Physics and Astronomy Condensed Matter Seminar
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  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  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.
 J. Shen et. al., Nature Commun. 11, 930 (2020).
 S. Lu et. al., Phys. Rev. A 101, 042318 (2020).
 S. J. Kuhn et. al., Phys. Rev. Research 3, 023227 (2021).
 A. A. Md. Irfan, P. Blackstone, R. Pynn, and G. Ortiz, New J. Phys. 23, 083022 (2021).
 Q. Le Thien, S. McKay, R. Pynn, and G. Ortiz, arXiv:2207.12419.
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.
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.
Dr. Ankur Das
Postdoctoral Research Associate
Weizmann Institute of Science
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.
Professor John Davis
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.
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.