Hyperfine structure of 23Na in a fullerene cage: a coupled cluster approach for electromagnetically induced transparency based quantum memory Mobassir Ahmad, Palki Gakkhar, Biplab Goswami, Rohit Kumar, Naincy Shrivastava, Brajesh K Mani, Jobin Jose, Raghavan K Easwaran Physica Scripta, 2026 Ab initio calculations are performed to investigate the effect of fullerene confinement on the hyperfine structure of sodium, aiming to tailor its characteristics for Electromagnetically Induced Transparency (EIT) based quantum memory (QM) applications. The hyperfine structure constants of the ground state and a few excited states for the bare and confined 23 Na are computed using the relativistic version of the Coupled Cluster Single Double (CCSD) approximation. The impact of the fullerene cage on these constants is investigated using the Gaussian annular square well (GASW) model potential at various depths. Our results demonstrate that confinement significantly tailors the hyperfine interactions, yielding engineered atomic states compatible with O-band (1260–1360 nm) operation in EIT-based quantum memory schemes. Notably, the lifetime of the F = 2 sublevel of the 3 S 1/2 state is ∼10 8 times enhanced upon increasing the confinement strength, providing a substantial reduction in decoherence between hyperfine ground states, which is a key requirement for a robust Λ-type configuration EIT protocol.
Relativistic Atomic Structure Calculations for the Study of Electron Dynamics of Sr+ Ion Confined Inside Fullerene Biplab Goswami, Mobassir Ahmad, Jobin Jose, Raghavan K. Easwaran Atoms, 2025 This article presents the maiden investigation of the electronic structural properties of the Sr+ ion confined inside fullerene. The Dirac equations are solved to calculate the energy levels, probability distributions, etc. for various confinement depths of the Gaussian Annular Square Well (GASW) potential using the Multi-Configuration Dirac Hartree–Fock (MCDHF) formalism. The wavelengths, transition probabilities, and oscillator strengths are reported for the 5S1/2⟷5P1/2 (D1 line) and 5S1/2⟷5P3/2 (D2 line) transitions of the encapsulated ion. We also estimate variations in the line intensity ratio, electron density, Coulomb coupling parameter, etc. A suggested direction for the calculation of electron impact ionization cross-section using the binary-encounter Bethe (BEB) model with the present data is also given.
Theoretical exploration of atomic structure calculation of sodium atom confined in the fullerene cage: a primer investigation for EIT applications Mobassir Ahmad, Jobin Jose, Biplab Goswami, Raghavan K Easwaran Journal of Physics B Atomic Molecular and Optical Physics, 2024 Alterations in the electronic structural properties of a sodium atom confined inside a fullerene cage are investigated in this manuscript; the engineered atom is explored to suit for the quantum technique applications. A Gaussian annular square well (GASW) model has been used to mimic the fullerene environment. Electronic properties such as energy levels, probabilities, the lifetime of the levels, etc, have been studied for various confinement depths of GASW using the multi-configuration Dirac Hartree–Fock technique. The wavelengths of the D lines of the sodium atom have been shifted from the typical yellow to the blue and then to the ultraviolet region upon confinement. Using the range-shifted blue D lines of the engineered atom, a typical Λ-type electromagnetically induced transparency configuration is proposed. Furthermore, we have shown the explicit dependency of relevant atomic parameters on the confinement depth, which showcases the tunability to suit the engineered atoms for various applications; for instance, increasing the confinement depth increases the lifetime of 3 D 5 / 2 and 3 D 3 / 2 states significantly from the typical lifetime value, which has potential applications in quantum technologies.
Effect of relaxation on the transfer of orbital angular momentum via four-wave mixing process in the four-level double lambda atomic system Rohit Kumar, Dixith Manchaiah, Mobassir Ahmad, Raghavan K Easwaran New Journal of Physics, 2024 In this work, we have theoretically studied the resonant four-wave mixing (FWM) in a four-level double Lambda (Λ) atomic system in connection with orbital angular momentum (OAM) transfer from probe to generated signal beam. The effect of the relaxation process is studied in the forward as well as backward FWM. Based on the semiclassical model, our analysis shows a strong dependence of conversion efficiency on spontaneous decay and decoherence rates. From the intensity and phase profile, we have confirmed the OAM nature of the generated signal beam. The physical explanation is given for the dependence of efficiency on the decay rate of the excited atomic state. We have shown that decoherence present in the system always leads to a deleterious effect on conversion efficiency. Our presentation treats forward and backward FWM in a unified way in the context of OAM transfer and sheds light on the parameter dependence of conversion efficiency.
Interaction of four level closed loop atomic systems in the presence of two vector beams Rohit Kumar, Dixith Manchaiah, Raghavan K Easwaran Physica Scripta, 2023 In this manuscript, we have theoretically studied the four level closed loop atomic systems in the presence of two vector beams. A spatially dependent transparency for the probe vector beam is obtained based on the semiclassical model. We have explicitly shown that the number of petals formed for probe absorption depends on the value of orbital angular momentum (OAM) of the constituting beams. A detailed study for absorption and dispersion of right circularly polarized (RCP) and left circularly polarized (LCP) components of the probe beam is carried out and the importance of the polarization state of the beams on Higher Order Poincare Sphere (HOPS) is highlighted. An explicit effect of the interferometer phase of the vector beam which is geometric in nature, is shown for probe beam response. Three types of four level closed loop atomic system is studied with particular emphasis given for double Λ and Diamond atomic system. A dark state analysis of the atomic system is carried out which facilitate a physical understanding of the obtained results. Our study has explored the effects of inhomogeneity in both polarization and intensity for probe and coupling beam in a closed loop atomic system which is phase dependent.
Normal and anomalous dispersion study on probe light propagation in the presence of structured coupling light using electromagnetically induced transparency protocol Dixith Manchaiah, Rohit Kumar, Mobassir Ahmad, Raghavan K. Easwaran Journal of the Optical Society of America B Optical Physics, 2023 Here, we present a study on the dispersion features obtained in an electromagnetically induced transparency (EIT) experiment using a three-level cascade configuration in an 87Rb atomic vapor medium in the presence of Laguerre–Gaussian (LG) light as a coupling. A doublet transmission structure was obtained experimentally, and dispersion spectra were extracted using transmission spectra to study the probe light behavior. Dispersive regions that exhibit normal and anomalous nature were studied considering the polarization of various orientations as a coupling light. We established that normal dispersive region shows steep positive slopes, and anomalous dispersive region shows negative slopes, which can be controlled by polarization orientations. Owing to the change in the slopes of dispersion, normal and anomalous dispersive region is observed, and spectrum shows the effects of subluminal and superluminal propagation of probe light. This work, to the best of our knowledge, is novel in the study of dispersive region arising out of double-resonance EIT transmission spectra in the presence of LG light with the l=10 and p=0 mode as a coupling light with various polarization orientations. In the discussion, we establish that single parameter θ is sufficient for identifying the orientation and ellipticity of the polarization ellipse and also determine that the polarization of coupling light acts as a tuning parameter for changing the behavior of normal and anomalous dispersive region. Slow and fast light or superluminal propagation of probe light arise as a consequence of positive or negative group index, and fast light does not violate the principle of causality. Slow and fast light have future applications in high-speed quantum information and quantum communication using EIT-based protocol.
Temporal Response of Atoms Trapped in an Optical Dipole Trap: A Primer on Quantum Computing Speed S. Baral, Raghavan K. Easwaran, J. Jose, Aarthi Ganesan, P. C. Deshmukh Atoms, 2023 An atom confined in an optical dipole trap is a promising candidate for a qubit. Analyzing the temporal response of such trapped atoms enables us to estimate the speed at which quantum computers operate. The present work models an atom in an optical dipole trap formed using crossed laser beams and further examines the photoionization time delay from such confined atoms. We study noble gas atoms, such as Ne (Z = 10), Ar (Z = 18), Kr (Z = 36), and Xe (Z = 54). The atoms are considered to be confined in an optical dipole trap using X-ray Free Electron Lasers (XFEL). The present work shows that the photoionization time delay of the trapped atoms is different compared with that of the free atoms. This analysis alerts us that while talking about the speed of quantum computing, the temporal response of the atoms in the trapped environment must also be accounted for.
Interplay of polarizations in a cascade EIT system in the presence of vortex coupling light in 87Rb atomic vapor medium Dixith Manchaiah, Rohit Kumar, Raghavan K Easwaran New Journal of Physics, 2023 We investigate both experimentally and theoretically the cascade electromagnetically induced transparency (EIT) in 5 S 1 / 2 − 5 P 3 / 2 − 5 D 5 / 2 configuration in 87Rb atomic vapor medium in the presence of vortex coupling Laguerre Gaussian (LG) light. We demonstrated Doppler free double resonance EIT structure in cascade configuration and observed transmission spectra for | H ⟩ − | H ⟩ and σ + − σ + polarized probe and coupling lights. We demonstrate that the double resonance structure can be identified by two photon transition probabilities and it is found to be F ′ ′ = 2 and F ′ ′ = 3 . By considering coupling LG light, several polarization combinations are taken into account, and their effects on amplifying and diminishing the EIT resonances are demonstrated experimentally. In order to understand the polarization effects of vortex coupling light on EIT spectrum in a degenerate multilevel atomic system, a theoretical model is developed by considering a simplified double hut level structure. Semi-classical density matrix analysis is used to understand the dynamics and also to establish the enhancement and reduction of EIT peak height with coupling light polarizations. The impact of two photon transition probabilities, polarization combinations and relative orientations of probe and coupling lights in degenerate multilevel atomic systems leads to modification of EIT resonances significantly. We establish quantitative agreement between our theory and experimental results.
RF spectroscopy in a resonant RF-dressed trap R Kollengode Easwaran, L Longchambon, P-E Pottie, V Lorent, H Perrin, B M Garraway Journal of Physics B Atomic Molecular and Optical Physics, 2010
RECENT SCHOLAR PUBLICATIONS
Hyperfine structure of 23 Na in a fullerene cage: a coupled cluster approach for electromagnetically induced transparency based quantum memory M Ahmad, P Gakkhar, B Goswami, R Kumar, N Shrivastava, BK Mani, ... Physica Scripta 101 (15), 155401 , 2026 2026
Impact of higher-order laguerre-gaussian modes on electromagnetically induced transparency resonances in Rb atomic vapor medium D Manchaiah, R Kumar, VS Chauhan, P Kumar, NK Nishchal, ... Journal of Optics 54 (5), 3147-3156 , 2025 2025 Citations: 2
Relativistic Atomic Structure Calculations for the Study of Electron Dynamics of Sr + Ion Confined Inside Fullerene B Goswami, M Ahmad, J Jose, RK Easwaran Atoms 13 (4), 36 , 2025 2025 Citations: 3
Theoretical exploration of atomic structure calculation of sodium atom confined in the fullerene cage: a primer investigation for EIT applications M Ahmad, J Jose, B Goswami, RK Easwaran Journal of Physics B: Atomic, Molecular and Optical Physics 57 (15), 155001 , 2024 2024 Citations: 8
Effect of relaxation on the transfer of orbital angular momentum via four-wave mixing process in the four-level double lambda atomic system R Kumar, D Manchaiah, M Ahmad, RK Easwaran New Journal of Physics 26 (5), 053045 , 2024 2024 Citations: 3
Interaction of four level closed loop atomic systems in the presence of two vector beams R Kumar, D Manchaiah, RK Easwaran Physica Scripta 98 (7), 075101 , 2023 2023 Citations: 3
Normal and anomalous dispersion study on probe light propagation in the presence of structured coupling light using electromagnetically induced transparency protocol D Manchaiah, R Kumar, M Ahmad, RK Easwaran Journal of the Optical Society of America B 40 (7), 1904-1910 , 2023 2023 Citations: 5
Temporal response of atoms trapped in an optical dipole trap: a primer on quantum computing speed S Baral, RK Easwaran, J Jose, A Ganesan, PC Deshmukh Atoms 11 (4), 72 , 2023 2023 Citations: 1
Transmission and dispersion management of room-temperature atomic vapor medium of Rb using EIT protocol R Kumar, D Manchaiah, A Barua, RK Easwaran The European Physical Journal Plus 138 (4), 304 , 2023 2023
Temporal Response of Atoms Trapped in an Optical Dipole Trap: A Primer on Quantum Computing Speed. Atoms 2023, 11, 72 S Baral, RK Easwaran, J Jose, A Ganesan, PC Deshmukh 2023
Interplay of polarizations in a cascade EIT system in the presence of vortex coupling light in 87 Rb atomic vapor medium D Manchaiah, R Kumar, RK Easwaran New Journal of Physics 25 (1), 013013 , 2023 2023 Citations: 8
Theoretical study of a four-level EIT-type<? TeX\break?> system in the presence of structured coupling light for microwave field detection R Kumar, D Manchaiah, RK Easwaran Applied Optics 61 (36), 10681-10687 , 2022 2022 Citations: 6
Electromagnetically Induced Transparency in the Presence of Coupling Ince Gaussian Mode D Manchaiah, A Barua, R Kumar, RK Easwaran JSAP Annual Meetings Extended Abstracts The 83rd JSAP Autumn Meeting 2022 … , 2022 2022
A theoretical analysis on quantum memory parameters in ultracold Rb and Cs alkali species using EIT protocol in the presence of structured light: D. Manchaiah … D Manchaiah, R Kumar, RK Easwaran Quantum Information Processing 21 (3), 110 , 2022 2022 Citations: 8
Single-mode optical fibers coupling: study of the field of view LM Shaker, S Osamah, AA Al-Amiery IOP Conference Series: Materials Science and Engineering 1045 (1), 012009 , 2021 2021 Citations: 9
Enhancement of electromagnetically induced transparency and absorption signals in 85 Rb atomic vapor medium by using a small external magnetic field VS Chauhan, R Kumar, D Manchaiah, RK Easwaran Journal of the Optical Society of America B 38 (2), 630-637 , 2021 2021 Citations: 4
Measurement of multi-frequency dispersions of Electromagnetically Induced Transparency windows using Spatial Light Modulator in rubidium vapor VS Chauhan, D Manchaiah, P Kumar, R Kumar, S Bhushan, ... Optik 225, 165707 , 2021 2021 Citations: 7
Theoretical design of quantum memory unit for under water quantum communication using electromagnetically induced transparency protocol in ultracold Rb atoms VS Chauhan, D Manchaiah, S Bhushan, R Kumar, RK Easwaran International Journal of Quantum Information 18 (05), 2050027 , 2020 2020 Citations: 4
Magnetic coil design for two dimensional magneto optical trap to realization of efficient quantum memory VS Chauhan, S Bhushan, RK Easwaran AIP Conference Proceedings 2241 (1), 020012 , 2020 2020 Citations: 1
Narrowing of electromagnetically induced transparency by using structured coupling light in 85 Rb atomic vapor medium VS Chauhan, R Kumar, D Manchaiah, P Kumar, RK Easwaran Laser Physics 30 (6), 065203 , 2020 2020 Citations: 19
MOST CITED SCHOLAR PUBLICATIONS
Quantum-interference-enhanced deep sub-Doppler cooling of K atoms in gray molasses D Nath, RK Easwaran, G Rajalakshmi, CS Unnikrishnan Physical Review A—Atomic, Molecular, and Optical Physics 88 (5), 053407 , 2013 2013 Citations: 104
Sub-Doppler deep-cooled bosonic and fermionic isotopes of potassium in a compact 2D + –3D MOT set-up V Gokhroo, G Rajalakshmi, RK Easwaran, CS Unnikrishnan Journal of Physics B: Atomic, Molecular and Optical Physics 44 (11), 115307 , 2011 2011 Citations: 77
Numerical investigations on photonic nanojet mediated surface enhanced Raman scattering and fluorescence techniques GM Das, AB Ringne, VR Dantham, RK Easwaran, R Laha Optics express 25 (17), 19822-19831 , 2017 2017 Citations: 64
Shedding light on helical microtubules: real-time observations of microtubule self-assembly by light microscopy HY Lee, H Oh, JH Lee, SR Raghavan Journal of the American Chemical Society 134 (35), 14375-14381 , 2012 2012 Citations: 40
RF spectroscopy in a resonant RF-dressed trap RK Easwaran, L Longchambon, PE Pottie, V Lorent, H Perrin, ... Journal of Physics B: Atomic, Molecular and Optical Physics 43 (6), 065302 , 2010 2010 Citations: 38
Influence of the Radio-Frequency source properties on RF-based atom traps O Morizot, L Longchambon, R Kollengode Easwaran, R Dubessy, ... The European Physical Journal D 47 (2), 209-214 , 2008 2008 Citations: 34
Narrowing of electromagnetically induced transparency by using structured coupling light in 85 Rb atomic vapor medium VS Chauhan, R Kumar, D Manchaiah, P Kumar, RK Easwaran Laser Physics 30 (6), 065203 , 2020 2020 Citations: 19
Effect of magnetic field on a multi window ladder type electromagnetically induced transparency with 87Rb atoms in vapour cell S Bhushan, VS Chauhan, RK Easwaran Physics Letters A 383 (31), 125885 , 2019 2019 Citations: 16
Ultracold Rydberg atoms for efficient storage of terahertz frequency signals using electromagnetically induced transparency S Bhushan, VS Chauhan, RK Easwaran Physics Letters A 382 (48), 3500-3504 , 2018 2018 Citations: 15
Theoretical design for generation of slow light in a two-dimensional magneto optical trap using electromagnetically induced transparency S Bhushan, RK Easwaran Applied Optics 56 (13), 3817-3823 , 2017 2017 Citations: 15
Single-mode optical fibers coupling: study of the field of view LM Shaker, S Osamah, AA Al-Amiery IOP Conference Series: Materials Science and Engineering 1045 (1), 012009 , 2021 2021 Citations: 9
Theoretical exploration of atomic structure calculation of sodium atom confined in the fullerene cage: a primer investigation for EIT applications M Ahmad, J Jose, B Goswami, RK Easwaran Journal of Physics B: Atomic, Molecular and Optical Physics 57 (15), 155001 , 2024 2024 Citations: 8
Interplay of polarizations in a cascade EIT system in the presence of vortex coupling light in 87 Rb atomic vapor medium D Manchaiah, R Kumar, RK Easwaran New Journal of Physics 25 (1), 013013 , 2023 2023 Citations: 8
A theoretical analysis on quantum memory parameters in ultracold Rb and Cs alkali species using EIT protocol in the presence of structured light: D. Manchaiah … D Manchaiah, R Kumar, RK Easwaran Quantum Information Processing 21 (3), 110 , 2022 2022 Citations: 8
Measurement of multi-frequency dispersions of Electromagnetically Induced Transparency windows using Spatial Light Modulator in rubidium vapor VS Chauhan, D Manchaiah, P Kumar, R Kumar, S Bhushan, ... Optik 225, 165707 , 2021 2021 Citations: 7
Theoretical study of a four-level EIT-type<? TeX\break?> system in the presence of structured coupling light for microwave field detection R Kumar, D Manchaiah, RK Easwaran Applied Optics 61 (36), 10681-10687 , 2022 2022 Citations: 6
Normal and anomalous dispersion study on probe light propagation in the presence of structured coupling light using electromagnetically induced transparency protocol D Manchaiah, R Kumar, M Ahmad, RK Easwaran Journal of the Optical Society of America B 40 (7), 1904-1910 , 2023 2023 Citations: 5
Enhancement of electromagnetically induced transparency and absorption signals in 85 Rb atomic vapor medium by using a small external magnetic field VS Chauhan, R Kumar, D Manchaiah, RK Easwaran Journal of the Optical Society of America B 38 (2), 630-637 , 2021 2021 Citations: 4
Theoretical design of quantum memory unit for under water quantum communication using electromagnetically induced transparency protocol in ultracold Rb atoms VS Chauhan, D Manchaiah, S Bhushan, R Kumar, RK Easwaran International Journal of Quantum Information 18 (05), 2050027 , 2020 2020 Citations: 4
Broadband quantum memory using electromagnetically induced transparency in atomic medium S Bhushan, VS Chauhan, RK Easwaran Journal of Modern Optics 66 (9), 992-997 , 2019 2019 Citations: 4
