Events

CS/Math Seminar - Jiahui Liu (UT Austin)

Copy-protection is the task of encoding a program into a quantum state to prevent illegal duplications. A line of recent works studied copy-protection schemes under ``1 -> 2 attacks'': the adversary receiving one program copy can not produce two valid copies. However, under most circumstances, vendors need to sell more than one copy of a program and still ensure that no duplicates can be generated. In this work, we initiate the study of collusion resistant copy-protection in the plain model. Our results are twofold:

IQC Special Seminar - Jeremy Young - JILA, University of Colorado

One of the major goals in the field of quantum science is to utilize the properties of quantum mechanics for applications in quantum computation, quantum simulation, and quantum sensing. In order to address this goal, a variety of different many-body quantum platforms have been developed. Many of these quantum platforms exhibit long-range interactions, particularly power-law interactions, including Rydberg atoms, polar molecules, and trapped ions, among others. This gives rise to a natural question: how does the long-range nature of these interactions affect the resulting quantum evolution? 
 

Debanjan Chowdhury: The good, the bad and the strange: Unconventional metallic behaviour in the vicinity of Mott insulators

Abstract: In recent years, we have witnessed remarkable experimental breakthroughs in uncovering the intriguing properties of correlated metals in the vicinity of Mott transitions. Describing these phenomena theoretically remains an open challenge. This talk will focus on three recent examples of puzzling electronic behavior near Mott insulating phases and address the various conundrums. In the first part of the talk, I will discuss the microscopic origin of an unconventional T-linear resistivity with Planckian scattering in a quasi-two-dimensional “good” metal with long mean-free path, consisting of highly conducting metallic and Mott insulating layers, respectively. In the second part, I will address the origin of a low-temperature “bad” metallic behavior in the vicinity of a continuous bandwidth-tuned metal-insulator transition in a moiré semiconductor. I will end by presenting some new theoretical insights into the experimental observation of an anomalous particle-hole continuum and overdamped plasmon in the density response of cuprate “strange” metals. 

IQC Special Seminar - Bradley Hauer, National Institute of Standards and Technology

In the current paradigm of quantum cavity optomechanics, the relatively weak parametric coupling between an electromagnetic cavity and a mechanical resonator is mediated by an external pump. While this strong cavity drive acts to enhance the optomechanical interaction, it obscures its intrinsic nonlinearity, restricting these systems to bilinear operations on Gaussian states. By increasing this coupling such that it dominates the decoherence rates of the system, one could instead use the fundamental optomechanical nonlinearity to prepare the mechanical resonator into complex, non-Gaussian states...

IQC Special Seminar, Xiaoqing Zhong, Senior Consultant Ernst & Young

Quantum communication has revolutionized the way we approach information processing and transmission. Building on the principles of quantum mechanics, quantum communication technologies offer capabilities that are impossible with classical communication.

AEQuO: A Comprehensive Measurement Allocation Protocol

IQC-QuICS MATH CS Seminar - Rolando Somma, Los Alamos National Laboratory

Fluctuation theorems provide powerful computational tools to study thermal equilibrium. Building upon these theorems, I will present a quantum algorithm to prepare the thermal state of a quantum system H1, at inverse temperature β≥0, from the thermal state of a quantum system H0.

Development of InSb Surface Quantum Wells for hybrid superconducting device applications. 

Abstract: Surface quantum well (QW) heterostructures in III-V semiconductors are compatible with proximitized superconductivity and offer a scalable planar platform for superconductor-semiconductor systems, such as those suggested for topological quantum computation and those suitable for topological phase transitions involving Majorana zero modes. Amongst III-V binary semiconductors, Indium Antimonide (InSb) has the smallest electron effective mass, highest spin orbit coupling and largest Land´e g-factor. Such material properties makes the pursuit of InSb QWs desirable for a number of quantum device applications, including quantum sensing, quantum metrology, and quantum computing.

Unfortunately, high quality two-dimensional electron gases (2DEGs) in InSb QWs have so far been difficult to realize. InSb QWs have generally relied on the use of modulation doping for 2DEG formation, but these structures have frequently reported issues with parasitic parallel conduction and unstable carrier densities. We report on the transport characteristics of field effect 2DEGs in surface InSb quantum wells which overcome these challenges and are suitable for future hybrid superconducting device applications.

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No, you have not discovered a Majorana Fermion

Abstract: Is what I tell myself. There was a time when I thought I may have discovered it, others did too. Around 2012 several groups including ours found evidence of these quantum excitations in electrical circuits containing nanowires of semiconductor covered by a superconductor. The dramatic signatures were peaks in conductance that appeared under conditions expected from theory for Majorana modes, which are their own anti-modes and may possess non-Abelian properties. But a few years later, similar features in the data were identified due to an interesting, but a more mundane effect - which we call trivial states such as Andreev bound states. Over time more and more data pointed at the trivial and not at the exotic explanation. But because Majorana claims kept coming, this led to some digging and even retractions. What we learned after 10 years is that we have a much better handle on what effects show up in these nanowires, which positions us well for the ultimate Majorana discovery which we should be able to tell apart from all the non-Majorana things we saw. The second lesson we learned is that materials quality of device constituents, superconductors and semiconductors, as well as how samples are fabricated - are the make-or-break factors for making this happen. So while  I cannot report an exciting physics discovery, I can walk you through the scientific process that took place, a 10-year event of independent value which taught me how to do science better.

Join us for Quantum Today, where we sit down with researchers from the University of Waterloo’s Institute for Quantum Computing (IQC) to talk about their work, its impact and where their research may lead.