arXiv subjects

Davinder Singh

Publications and source records attributed to Davinder Singh.

14 recordsLinked to original sources

arXiv2026

Coherent Control of Energy Transport at Room Temperature in a Noisy Bath

Coherent control of energy transport in a non-equilibrium steady-state (NESS) in a reaction-center-connected donor-acceptor pair is proposed. The pigments are considered to be continuously interacting with incoherent radiation and a phonon bath while being driven by phase-controlled coherent fields. Coherent excitation of the donor-acceptor pair is shown to induce interference between excitation pathways, resulting in phase dependent modulation of the flux. As a consequence one can enhance or suppress energy transfer via interference, e.g. an optical energy switch. The persistence of such interference enables coherent control at a NESS in dissipative regime suggests an extension of the operational scope of quantum control from traditional transient domain with low dissiaption to noisy environment NESS at room temperature.

quant-ph↗

arXiv2024

Machine Learning Optimization of non-Kasha Behavior and of Transient Dynamics in Model Retinal Isomerization

Designing a model of retinal isomerization in Rhodopsin, the first step in vision, that accounts for both experimental transient and stationary state observables is challenging. Here, multi-objective Bayesian optimization is employed to refine the parameters of a minimal two-state-two-mode (TM) model describing the photoisomerization of retinal in Rhodopsin. With an appropriate selection of objectives, the optimized retinal model predicts excitation wavelength-dependent fluorescence spectra that closely align with experimentally observed non-Kasha behavior in the non-equilibrium steady state. Further, adjustments to the potential energy surface within the TM model reduce the discrepancies across the time domain. Overall, agreement with experimental data is excellent.

physics.bio-ph↗

arXiv2023

Fundamental trade-off between the speed of light and the Fano factor of photon current in three-level lambda systems

Electromagnetically induced slow-light medium is a promising system for quantum memory devices, but controlling its noise level remains a major challenge to overcome. This work considers the simplest model for such medium, comprised of three-level $Λ$-systems interacting with bosonic bath, and provides a new fundamental trade-off relation in light-matter interaction between the group velocity of light and the Fano factor of photon current due to radiative transitions. Considering the steady state limits of a newly derived Lindblad-type equation, we find that the Fano factor of the photon current maximizes to 3 at the minimal group velocity of light, which holds true universally regardless of detailed values of parameters characterizing the medium.

quant-ph↗

arXiv2021

The origin of loose bound of the thermodynamic uncertainty relation in a dissipative two-level quantum system

The thermodynamic uncertainty relations (TURs), originally discovered for classical systems, dictate the trade-off between dissipation and fluctuations of irreversible current, specifying a minimal bound that constrains the two quantities. In a series of effort to extend the relation to the one under more generalized conditions, it has been noticed that the bound is less tight in open quantum processes. To study the origin of the loose bounds, we consider an external field-driven transition dynamics of two-level quantum system weakly coupled to the bosonic bath as a model of open quantum system. The model makes it explicit that the imaginary part of quantum coherence, which contributes to dissipation to the environment, is responsible for loosening the TUR bound by suppressing the relative fluctuations in the irreversible current of transitions, whereas the real part of the coherence tightens it. Our study offers a better understanding of how quantum nature affects the TUR bound.

quant-ph↗

arXiv2020

Using modern motion estimation algorithms in existing video codecs

Motion estimation is a key component of any modern video codec. Our understanding of motion and the estimation of motion from video has come a very long way since 2000. More than 135 different algorithms have been recently reviewed by Scharstein et al http://vision.middlebury.edu/flow/. These new algorithms differ markedly from Block Matching which has been the mainstay of video compression for some time. This paper presents comparisons of H.264 and MP4 compression using different motion estimation methods. In so doing we present as well methods for adapting pre-computed motion fields for use within a codec. We do not observe significant gains to be had with the methods chosen w.r.t. Rate Distortion tradeoffs but the results reflect a significantly more complex interrelationship between motion and compression than would be expected. There remains much more to be done to improve the coverage of this comparison to the emerging standards but these initial results show that there is value in these explorations.

eess.IV↗

arXiv2020

IoT-based Remote Control Study of a Robotic Trans-esophageal Ultrasound Probe via LAN and 5G

A robotic trans-esophageal echocardiography (TEE) probe has been recently developed to address the problems with manual control in the X-ray envi-ronment when a conventional probe is used for interventional procedure guidance. However, the robot was exclusively to be used in local areas and the effectiveness of remote control has not been scientifically tested. In this study, we implemented an Internet-of-things (IoT)-based configuration to the TEE robot so the system can set up a local area network (LAN) or be configured to connect to an internet cloud over 5G. To investigate the re-mote control, backlash hysteresis effects were measured and analysed. A joy-stick-based device and a button-based gamepad were then employed and compared with the manual control in a target reaching experiment for the two steering axes. The results indicated different hysteresis curves for the left-right and up-down steering axes with the input wheel's deadbands found to be 15 deg and deg, respectively. Similar magnitudes of positioning errors at approximately 0.5 deg and maximum overshoots at around 2.5 deg were found when manually and robotically controlling the TEE probe. The amount of time to finish the task indicated a better performance using the button-based gamepad over joystick-based device, although both were worse than the manual control. It is concluded that the IoT-based remote control of the TEE probe is feasible and a trained user can accurately manipulate the probe. The main identified problem was the backlash hysteresis in the steering axes, which can result in continuous oscillations and overshoots.

cs.RO↗

arXiv2019

PlantDoc: A Dataset for Visual Plant Disease Detection

India loses 35% of the annual crop yield due to plant diseases. Early detection of plant diseases remains difficult due to the lack of lab infrastructure and expertise. In this paper, we explore the possibility of computer vision approaches for scalable and early plant disease detection. The lack of availability of sufficiently large-scale non-lab data set remains a major challenge for enabling vision based plant disease detection. Against this background, we present PlantDoc: a dataset for visual plant disease detection. Our dataset contains 2,598 data points in total across 13 plant species and up to 17 classes of diseases, involving approximately 300 human hours of effort in annotating internet scraped images. To show the efficacy of our dataset, we learn 3 models for the task of plant disease classification. Our results show that modelling using our dataset can increase the classification accuracy by up to 31%. We believe that our dataset can help reduce the entry barrier of computer vision techniques in plant disease detection.

cs.CV↗

arXiv2019

Robotic-assisted Ultrasound for Fetal Imaging: Evolution from Single-arm to Dual-arm System

The development of robotic-assisted extracorporeal ultrasound systems has a long history and a number of projects have been proposed since the 1990s focusing on different technical aspects. These aim to resolve the deficiencies of on-site manual manipulation of hand-held ultrasound probes. This paper presents the recent ongoing developments of a series of bespoke robotic systems, including both single-arm and dual-arm versions, for a project known as intelligent Fetal Imaging and Diagnosis (iFIND). After a brief review of the development history of the extracorporeal ultrasound robotic system used for fetal and abdominal examinations, the specific aim of the iFIND robots, the design evolution, the implementation details of each version, and the initial clinical feedback of the iFIND robot series are presented. Based on the preliminary testing of these newly-proposed robots on 42 volunteers, the successful and re-liable working of the mechatronic systems were validated. Analysis of a participant questionnaire indicates a comfortable scanning experience for the volunteers and a good acceptance rate to being scanned by the robots.

cs.RO↗

arXiv2019

Nano-Mechanical Behaviour Of MnTiO3 Ceramics

Here we investigate the mechanical behavior of the MnTiO3 ceramic. Nanoindentation tests in a manganese titanate polycrystalline sample were performed using a Berkovich indenter with a tip radius of 150 nm. On applying the load, it shows the elastic and plastic behavior. The work done during the elastic and plastic processes are 16757.78 μN.nm and 10045.72 μN.nm, respectively. The estimated values of reduced modulus and hardness are 158GPa and 10.5GPa, respectively. This suggests that this compound exhibits a significant plastic character.

cond-mat.str-el↗

arXiv2018

Effect of 8th Chromophore: A Comprehensive Study of Excitation Energy Transfer in FMO complex

The excitation energy transfer (EET) in Fenna-Matthews-Olson (FMO) complex has been investigated in the presence of realistic inhomogeneous protein environment around different bacteriochlorophyll-a (BChla) sites of a 8-site monomer. We studied the effect of initial coherence and the 8th chromophore on the EET dynamics considering relative orientation of transition dipole moments of all the BChla sites. We choose femtosecond coherent laser pulse to prepare initial coherent superposition state. Our non-Markovian simulation reveals that the initial coherence between excited states of BChla sites accelerate the excitation energy transfer process as compared to initial mixed state. Even more impressively, in the presence of the 8th chromophore, the initial pure state relaxes much faster than in the 7-site monomer. Hence the inclusion of 8th chromophore additionally enhances the EET relaxation.

physics.bio-ph↗

arXiv2018

Influence of pigment-protein coupling on excitation energy transfer in FMO complex

To explain experimentally observed oscillatory dynamics of highly efficient process of excitation energy transfer (EET) in Fenna-Matthews-Olson (FMO) complex, most theoretical models assume the same local protein environment around all the bacteriochlorophyll-a (BChla) sites, contradictory to the structural analysis of FMO complex. Using different values of pigment-protein couplings for different BChla sites, measured in the adiabatic limit of electron transfer, we theoretically investigate the effect of inhomogeneous local protein environment on excitation energy transfer. By employing non-Markovian master equation we demonstrate that the asymmetric system-bath coupling leads to the results consistent with the experimental observations. Quantum dynamical simulation suggests that the correlated fuctuations preserve the oscillation of excitation for long time-scales. Further different BChla sites have asymmetric time-scales of oscillations of excitation due to in-homogeneous pigment-protein couplings also.

physics.bio-ph↗

arXiv2018

Role of Coherence in Excitation Transfer Efficiency to the Reaction Center in Photosynthetic Bacteria Chlorobium Tepidum

We investigate the effect of coherence to the excitation transfer efficiency (ETE) in photosynthetic bacteria Chlorobium Tepidum. We have modeled the monomer of Fenna-Matthews-Olson (FMO) complex as consisting of eight bacteriochlorophyll-a sites, while explicitly consider reaction center core complex (RCC) as an additional site. With the use of realistic bath spectrum and several dominant vibronic modes in the non-Markovian master equation, in an effective 9-site model, we have compared the ETE for an initial pure state and an initial mixed state. We observe that the initial pure state relaxes efficiently to increase the trapping at the RCC. We further illustrate that the coherence play a competitive role to block the back transfer of excitation from RCC pigment to FMO complex and hence to maximize the ETE.

physics.bio-ph↗

arXiv2017

Role of Initial Coherence in Excitation Energy Transfer in Fenna-Matthews-Olson Complex

We theoretically show that the initial coherence plays a crucial role in enhancing the speed of excitation energy transfer (EET) in Fenna-Matthews-Olson (FMO) complex. We choose a simplistic eight-level model considering all the bacateriochlorophyll-a sites in a monomer of FMO complex. We make a comparative numerical study of the EET, in terms of non-Markovian evolution of an initial coherent superposition state and a mixed state. A femto-second coherent laser pulse is suitably chosen to create the initial coherent superposition state. Such an initial state relaxes much faster than a mixed state thereby speeding up the EET. In this analysis, we have taken into account the relative orientation of the transition dipole moments of the bacateriochlorophyll-a sites and their relative excitation energies. Our results reveal that for 2D electronic spectroscopy experiments, the existing two-pathway model of energy transfer in FMO complex may not be suitable in our understanding of EET.

physics.bio-ph↗

arXiv2017

Coherence and its Role in Excitation Energy Transfer in Fenna-Mathews-Olson Complex

We show that the coherence between different bacteriochlorophyll-a (BChla) sites in the Fenna-Mathews-Olson complex is an essential ingredient for excitation energy transfer between various sites. The coherence delocalizes the excitation energy, which results in the redistribution of excitation among all the BChla sites in the steady state. We further show that the system remains partially coherent at the steady state. In our numerical simulation of the non-Markovian density matrix equation, we consider both the inhomogeneity of the protein environment and the effect of active vibronic modes.

physics.chem-ph↗