Mini Workshop: Quantum World at the IFFS
Friday 21 September 2018
Institute of Fundamental and Frontier Sciences Room 725
Speaker: Alexander Govorov
Title: Plasmonic Bio-Assemblies and Nanostructures: Long-range energy transfer, hot electrons and chirality
Abstract: Metal nanocrystals and semiconductor quantum dots have the ability to absorb and scatter light very efficiently. This study concerns special designs of hybrid nanostructures with electromagnetic hot spots, where the electromagnetic field becomes strongly enhanced and concentrated. Overall, plasmonic nanostructures with hot spots demonstrate strongly amplified optical and energy-related effects.
(1) Using nanoparticle arrays made of different metals, one can transfer plasmonic signals coherently and with small losses .
(2) Plasmonic hot spots efficiently generate energetic electrons, which can be used for photochemistry and photodetection [2,3].
(3) Nanostructures with hot spots can strongly enhance the optical generation of heat, and also confine high photo-temperatures in small volumes [4,5,6].
(4) Colloidal nanocrystal assemblies and metasurfaces with plasmon resonances allow us to strongly enhance chiral optical responses (circular dichroism) of biomolecules and drugs[7,8,9].
 E.-M. Roller, et al., Nature Physics, 13, 761 (2017).
 A.O. Govorov, H. Zhang, H.V. Demir and Y. K. Gun’ko, Nano Today 9, 85 (2014).
 H. Harutyunyan, et al., Nature Nanotech. 10, 770 (2015).
 A. O. Govorov and H. Richardson, Nano Today 2, 20 (2007).
 C. Jack, et al., Nat. Commun. 7, 10946 (2016).
 X.-T. Kong, et al., Nano Letters, DOI: 10.1021/acs.nanolett.7b05446
 A. O. Govorov, et al., Nano Letters 10, 1374–1382 (2010).
 A. Kuzyk, et al., Nature 483, 311 (2012).
 X.-T. Kong, et al., Nano Letters 17, 5099–5105 (2017).
Speaker: Yanning Zhang
Title: Theoretical Understanding and Design of Transition Metal Sulfides and Their New Energy Applications
Abstract: With the excellent electrochemical and optical properties, transition-metal sulfides,such as Fem-, Com-, Nim- and MomSn, have been attracting considerable attention inmultidisciplinary research fields including thin-film solar cells, supercapacitors, batteries, andcatalysts. In particular, theoretical studies provide deep understandings on the physicalmechanism beyond experimental observations. In this talk we will review our recent progresson some typical pyrite-type transition metal sulfides, as well as their energy-relatedapplications. Systematic density functional theory studies on the basic structure, surface,physical and electronic properties of FeS2, CoS2 and Ni3S2 were performed, and the effects ofnative defects and impurities on the features above were also discussed. Moreover, we studiedthe interaction of atomic hydrogen on several surfaces and further their HER activity. We areworking on the search of the relationship between the structural/electronic features and performance, providing useful guidelines for new experimental designs.
Speaker: Zizhu Wang
Title: Blind men and an elephant: certifying global quantum properties from local information
Abstract: Entanglement and nonlocality are the two hallmark features of quantum physics,signifying the departure from its classical counterpart. Their study allows us to determine thetypes of correlations furnished by the quantum system and how these correlations can be usedin information processing tasks. But what can we infer about global quantum properties of asystem when only local access is allowed, similar to the story "Blind men and an elephant"? Topartially answer this question, we draw inspiration from a classical math problem: the marginalproblem, and use the theory of convex polytopes to characterize near-neighbor marginaldistributions of 1- and 2D translation-invariant distributions on an Euclidean lattice. From thesepolytopes we can characterize Bell inequalities using results in the study of nonlocality. To showquantum systems can violate some of these inequalities we employ powerful numericalalgorithms based on matrix product states and tensor network states to approximate theground state properties of infinite translation-invariant quantum systems with localinteractions. Certain inequalities which can be violated will provide us with qualitativeinformation about global quantum properties of the infinite quantum system. For those inequalities which cannot be violated we will use convex optimization theory to find 1- and 2Dsize witnesses from them.
Speaker: Abolfazl Bayat
Title: Quantum simulation using solid state systems
Abstract: Quantum simulators are certain quantum systems which emulate the behavior ofanother system with higher controllability and precision. They are the first step towardsrealization of universal quantum computers. So far, cold atoms and ions have beenpredominantly exploited for serving as quantum simulators thanks to their high controllabilityand long coherence times. Nevertheless, any solid state effects cannot be easily simulated bysuch systems, take spin-orbit interaction as an example. Therefore, having asolid state based quantum simulator is very desirable. We propose quantum dot arrays forserving as quantum simulators. In particular, we focus on realization of the ground state of theHeisenberg spin chain in realistic experimental conditions. Furthermore, we provide aneffective method for the certification of our quantum simulator via singlet-tripletmeasurements. Finally, we demonstrate the conformal field theory physics using our solid statequantum simulator.