Performing Hong-Ou-Mandel-type numerical experiments with repulsive condensates: the case of dark and dark-bright solitons

The Hong-Ou-Mandel experiment leads indistinguishable photons simultaneously reaching a 50:50 beam splitter to emerge on the same port through a two-photon interference. Motivated by this phenomenon, we consider numerical experiments of the same flavor for classical wave objects in the setting of repulsive condensates. We examine dark solitons interactingwith a repulsive barrier, a case inwhich we find no significant asymmetries in the emerging waves after the collision, presumably due to their topological nature. We also consider case examples of two-component systems, where the dark solitons trap a bright structure in the second component (dark-bright solitary waves). For these, pronounced asymmetries upon collision are possible for the nontopological bright component. We also show an example of a similar phenomenology for ring dark-bright structures in two dimensions

Carers Create: carer perspectives of a creative programme for people with dementia and their carers on the relationship within the (carer and cared for) dyad

Introduction Relationships between people with dementia and their carers can prove challenging over the trajectory of the disease. Interventions with a potential to address this include arts and music-based activities. This research project aimed to evaluate a community engagement programme (Carers Create) where both people with dementia and their carers participate together in singing and other activities. A specific focus was on the impact of the sessions on the dyadic relationship. Methods A grounded theory approach involved conducting three focus group interviews with carers of people with dementia (n=16) facilitated by members of a local U3A (University of the Third Age) who were trained and supported by university researchers. Recorded conversations were transcribed and analysed using a three-stage coding and thematic development technique. Results Four overarching themes were identified from the discourse: remembering the positive qualities of the cared-for; the physical and emotional demands of caring; Carers Create as a shared, beneficial activity; the enduring value of Carers Create. Conclusion Carers found the sessions to positively influence the relationship with the person they cared for through offering some relief from the day-to-day pressures of caring and in some cases restoring elements of a previously strong relationship. Crucial to the experience was the fact that the sessions included both carer and cared-for, offering activities to do together, and that they took place within a group, thereby offering a degree of mutual support. In addition, some carers were able to build on learning which had taken place and use certain techniques, such as singing, to help manage care, thus extending the improved relationship.

Orbital Josephson effect and interactions in driven atom condensates on a ring

In a system of ac-driven condensed bosons we study a new type of Josephson effect occurring between states sharing the same region of space and the same internal atom structure. We first develop a technique to calculate the long time dynamics of a driven interacting many-body system. For resonant frequencies, this dynamics can be shown to derive from an effective time-independent Hamiltonian which is expressed in terms of standard creation and annihilation operators. Within the subspace of resonant states, and if the undriven states are plane waves, a locally repulsive interaction between bosons translates into an effective attraction. We apply the method to study the effect of interactions on the coherent ratchet current of an asymmetrically driven boson system. We find a wealth of dynamical regimes which includes Rabi oscillations, self-trapping, and chaotic behavior. In the latter case, a full many-body calculation deviates from the mean-field results by predicting large quantum fluctuations of the relative particle number.Comment: Published versio