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Monday, 09 May 2022

Sourav Dutta
Title: Basics of cold atom physics (Lecture 1)
Abstract:

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Saikat Ghosh
Title: Theory of Measurements (Lecture 1)
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Sourav Dutta
Title: Basics of Cold Atom Physics (Lecture 2)
Abstract:

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Saikat Ghosh
Title: Theory of Measurements (Lecture 2)
Abstract:

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Girish Agarwal
Title: Quantum Metrology: From Theoretical Perspectives to Experiments
Abstract:

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Tuesday, 10 May 2022

Subhasish Dutta Gupta
Title: Introduction to Density Matrices: Application to Semiclassical Laser Theory
Abstract:

Lecture Notes - https://www.icts.res.in/sites/default/files/seminar%20doc%20files/Lecture%20notes.zip

(Please note there could be typos in the written lecture notes)

Bimalendu Deb
Title: Correlations and Fluctuations in Quantum Optics and Open Quantum Systems
Abstract:

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Arnab Ghosh
Title: Introduction to Quantum Thermodynamics (Lecture 1)
Abstract:

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Arnab Ghosh
Title: Introduction to Quantum Thermodynamics (Lecture 2)
Abstract:

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Rainer Blatt
Title: Quantum Computation and Quantum Simulation with Trapped Ca + Ions
Abstract:

The state-of-the-art of the Innsbruck trapped-ion quantum computer is briefly reviewed. We present an overview on the available quantum toolbox and discuss characteristic features of the setup. With strings of trapped ions, we implement analog, digital and variational quantum simulations. Employing universal quantum computations, we investigate the dynamics of the Lattice Schwinger model [1], a gauge theory of 1D quantum electrodynamics and using a hybrid-classical ansatz, we determine steady-state properties of the Hamiltonian [2]. With 20-50 fully controlled ion qubits we perform quantum simulations investigating quantum transport [3] and emerging hydro-dynamics features [4]. Ways towards scaling the approach will be indicated and discussed.
[1] E. A. Martinez et al., Nature 534, 516 (2016).
[2] C. Kokail et al., Nature 569, 355–360 (2019).
[3] C. Maier et al., Phys. Rev. Lett. 122, 050501 (2019)
[2] M. K. Joshi et al., arXiv:2107.00033 (2021)

Wednesday, 11 May 2022

Joyee Ghosh
Title: News from the Quantum Photonics Lab in IIT Delhi: Entangled Photons & Hot Atoms -- Experiments & QI Applications
Abstract:

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Ashok Mohapatra
Title: Quantum Sensors for Radio Frequency Electromagnetic Fields
Abstract:

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Ajay Wasan
Title: Quantum Computers - Physical Realization
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Sankar De
Title: Effects of vector magnetic field on electromagnetically induced transparency with lin ⊥ lin polarization
Abstract:

The coherent interaction of the electric fields with the atomic medium which leads to phenomena like electromagnetically induced transparency (EIT) are highly sensitive to the external magnetic fields. Using this fact, magnetic field with good spatial resolution and high sensitivity can be measured. In addition to the magnetic field strength, knowing the direction of the magnetic field is also important. Combining the coherent optical effects like EIT with the longitudinal and transverse magnetic fields create an opportunity for developing an EIT based atomic vector magnetometer which is sensitive to the direction of the magnetic field. In our laboratory, we have developed an apparatus to study the effects of static longitudinal and transverse magnetic fields in a hyperfine -type EIT system. We have shown how the EIT resonance is highly sensitive to the magnetic field direction as well as the polarization direction of the applied electric fields. The selection rules of the EIT resonances can be controlled by controlling the polarization component of the laser fields with respect to the quantization axis. On the theoretical front, apart from developing a numerical solution to support the experimental observation, a toy model consisting of nine level Zeeman sub-system, has been derived in order to analytically understand the phenomena.
Reference:
1. Bankim Chandra Das, Arpita Das, Dipankar Bhattacharya and Sankar De, Journal of the Optical Society of America B, 38, 584 (2021).

B Prasanna Venkatesh
Title: Light-induced Density Wave in a Magnetic Dipolar-BEC
Abstract:

In this talk, we consider a magnetic dipolar BEC subject to counter-propagating, orthogonally polarized laser beams. The laser light-induced interaction in competition with the magnetic dipole-dipole interaction leads to a fascinating phase diagram with differing density wave patterns. Apart from delineating the phase diagram and the property of the phases, we also consider protocols to prepare such states in realistic experiments with Dysprosium BEC.

Tarak Nath Dey
Title: Guiding and Polarization Shaping of Vector Beam in an Anisotropic Media
Abstract:

Vector beams (VB) have a great advantage over their scalar counterparts, due to their spatially inhomogeneous polarization distribution. Coherent control of polarization, phase and amplitude gives complete freedom to manipulate fully structuring light(FSL). A vector superposition of two orthogonally polarized components can produce VB or FSL  beam. This lecture discusses a scheme to guide a weak vector beam using optically written waveguides inside atomic vapor, whilst controlling its polarization rotation. The polarization rotation control is achieved using the anisotropic property of a four-level tripod atomic system which under a specific configuration, can generate different refractive indices for the left and right circularly polarized components of the vector beam. The refractive indices of the two vector beam components can be varied by changing their detunings. The waveguiding of the vector beam is achieved through a strong control field with an appropriate transverse intensity profile, which generates a ``core and cladding" type refractive index profile inside the medium.

Saptarishi Chaudhuri
Title: Experiments with Mixtures of Cold Atoms: Quantum Sensors
Abstract:

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Arijit Sharma
Title: Towards developing the next generation portable, atomic sensors using two-photon transitions in warm atomic vapors for quantum sensing applications
Abstract:

Optical clocks represent the pinnacle of precise timekeeping. Laboratory-based precision atomic clocks which provide the highest level of sensitivity are based on transitions in the microwave/optical domain using neutral atoms or trapped atomic ions and define international timescales, provide a basis for testing the time invariance of fundamental constants and lead to the search for new physics beyond the Standard Model. The other domain is the regime of portable atomic clocks based on warm atomic vapor, that are compact, low power consuming and are field deployable with a multitude of targeted applications in telecommunications, navigation (GPS), sensing and precision timing. With the increasing use of field-deployable atomic clocks and frequency standards, many commercial and strategic applications including sensing,

communications and navigation, are getting a tremendous technological boost. Chip-scale atomic clocks (CSACs) based on Coherent Population Trapping (CPT) have been increasingly popular due to their small size and low power consumption. However, the inherent limitation in frequency sensitivity presented by CSACs stems from the use of microwave-based transitions to derive the frequency reference. Optical transition-based field deployable clocks using two-photon resonances offer a promising alternative with a possibility of surpassing existing commercial clocks (CSACs) by at least a factor of 10 in both short- and long-term stability. Two-photon transitions in alkali and alkaline earth metals are thus considered promising candidates for simple, field-deployable optical frequency references and optical clocks. One may utilize counter propagating beams to drive the two-photon transition in the Doppler-free regime, resulting in narrow lines.

At IIT Tirupati, we are engaged in developing the next generation atomic vapor based portable frequency standards using optical two-photon transitions in Rubidium (Rb) for for quantum sensing and quantum positioning applications. We are working towards development of precision laser sources, electronics, and miniaturized vapor cells for the two-photon frequency standard. We shall present a brief overview of our research activities at IIT Tirupati and discuss some of the challenges, opportunities and commercial benefits related to the development of a portable, precision atomic sensor for a host of quantum technology applications.

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Title: Discussion
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Thursday, 12 May 2022

Manas Kulkarni
Title: Collective Description of Trapped Fermions: Exact Results
Abstract:

Exact results for collective behaviour of trapped Fermions have remained elusive.  Apart from mean-field approaches (Local
Density/Thomas-Fermi approximation), there has hardly been any progress on studying collective phenomena. I will give a brief review of some exact results in low dimensions. I will then discuss our recent results [1] for the collective description of noninteracting fermions in a 2D harmonic trap rotating with a constant frequency and in the presence of an additional repulsive central potential. I will show that in the large-N limit, the bulk density has a rich and nontrivial profile with a hole at the center of the trap and surrounded by a multilayered “wedding cake” structure. I will discuss a rich phase diagram that emerges in this system. I will then discuss connections to orthogonal polynomials, unitary evolution of certain quantum spin chains and Random Matrix Theory.

[1] M. Kulkarni, S. N. Majumdar, G. Schehr, Phys. Rev. A 103, 033321 (2021)

Srinivasa Prasannaa V
Title: Electron Electric Dipole Moment Searches Using Ultracold Molecules
Abstract:

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Sonjoy Majumder
Title: Quantum Instability @Driven Bose-Einstein Condensate (BEC)
Abstract:

In this presentation, I would like to discuss the spontaneous formation of quantum turbulence at the surface (single) and interface (binary) of Bose-Einstein condensate (BEC). I will highlight the physics behind the generation of different oscillating patterns parametrically excited by modulating the scattering lengths. The effective Mathieu equation and Floquet analysis are used here to characterize the patterns [1,2]. The characterizations are supported by experimental observation [2]. I will briefly explain how our theory can predict the generated interfacial tension useful to characterize the condensate. In the end, I will summarize the presentation with the future scopes of these works with different experimental realizations and applications of high-lying collective excitations leading to quantum turbulence.
Reference:
1) Parametrically excited star-shaped patterns at the interface of binary Bose-Einstein condensates; DK Maity, K Mukherjee, SI Mistakidis, S Das, PG Kevrekidis, S Majumder, P Schmelcher; Physical Review A 102 (3), 033320 (2020)
2) Spontaneous Formation of Star-Shaped Surface Patterns in a Driven Bose-Einstein Condensate; Kiryang Kwon, K Mukherjee, SJ Huh, K Kim, SI Mistakidis, DK Maity, PG Kevrekidis, S Majumder, P Schmelcher, J-y Choi; Physical Review Letters, 127, 113001 (2021)

Kanhaiya Pandey
Title: Laser Cooling and Trapping of Rb 5S 1/2 - 6P Blue Transition
Abstract:

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Bijaya Sahoo
Title: New Directions for Isotope Shift Studies
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Yoji Ohashi
Title: Isothermal compressibility and effects of three-body molecular interaction in a strongly interacting ultracold Fermi atomic gas (Online)
Abstract:

We theoretically discuss the isothermal compressibility in the normal state of an ultracold Fermi gas with a tunable pairing interaction associated with a Feshbach resonance. Including strong pairing fluctuations caused by this tunable interaction within the framework of the self-consistent T-matrix approximation (SCTMA), we numerically evaluate this thermodynamic quantity over the entire BCS-BEC crossover region. In the unitary limit, the calculated isothermal compressibility is shown to agree well with the recent experiment on a 6Li Fermi gas. In the strong-coupling BEC regime, we also show that, not only a two-body interaction between Cooper-pair molecules, but also a three-body molecular interaction sizably contribute to the isothermal compressibility. Our results indicate that the isothermal compressibility is a useful quantity for the study of how Cooper pairs are correlated to each other in a strongly interacting Fermi gas. 

Ozgur E. Mustecaplioglu
Title: Quantum Optics of Heat Engines and Thermal Devices
Abstract:

Quantum optics is the branch of science that investigates the statistical properties of light interacting with matter. Statistical mechanics and thermodynamics lie at the heart of quantum optics, and more generally, quantum mechanics, starting with Max Planck’s explanation of ultraviolet catastrophe in blackbody radiation in 1900. Modern efforts to understand to which extent thermodynamical laws apply to microscopical systems, including our ever-shrinking technological devices, led to the rapidly emerging field of quantum thermodynamics. Not surprisingly, quantum optics gave the impetus to the growth of interest in quantum thermodynamics. Many years after the recognition of maser as a heat engine in 1959 by Scovil and Schulz-DuBois [1], Marlan O. Scully and co workers came up with the idea of using quantum superposition states, or quantum coherence, as a resource to power up a photonic Carnot engine in 2003[2]. The proposal is based on the paradigmatic quantum optical system, a micromaser consisting of an optical cavity pumped by a beam of atoms. In the following decades, researchers in quantum thermodynamics revealed the interplay of quantum information and energetics of quantum systems by generalizing the traditional thermodynamical concepts of heat and work in the quantum realm [3]. Quantum optical systems were again the typical testbeds as well as a medium for applications, such as quantum photovoltaics [4], quantum thermal diodes and transistors [5], quantum sensors [6], and so on, based on these conceptual developments. This lecture will first briefly review the basics of quantum thermodynamics from a quantum optical perspective. The second part of the lecture will discuss examples and applications of quantum thermodynamical theories in photonic systems and devices.
[1] H. E. D. Scovil and E. O. Schulz-DuBois, Phys. Rev. Lett. 2, 262 (1959).
[2] M. O. Scully, M. S. Zubairy, G. S. Agarwal, and H. Walther, Science 299, 862 (2003).
[3] A. T. Ozdemir and O. E. Mustecaplioglu, Turk. J. Phys. 44, 404 (2020).
[4] M. O. Scully, Phys. Rev. Lett. 104, 207701 (2010).
[5] M. T. Naseem, A. Misra, O. E. Mustecaplioglu, and G. Kurizki, Phys. Rev. Research 2, 033285 (2020).
[6] S. Bhattacharjee, U. Bhattacharya, W. Niedenzu, V. Mukherjee, and A. Dutta, New J. Phys. 22, 013024 (2020).

Utpal Roy
Title: Quantum Simulation and Quantum Sensing with Trapped Ultracold Atoms
Abstract:

Bose-Einstein condensate (BEC) is a highly coherent and tunable quantum matter, which has opened up huge possibility towards emerging areas like quantum simulation and quantum sensing [1,2]. Applications of ultracold atoms as quantum simulator mostly rely on the external trap which can efficiently be engineered to a desired shape due to the unprecedented progress in the experimental front. However, investigating the dynamics of such system through exact theoretical approach becomes quite nontrivial due to its nonlinear nature and the presence of varying external trap upon engineering. Various optical lattices are found to be the most favorable candidates for quantum simulation and the underlying dynamics can exhibit various novel and complex quantum phenomena like Anderson-like localization, negative absolute temperature etc. [3-7]. In this talk, I will present analytical approaches for quasi-periodic optical lattices which can hold and mould matter waves in self similar form like soliton. Applications of BEC under a bi-chromatic optical lattice, engineered superlattices and for quantum precision measurements will be addressed [2,4,6,8].

References:
1. C. Gross and I. Bloch, Science 357, 6355, 995 (2017).
2. J. Bera, S. Ghosh, L. Salasnich, and Utpal Roy, Phys. Rev. A 102, 063323 (2020); S. Ghosh, J. Bera, P. K. Panigrahi and Utpal Roy, Int. J. Quant. Inf. 17, 1950019 (2019).
3. S. Braun et al., Science 339, 52 (2013).
4. A. Nath, J. Bera, S. Ghosh, and Utpal Roy, Sci. Reports 10, 9016 (2020).
5. A. Nath, and Utpal Roy, Laser Phys. Lett 11, 115501 (2014).
6. N. Kundu, A. Nath, J. Bera, S. Ghosh and Utpal Roy, Phys. Lett. A 427, 127922 (2022).
7. A. Nath, J Bera, S Ghosh, P K Panigrahi and Utpal Roy, Eur. Phys. J. D 74, 27 (2020).
8. B. Halder, S. Ghosh, P. Basu, J. Bera, B. Malomed and Utpal Roy, Symmetry 14, 49 (2022). (Special issue on ‘Symmetry in Many-Body Physics’)

Sebastian Wuster
Title: Rydberg atoms in Bose-Einstein condensed environments: from bubble chambers to controllable open quantum systems
Abstract:

Abstract: Rydberg Atoms in highly excited electronic states with n=30-120 can be excited within Bose-Einstein condensates (BECs), and while lifetimes are shorter than in vacuum [1,2], they live long enough to interestingly interact with the BEC [3]. We theoretically study this interaction in the mean-field limit and beyond.

For multiple Rydberg atoms in a single electronic state, we show that the phase coherence of the condensate allows the tracking of mobile Rydberg impurities akin to bubble chambers in particle physics [4,5]. For a single Rydberg atom with multiple electronic states, we provide spectral densities of the BEC as a decohering environment [6], and show that the BEC can image a signature of the entangling evolution that causes Rydberg qu-bit decoherence [7]. Finally, an aggregate of multiple  Rydberg atoms in BEC shows promise for quantum simulations of photosynthetic energy transport, extending [8].

[1] Schlagmüller et al. PRX 6 (2016) 031020.

[2] Kanungo et al. PRA 102 (2020) 063317.

[3] Balweski et al. Nature 502 (2013) 664.

[4] Tiwari et al. PRA 99 (2019) 043616.

[5] Tiwari et al. https://arxiv.org/abs/2111.05031 (2021).

[6] Rammohan et al. PRA 103 (2021) 063307.

[7] Rammohan et al. PRA (Letters) 104  (2021) L06020.

[8] Schönleber, et al. PRL 114 (2015) 123005.

Rejish Nath
Title: Overlapping Bright Solitons in Spin-1 Bose-Einstein Condensates
Abstract:

We discuss the dynamics of both population and spin densities, emerging from the spatial overlap between two distinct polar bright solitons in Spin-1 Spinor Condensates. The dynamics of overlapping solitons in scalar condensates exhibits soliton fusion, atomic switching from one soliton to another and repulsive dynamics depending on the relative phase between the solitons. In the spinor case, non-trivial dynamics emerges in both spatial and spin degrees of freedom, depending on the relative phase and the ratio between the spin-dependent and spin-independent interactions.

Friday, 13 May 2022

Bijay Agarwalla
Title: Understanding Quantum Transport in Quasi-Periodic Lattice Systems
Abstract:

In this talk, I will first give a brief overview of quasi-periodic lattice systems and the nature of single-particle states. I will then discuss how to read out the underlying transport properties of such lattices by coupling them to a qubit that acts as a probe. In the second half of the talk, I will briefly discuss how attaching Buttiker probes to such lattices modifies the charge and energy transport properties.

References:
1. Madhumita Saha, Bijay Kumar Agarwalla, and B. Prasanna Venkatesh, Read-out of Quasi-periodic Systems using Qubits,  Phys. Rev. A  103, 023330 (2021

2. M. Saha, B. Prasanna Venkatesh, and Bijay Kumar Agarwalla, ​​Quantum transport in quasi-periodic lattice systems in presence of Buttiker probes, arXiv: 2202.14033

Satya Ram Mishra
Title: Trapping and Manipulation of Atoms for Precision Measurements
Abstract:

Lasers, RF-fields and static magnetic fields work as tools to cool and trap the neutral atoms for different applications. Advanced methods for trapping and manipulation of cold atoms in different geometries will be discussed. The experimental progress made in RRCAT for precision measurements using cold atoms will be discussed.

Subhadeep De
Title: Progress Towards Development of the Optical Atomic Clock at IUCAA
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Bubai Rahaman
Title: High Resolution Measurement of Hyperfine Structure of 7d States in Cesium
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Arnab Sarkar
Title: Cooling of Mechanical Mode at Room Temperature Through Frequency Modulation Technique
Abstract:

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Pratik Adhikary
Title: Observation of Quantum Synchronization and Metrological Gain Using Polariton Interferometer
Abstract:

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