arXiv subjects

P. K. Pathak

Publications and source records attributed to P. K. Pathak.

At least 19 recordsLinked to original sources

arXiv2025

Two-mode hyperradiant lasing in a system of two quantum dots embedded in a bimodal photonic crystal cavity

We propose a scheme for two-mode hyperradiant lasing in a system comprising two incoherently pumped quantum dots (QDs) coupled to a bimodal photonic crystal cavity. To account for the exciton-phonon interactions, we employ a time-convolutionless polaron-transformed master equation. Both resonant and off-resonant couplings of the QDs to the cavity modes are considered, and we analyze the resulting radiance witness as well as the intra- and inter-mode photon correlations. Furthermore, we demonstrate that phonon-induced cooperative two-mode two-photon processes significantly enhance the radiance witness. This enhancement is quantified by evaluating the emission and absorption rates associated with both single-mode and two-mode two-photon transitions. Finally, we compare the radiance witness and emission spectral linewidths for QDs coupled to single-mode and bimodal cavities, revealing that an increase in radiance witness is accompanied by a narrowing of the emission linewidth.

quant-ph↗

arXiv2024

Correlated emission lasing in a single quantum dot embedded inside a bimodal photonic crystal cavity

We investigate the phenomenon of correlated emission lasing in a coherently driven single quantum dot coupled to a bimodal photonic crystal cavity, utilizing a master equation to describe the system dynamics. To account for exciton-phonon interactions, we incorporate a non-perturbative approach through a polaron transformed master equation. By analyzing fluctuations in the Hermitian operators associated with relative and average phase, we derive a Fokker-Planck equation to assess phase drift and diffusion coefficients, demonstrating that correlated emission suppresses quantum noise in the presence of exciton-phonon interaction at low temperature. Additionally, we calculate the single and two-photon excess emission rates (difference between emission and absorption rates) into the cavity modes and explore the generation of continuous-variable entanglement between these modes.

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

Cooperative two-photon lasing in two Quantum Dots embedded inside Photonic microcavity

We propose cooperative two-photon lasing in two quantum dots coupled to a single mode photonic crystal cavity. We consider both quantum dots are driven either incoherently or coherently using external pump. We incorporate exciton-phonon coupling using polaron transformed master equation. Using quantum laser theory, single and multi-photon excess emission (difference between emission and absorption) into cavity mode are investigated. The single and two-photon excess emission contribute to cavity photons, predominantly. Varying the pump strength can lead to single-photon excess emission change from negative to positive and thus by appropriately selecting pump strength single-photon excess emission can be made negligible.

quant-ph↗

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

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↗

arXiv2019

Continuous two-photon source using a single quantum dot in a photonic crystal cavity

We propose methods for realization of continuous two photon source using coherently pumped quantum dot embedded inside a photonic crystal cavity. We analyze steady state population in quantum dot energy levels and field inside the cavity mode. We find conditions for population inversion in coherently pumped and incoherently pumped quantum dot. We show that squeezing in the output for two two photon laser is not visible using coherent as well as incoherent pump. We discuss effect of phonon coupling using recently developed polaron transformed master equation at low temperatures. We also propose scheme for generating squeezed state of field using four wave mixing.

quant-ph↗

arXiv2019

Interaction between two modes of field mediated by two quantum dots in a photonic crystal cavity

We show unusual cooperative two-photon resonance between two-modes of field inside a photonic crystal cavity. The two-photon resonance occurs when two off resonant quantum dots emit one photon in each cavity mode and de-excite simultaneously. In the presence of phonon coupling the conditions for two-photon resonance change significantly. Using such two-photon two-mode interaction we propose to generate entangled state of two qutrits. The basis of a qutrit are formed by the state of the cavity mode containing $0$, $1$ and $2$ photons. We also discuss effect of phonon coupling on negativity of the generated entangled state.

quant-ph↗

arXiv2018

Effect of phonon coupling on the generated entangled states of photons from a single quantum dot embedded inside a microcavity

We discuss the generation of two types of entangled state of two photons-- noon state which is entangled in number and polarization, and polarization entangled state which is entangled in polarization and frequency. We consider a single quantum dot coupled with a bimodal cavity in strong coupling regime. We analyze the effect of exciton-phonon coupling on the concurrence of the generated entangled states. We find that for both states concurrence is maximum in the absence of the anisotropic energy gap between exciton states and remains unchanged in the presence of exciton-phonon coupling. However, for finite anisotropic energy gap concurrence decreases on the increasing temperature of phonon bath.

cond-mat.mes-hall↗

arXiv2018

Effect of phonon coupling on cooperative two-photon emission from two-quantum dots

We predict dominating cooperative two-photon emission from two quantum dots coupled with a single mode photonic crystal cavity. The cooperative two photon emission occurs when excitons in two off-resonantly coupled quantum dots decay simultaneously. The interaction with common cavity field leads to cavity induced two-photon emission which is strongly inhibited by electron phonon coupling. The interaction with common phonon bath produces phonon induced two-photon emission which increases on increasing temperature. For identical quantum dots cavity induced two-photon emission is negligible but phonon induced two-photon emission could be large.

quant-ph↗

arXiv2017

Generation of the superposition of mesoscopic states of nano-mechanical resonator by a single two-level system

We propose measurement based conditional generation of superposition of motional states of nanomechanical resonator. We consider a two level quantum mechanical system coupled with nanomechanical resonator through phonon exchange. An interaction, which produces shifts in the state of nanomechanical resonator depending on the state of the qubit, is realized by driving qubit through two resonant lasers. The measurement of the state of quantum mechanical system produces superposition states of nanomechanical resonator. We show that the quantum interference between states in superposition may lead to arbitrary large displacement in resonator. We also discuss decoherence of generated states using Wigner function.

quant-ph↗

arXiv2010

Generation of time-bin entangled photon pairs using a quantum-dot cavity system

We present a scheme to realize a deterministic solid state source of time-bin entangled photon pairs using cavity-assisted stimulated Raman adiabatic passage (STIRAP) in a single quantum dot. The quantum dot is embedded inside a semiconductor cavity, and the interaction of a coherent superposition of two temporally separated input pulses and the cavity mode leads to a two-photon Raman transition, which produces a time-bin entangled photon pair through the biexciton-exciton cascade. We show that the entanglement of the generated state can be measured using triple coincidence detection, and the degree of entanglement is quantified as the visibility of the interference. We also discuss the effect of pure dephasing on entanglement of the generated photon pair. Pronounced interference visibility values of greater than $1/\sqrt{2}$ are demonstrated in triple coincidence measurement using experimentally achievable parameters, thus demonstrating that the generated photons are suitable for applications with Bell's inequality violation and quantum cryptography.

quant-ph↗

arXiv2009

Generation of "triggered single photons" from a coherently-pumped quantum dot

A deterministic "on demand" source of single photons is a basic building block for linear quantum computation \cite{linear}, quantum cryptography \cite{crypto}, quantum teleportation \cite{teleport}, and quantum networks \cite{network}. In all these applications, quantum interference between two single-photon pulses on a symmetric beam splitter has been exploited \cite{review}, which imposes stringent requirement for the implemented single photons to be indistinguishable in all degrees of freedom, including their frequencies, spectral widths, pulse shapes, and polarizations. To generate single photons one requires a pumping mechanism to excite a "two-level emitter" and an efficient channeling of the subsequently emitted photons. The efficiency of the source can be enhanced by coupling the emitter to the waveguide \cite{manga} or a microcavity mode \cite{cklaw}. However, hitherto the solid-state single photon sources realized by using a quantum dot coupled with a microcavity rely on incoherent pumping of excitons, which leads to problems with timing jitter \cite{kiraz}, leading to a trade off between efficiency and indistinguishability. Here we introduce a means to realize a highly efficient solid state source of indistinguishable single photons using cavity-assisted adiabatic Raman passage in a single quantum dot - cavity system. We demonstrate pulse-triggered single photons with 100% efficiency and $>90$% indistinguishability using currently available experimental parameters.

cond-mat.other↗

arXiv2009

Nonlinear photoluminescence spectra from a quantum dot-cavity system: Direct evidence of pump-induced stimulated emission and anharmonic cavity-QED

We investigate the power-dependent photoluminescence spectra from a strongly coupled quantum dot-cavity system using a quantum master equation technique that accounts for incoherent pumping, pure dephasing, and fermion or boson statistics. Analytical spectra at the one-photon correlation level and the numerically exact multi-photon spectra for fermions are presented. We compare to recent experiments on a quantum dot-micropiller cavity system and show that an excellent fit to the data can be obtained by varying only the incoherent pump rates in direct correspondence with the experiments. Our theory and experiments together show a clear and systematic way of studying stimulated-emission induced broadening and anharmonic cavity-QED.

cond-mat.mes-hall↗

arXiv2009

Fast generation of entangled photon pairs from a single quantum dot embedded in a photonic crystal cavity

We present a scheme for the fast generation of entangled photons from a single quantum dot coupled to a planar photonic crystal that support two orthogonally polarized cavity modes. We discuss ``within generation'' and ``across generation'' of entangled photons when both biexciton to exciton, and exciton to ground state transitions, are coupled through cavity modes. In the across generation, the photon entanglement is restored through a time delay between the photons. The two photon concurrence, which is a measure of entanglement, is greater than 0.7 and 0.8 using experimentally achievable parameters in across generation and within generation, respectively. We also show that the entanglement can be distilled in both cases using a simple spectral filter.

cond-mat.mes-hall↗

arXiv2009

Comment on "Entanglement on Demand through Time Reordering"

In a recent Letter [Phys. Rev. Lett. {\bf 100}, 120501 (2008)], Avron {\em et al.} discuss a time reordering scheme to achieve efficient "across-generation" of entangled photon pairs in a semiconductor quantum dot with a suppressed biexciton binding energy. They demonstrate that the scheme can be implemented using time delay between the generated photons. In this Comment, we derive an exact expression for the concurrence of the time delayed photons, and show that the predicted values by Avron {\em et al.} are not achievable, which stems from an approximation used in their approximate theoretical analysis.

cond-mat.mes-hall↗

arXiv2008

Generation of entangled photon-pairs from a single quantum dot embedded in a planar photonic-crystal cavity

We present a formal theory of single quantum-dot coupling to a planar photonic crystal that supports quasi-degenerate cavity modes, and use this theory to describe, and optimize, entangled-photon-pair generation via the biexciton-exciton cascade. In the generated photon pairs, either both photons are spontaneously emitted from the dot, or one photon is emitted from the biexciton spontaneously and the other is emitted via the leaky-cavity mode. In the strong-coupling regime, the generated photon pairs can be maximally entangled, in qualitative agreement with the simple dressed-state predictions of Johne {\em et al.} [Phys. Rev. Lett. vol. 100, 240404 (2008)]. We derive useful and physically-intuitive analytical formulas for the spectrum of the emitted photon pairs in the presence of exciton and biexciton broadening, which is necessary to connect to experiments, and demonstrate the clear failure of using a dressed-state approach. We also present a method for calculating and optimizing the entanglement between the emitted photons, which can account for post-sample spectral filtering. Pronounced entanglement values of greater than 80% are demonstrated using experimentally achievable parameters, even without spectral filtering.

cond-mat.other↗

arXiv2008

Edge-state Fabry-Perot interferometer as a high sensitivity charge detector

We present a scheme for high sensitivity charge detection in the integer quantum Hall regime using two point contacts in a series. The setup is an electronic analog of an optical Fabry-Perot interferometer. We show that for small transmission through the point contacts the sensitivity of the interferometer is very high due to multiple reflections at the point contacts. The sensitivity can be further enhanced twice by using electrons in spin entangled state. We show that for point contacts having different reflection probabilities, the interferometer can be tuned for the quantum limited measurement.

cond-mat.mes-hall↗