Events

Exponential Separation between Quantum Communication Complexity and Classical Information Complexity

Dave Touchette, IQC

We exhibit a Boolean function for which the quantum communication complexity is exponentially larger than the classical information complexity. An exponential separation in the other direction was already known from the work of Kerenidis et. al. [SICOMP 44, pp. 1550--1572], hence our work implies that these two complexity measures are incomparable. As classical information complexity is an upper bound on quantum information complexity, which in turn is equal to amortized quantum communication complexity, our work implies that a tight direct sum result for distributional quantum communication complexity cannot hold.

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].

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.

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.

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.

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.

Informal conversation with Dr. Milena Grifoni, University of Regensburg

​Presented by: Fem Phys and Women in Science

​Join Fem Phys and Women in Science for an informal conversation with Dr. Milena Grifoni about her career in physics. Dr. Grifoni researches quantum transport in nanoscale systems and quantum dissipation at the University of Regensburg in Germany. Coffee and cookies will be provided. All are welcome.