arXiv subjects

Madhura Ghosh Dastidar

Publications and source records attributed to Madhura Ghosh Dastidar.

6 recordsLinked to original sources

arXiv2026

Passive Imaging with Quantum Advantage

Far-field optical imaging inevitably involves low-pass spatial filtering, limiting the resolution. Moreover, conventional imaging suppresses high spatial frequency components close to the cutoff, making them invisible under noise, particularly the shot noise arising from discrete and random nature of quantum light. Here we propose and implement a method for reducing the effect of this noise by optically pre-processing the incoming light prior to detection, thereby optimizing the quantum measurement performed on it. Our scheme, termed Fourier Domain Division (FDD), partitions the Fourier plane into multiple regions for independent detection and subsequent post-processing for image reconstruction. By analyzing the quantum and classical Fisher information, we show that our method is advantageous with respect to direct imaging for high spatial-frequency components. As a result, the number of photons required to achieve a certain signal-to-noise-ratio in the Fourier domain is reduced, thus enhancing the overall resolution in the photon-starved regime. We demonstrate our method in microscopy, achieving 5-fold improvement of Fisher information on high spatial-frequency components. Unlike active super-resolution methods, FDD is passive, making it broadly applicable in microscopy and other imaging scenarios where active illumination is impractical, including astronomy and remote sensing. Our work establishes a general strategy for designing quantum optimized superresolution imaging systems, bridging fundamental quantum limits, practical image analysis and computer vision applications.

quant-ph↗

arXiv2024

Signatures of superradiance in intensity correlation measurements in a two-emitter solid-state system

We perform intensity correlation ($g^{(2)}(τ)$) measurements on nitrogen-vacancy (NV) emitters embedded in diamond nanopillars. We observe an increase in transition rates from both the singlet and triplet states by a factor of $\approx 6$, indicating cooperative effects between the multiple emitters in the pillar, at room temperature. We simultaneously observe a $g^{(2)}(0) > 0.5 (\to 1$) as opposed to $g^{(2)}(0) < 0.5$ for others (and as expected for single emitters), indicating the presence of at least two emitters. Furthermore, we observe a triple exponential behaviour for the $g^{(2)}$ in contrast to the standard double exponential behaviour seen for single NV emitters. To understand our experimental observations, we developed a theoretical model. We solve the Lindblad master equation, tailored for single and two NV centers, to study their dissipative dynamics when coupled to a common electromagnetic field, at a finite temperature. Through this, we identify superradiant emission from a two-emitter system as the most likely explanation for our observed data. We also find that random number generation using the coupled emitter system performs better under the NIST test suite and explain it in terms of an entropy-driven model for a coupled emitter system. Our results provide a new signature for multiphotonic states, such as superradiant states, using intensity correlation measurements, that will become important for quantum photonic technologies progress.

quant-ph↗

arXiv2023

Synchronized Bell protocol for detecting non-locality between modes of light

In the following paper, we discuss a possible detection of non-locality in two-mode light states in the Bell protocol, where the local observables are constructed using displacement operators, implemented by Mach-Zender Interferometers fed by strong coherent states. We report numerical results showing that maximizing the Braunstein-Caves Chained Bell (BCCB) inequalities requires equal phases of displacements. On the other hand, we prove that non-locality cannot be detected if the phases of displacements are unknown. Hence, the Bell experiment has to be equipped with a synchronization mechanism. We discuss such a mechanism and its consequences.

quant-ph↗

arXiv2023

Using Entangled Generalized Coherent States for Photonic Quantum Metrology

Quantum metrology aims at achieving enhanced performance in measuring unknown parameters by utilizing quantum resources. Thus, quantum metrology is an important application of quantum technologies. Photonic systems can implement these metrological tasks with simpler experimental techniques. We present a scheme for improved parameter estimation by introducing entangled generalized coherent states (EGCS) for photonic quantum metrology. These states show enhanced sensitivity beyond the classical and Heisenberg limits and prove to be advantageous as compared to the entangled coherent and NOON states. Further, we also propose a scheme for experimentally generating certain entangled generalized coherent states with current technology.

quant-ph↗

arXiv2022

Detecting Entanglement Between Modes of Light

We consider a subgroup of unitary transformations on a mode of light induced by a Mach-Zehnder Interferometer and an algebra of observables describing a photon-number detector proceeded by an interferometer. We explore the uncertainty principles between such observables and their usefulness in performing a Bell-like experiment to show a violation of the CHSH inequality, under physical assumption that the detector distinguishes only zero from non-zero number of photons. We show which local settings of the interferometers lead to a maximal violation of the CHSH inequality.

quant-ph↗

arXiv2021

Pattern Formation and Evidence of Quantum Turbulence in Binary Bose-Einstein Condensates Interacting with a Pair of Laguerre-Gaussian Laser Beams

We theoretically investigate the out-of-equilibrium dynamics in a binary Bose-Einstein condensate confined within two-dimensional box potentials. One species of the condensate interacts with a pair of oppositely wound, but otherwise identical Laguerre-Gaussian laser pulses, while the other species is influenced only via the interspecies interaction. Starting from the Hamiltonian, we derive the equations of motion that accurately delineate the behavior of the condensates during and after the light-matter interaction. Depending on the number the helical windings (or the magnitude of topological charge), the species directly participating in the interaction with lasers is dynamically segmented into distinct parts which collide together as the pulses gradually diminish. This collision event generates nonlinear structures in the related species, coupled with the complementary structures produced in the other species, due to the interspecies interaction. The long-time dynamics of the optically perturbed species is found to develop the Kolmogorov-Saffman scaling law in the incompressible kinetic energy spectrum, a characteristic feature of the quantum turbulent state. However, the same scaling law is not definitively exhibited in the other species. This study warrants the usage of Laguerre-Gaussian beams for future experiments on quantum turbulence in Bose-Einstein condensates.

cond-mat.quant-gas↗