arXiv subjects

Tarak Nath Dey

Publications and source records attributed to Tarak Nath Dey.

At least 19 recordsLinked to original sources

arXiv2026

Squeezing enhanced homodyne weak force sensing in cavity optomechanics

Cavity optomechanical systems have emerged as a promising platform for quantum sensing. Quantum mechanics imposes a standard quantum limit (SQL) on the force-sensitivity for the standard homodyne phase quadrature measurement of the cavity's output field. In this paper, we investigate ways to enhance weak force sensitivity beyond SQL by employing a variational homodyne quadrature readout and quantum squeezing. Our study reveals a remarkable improvement in the force sensitivity of a cavity optomechanical sensor at a suitable homodyne angle, compared with standard phase quadrature detection of the cavity output field within a specific frequency band. We further demonstrate improved force sensitivity via intra-cavity squeezing (ICS) or injected external squeezing (IES) of the cavity mode. Both variational homodyne readout and quantum squeezing induce quantum correlations between the amplitude and phase quadratures of the cavity's output field, thereby improving force sensitivity. Our results suggest that IES is preferable to ICS for sub-SQL force sensing with system stability and lower probe power requirements. The squeezing-enhanced variational homodyne detection scheme can enable high-precision quantum sensing across various hybrid quantum platforms.

quant-ph↗

arXiv2026

Supersolid Rotation in an Annular Bose-Einstein Condensate coupled to a Ring Cavity

We theoretically investigate an annularly confined Bose-Einstein Condensate (BEC) coupled to a four-mirror ring cavity supporting traveling-wave optical modes. Under symmetric driving by counter-propagating Laguerre-Gaussian beams carrying equal and opposite orbital angular momenta, the system realizes supersolid phases coexisting with persistent superfluid circulation. Specifically, we obtain a supersolid state if we start with a BEC of winding number $L_p$ as well as supersolid packets with coherent superpositions of two different BEC $L_p$ values. Under asymmetric pumping, realized with Laguerre-Gaussian beams of different orbital angular momenta, chiral symmetry is broken in the system, resulting in asymmetric cavity field amplitudes, directional density modulations, and tunable rotational dynamics of the resulting supersolid lattice. This leads to rotating supersolid density structures for a single winding-number state, and rotating wave packets for an initial superposition of rotational eigenstates. Finally, we probe the presence of Goldstone and Higgs modes which can be observed using minimally destructive measurements of the cavity output spectrum. Our mean-field theory reveals interference-driven rotation without physical stirring, and distinguishes our work from prior static cavity supersolids. Our results establish the ring cavity annular BEC as a versatile platform for generating chiral quantum matter, implementing rotation-sensing devices and generating atomtronic circuits with supersolids.

cond-mat.quant-gas↗

arXiv2026

Structured beam controlled super-resolution in quantum dots via rapid adiabatic passage

We theoretically investigate rapid adiabatic passage (RAP) based super-resolution microscopy in a two-level quantum dot (QD) system. The system consists of a QD interacting with two structured beams, accompanied by chirping and a time delay. The central concept of this work is inspired by the stimulated emission depletion (STED) microscopy technique. To understand the physical mechanism behind super-resolved spot formation, we employ a variational master equation for the density matrix, incorporating both radiative and non-radiative decay processes. A suitably chosen spatiotemporal envelope of the structured beams enables the formation of a super-resolved image. Unwanted low-intensity circular rings around the focal spot are suppressed using Bessel-modulated truncated structured Laguerre-Gaussian (LG) and super-Gaussian (SG) beams. We also study the temperature dependence of the imaging scheme. The numerical results confirm that at low pulse areas, exciton-phonon coupling distorts the image, whereas at higher pulse areas, exciton-phonon decoupling preserves the image resolution. Hence, the proposed scheme may open up new possibilities for nanoscale imaging and bioimaging applications using QDs.

cond-mat.mes-hall↗

arXiv2026

Coherent Control of Population and Quantum Coherence in Superconducting Circuits

Quantum mechanics, with its counterintuitive principles and probabilistic nature, has long been confined to the microscopic realm of atoms and photons. Yet, recent breakthroughs have pushed the boundaries of quantum behavior into the macroscopic world, where objects are visible to the naked eye and governed by classical physics. This review article traces the extraordinary progress toward achieving coherent control of population distributions among multiple quantum levels, as well as manipulation of absorption and refractive index, in such large-scale quantum systems, a feat once considered beyond reach.

quant-ph↗

arXiv2025

A comparative study of focusing with scalar and vector beams in an active Raman gain system

We investigate the focusing characteristics of scalar and vector beams within an atomic medium. An active-Raman-gain configuration is employed to achieve significant Kerr nonlinearity in a four-state atomic system. The probe beams can attain focusing within the medium through careful selection of input beam intensities and the spatial profile of the control field. We analytically derive the linear and third-order nonlinear susceptibilities for both scalar and vector probe beams. Our observations indicate that, in addition to the energy transfer from the control beam to the probe beam, the giant cross-Kerr nonlinearity facilitates the focusing of the scalar probe beam into a significantly smaller spot size. Conversely, the vector probe beams exhibit gain-induced narrowing. Furthermore, we evaluate the state of polarization for the vector beam at the minimum beam waist, observing a polarization rotation and a change in ellipticity during propagation. Through the mechanism of focusing, we achieve a reduced spot size for the probe beam, which may have substantial implications for resolution enhancement in microscopy applications.

physics.optics↗

arXiv2025

Unconventional photon blockade in cavity QED with parametric amplification

We theoretically investigate the quantum-interference-induced photon blockade effect in a single two-level atom-cavity quantum electrodynamics (QED) system with degenerate parametric amplification. The analytical calculations reveal the optimal parametric gain and phase parameters for achieving optimum unconventional photon blockade conditions. Under the optimal parameter regime, the numerical results of the second-order correlation function demonstrate strong photon antibunching consistent with the analytical results. Furthermore, the numerical results corroborate that coherently driving the atom leads to a stronger photon blockade than a coherently driven cavity with the optimal parameters. We numerically demonstrate that the UPB effect is compromised by a non-zero cavity-atom coupling in the cavity-driven configuration. However, stronger photon antibunching can be attained with a non-zero cavity-atom coupling in the atom-driven configuration. This work may be suitable for experimentally realising a strongly antibunched single-photon source for applications in quantum technology.

quant-ph↗

arXiv2025

Controllable Single Photon Scattering via Coupling of Driven $Λ$ System with Topological Waveguide

We investigate the coherent single photon scattering process in a topological waveguide coupled with a driven $Λ$ system. We derive an analytical expression for transmittance by using the scattering formalism for three different sublattice sites (A, B, and AB), which couples to the $Λ$ system. We have demonstrated that the system's response is topology-independent for A and B sublattice-site coupling and becomes topology-dependent for AB sublattice-site coupling. In a weak control field regime, the system behaves as a perfect mirror in all of these configurations. Upon the control field strength enhancement, the transmission spectrum evolves from Electromagnetically Induced Transparency (EIT) to Autler-Townes splitting (ATS) in A and B sublattice-site coupling. The manipulation of transmission from opaque to transparent holds the key mechanism of a single photon switch. Further, the topology-dependent AB sublattice configuration allows the sharper Fano line shape that is absent in topology-independent A and B sublattice configurations. This characteristic of the Fano line can be used as a tunable single-photon switch and for sensing external perturbations. Furthermore, our study paves the way for the robustness and tunability of systems with applications in quantum technologies such as quantum switches, sensors, and communication devices.

quant-ph↗

arXiv2024

Arbitrary vector beam generation in semiconductor quantum dots

We have proposed an arbitrary vector beam (VB) generation scheme in a thin disk-shaped quantum dot (QD) medium considering phonon interaction. The QD biexciton system exhibits interplay between first and third-order nonlinear susceptibility between two orthogonal circular polarisation transitions. Three QD transitions are coupled with one applied weak and two strong control orbital angular momentum (OAM) carrying fields. Therefore, the applied field experiences absorption, and a new field with the desired OAM is generated via four-wave mixing (FWM). These two orthogonal field superpositions produce VB at the QD medium end. We have also demonstrated the polarization rotation of a VB by changing only the relative control field phase. Additionally, we have analyzed the effect of temperature on the VB generation.

quant-ph↗

arXiv2024

Linear and nonlinear propagation of cylindrical vector beam through a non-degenerate four level atomic system

We investigate the phase-induced susceptibilities for both components of the probe vector beam (PVB) within an atomic system. The atoms are prepared in a non-degenerate four-level configuration. The transitions are coupled by a $π$ polarized control field and two orthogonally polarized components of a PVB. We show that the linear susceptibility of the medium depends on the phase shift between the control field and PVB, characterizing loss or gain in the system. Additionally, the phase shift causes polarization rotation in the vector beams (VBs) as they propagate. We further study the effect of nonlinearity on the VB propagation through the medium for a couple of Rayleigh lengths. The self-focusing and defocusing phenomena are observed for radial, azimuthal, and spiral VBs. The special chain-like self-focusing and defocusing leads to the formation of consecutive smaller spot sizes with moderate gain. Therefore, the mechanism of control of susceptibility and self-focusing may hold promise for applications such as transitioning from an absorber to an amplifier, high-resolution microscopy, and optical trap systems.

physics.optics↗

arXiv2023

Ring Bose-Einstein condensate in a cavity: Chirality Detection and Rotation Sensing

Recently, a method has been proposed to detect the rotation of a ring Bose-Einstein condensate, in situ, in real-time and with minimal destruction, using a cavity driven with optical fields carrying orbital angular momentum. This method is sensitive to the magnitude of the condensate winding number but not its sign. In the present work, we consider simulations of the rotation of the angular lattice formed by the optical fields and show that the resulting cavity transmission spectra are sensitive to the sign of the condensate winding number. We demonstrate the minimally destructive technique on persistent current rotational eigenstates, counter-rotating superpositions, and a soliton singly or in collision with a second soliton. Conversely, we also investigate the sensitivity of the ring condensate, given knowledge of its winding number, to the rotation of the optical lattice. This characterizes the effectiveness of the optomechanical configuration as a laboratory rotation sensor. Our results are important to studies of rotating ring condensates used in atomtronics, superfluid hydrodynamics, simulation of topological defects and cosmological theories, interferometry using matter-wave solitons, and optomechanical sensing.

cond-mat.quant-gas↗

arXiv2023

Nondegenerate two-photon lasing in a single quantum dot

We propose two-mode two-photon microlaser using a single semiconductor quantum dot grown inside a two-mode microcavity. We explore both incoherent and coherent pumping at low temperatures to achieve suitable conditions for two-mode two-photon lasing. The two-mode two-photon stimulated emission is strongly suppressed but the single-photon stimulated emission is enhanced by exciton-phonon interactions. In coherently pumped quantum dot one can achieve large two-mode two-photon lasing where single-photon lasing is almost absent. We also discuss generation of steady state two-mode entangled state using two-photon resonant pumping.

quant-ph↗

arXiv2023

Coherent population transfer with polariton states in circuit QED

This article proposes a new method to increase the efficiency of stimulated Raman adiabatic passage (STIRAP) in superconducting circuits using a shortcut to the adiabaticity (STA) method. The STA speeds up the adiabatic process before decoherence has a significant effect, thus leading to increased efficiency. This method achieves fast, high-fidelity coherent population transfer, known as super-adiabatic STIRAP (saSTIRAP), in a dressed state-engineered $Λ$ system with polariton states in circuit QED.

quant-ph↗

arXiv2023

Cavity optomechanical detection of persistent currents and solitons in a bosonic ring condensate

We present numerical simulations of the cavity optomechanical detection of persistent currents and bright solitons in an atomic Bose-Einstein condensate confined in a ring trap. This work describes a novel technique that measures condensate rotation in situ, in real-time, and with minimal destruction, in contrast to currently used methods, all of which destroy the condensate completely. For weakly repulsive inter-atomic interactions, the analysis of persistent currents extends our previous few-mode treatment of the condensate [P. Kumar et al. Phys. Rev. Lett. 127, 113601 (2021)] to a stochastic Gross-Pitaevskii simulation. For weakly attractive atomic interactions, we present the first analysis of optomechanical detection of matter-wave soliton motion. We provide optical cavity transmission spectra containing signatures of the condensate rotation, sensitivity as a function of the system response frequency, and atomic density profiles quantifying the effect of the measurement backaction on the condensate. We treat the atoms at a mean-field level and the optical field classically, account for damping and noise in both degrees of freedom, and investigate the linear as well as nonlinear response of the configuration. Our results are consequential for the characterization of rotating matter waves in studies of atomtronics, superfluid hydrodynamics, and matter-wave soliton interferometry.

cond-mat.quant-gas↗

arXiv2023

Self-induced Transparency in a Semiconductor Quantum Dot medium at ultra-cold temperatures

We investigate the feasibility of minimum absorption and minimum broadening of pulse propagation in an inhomogeneously broadened semiconductor quantum dot medium. The phonon interaction is inevitable in studying any semiconductor quantum dot system. We have used the polaron transformation technique to deal with quantum dot phonon interaction in solving system dynamics. We demonstrate that a short pulse can propagate inside the medium with minimal absorption and broadening in pulse shape. The stable pulse area becomes slightly higher than the prediction of the pulse area theorem and is also dependent on the environment temperature. The change in the final pulse shape is explained very well by numerically solving the propagation equation supported by the susceptibility of the medium. Our system also exhibits the pulse breakup phenomena for higher input pulse areas. Therefore, the considered scheme can have important applications in quantum communication, quantum information, and mode-locking with the advantage of scalability and controllability.

quant-ph↗

arXiv2022

Enhancing the force sensitivity of squeezed light optomechanical interferometer

Application of frequency-dependent squeezed vacuum improves the force sensitivity of optomechanical interferometer beyond the standard quantum limit by a factor of $e^{-r}$, where $r$ is the squeezing parameter. In this work, we show that the application of squeezed light along with quantum optical restoring force can enhance the sensitivity beyond the standard quantum limit by a factor of $\sqrt{e^{-2r}ζ/4Δ}$, where $0< ζ/Δ<1$, with $ζ$ as the optomechanical cavity decay rate and $Δ$ as the detuning between cavity eigenfrequency and driving field. The technique described in this article is restricted to frequencies much smaller than the resonance frequency of the optomechanical mirror.

physics.optics↗

arXiv2022

Pulse amplification in a closed loop $Λ$ system with permanent dipole moments

Propagation of a weak Gaussian probe pulse through a closed loop $Λ$ system with permanent dipole moments (PDMs) is investigated in presence of a strong control field along with a third field. The presence of PDMs allows multi photon excitation, which are otherwise forbidden. The PDMs modify the Rabi frequencies of the probe, control, and the third field inside the medium which noticeably affects the propagation of probe pulse. The probe pulse is amplified during propagation with its Gaussian shape intact. Due to unprohibited two photon excitation it is possible to amplify a probe pulse whose frequency is twice of the control field's frequency, with the help of the third field.

physics.optics↗

arXiv2021

Shape preserving atomic pulse amplifier

Propagation of a weak probe pulse through a $Λ$ system in a resonant gain configuration is investigated. We employ the control field intensity that permits the amplification of probe pulse during propagation, without instability at two photon resonance. Posterior to amplification, a broadened probe pulse is obtained, which retains its initial pulse shape and travels at the speed of light in vacuum, without experiencing any delay, absorption, and dispersion. The salient feature of this technique lies in the fact that in addition to preserving the initial pulse shape, it also ensures stable pulse propagation after amplification. It also works for arbitrary probe pulse shapes.

physics.optics↗

arXiv2020

Microwave assisted optical waveguide in Rydberg atoms

We theoretically demonstrate an efficient scheme to build a microwave (MW) assisted optical waveguide in an inhomogeneously broadened vapor medium that is made of active 87 Rb atoms and inactive buffer gas atoms. We exploit the sensitive behaviour of MW field coupled between highly excited Rydberg states to create distinctly responsive and tunable atomic waveguide. The buffer gas induced collision further manipulates the features of the waveguide by widening the spatial transparency window and enhancing the contrast of the refractive index. We numerically solve Maxwell's equations to demonstrate diffractionless propagation of 5 micrometer narrow paraxial light beams of arbitrary mode to several Rayleigh lengths. The presence of the buffer gas significantly enhances output intensity of the diffraction controlled light beam from 10 percent to 54 percent. This efficient diffraction elimination technique has important applications in high-resolution imaging and high-density optical communication.

physics.optics↗