arXiv subjects

Sankar Davuluri

Publications and source records attributed to Sankar Davuluri.

8 recordsLinked to original sources

arXiv2025

Dual frequency calibration to build a portable vapor cell optical clock with improved stability and without a frequency comb

This article theoretically proposes a new dual interferometer technique to accurately calibrate two laser frequencies simultaneously using four-wave mixing in an alkali metal vapor cell. The two frequency-calibrated lasers are mixed to create a beat signal at radio frequency to build a portable optical atomic clock (OAC) without an optical frequency comb (OFC). Removal of the OFC improves the portability of OAC, while the dual interferometer setup enhances the one second stability to $1.3\times 10^{-15}$, which is better than the current portable OAC. Thermal noise in the OAC is minimized by choosing the double-lambda atomic scheme with co-propagating laser fields. Using D2 transition of Rb-87, the standard quantum limited frequency sensitivity and stability of the OAC are estimated as $3.2\;\sqrt{\mbox{Hz}}$, and $1.3\times10^{-15}\sqrt{\mbox{Hz}^{-1}}$, respectively. After considering broadening effects due to $357\,$K temperature and collisions, the optimum stability of the OAC is reduced to $3.3\times10^{-15}\sqrt{\mbox{Hz}^{-1}}$ for a laser with $1\,$KHz linewidth and $0.54$ mW power at the input of the vapor cell.

physics.atom-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 $\Lambda$ system with polariton states in circuit QED.

quant-ph↗

arXiv2023

Optical ranging with quantum advantage

The quantum illumination technique requires joint measurement between the idler and the probe reflected from the low-reflective target present in a noisy environment. The joint measurement is only possible with prior knowledge about the target's location. The technique in this article overcomes this limitation by using entanglement and a cross-correlated homodyne measurement. This technique does not require quantum storage of the idler and prior knowledge about the target's distance. The cross-correlation measurement makes this technique completely immune to environmental noise, as the correlation between the idler and the environment is zero. The low reflectivity of the target is negated by increasing the intensity of the reference fields (non-entangled) in the homodyne. Based on heuristic arguments, a lower bound of the target's reflectivity for optimum application of this technique is described.

quant-ph↗

arXiv2023

Continuous variable entanglement between propagating optical modes using optomechanics

This article proposes a new method to entangle two spatially separated output laser fields from an optomechanical cavity with a membrane in the middle. The radiation pressure force coupling is used to modify the correlations between the input and the output field quadratures. Then the laser fields at the optomechanical cavity output are entangled using the quantum back-action nullifying meter technique. The effect of thermal noise on the entanglement is studied. For experimentally feasible parameters, the entanglement between the laser fields survives upto room temperature.

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

Light as quantum back-action nullifying meter

We propose a new method to overcome quantum back-action in a measurement process using oscillators. An optical oscillator is used as a meter to measure the parameters of another open oscillator. The optical oscillator is synthesized such that the optical restoring force counters any perturbations induced by the quantum back-action phenomena. As a result, it is shown that the quantum back-action in continuous measurement is suppressed in the low frequency regime i.e., for frequencies much smaller than the resonance frequency of the open oscillator. As the meter plays the role of measuring parameters as well as suppressing the quantum back-action, we call it as quantum back-action nullifying meter. As an application of this method, synthesis of quantum back-action nullifying optical oscillator for suppressing radiation pressure force noise in linear and non-linear optomechanics is described.

physics.optics↗

arXiv2018

Shot noise limited interferometry for measuring classical force

We propose an interferometry technique, by using electromagnetically induced transparency phenomena, for measuring classical force. The classical force is estimated by measuring the phase at the output of the interferometer. The proposed measurement mechanism satisfies quantum non-demolition measurement conditions leading to back-action evasion. We further derive the sufficient condition under which the thermal noise in the interferometer is negligible. With no back-action noise and no thermal noise, the sensitivity of this technique is limited by shot noise only.

quant-ph↗

arXiv2018

Quantum limit of hybrid atom-mechanical gyroscope based on electro-magnetically induced transparency

Application of hybrid atom-mechanical oscillator for absolute rotation detection is studied. The hybrid atom-mechanical oscillator consists of an atomic cell, filled with three level atoms, which is fixed on a mechanical oscillator. The atom-mechanical oscillator is placed on a rotating table such that the Coriolis force moves the atomic cell with respect to the incoming laser field. Thus the atomic resonance frequencies are Doppler shifted, and the phase of the laser field interacting with the atomic medium changes. Absolute rotation parameters are estimated by measuring the phase change in the laser field at the output of the atomic cell. Large dispersion is created in the atomic medium, using electromagnetically induced transparency, to enhance the phase change in the laser field interacting with the atomic medium. Contribution of the shot noise, the atomic noise and the noise due to the mechanical oscillation of the atomic cell are studied. We show that, under certain conditions, noise due to the mechanical oscillation of the atomic cell is on the same order of magnitude as the shot noise. The quantum limit of detectable rotation rate is estimated as $8.1\times10^{-19}$\,rad/s.

physics.optics↗