Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

Objectives: Motivation of this study is to check the sensitivity of dosimetric tool gamma with 2D detector array combination when unexpected errors occur while transferring intensity-modulated radiation therapy treatment plans from planning system to treatment unit. Methods: This study consists of 17 head and neck cancer patient’s treatment plans. Nine types of verification plans are created for all 17 clinically approved treatment plans by consecutively deleting different segments (up to eight) one by one from each field of the plan. Decrement factor (χ) is introduced in our study which illustrated the degree of decay of gamma passing rate when intentional errors are introduced. We analyzed the data by two different methods—one without selecting the region of interest (ROI) in dose distributions and the other by selecting the region of interest. Results: By linear regression, the absolute value of slopes is 0.025, 0.024 and 0.015 without ROI and 0.030, 0.027 and 0.015 with ROI for 2%/2 mm, 3%/3 mm and 5%/5 mm criteria, respectively. The higher absolute value of the fitted slope indicates the higher sensitivity of this method to identify erroneous plan in treatment unit. The threshold value for 2%/2 mm equivalent to 95% passing criteria in 3%/3 mm used in clinical practice is obtained as 83.44%. Conclusions: The 2D detector array with dosimetric tool gamma is less sensitive in detecting errors when unprecedented errors of segment deletion occur within the treatment plans. © 2020, Italian Society of Medical Radiology.

World University root node

Department of Physics

School of Advanced Sciences

Vellore Campus

Department of Chemistry

Radiologia Medica

A technique for quantifying the sensitivity of dosimetric tool gamma with 2D detector array in pretreatment IMRT plans by segment deletion method

Time dependent density functional theory is used to systematically examine the band gap variation of Li-substituted adamantanes upon fluorination. It is realized that the absorption wavelength of Li-Adamantane can be fine tuned within UV–Visible region by changing the degree of fluorination. The static and dynamic hyperpolarizabilities of fluorinated Li-Adamantane derivatives were computed using coupled perturbed Kohn Sham theory. In this article, we report Pockel, dc-Kerr, ESHG, degenerate four wave mixing coefficients and nonlinear refractive indices from the first and second order hyperpolarizability calculations. A high positive nonlinear refractive index and significant second harmonic generation efficiency at Nd:YAG Laser wavelength are observed in F3Li-Adm derivative. © 2018 Elsevier B.V.

Chemical Physics Letters

Effect of fluorination on bandgap, first and second order hyperpolarizabilities in lithium substituted adamantane: A time dependent density functional theory

The complexity of multiple energy levels associated with each atomic system determines the various processes related to light-matter interactions. It is necessary to understand the influence of different levels in a given atomic system. In this work we focus on multi-level atomic schemes with the application of magnetic field. We analyze the different EIT windows which appears in the presence of moderately high magnetic field (∼ 10 G) strength. © Published under licence by IOP Publishing Ltd.

Fulltext

Journal of Physics: Conference Series

Study of multi-level atomic systems with the application of magnetic field

Magnetic resonance imaging (MRI) has a wide range of applications towards imaging the human body. In this work we have solved the Bloch equations for different magnetic field gradients along the transverse direction. We have modified the magnetic field components based on the relaxation terms and solved the field gradient as well as the field components for both off-pulse and on-pulse configurations. In particular we focus on different pulse sequences and optimize them to realize the best possible output. We have analyzed the field components along transverse direction because the rotation of the object to form the image by emitting signal is along the xy plane. © Published under licence by IOP Publishing Ltd.

Optimization of Pulse Sequences in MRI Scheme

We present the variation of intensity in Doppler-free hyperfine lines for rubidium atoms with the application of magnetic field. Different polarization configurations have been studied systematically with varying magnetic fields. There is a significant increase in the intensity variation with applied magnetic field related to different polarization configurations. These variations are explained with the theoretical calculations. The calculations are performed by adopting Nakayama's four level model with the varying magnetic field induced transition probability. © Published under licence by IOP Publishing Ltd.

IOP Conference Series: Materials Science and Engineering

Magnetic field dependent intensity variation in the hyperfine split Rb D1 and D2 lines

We present the magnetic and optical field induced rotation of polarization in 87Rb and 85Rb atoms at geophysical magnetic fields. The line shape varies considerably in the presence of a magnetic field of the order of a few mG. Multiple Zeeman sublevel EIT systems involving rubidium atoms are investigated. Theoretical formalism of optical field induced polarization rotation in the presence of a magnetic field is discussed by considering all the Zeeman sublevels. It is noted that the ground state population distribution also plays a major role. © Published under licence by IOP Publishing Ltd.

Optical field induced rotation of polarization in rubidium atoms with the additional magnetic field

This chapter describes progress towards the realization of quantum networks through optical interconnections between isolated solid-state spin quantum bits (qubits) in diamond. Measurement-induced nonlinearity between photons emitted by two such qubits, and the resulting heralded entangled state, represents a key starting primitive in many theoretical protocols for quantum networks. This chapter first reviews the theory behind heralded entanglement generation, and then discusses the key requirements and some recent experiments that demonstrate all the ingredients necessary to achieve remote entanglement between spin qubits in diamond. © 2014 Elsevier Ltd. All rights reserved.

Quantum Information Processing with Diamond: Principles and Applications

Spin-photon entanglement in diamond for quantum optical networks

Magnetic sensors capable of detecting nanoscale volumes of spins allow for non-invasive, element-specific probing. The error in such measurements is usually reduced by increasing the measurement time, and noise averaging the signal. However, achieving the best precision requires restricting the maximum possible field strength to much less than the spectral linewidth of the sensor. Quantum entanglement and squeezing can then be used to improve precision (although they are difficult to implement in solid-state environments). When the field strength is comparable to or greater than the spectral linewidth, an undesirable trade-off between field strength and signal precision occurs. Here, we implement novel phase estimation algorithms on a single electronic spin associated with the nitrogen-vacancy defect centre in diamond to achieve an ∼8.5-fold improvement in the ratio of the maximum field strength to precision, for field magnitudes that are large (∼0.3 mT) compared to the spectral linewidth of the sensor (∼4.5 μT). The field uncertainty in our approach scales as 1/T0.88, compared to 1/T0.5 in the standard measurement approach, where T is the measurement time. Quantum phase estimation algorithms have also recently been implemented using a single nuclear spin in a nitrogen-vacancy centre. Besides their direct impact on applications in magnetic sensing and imaging at the nanoscale, these results may prove useful in improving a variety of high-precision spectroscopy techniques. © 2012 Macmillan Publishers Limited. All rights reserved.

Nature Nanotechnology

High-dynamic-range magnetometry with a single electronic spin in diamond

We study resonant nonlinear magneto-optic rotation (NMOR) in a paraffin-coated Rb vapor cell as the magnetic field is swept. At low sweep rates, the nonlinear rotation appears as a narrow resonance signal with a linewidth of about "300 μG" (2π×420 Hz). At high sweep rates, the signal shows transient response with an oscillatory decay. The decay time constant is of order 100 ms. The behavior is different for transitions starting from the lower or the upper hyperfine level of the ground state because of optical pumping effects. © 2010 The American Physical Society.

Physical Review A - Atomic, Molecular, and Optical Physics

Transient response of nonlinear magneto-optic rotation in a paraffin-coated Rb vapor cell

Zeeman splitting in the D2 line of rubidium atoms ( 87Rb and 85Rb) has been studied using 'Doppler broadened' as well as 'saturation absorption spectroscopy'. While a linearly polarized beam was used for the former experiment, in the latter case a (π, σ±) polarization configuration was employed for both pump and probe beams. Zeeman lines have been observed by applying a field up to 5 mT. The field variation of relative line intensities in Doppler-broadened spectrum was determined following Tremblay et al and Nakayama's four-level model. For the saturation spectrum, a four-level model was used. Because the enhancement of absorption at the field is as low as 1 mT, the Fg ≤ 2 to Fe ≤ 3 transition for 87Rb can be used as the reference for laser locking. Level crossing is observed in 85Rb at fields less than 5 mT. © 2007 IOP Publishing Ltd.

Journal of Physics B: Atomic, Molecular and Optical Physics

Variations of intensity in Rb D2 line at weak/intermediate fields

Doppler-broadened absorption spectrum of rubidium (87Rb and 85Rb) D2 line has been studied in the presence of a magnetic field of intermediate strength i.e. up to 5mT. Resonant non - linear magneto optical rotation is measured in the Doppler broadened spectrum of rubidium atomic vapour. Low light intensity approximation in the intermediate field region has been made to calculate the magneto optical rotation and to compare with experimental data. The enhancement of non-linear magneto optical rotation is discussed taking into account hole burning and circular birefringence in the intermediate field region. © 2007 IOP Publishing Ltd.