You can find all of the previous Quantum Colloquia recordings below.

Thirupathaiah Vasantam

An Entanglement Generation Switch (EGS) is a quantum network hub that provides entangled states to a set of connected nodes by enabling them to share a limited number of hub resources. As entanglement requests arrive, they join dedicated queues corresponding to the nodes from which they originate. We propose a load-balancing policy wherein the EGS queries nodes for entanglement requests by randomly sampling d of all available request queues and choosing the longest of these to service. This policy is an instance of the well-known power-of- d-choices paradigm previously introduced for classical systems such as data-centers. In contrast to previous models, however, we place queues at nodes instead of directly at the EGS, which offers some practical advantages. Additionally, we incorporate a tunable back-off mechanism into our load-balancing scheme to reduce the classical communication load in the network. To study the policy, we consider a homogeneous star network topology that has the EGS at its center, and model it as a queueing system with requests that arrive according to a Poisson process and whose service times are exponentially distributed. We provide an asymptotic analysis of the system by deriving a set of differential equations that describe the dynamics of the mean-field limit and provide expressions for the corresponding unique equilibrium state. Consistent with analogous results from randomized load-balancing for classical systems, we observe a significant decrease in the average request processing time when the number of choices d increases from one to two during the sampling process, with diminishing returns for a higher number of choices. We also observe that our mean-field model provides a good approximation to study even moderately-sized systems.

This is a joint work with Guo Xian Yau (TU Delft), Gayane Vardoyan (UMass, Amherst)

Peter Bradshaw

Algebraic approaches to physics are an active and growing area of research. Such theories often capture properties of a physical system in a simple and intuitive way [1], and often can yield new insights into established phenomena [2]. Their study also often avoids the need for explicit matrix or analytical representations, providing an elementary, flexible, and extensible way to describe a system coordinate-free and isolated from unnecessary additional structure. As such, they offer deep insights into the essential foundations of physical phenomena. In this talk, we will discuss a new algebraic theory to describe the spin of arbitrary non-relativistic systems, as derived in [3]. These algebras are real and written in terms of, and entirely characterised by, the complete set of physically distinct observables of the system, offering a novel characterisation of spin based on its physical properties instead of eigenvalues. This construction is realised directly from the symmetries of Euclidean three-space without: dynamical notions like angular momentum and time; nor additional mathematical structure, such as complex numbers. This indicates that spin is more fundamentally related to geometry than dynamics; this connection will be made more concrete by realising the spin of a non-relativistic system within a natural non-commutative geometry of position operators, without the need for "internal" degrees of freedom, following [4].