nearest layers are promising for the generation of coherent terahertz radiation. We show how, also for the light emitted by the condensates in the visible range, they introduce new regimes of emission. Namely, the quantum statistics of bosonic cascades exhibit super-bunching plateaus. This demonstrates further potentialities of bosonic cascade lasers for the engineering of quantum properties of light useful for imaging applications.

cond-mat.quant-gas↗

arXiv2015

Coherent control of light transport in a dense and disordered atomic ensemble

Light transport in a dense and disordered cold atomic ensemble, where the cooperation of atomic dipoles essentially modifies their coupling with the radiation modes, offers an alternative approach to light-matter interfacing protocols. Here, we show how the cooperativity and quasi-static dipole interaction affect the process of light propagation under the conditions of electromagnetically-induced transparency (EIT). We perform comparative analysis of the self-consistent approach with ab-initio microscopic calculations and emphasize the role of the interatomic interaction in the dipoles' dynamics. Our results show that in such a dense and strongly disordered system the EIT-based light storage protocol stays relatively insensitive to configuration variations and can be obtained with essentially less atoms than it is normally needed for dilute configurations.

quant-ph↗

arXiv2014

Exciton-photon correlations in bosonic condensates of exciton-polaritons

Exciton-polaritons are mixed light-matter quasiparticles. We have developed a statistical model describing stochastic exciton-photon transitions within a condensate of exciton polaritons. We show that the exciton-photon correlator depends on the "hidden variable" which characterizes the rate of exciton-photon transformations in the condensate. We discuss implications of this effect for the quantum statistics of photons emitted by polariton lasers.

cond-mat.mes-hall↗

arXiv2013

Multiple light scattering on the F = 1 - F' = 0 transition in a cold and high density 87Rb vapor

We report an experimental study of near resonance light scattering on the $F = 1 \rightarrow F' = 0$ component of the $D_2$ line in atomic $^{87}Rb$. Experiments are performed on spatially bi-Gaussian ultracold gas samples having peak densities ranging from about $5 \cdot 10^{12} - 5 \cdot 10^{13}$ atoms/cm$^{3}$ and for a range of resonance saturation parameters and detunings from atomic resonance. Time resolution of the scattered light intensity reveals dynamics of multiple light scattering, optical pumping, and saturation effects. The experimental results in steady-state are compared qualitatively with theoretical models of the light scattering process. The steady-state line shape of the excitation spectrum is in good qualitative agreement with these models.

physics.atom-ph↗

arXiv2013

A reversible optical memory for twisted photons

We report on an experiment in which orbital angular momentum of light is mapped at the single-photon level into and out of a cold atomic ensemble. Based on the dynamic electromagnetically-induced transparency protocol, the demonstrated optical memory enables the reversible mapping of Laguerre-gaussian modes with preserved handedness of the helical phase structure. The demonstrated capability opens the possibility to the storage of qubits encoded as superpositions of orbital angular momentum states and to multi-dimensional light-matter interfacing.

quant-ph↗

arXiv2012

Experimental Investigation of the Transition between Autler-Townes Splitting and Electromagnetically-Induced Transparency

Two phenomena can affect the transmission of a weak signal field through an absorbing medium in the presence of a strong additional field: electromagnetically induced transparency (EIT) and Autler-Townes splitting (ATS). Being able to discriminate between the two is important for various applications. Here we present an experimental investigation into a method that allows for such a disambiguation as proposed in [Phys. Rev. Lett. 107, 163604 (2011)]. We apply the proposed test based on Akaike's information criterion to a coherently driven ensemble of cold cesium atoms and find a good agreement with theoretical predictions, therefore demonstrating the suitability of the method. Additionally, our results demonstrate that the value of the Rabi frequency for the ATS/EIT model transition in such a system depends on the level structure and on the residual inhomogeneous broadening.

physics.atom-ph↗

arXiv2011

Electromagnetically induced transparency in inhomogeneously broadened Lambda-transition with multiple excited levels

Electromagnetically induced transparency (EIT) has mainly been modelled for three-level systems. In particular, a considerable interest has been dedicated to the Lambda-configuration, with two ground states and one excited state. However, in the alkali-metal atoms, which are commonly used, hyperfine interaction in the excited state introduces several levels which simultaneously participate in the scattering process. When the Doppler broadening is comparable with the hyperfine splitting in the upper state, the three-level Lambda model does not reproduce the experimental results. Here we theoretically investigate the EIT in a hot vapor of alkali-metal atoms and demonstrate that it can be strongly reduced due to the presence of multiple excited levels. Given this model, we also show that a well-designed optical pumping enables to significantly recover the transparency.

quant-ph↗

arXiv2010

Atomic quantum memories for light

We consider the coherent stimulated Raman process developing in an optically dense and disordered atomic medium in application to the quantum memory scheme. Our theoretical model predicts that the hyperfine interaction in the excited state of alkali atoms can positively affect on the quantum memory efficiency. Based on the concept of the coherent information transfer we analyze and compare the memory requirements for storage of single photon and macroscopic multi-photon light pulses.

quant-ph↗