Recovering Classical Dynamics from Coupled Quantum Systems Through Continuous Measurement

We study the role of continuous measurement in the quantum to classical transition for a system with coupled internal (spin) and external (motional) degrees of freedom. Even when the measured motional degree of freedom can be treated classically, entanglement between spin and motion causes strong measurement back action on the quantum spin subsystem so that classical trajectories are not recovered in this mixed quantum classical regime. The measurement can extract localized quantum trajectories that behave classically only when the internal action also becomes large relative to ħ

Transition to Classical Chaos in a Coupled Quantum System Through Continuous Measurement

Continuous observation of a quantum system yields a measurement record that faithfully reproduces the classically predicted trajectory provided that the measurement is sufficiently strong to localize the state in phase space but weak enough that quantum backaction noise is negligible. We investigate the conditions under which classical dynamics emerges, via a continuous position measurement, for a particle moving in a harmonic well with its position coupled to internal spin. As a consequence of this coupling, we find that classical dynamics emerges only when the position and spin actions are both large compared to ħ. These conditions are quantified by placing bounds on the size of the covariance matrix which describes the delocalized quantum coherence over extended regions of phase space. From this result, it follows that a mixed quantum-classical regime (where one subsystem can be treated classically and the other not) does not exist for a continuously observed spin-1/2 particle. When the conditions for classicality are satisfied (in the large-spin limit), the quantum trajectories reproduce both the classical periodic orbits as well as the classically chaotic phase space regions. As a quantitative test of this convergence, we compute the largest Lyapunov exponent directly from the measured quantum trajectories and show that it agrees with the classical value

An insight into the properties of magnesite and magnesite-chromite refrectories for ferro-chrome industry

A few qualities of magnesite and magnesite-chromite bricks and magnesite ramming masses manufactured indi-genously are being used in making ferro-chrome alloy in India. In this paper an attempt has been made for evalu-ating different qualities of magnesite and magnesitech-romite refractories by studying the relevant physico-chemical properties. As the bricks are to withstand severe corrosion and erosion by the molten metal and slag at high temperatures, the mineralogy, microstructure and the modulus of rupture at different temperatures were studied. The hot modulus of rupture values are correlated with the mineralogical compositions of the bricks. A ramming mass based on sea water magnesia has been developed for chute area application and the detailed properties of the same are given

Stress causing dynamic changes of four phytohormones in tobacco and tomato: A GC-MS analysis

Many analytical procedures have been developed to determine the importance of phytohormones in different plants. The work reported here provides a sensitive, accurate and readily accessible gas chromatography coupled to mass spectrometry (GC-MS) technique designed for the simultaneous quantitation of phytohormones indole-3-aceticacid (IAA), abscisic acid (ABA), jasmonic acid (JA) and salicylic acid (SA). These signalling molecules were analysed in two different plants, Tomato and Tobacco grown in vitro. The protocol designed to assess the dynamic changes in endogenous concentrations of hormones to study plant responses to abiotic stresses in leaf tissues. A hormone profiling is obtained from leaves of plants exposed to salt stress show that different plant hormones are involved in diverse physiologicsl processes. Crosstalk between these hormones result in synergetic or antagonic interactions which have important roles to play in abiotic stress response

Quantum And Classical Dynamics Of Atoms In A Magneto-optical Lattice

The transport of ultra-cold atoms in magneto-optical potentials provides a clean setting in which to investigate the distinct predictions of classical versus quantum dynamics for a system with coupled degrees of freedom. In this system, entanglement at the quantum level and chaos at the classical level arise from the coupling between the atomic spin and its center-of- mass motion. Experiments, performed deep in the quantum regime, correspond to dynamic quantum tunneling. This nonclassical behavior is contrasted with the predictions for an initial phase space distribution produced in the experiment, but undergoing classical Hamiltonian flow. We study conditions under which the trapped atoms can be made to exhibit classical dynamics through the process of continuous measurement, which localizes the probability distribution to phase space trajectories, consistent with the uncertainty principle and quantum back-action noise. This method allows us to analytically and numerically identify the quantum-classical boundary.Comment: Contribution to the Proceedings of the 7th Experimental Chaos Conference describing recent experimental and theoretical result

Biography and Homoeopathy in Bengal: Colonial lives of a European heterodoxy

AbstractDespite being recognized as a significant literary mode in understanding the advent of the modern self, biographies as agenrehave received relatively little attention from South Asian historians. Likewise, histories of science and healing in British India have largely ignored the colonial trajectories of those sectarian, dissenting, supposedly pseudo-sciences and medical heterodoxies that have flourished in Europe since the late eighteenth century. This article addresses these gaps in the historiography to identify biographies as a principal mode through which an incipient, ‘heterodox’ Western science like homoeopathy could consolidate and sustain itself in Bengal. In recovering the cultural history of a category that the state archives render largely invisible, this article argues that biographies are more than a mere repository of individual lives, and in fact are a veritable site of power. In bringing histories of print and publishing, histories of medicine, and histories of life writing practices together, it pursues two broad themes: first, it analyses the sociocultural strategies and networks by which scientific doctrines and concepts are translated across cultural borders. It explores the relation between medical commerce, print capital, and therapeutic knowledge to illustrate that acculturation of medical science necessarily drew upon and reinforced local constellations of class, kinship, and religion. Second, it simultaneously reflects upon the expanding genre of homoeopathic biographies published since the mid-nineteenth century: on their features, relevance, and functions, examining in particular the contemporary status of biography vis-à-vis ‘history’ in writing objective pasts.This is the accepted manuscript. The final version is available from CUP at http://dx.doi.org/10.1017/S0026749X1400057

The transition to classical chaos in a coupled quantum system through continuous measurement

Continuous observation of a quantum system yields a measurement record that faithfully reproduces the classically predicted trajectory provided that the measurement is sufficiently strong to localize the state in phase space but weak enough that quantum backaction noise is negligible. We investigate the conditions under which classical dynamics emerges, via continuous position measurement, for a particle moving in a harmonic well with its position coupled to internal spin. As a consequence of this coupling we find that classical dynamics emerges only when the position and spin actions are both large compared to $\hbar$. These conditions are quantified by placing bounds on the size of the covariance matrix which describes the delocalized quantum coherence over extended regions of phase space. From this result it follows that a mixed quantum-classical regime (where one subsystem can be treated classically and the other not) does not exist for a continuously observed spin 1/2 particle. When the conditions for classicallity are satisfied (in the large-spin limit), the quantum trajectories reproduce both the classical periodic orbits as well as the classically chaotic phase space regions. As a quantitative test of this convergence we compute the largest Lyapunov exponent directly from the measured quantum trajectories and show that it agrees with the classical value.Comment: 8 pages, 5 figure

Impact of COVID-19 on cancer services and patients' outcomes: a retrospective single-center study.

Our main objective was to assess the impact of the coronavirus disease 2019 (COVID-19) on cancer services and cancer patients in terms of disease severity, morbidity and mortality. Secondary objectives were to characterize cancer type, affected age groups, gender, comorbidities, infectivity, and to identify cancer treatment delay and its complications after COVID-19 infection. A retrospective analysis of electronic health records of polymerase chain reaction (PCR)-confirmed severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infected cancer patients from April 2020 to March 2021 was done. The following parameters were investigated upon-new and follow-up cases during the pandemic and its preceding years (2018-2019, 2019-2020), age, sex, type of cancer, comorbidities, presentation, symptomatology and treatment for COVID-19, time to recovery, complications, delay in treatment and survival outcome. Statistical analysis using chi-square testing was done on the above variables. There was a 50.49% reduction in the number of new and follow-up cases as compared to that of the previous years. Seventy-four out of 310 (23.87%) COVID-19 positive cancer patients were aged in their sixth decade with the commonest type being hematological malignancies. A proportion of 84.8% (n=263) patients were asymptomatic. Univariate analysis was statistically significant for mortality with regard to age ≥60 years (P=0.034), type of malignancy (P=0.000178), hypertension (P=0.0028), symptomatology of COVID-19 infection (P=0.0016), site of treatment and oxygen/intervention (P2 L/min) were responsible for the 20.65% mortality rate. The pandemic significantly affected the care of cancer patients with decreased cases, late presentation, delayed treatment with potentially worse mortality outcome. Although they have decreased immunity, majority were asymptomatic. Most of the fatalities were in the GI and HPB malignancies. [Abstract copyright: 2023 Annals of Translational Medicine. All rights reserved.