arXiv subjects

Amarendra K. Sarma

Publications and source records attributed to Amarendra K. Sarma.

At least 55 records · Page 3Linked to original sources

arXiv2019

Delayed sudden death of entanglement at exceptional points

Almost a decade ago, physicists encountered a strange quantum phenomenon that predicts an unusual death of entanglement under the influence of local noisy environment,known as entanglement sudden death (ESD). This could be an immediate stumbling block in realizing all the entanglement based quantum information and computation protocols. In this work, we propose a scheme to tackle such shortcomings by exploiting the phenomenon of exceptional points (EP). Starting with a binary mechanical $\mathcal{PT}$ symmetric system, realized over an optomechanical platform, we show that a substantial delay in ESD can be achieved via pushing the system towards an exceptional point. This finding has been further extended to higher (third) order exceptional point by considering a more complicated tripartite entanglement into account.

quant-ph↗

arXiv2019

Tailoring $\mathcal{PT}$-symmetric soliton switch

We theoretically demonstrate soliton steering in $\mathcal{PT}$-symmetric coupled nonlinear dimers. We show that if the length of the $\mathcal{PT}$-symmetric system is set to $2π$ contrary to the conventional one which operates satisfactorily well only at the half-beat coupling length, the $\mathcal{PT}$ dimer remarkably yields an ideal soliton switch exhibiting almost 99.99% energy efficiency with an ultra-low critical power.

nlin.PS↗

arXiv2018

Non-Hermitian Optics

Non-Hermitian optics, mostly known as 'Parity-time symmetric optics', is considered as one of the frontiers areas of research in optical sciences at present. This area is largely inspired by the so-called non-Hermitian quantum physics. While the non-Hermitian quantum mechanics is yet to be accepted widely, parity-time symmetric optics is already a craze among physicists with many experimental results and demonstrations to its support. In this article, keeping under graduate students in mind, in particular, we are giving a brief introduction to this promising area of research in physics.

physics.pop-ph↗

arXiv2018

Unconventional photon blockade in three-mode optomechanics

We analyze the photon correlations in an optomechanical system containing two nonlinear optical modes and one mechanical mode which are coupled via a three-mode mixing. Under a weak driving condition, we determine the optimal conditions for photon antibunching in the weak Kerr-nonlinear regime and we find that the analytical calculations are consistent with the numerical results. The photon blockade effect is attributed to destructive quantum interference in the two-photon excitation pathways created as a result of the three-mode interaction.

quant-ph↗

arXiv2018

Tunable phonon blockade in weakly nonlinear coupled mechanical resonators via Coulomb interaction

Realizing quantum mechanical behavior in micro- and nanomechanical resonators has attracted continuous research effort. One of the ways for observing quantum nature of mechanical objects is via the mechanism of phonon blockade. Here, we show that phonon blockade could be achieved in a system of two weakly nonlinear mechanical resonators coupled by a Coulomb interaction. The optimal blockade arises as a result of the destructive quantum interference between paths leading to two-phonon excitation. It is observed that, in comparison to a single drive applied on one mechanical resonator, driving both the resonators can be beneficial in many aspects; such as, in terms of the temperature sensitivity of phonon blockade and also with regard to the tunability, by controlling the amplitude and the phase of the second drive externally. We also show that via a radiation pressure induced coupling in an optomechanical cavity, phonon correlations can be measured indirectly in terms of photon correlations of the cavity mode.

quant-ph↗

arXiv2018

Chaotic Dynamics and Optical Power Saturation in Parity-Time (PT) Symmetric Double Ring Resonator

We report emergence of saturation and chaotic spiking of optical power in a double ring resonator with balanced loss and gain, obeying the so-called parity-time symmetry. We have modeled the system using a discrete-time iterative equation known as the Ikeda Map. In the linear regime, evolution of optical power in the system shows power saturation behavior below the PT threshold and exponential blow-up above the PT threshold. We found that in the unbroken PT regime, optical power saturation occurs owing to the existence of stable stationary states, which lies on the surface of 4-dimensional hypersphere. Inclusion of Kerr nonlinearity into our model leads to the emergence of a stable, chaotic and divergent region in the parameter basin for period-1 cycle. A closer inspection into the system shows us that the largest Lyapunov exponent blows up in the divergent region. It is found that the existence of high non-negative largest Lyapunov exponent causes chaotic spiking of optical power in the resonators.

physics.optics↗

arXiv2018

Highly Amplified Light Transmission in Parity-Time Symmetric Multilayered Structure

We propose a parity-time symmetric dielectric-nanofilm-dielectric multilayered structure that could facilitate highly amplified transmission of optical power in the infrared spectrum. We have theoretically studied our model using the transfer matrix formalism. The reflection and the transmission coefficients of the S-matrix are evaluated. The theoretical results are validated by FDTD numerical simulation. We have shown how the thickness of the layers and the gain/loss coefficient of the active layers could generate spectral singularities in the S-matrix and how these singularities could be exploited to achieve amplified transmission of a single wavelength through the structure.

physics.optics↗

arXiv2017

Entanglement dynamics of two coupled mechanical oscillators in modulated optomechanics

We study the entanglement dynamics of two coupled mechanical oscillators, within a modulated optomechanical system. We find that, depending on the strength of the mechanical coupling, one could observe either a stationary or a dynamical behavior of the mechanical entanglement, which is extremely robust against the oscillator temperature. Moreover, we have shown that this entanglement dynamics is strongly related to the stability of the normal modes. Taking mechanical damping effects into account, an analytical expression corresponding to the critical mechanical coupling strength, where the transition from stationary to dynamical entanglement occurs is also reported. The proposed scheme is analysed with experimentally realistic parameters, making it a promising mean to realize macroscopic quantum entanglement within current state-of-the-art experimental setups.

quant-ph↗

arXiv2017

Nonlinear compression of temporal solitons in an optical waveguide via inverse engineering

We propose a novel method based on the so-called shortcut to adiabatic passage techniques to achieve fast compression of temporal solitons in a nonlinear waveguide. We demonstrate that soliton compression could be achieved, in principle, at an arbitrarily small distance by inverse engineering the pulse width and the nonlinearity of the medium. The proposed scheme could possibly be exploited for various short-distance communication protocols and may be even in nonlinear guided wave-optics devices and generation of ultrashort soliton pulses.

physics.optics↗

arXiv2017

Plasmon induced transparency in graphene based terahertz metamaterials

Plasmon induced transparency (PIT) effect in a terahertz graphene metamaterial is numerically and theoretically analyzed. The proposed metamaterial comprises of a pair of graphene split ring resonators placed alternately on both sides of a graphene strip of nanometer scale. The PIT effect in the graphene metamaterial is studied for different vertical and horizontal configurations. Our results reveal that there is no PIT effect in the graphene metamaterial when the centers of both the split ring resonators and the graphene strip are collinear to each other. This is a noteworthy feature, as the PIT effect does not vanish for similar configuration in a metal-based metamaterial structure. We have further shown that the PIT effect can be tuned by varying the Fermi energy of graphene layer. A theoretical model using the three level plasmonic system is established in order to validate the numerical results. Our studies could be significant in designing graphene based frequency agile ultra-thin devices for terahertz applications.

physics.optics↗

arXiv2017

Transitionless quantum driving based wireless power transfer

Shortcut to adiabaticity (STA) techniques have the potential to drive a system beyond the adiabatic limits. Here, we present a robust and efficient method for wireless power transfer (WPT) between two coils based on the so-called transitionless quantum driving (TQD) algorithm. We show that it is possible to transfer power between the coils significantly fast compared to its adiabatic counterpart. The scheme is fairly robust against the variations in the coupling strength and the coupling distance between the coils. Also, the scheme is found to be reasonably immune to intrinsic losses in the coils.

quant-ph↗

arXiv2017

Single Photon Generation in a Cavity Optomechanical System induced by a Nonlinear Photonic Crystal

We propose a novel scheme for realizing single-photon blockade in a weakly driven hybrid cavity optomechanical system consisting of a nonlinear photonic crystal. Sub-Poissonian statistics is realized even when the single-photon optomechanical coupling strength is smaller than the decay rate of the optical mode. The scheme relaxes the requirement of strong coupling for photon blockade in optomechanical systems. It is shown that photon blockade could be generated at the telecommunication wavelength.

physics.optics↗

arXiv2016

Single-photon blockade in optomechanical photonic crystal cavity with third-order nonlinearity

Photon statistics in a weakly driven optomechanical photonic crystal cavity, with Kerr-type nonlinearity, is analyzed both analytically and numerically. Single-photon blockade effect is demonstrated via calculations of the zero-time-delay second-order correlation function $g^{(2)}(0)$. The analytical results obtained by solving the Schrödinger equation are in complete conformity with the results obtained through numerical solution of the quantum master equation. The experimental feasibility with state-of-the-art device parameters is discussed. It is observed that photon blockade could be generated at the telecommunication wavelength, even at lower values of the nonlinear susceptibility parameters and in the weak single-photon optomechanical coupling regime.The system is found to be robust against pure dephasing-induced decoherences.

physics.optics↗

arXiv2016

Enhancing quantum correlations and entanglement in an optomechanical system via cross-Kerr nonlinearity

In this work, we theoretically study the quantum correlations present in an optomechanical system by invoking an additional cross-Kerr coupling between the optical and mechanical mode. Under experimentally achievable conditions, we first show that a significant enhancement of the steady-state entanglement could be achieved at a considerably lower driving power, which is also extremely robust with respect to system parameters and environmental temperature. Then, we employ Gaussian quantum discord as a witness of the genuine quantumness of the correlation present in the system and discuss its dependence on the cross-Kerr nonlinearity.

physics.optics↗

arXiv2016

Perturbative Dynamics of Stationary States in Nonlinear Parity-Time Symmetric Coupler

We investigate the nonlinear parity-time (PT) symmetric coupler from a dynamical perspective. As opposed to linear PT-coupler where the PT threshold dictates the evolutionary characteristics of optical power in the two waveguides, in a nonlinear coupler, the PT threshold governs the existence of stationary points. We have found that the stability of the ground state undergoes a phase transition when the gain/loss coefficient is increased from zero to beyond the PT threshold. Moreover, we found that instabilities in initial conditions can lead to aperiodic oscillations as well as exponential growth and decay of optical power. At the PT threshold, we observed the existence of a stable attractor under the influence of fluctuating gain/loss coefficient. Phase plane analysis has shown us the presence of a toroidal chaotic attractor. The chaotic dynamics can be controlled by a judicious choice of the waveguide parameters.

nlin.CD↗

arXiv2016

Controllable chaotic dynamics in a nonlinear fiber ring resonators with balanced gain and loss

We show the possibility of controlling the dynamical behavior of a single fiber ring (SFR) resonator system with the fiber being an amplified (gain) channel and the ring being attenuated (loss) nonlinear dielectric medium. Our model is based on the simple alterations in the parity time symmetric synthetic coupler structures proposed recently [A. Regensburger et al., Nature 488, 167 (2012)]. The system has been modeled using the transfer matrix formalism. We find that this results in a dynamically controllable algorithm for the chaotic dynamics inherent in the system. We have also shown the dependence of the period doubling point on the input amplitude, emphasizing on the dynamical aspects. Moreover, the fact that the resonator essentially plays the role of a damped harmonic oscillator has been elucidated with the non-zero intensity inside the resonator due to constant influx of input light.

nlin.CD↗

arXiv2016

High-Fidelity Entangled Bell States via Shortcuts to Adiabaticity

We present a couple of protocols based on shortcut to adiabaticity techniques for rapid generation of robust entangled Bell states in a system of two two-state systems. Our protocols rely on the so-called transitionless quantum driving (TQD) algorithm and Lewis-Riesenfeld invariant (LRI) method. Both TQD and LRI methods result in high fidelity in population transfer.Our study shows that it is possible to prepare an entangled state in infinitely short time without losing robustness and efficiency.

quant-ph↗

arXiv2016

Ground state cooling of micromechanical oscillators in the unresolved sideband regime induced by a quantum well

Ground state cooling of micromechanical oscillator is a paradigmatic goal for observing quantum mechanical effects in cavity optomechanics. We study theoretically the ground state cooling of a mechanical oscillator in an optomechanical cavity in presence of a quantum well placed inside the cavity. Due to mode tailoring in presence of the quantum well, the cavity response gets modified and leads to asymmetric heating and cooling processes. This facilitates the cooling of the mechanical oscillator even in the unresolved-sideband regime, via inhibition of Stokes scattering.

physics.optics↗