Seminars



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Tue Apr 09, 2024 (1403/1/21)

       

Apr 09
1403/1/21

14:00
 

Model Selection Approach and Tension Metrics in Cosmology

Abstract:Cosmology is a field that deals with a vast amount of data, and it is crucial to ensure consistency and measure the tension between data sets. Tension indicates either discordance between data sets or a problem with the underlying model. One of the most famous examples of tension in cosmology is the Hubble tension, which is a 3.5Ï? discrepancy between supernovae and CMB data in estimating the age of the Universe. While alternative models have been introduced to resolve this tension, it is necessary to use tension metrics to verify if these data sets are still discordant or in agreement even in alternative models. Furthermore, the existence of different models means that one has to choose the best model among competing models that fits observational data. Nested Sampling, a recent computational algorithm, enables us to perform a model selection approach alongside quantifying tension between different data sets. In this talk, we will discuss the tension metric and the model selection approach in cosmology.
Lecturer(s): Mohsen Khorasani
From : School of Physics, IPM
Research Group: HEPCO Group Weekly Seminar
More Info. : Link

Tue Apr 02, 2024 (1403/1/14)

       

Apr 02
1403/1/14

14:00
 

Anthropic Carbon Emission And the footprint of HEPCO researchers on Earth

Abstract:The atmospheric CO2 has reached unprecedented amounts and the impact of human activities on the current situation is undeniable. In this talk, I briefly explain the problem of atmospheric CO2 variation and introduce the main strategies to control our carbon footprint as a HEPCO researcher according to the Arxiv 2403.03308
Lecturer(s): Saeed Ansari Fard
From : School of Physics, IPM
Research Group: HEPCO Weekly Seminar Special Series
More Info. : Link

Sat Mar 02, 2024 (1402/12/12)

       

Mar 02
1402/12/12

14:00
 

Variational Quantum Algorithms: From Many-Body Simulation to Machine Learning Problems

Abstract:Near-term quantum simulators suffer from various imperfections. A key question is whether such noisy quantum devices can outperform classical computers. Several demonstrations for quantum advantage have been achieved for sampling problems in superconducting and optical platforms. While these proof of principle experiments show the superiority of quantum computers, they do not offer an immediate practical advantage due to the limited practicality of sampling problems. Variational quantum algorithms are the most promising approach for achieving practical quantum advantage. These algorithms benefit from a hybrid combination of quantum devices and classical optimizers. In this seminar, we show two distinct applications for such algorithms, namely: (i) quantum simulation of many-body systems; and (ii) machine learning problems. In the former, we show how symmetries can be harnessed in optimizing circuit design [1] and be implemented experimentally in superconducting quantum simulators [2]. For the latter, a novel error-mitigation algorithm is presented which significantly enhances the performance of variational quantum algorithms for supervised machine learning problems [3]. References: [1] Symmetry enhanced variational quantum eigensolver C. Lyu, X. Xu, M.-H. Yung, A. Bayat, Quantum 7, 899 (2023) [2] Multi-Level Variational Spectroscopy using a Programmable Quantum Simulator Z. Han, et. al., Phys. Rev. Research 6, 013015 (2024) [3] Ensemble-learning variational shallow-circuit quantum classifiers Q. Li, Y. Huang, X. Hou, Y. Li, X. Wang, A. Bayat, Phys. Rev. Research 6, 013027 (2024)
Lecturer(s): Abolfazl Bayat
From : University of Electronic Science and Technology of China
Research Group: QIS Biweekly Seminars
More Info. : Link

Sat Feb 24, 2024 (1402/12/5)

       

Feb 24
1402/12/5

14:00
 

Classical algorithm for simulating experimental Gaussian boson sampling

Abstract: Classical algorithm for simulating experimental Gaussian boson sampling Changhun Oh, Minzhao Liu, Yuri Alexeev, Bill Fefferman, and Liang Jiang https://arxiv.org/abs/2306.03709
Lecturer(s): Fatemeh Tarighi Tabesh
From : School of Physics, IPM
Research Group: QIS Group Journal Club
More Info. : Link

Tue Feb 20, 2024 (1402/12/1)

       

Feb 20
1402/12/1

14:56
 

Late-time domain walls in cosmological simulations

Abstract:The study of domain walls and topological defects has a rich history in cosmology and they provide a wide range of novel phenomenology to experimentally test them. The motivations that they have been studied under include seeding the initial overdensities for structure formation, driving inflation, seeding a stochastic gravitational wave background like the one in NANOGrav, and providing the skeleton for the formation of larger structures than you would expect in LCDM. They have furthermore been linked to resolutions of some of the late-time cosmological tensions. I will in this talk present the asymmetron dark energy model, that exhibits late-time cosmological domain walls, and our implementation of it in the cosmological N-body code gevolution. I present some details on the domain walls' dynamics, their GW emission, their effect on clustering, and some observational signatures.
Lecturer(s): Ã?yvind Christiansen
From : Institute for Theoretical Astrophysics (ITA), University of Oslo (UiO)
Research Group: HEPCO Group Weekly Seminar
More Info. : Link

Sat Feb 17, 2024 (1402/11/28)

       

Feb 17
1402/11/28

14:00
 

How fast can a quantum system evolve?

Abstract:Quantum mechanics imposes many limitations, the most famous one is the Heisenberg uncertainty relation, i.e. the limitation on the precision with which certain pairs of physical properties such as position and momentum can be simultaneously known. Other fundamental limitation is the quantum speed limit which imposes a fundamental bound on how fast can a quantum state change with time. In this talk, I will address this question and present a framework to obtain the optimal speed of a d-dimensional system evolved unitarily under a time-independent Hamiltonian. As the quantum resources could cause speed up quantum evolution leading to a smaller quantum speed limit, I will also discuss the effects of quantum coherence and quantum entanglement on the maximum speed of dynamical evolution.
Lecturer(s): Seyed Javad Akhtarshenas
From : Ferdowsi University of Mashhad
Research Group: QIS Biweekly Seminars
More Info. : Link

Tue Feb 06, 2024 (1402/11/17)

       

Feb 06
1402/11/17

14:00
 

Near horizon limit of the near extremal Reissner-Nordstrom black holes in 4 dimensions and the SYK model

Abstract:In this talk we first review the near horizon limit of charged black holes at very low temperature in four dimensions, called the Jackiw-Teitelboim (JT) gravity. In the resulting theory, the dynamical degrees of freedom are located on the boundary and are described by the Schwarzian action. Next, we review the Sachdev-Ye-Kitaev (SYK) model as a UV theory whose IR dynamics effectively render the same ``gravitational'' action. We then argue that this correspondence must be extended to higher dimensions.
Lecturer(s): Pouria Dadras
From : California Institute of Technology
Research Group: HEPCO Group Weekly Seminar
More Info. : Link

Sat Feb 03, 2024 (1402/11/14)

       

Feb 03
1402/11/14

14:00
 

Tip of the Quantum Entropy Cone

Abstract:Tip of the Quantum Entropy Cone Matthias Christandl, Bergfinnur Durhuus, and Lasse Harboe Wolff https://arxiv.org/abs/2306.00199 Phys. Rev. Lett. 131, 240201 (2023)
Lecturer(s): Zohreh Nafari Ghale
From : IPM, School of Physics
Research Group: QIS Group Journal Club
More Info. : Link

Tue Jan 30, 2024 (1402/11/10)

       

Jan 30
1402/11/10

14:00
 

On Torsion Contribution to Chiral Anomaly via Nieh-Yan Term

Abstract:In this talk, we present a solution to the question of whether or not, in the presence of torsion, the topological Nieh-Yan term contributes to chiral anomaly. The integral of Nieh-Yan term is non-zero if topology is non-trivial; the manifold has a boundary or vierbeins have singularities. Noting that singular Nieh-Yan term could be written as a sum of delta functions, we argue that the heat kernel expansion cannot end at finite steps. This leads to a sinusoidal dependence on the Nieh-Yan term and the UV cut-off of the theory (or alternatively the minimum length of spacetime). We show this ill-behaved dependence can be removed if a quantization condition on length scales is applied. It is expected as the Nieh-Yan term can be derived as the difference of two Chern class integrals (i.e. Pontryagin terms). On the other hand, in the presence of a cosmological constant, we find that indeed the Nieh-Yan term contributes to the index with a dimensionful anomaly coefficient that depends on the de Sitter length or equivalently inverse Hubble rate. We find similar result in thermal field theory where the anomaly coefficient depends on temperature. In both examples, the anomaly coefficient depends on IR cut-off of the theory. Without singularities, the Nieh-Yan term can be smoothly rotated away, does not contribute to topological structure and consequently does not contribute to chiral anomaly.
Lecturer(s): Ida Mehin Rasulian
From : School of Physics, IPM
Research Group: HEPCO Group Weekly Seminar
More Info. : Link

Sat Jan 27, 2024 (1402/11/7)

       

Jan 27
1402/11/7

14:00
 

Quantum maximal correlation for Gaussian states

Abstract:Quantum maximal correlation is a measure of correlation with the monotonicity and tensorization properties that can be used to study whether an arbitrary number of copies of a resource state can be locally transformed into a target state without classical communication, known as the local state transformation problem. In this talk, I will introduce a closed-form expression for the quantum maximal correlation of Gaussian states, which are readily available in the laboratory and can be used as resource states to prepare other states. I will also discuss Gaussian maximal correlation, another measure of correlation for Gaussian states, which is based on considering the class of local Gaussian observables associated with homodyne measurements
Lecturer(s): Saleh Rahimi Keshari
From : School of Physics, IPM
Research Group: QIS Biweekly Seminars
More Info. : Link

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