Seminar

Entanglement in a synthetic quantum magnet made of hundreds of trapped ions

Justin Bohnet, National Institute of Standards and Technology, Boulder

Entanglement between individual quantum objects exponentially increases the complexity of quantum many-body systems, such that models with more than 40 quantum bits cannot be fully studied using conventional techniques on classical computers. To make progress at this frontier of physics, Feynman’s pioneering ideas of quantum computation and quantum simulation are now being pursued in a wide variety of well-controlled platforms.

Research with very cold and ultra-cold neutrons at the Institute Laue Langevin in Grenoble

Peter Geltenbort, Institute Laue Langevin, Grenoble

Due to their outstanding property to be storable and hence observable for long periods of time (several hundreds of seconds) in suitable material or magnetic traps, ultra-cold neutrons (UCN) with energies around 100 neV are an unique tool to study fundamental properties of the free neutron, like its beta-decay lifetime, its electric dipole moment and its wave properties.

Airborne demonstration of a QKD payload receiver

Chris Pugh, IQC

We demonstrate the viability of components of a quantum receiver satellite payload by successfully performing quantum key distribution in an uplink configuration to an airplane. Each component has a clear path to flight for future satellite integration.

Probing light-matter entanglement in the non-perturbative regime of a strongly driven spin-boson system

Milena Grifoni, University of Regensburg

The spin-boson model is an archetype model to study the impact of a thermal reservoir on the coherent dynamics of a two-level quantum particle. When the coupling between qubit and environment crosses a threshold, a transition from coherent to incoherent tunneling between the two qubit eigenstates occurs. At even larger coupling, the dynamics is fully quenched, signaling a strong entanglement of the qubit with the reservoir’s continuum.

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.