Environmental dynamics, correlations, and the emergence of noncanonical equilibrium states in open quantum systems

Quantum systems are invariably open, evolving under surrounding influences rather than in isolation. Standard open quantum system methods eliminate all information on the environmental state to yield a tractable description of the system dynamics. By incorporating a collective coordinate of the environment into the system Hamiltonian, we circumvent this limitation. Our theory provides straightforward access to important environmental properties that would otherwise be obscured, allowing us to quantify the evolving system-environment correlations. As a direct result, we show that the generation of robust system-environment correlations that persist into equilibrium (heralded also by the emergence of non-Gaussian environmental states) renders the canonical system steady-state almost always incorrect. The resulting equilibrium states deviate markedly from those predicted by standard perturbative techniques and are instead fully characterised by thermal states of the mapped system-collective coordinate Hamiltonian. We outline how noncanonical system states could be investigated experimentally to study deviations from canonical thermodynamics, with direct relevance to molecular and solid-state nanosystems.Comment: 10 pages, 4 figures, close to published versio

HvZ Website: The Re-Engineering

As part of our Software Design and Development class, we were given a customer and tasked with providing them a product that they specifically request. Our customer was the Humans vs Zombies (HvZ) student group here on campus. They are a group that periodically plays a campus-wide game of tag using their own online resources, and they requested that we provide them a new, updated website. Their problem was that they needed to both update their site and acquire a more maintable version. The current site that they own now is three years old with code that is difficult to decipher

Interleukin 6 plays a role in the migration of magnetically levitated mesenchymal stem cells spheroids

Mesenchymal stem cells (MSCs) reside quiescently within a specialised ‘niche’ environment in the bone marrow. However, following appropriate signalling cues, MSCs mobilise and migrate out from the niche, typically toward either sites of injury (a regenerative response) or toward primary tumours (an intrinsic homing response, which promotes MSCs as cellular vectors for therapeutic delivery). To date, very little is known about MSC mobilisation. By adopting a 3D MSC niche model, whereby MSC spheroids are cultured within a type I collagen gel, recent studies have highlighted interleukin-6 (IL-6) as a key cytokine involved in MSC migration. Herein, the ability of IL-6 to induce MSC migration was further investigated, and the key matrix metalloproteinases used to effect cell mobilisation were identified. Briefly, the impact of IL-6 on the MSC migration in a two-dimensional model systems was characterised—both visually using an Ibidi chemotaxis plate array (assessing for directional migration) and then via a standard 2D monolayer experiment, where cultured cells were challenged with IL-6 and extracted media tested using an Abcam Human MMP membrane antibody array. The 2D assay displayed a strong migratory response toward IL-6 and analysis of the membrane arrays data showed significant increases of several key MMPs. Both data sets indicated that IL-6 is important in MSC mobilisation and migration. We also investigated the impact of IL-6 induction on MSCs in 3D spheroid culture, serving as a simplistic model of the bone marrow niche, characterised by fluorescently tagged magnetic nanoparticles and identical membrane antibody arrays. An increase in MMP levels secreted by cells treated with 1 ng/mL IL-6 versus control conditions was noted in addition to migration of cells away from the central spheroid mass

Quantum correlations of light and matter through environmental transitions

One aspect of solid-state photonic devices that distinguishes them from their atomic counterparts is the unavoidable interaction between system excitations and lattice vibrations of the host material. This coupling may lead to surprising departures in emission properties between solid-state and atomic systems. Here we predict a striking and important example of such an effect. We show that in solid-state cavity quantum electrodynamics, interactions with the host vibrational environment can generate quantum cavity-emitter correlations in regimes that are semiclassical for atomic systems. This behaviour, which can be probed experimentally through the cavity emission properties, heralds a failure of the semiclassical approach in the solid-state, and challenges the notion that coupling to a thermal bath supports a more classical description of the system. Furthermore, it does not rely on the spectral details of the host environment under consideration and is robust to changes in temperature. It should thus be of relevance to a wide variety of photonic devices.Comment: 8 pages, 7 figures. v2 - minor edits. v3 - more substantial edits to the text. Title changed and new results on correlations added in Fig. 3. v4 - close to published version, presentation clarifie

The Effect of Music on Body Sway When Standing in a Moving Virtual Environment

poster abstractMovement of the visual surrounding using virtual reality (VR) is an established tool for testing body sway for clinical and research purposes. There are, however, no conclusive studies showing the effects music can have on body sway especially if it is heard in conjunction with a shifting visual surrounding. For this study subjects stood quietly with their eyes closed, with their eyes open, and with their eyes open as they viewed a VR environment translating forward and backward at 0.1 Hz. In addition to these visual conditions, they simultaneously experienced “no sound” and music conditions. The music conditions consisted of their hearing a section of Mozart’s Jupiter and a section of the subjects’ self-selected popular music played normally and also modified so that the loudness and frequency shifted in sync with the VR movement. Body sway was assessed through analysis of center of pressure movement (COP) recorded with force plate, a commonly used device for assessing balance. To date, we have analyzed the body sway of one subject and have found, for that subject, that the addition music enhanced the effect of the translating scene on body sway as measured by increased COP variability, velocity, and a shift in median COP frequency. For this subject, however, it did not appear neither to make a difference whether the subject heard Mozart’s Jupiter or listened to their own self-selected music nor whether the music’s frequency or loudness was synced to the movement of the scene. Should these findings hold with further body sway analysis of more subjects, they would be of interest to clinicians and researchers examining the impact of sound on balance as well as to video game and computer graphics designers looking to create more immersive VR environments

Environmental Nonadditivity and Franck-Condon physics in Nonequilibrium Quantum Systems

We show that for a quantum system coupled to both vibrational and electromagnetic environments, enforcing additivity of their combined influences results in non-equilibrium dynamics that does not respect the Franck-Condon principle. We overcome this shortcoming by employing a collective coordinate representation of the vibrational environment, which permits the derivation of a non-additive master equation. When applied to a two-level emitter our treatment predicts decreasing photon emission rates with increasing vibrational coupling, consistent with Franck-Condon physics. In contrast, the additive approximation predicts the emission rate to be completely insensitive to vibrations. We find that non-additivity also plays a key role in the stationary non-equilibrium model behaviour, enabling two-level population inversion under incoherent electromagnetic excitation.Comment: 9 pages (including supplementary information), 4 figures. V2 - minor clarifications to main text and new section in the supplemen