Seminar

Real-time dynamics of lattice gauge theories with a few-qubit quantum computer

Christine Muschik, University of Innsbruck

Gauge theories are fundamental to our understanding of interactions between the elementary constituents of matter as mediated by gauge bosons. However, computing the real-time dynamics in gauge theories is a notorious challenge for classical computational methods. In the spirit of Feynman's vision of a quantum simulator, this has recently stimulated theoretical effort to devise schemes for simulating such theories on engineered quantum-mechanical devices, with the difficulty that gauge invariance and the associated local conservation laws (Gauss laws) need to be implemented.

An inversion-symmetry-broken order inside the pseudogap region of a cuprate revealed by optical second harmonic generation

Liuyan Zhao, University of Michigan

The phase diagram of cuprate high-temperature superconductors features an enigmatic pseudogap region that is characterized by a partial suppression of low-energy electronic excitations. In order to understand its microscopic nature, it is imperative to identify the full symmetries both prior to and within the pseudogap region. In this talk, I will describe our experimental results of symmetry properties on YBa2Cu3Oy across a wide temperature and doping range using a recently developed nonlinear optical rotational anisotropy technique.

Principles of AFM and its applications

Deler Langenberg, IQC

Experiments designed to prove certain ideas have often ended up showing them to be wrong. Consequently, all physical concepts must be verified experimentally if they are to be accepted as representing laws of nature.

Accordingly, the goals of my talk are:

First, To provide an experimental foundation for the theoretical concepts introduced in the lectures. It is important that students have an opportunity to verify some of the ideas for themselves.

Quantum entanglement for precision sensing with atoms and light

Onur Hosten, Stanford University

In the last decades, advances in the level of precision in controlling atomic and optical systems opened up the low-energy precision frontier to fundamental physics tests in addition to yielding new applied sensing technologies. In this talk I will focus on our experiments with cold atoms highlighting some of the most recent developments in the prospect of using quantum entanglement to further improve the precision of atomic and optical sensors.

Ground State Degeneracies of Topological Orders on Open Surfaces via Anyon Condensation

Yidun Wan, Fudan University

In this talk, I will solve the problem of the ground state degeneracies of topological orders on open surfaces, using a mechanism called anyon condensation. Along with solving the problem, I will also show that anyon condensation serves as a framework that may unify various aspects of topological orders, such as topological phases, symmetry-protected topological phases, symmetry-enriched topological phases, and so on.

Making polarization-entangled photon-pair sources for nanosatellites: Size, Weight and Power Considerations

Alexander Ling, Centre for Quantum Technologies, National University of Singapore

Entanglement-distribution is going to be an important element of any future quantum internet. A number of interesting concepts are being considered at the moment, ranging from fiber-compatible quantum repeaters to long-lived quantum memories that can enable quantum states to be physically shipped or trucked. One of the approaches being considered is to utilise free-space links from satellites to enable fast global coverage.

The 2xM separability problem investigated via semidefinite programming and normal completions

Hugo J. Woerdeman, Drexel University

This talk discusses two different viewpoints of the 2xM separability problem. One method results in a construction of an increasing sequence of cones whose closed union consists of all 2xM separable states. Membership in each cone can be checked via semidefinite programming.

Experimental demonstration of Gaussian protocols for one-sided device-independent quantum key distribution

Sara Hosseini, The Australian National University

Nonlocal correlations, which was a longstanding foundational topic in quantum information, have recently found application as a resource for cryptographic tasks where not all devices are trusted. For example, the asymmetric phenomena of Einstein-Podolsky-Rosen steering plays a key role in one-sided device-independent quantum key distribution (1sDI-QKD) protocols.

NMR 'diffraction' in solids

Holger Haas, IQC

Peter Mansfield and Peter Grannell discussed the possibility of NMR crystallography in their 1973 seminal paper 'NMR 'diffraction' in solids?', however, an experimental realisation of NMR 'diffraction' is yet to be demonstrated. I will discuss the feasibility of NMR crystallography in the light of recent advances in nanoscale MRI which combine numerical control finding algorithms and state of the art force detected magnetic resonance techniques.

Two-dimensional coherent photocurrent excitation spectroscopy of a hybrid lead-halide perovskite solar cell

Carlos Silva, Université de Montréal

Hybrid halide perovskite (for example, CH3NH3PbI3) solar cells now display solar power conversion efficiencies exceeding 20% [1]. In these materials, excitonic and free-carrier regimes of primary photoexcitations are possible depending on crystalline microstructure of the active layer and excitation density [2].