Colloquium Schedule

Spring 2024

Networking Quantum Computers

Abram Falk ('03), IBM Watson Research Center
Friday, September 20, at 12:45

As the quantum computing industry continues its rapid growth, the need to distribute quantum information across networks is becoming increasingly pressing. However, the fragility of quantum states makes quantum networking a challenging problem, especially when the quantum bits (qubits) comprise microwave photons, which rapidly thermalize at ambient conditions. In this colloqium, I will introduce quantum computing, superconducting quantum qubits, and strategies for networking qubits using quantum transducers, which are devices that can convert the frequency of individual photons a single-photon basis. Although these devices invariably lead to the transmission of imperfect quantum states, there is nonetheless a possibility for high quality quantum networks via techniques such as entanglement heralding and distillation.

Grain-scale dynamics and force transmission in sticking and slipping granular materials: effects of friction and grain shape

Ryan Kozlowski, College of the Holy Cross
Friday, October 4, at 12:45

Granular materials are ubiquitous in nature, from household table salt to mountainside boulders, silty river beds, and distant  protoplanetary disks. Despite their prevalence in daily life and countless industries like agriculture and pharmaceuticals, the stability, flow, and responses of these materials to external perturbations are all active areas of physics research: unlike conventional solids or liquids, they often exist in non-equilibrium states, interact dissipatively, and have constituent particles of infinite variety in size, shape, and frictional properties. In this talk, I will present experiments specifically probing how grain shape and friction with boundaries influence the stick-slip dynamics of driven granular materials. In stick-slip dynamics, the granular material transitions back and forth between stable sticking periods and rapid, energy-releasing slip events, like the destructive sliding between tectonic plates that generates earthquakes. I begin by analyzing macroscopic stick-slip of driven granular materials and then connect these observations with grain-scale flow and interparticle stresses, demonstrating that grain-scale interactions indeed influence bulk granular material stability and yielding. In particular, I show that friction between grains and a substrate dramatically stabilizes the material against an intruding load, and that strongly angular grains exhibit both greater stability in sticking periods and more energetic slip events than less angular grains.