Seminar

Jiawei Mei - Southern University of Science and Technology, China

The toric code is a topological quantum error correcting code, and an example of a stabilizer code, defined on a two-dimensional spin lattice. It also represents the simplest example of topological order -- Z2 topological order that was first studied in the context of Z2 spin liquid. I will talk about our recent progress in the search for a toric code topological order in the kagome antiferromagnetic spin system.

Colloquium: Mohammad Hafezi, University of Maryland/Joint Quantum Institute

There are tremendous efforts underway to better understand systems with topological order --- global properties that are not discernible locally. The best-known examples are quantum Hall effects in electronic systems, where insensitivity to local properties manifests itself as conductance through edge states which are insensitive to defects and disorder.

Producing Polarization Entangled States Using a Bright Single Photon Source

Daniel Tennant - University of Texas, Austin

I will report on dynamical magnetic susceptibility measurements of
both bulk and thin film samples of the spin glass Copper Manganese.
By studying the Thermoremanent Magnetization (TRM) of multi-layer thin
films of various thicknesses, we are able to show the maximum energy
barrier encountered during correlated spin flip transitions is cut off
by the thickness of the film and is independent of temperature. The
distribution of energy barriers is shown to follow from a hierarchical

Evan Meyer-Scott, Universität Paderborn 

I will present a realization of a great photon pair source based on parametric down-conversion, and discuss a not-so-great limit to the performance of photon pair sources in general. The former is a fully fiber-coupled waveguide pair source with 46% raw heralding efficiency, and no optical alignment required. The latter restricts the achievable heralding efficiency, when spectrally filtering the photons to increase the purity.

Giuseppe Di Molfetta, University of Marseille

As we know, spacetime is not flat at the cosmological scale. In order to describe spacetime, in General Relativity theory (GR), we need a continuous and differentiable manifold and a formal way to account for the continuous distortion of the metrics. The main point is that changing coordinate systems should not affect physics laws (General Covariance). However at the Planck length, matter is not continuous and obeys Quantum Theory (QT).

Behrooz Semnani, PhD candidate, Department of  Electrical and Computer Engineering, University of Waterloo  

Recent rapid advancements in nanofabrication technologies have widened the realm of possibilities in nanophotonics, nonlinear and sub-wavelength optics. Realizing nonlinear optics in subwavelength scale paves the way for low cost integrated photonics. Ultra-high-Q photonic crystal nanocavities and nanostructured materials are examples of such structures. Those structures offer very small mode volume guaranteeing highly enhanced field intensity.

Hugo Zbinden, Université de Genève

An approach to quantum random number generation based on unambiguous quantum state discrimination (USD) is developed. We consider a prepare-and-measure protocol, where two non-orthogonal quantum states can be prepared, and a measurement device aims at unambiguously discriminating between them.

Mark Howard & Earl T. Campbell

Motivated by their necessity for most fault-tolerant quantum computation schemes, we formulate a resource theory for magic states. We first show that robustness of magic is a well-behaved magic monotone that operationally quantifies the classical simulation overhead for a Gottesman-Knill type scheme using ancillary magic states. Our framework subsequently finds immediate application in the task of synthesizing non-Clifford gates using magic states.

Hsi-Sheng Goan - Department of Physics and Center for Quantum Science and Engineering, National Taiwan University, Taipei

An essential prerequisite for quantum information processing is precise coherent control of the dynamics of quantum systems or quantum bits (qubits). Most of the control sequences implemented in quantum experiments are developed and designed based on the assumption of having ideal (closed) quantum coherent systems.