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Physics and Astronomy Condensed Matter Seminar

Fundamentals of Entangled Probes for Entangled Matter

Advancing the frontiers of science often requires the creation of new probes to uncover the
underlying microscopic mechanisms giving rise to exotic macroscopic phenomena, such as high-
temperature superconductivity. Can quantum entangled probes uncover the inherent
entanglement of the target matter? We have recently [1-3] developed an entangled neutron
beam where individual neutrons can be entangled in spin, trajectory, and energy. To
demonstrate entanglement in these beams we crafted neutron interferometric measurements
of contextuality inequalities whose violation provided an indication of the breakdown of
Einstein's local realism. In turn, the tunable entanglement (spin-echo) length of the neutron
beam from nanometers to microns and energy differences from peV to neV opens a pathway to
a future era of entangled neutron scattering in matter. What kind of information can be
extracted with this novel entangled probe? A recent general quantum many-body entangled-
probe scattering theory [4] provides a framework to respond to this question. Interestingly, by
carefully tuning the probe's entanglement and inherent coherence properties, one can directly
access the intrinsic entanglement of the target material. This theoretical framework supports
the view that our entangled beam can be used as a multipurpose scientific tool. We are
currently [5] pursuing several ideas and developing new spin-textured entangled beams with
OAM for future experiments in candidate quantum spin liquids, unconventional
superconductors, and chiral quantum materials.

[1] J. Shen et. al., Nature Commun. 11, 930 (2020).
[2] S. Lu et. al., Phys. Rev. A 101, 042318 (2020).
[3] S. J. Kuhn et. al., Phys. Rev. Research 3, 023227 (2021).
[4] A. A. Md. Irfan, P. Blackstone, R. Pynn, and G. Ortiz, New J. Phys. 23, 083022 (2021).
[5] Q. Le Thien, S. McKay, R. Pynn, and G. Ortiz, arXiv:2207.12419.

Date:
Location:
Chemistry-Physics Bldg. Room 179
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Topological Gravitational Response: Novel physics, principles and predictions

What physics does one hope to learn by looking closely at exotic quantum states of matter, esoteric to begin with, but even more so on curved surfaces?! In this talk first I will remind the audience why quantum hall states serve as paradigmatic topological quantum states of matter, highlighting their signature property: the quantization of Hall conductance, which is independent of sample-specific details to the extent that it is used for precise measurements of fundamental constants. Tracing the topological origin of this remarkable property, I will motivate by analogy the interplay between the geometry of these states and their response to “gravitational” perturbations, i.e., deformations to the real space manifold they are embedded in — on a cone, for example! This then naturally leads to a discussion of what, if any, universal signatures characterize this response. Finally, some reflections on the broader implications of these excursions, and connections to other branches of physics, including classical soft matter systems.

Short bio:
Dr. Biswas received his PhD from Harvard University, working with Prof. Subir Sachdev on experimentally relevant exotic quantum states of matter.  Prof. Bert Halperin served as mentor. While at Harvard Rudro held several fellowships including the James Mills Pierce Fellowship Award, the Purcell Fellowship and the Harvard Center for Energy and Environment Fellowship. Following postdoctoral research as an Institute of Condensed Matter Theory Fellow at UIUC, Rudro became an Assistant Professor of Physics at Purdue University, where he is currently.

 

Date:
Location:
Chemistry-Physics Bldg. Room 179
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Carbon Based Nano Electromechanics: Physics and Applications

Carbon Based Nano Electromechanics: Physics and Applications
 
Sang Wook Lee
 
Department of Physics, Ewha Womans University, Seoul, 03760, Korea
 
In this presentation, physical properties and possible applications of carbon based nano electro-mechanical devices
(NEMS) will be introduced. Our research started from carbon nanotube based nano electro-mechanical relay
structure and expanded to graphene-based xylophone and drum like devices. Micro contact transfer method is
applied to realize the suspended nano structures with various electrodes under the nano materials. Recently
developed pick-up and transfer technique made us possible to fabricate various stacking and suspended nano
structures. After introducing some interesting physical properties, such as basic mechanical switching and
resonance behaviour and light emission of suspended graphene structures, possible application of carbon based
nano electro-mechanical devices will be suggested. Graphene based ultra-sensitive mass detector will be suggested
for one of the promising applications of our devices and our recent research project on single protein sequencing
using graphene-based mass detector will be introduced at the end of presentation.
Date:
Location:
Chemistry-Physics Bldg. Room 179
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Detection of 5/2 phases

Dr. Ankur Das

Postdoctoral Research Associate

Weizmann Institute of Science

Rehovot, Israel

 

Title: Detection of 5/2 phases

Abstract: The phases of the \nu=5/2 state have been shown to be very elusive but one of the most interesting ones as it is proposed to contain Majorana modes with non-abelian statistics. There is more than one candidate for the non-abelian state and among that three are the most promising ones namely pfaffian, anti-pfaffian, and particle-hole symmetric pfaffian. Quite a few experiments later the issue has not been settled. Previous efforts proposed methods to distinguish the candidates including the proposals where the order can be determined by measuring both thermal conductances and shot noise on the same device [Park et al. PRL 125, 157702 (2020)] or by only measuring the unequilibrated electrical conductance [Yutushui et al. PRL 128, 016401 (2022)]. To avoid some of the experimental challenges and limitations of the proposals including the above-mentioned ones we propose a new device made out of interfaces of the \nu=5/2 state and Abelian states. We propose to measure electrical shot noise to resolve among these states.

Date:
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Location:
TBA
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Superfluid Helium Electromechanics

Professor John Davis

Associate Professor

University of Alberta

Department of Physics

 

Title:  Superfluid Helium Electromechanics

Abstract: Liquid helium posses many properties that make it an attractive medium for studies of mechanical systems in the quantum regime, such as low mechanical and dielectric losses.  The flip side of this is to imagine using optomechanics or electromechanics to revisit the novel physics of superfluid helium, including bosonic helium-4 and fermionic helium-3.  In particular, when spatially restricted in one dimension, helium superfluids are expected to demonstrate quasi-two dimensional behavior with qualitatively different physics than in three dimensions.  By using nanofabrication techniques to both confine the helium and provide an electromechanical detection scheme, we are beginning the journey of studying such two-dimensional superfluids.

Date:
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Location:
Zoom
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TBA

Dr. Allen Scheie

Postdoctoral Research Associate

Oak Ridge National Laboratory

Neutron Scattering Division

Title: Witnessing entanglement in quantum magnets using neutron scattering

Abstract: In this talk I show how information about solid state quantum entanglement can be extracted from magnetic neutron scattering using model-independent techniques. Using the 1D spin chain KCuF3, we examine three entanglement witnesses applicable to neutron scattering: one tangle, two tangle, and Quantum Fisher Information (QFI). We find that QFI is the most experimentally robust, giving good agreement between theory and experiment over all measured temperatures, and witnessing multipartite entanglement up to 75 K. We then apply the entanglement witnesses to the 2D triangular lattice KYbSe2, showing the presence of appreciable entanglement in the low temperature phase. We then use diffuse scattering fits, heat capacity comparisons, and nonlinear spin wave fits to demonstrate that KYbSe2 is proximate to a quantum spin liquid. We thus provide a rigorous route to studying and understanding highly entangled quantum phases.

Date:
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Location:
Blazer 339
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