Quantum solitons and cluster states with well-defined atom number

Particles at ultra-low temperatures can show surprising quantum effects, such as tunnelling and entanglement. Typically, those quantum effects are strongest for individual particles but decrease for large many-body systems. Especially many-body systems of bosons, i.e. particles which allow for a simultaneous occupation of the same state, are well described by a collective wave function, with similar properties as a classical fluid. The crossover between this classical, fluid-like regime and systems with individual particles is currently studied, and the particle number, required to observe quantum effects, is actively debated. The goal of this project is to detect and study two states of ultracold atomic gases in this crossover regime - "quantum bright solitons"' and large "cluster states". Both states are expected to exist for similar experimental parameters with between five and a few hundred atoms, but they approach the crossover regime from opposite sides.

Bright solitons are dispersionless wave-packets that propagate without changing their shape, and they present a typical property of nonlinear fluids. For reduced particle number, bright solitons are expected to acquire properties which are characteristic for a single quantum object, such as discrete tunnelling, uncertainty relationships and entanglement. Cluster states on the other hand are loosely bound states of few particles, similar to molecules. They are expected to lose quantum properties with increasing particle number. The goal of the project is to experimentally prepare bright solitons and cluster states with a well-defined number of ultracold atoms, and to probe the properties of the system as the atom number is changed.

The research will broaden our understanding of the boundary between few-body and many-body physics, and it has the potential to advance technical applications, e.g. with the development of new quantum technologies based on large and complex quantum states.

Knowledge:
I expect this work to have a long-term impact on a variety of Quantum Technologies, in particular on quantum measurement and sensing devices. This proposal directly addresses EPSRC's Physics Grand Challenge "Quantum Physics for New Quantum Technologies", as the results emerging from its research programme will lead to better understanding and exploitation of fundamental quantum physical phenomena, such as interaction and dynamics in few-particle quantum systems, coherence and entanglement. Deepening our knowledge of these effects plays an increasing role in Quantum Technologies. While it is often desirable for an improved robustness and sensitivity of Quantum Technologies to employ large systems, many quantum effects, such as entanglement and coherence, typically decrease for larger system sizes. Mesoscopic few-body states might allow for the development of Quantum Technologies, with an enhanced sensitivity, robustness and scalability of measurement and sensing devices.

People:
This project will contribute to the training and education of UK physicists with multidisciplinary knowledge and with experimental skills to develop technical applications. In particular, the project will help to close the skills gap in the UK for the development of Quantum Technologies. The project will provide excellent training for two PhD students, one PDRA, and at least three undergraduate students. The team members will attend national and international conferences, and they will profit from a wide range of training courses and workshops at the University of Strathclyde.

Societal impact and engagement with the public:
This project will provide me with the opportunity to advocate fundamental sciences and their role in the development of next-generation technologies. We will advertise our research and engage with the public at public outreach activities, such as the Glasgow Science Festival, the European Researchers' Night, the STEMfest, and University Open Days.

Boosting impact through dissemination:
We will continue to publish our work in high-impact peer-reviewed journals, and the publications will be made open access. In addition to conferences in the UK, we intend to present our work at major international meetings. High-profile publications will be highlighted by social media, newspapers, magazines, and international science websites to reach a broader audience. In addition, we will set up a dedicated website for my group and this project, to communicate with the general public and disseminate our research.