Room acoustics simulation - modelling acoustic wave propagation within an enclosed space - is one of the fundamental applications of audio signal processing. Given pre-defined sound-source/listener locations and a surrounding geometry the resulting room impulse response (RIR) of the system can be found. Convolution with this RIR allows any audio signal to be placed in the room at the source location and auditioned by a listener placed at the receiver location. Essentially this allows any sound source to be heard within any room. There are three main applications for this technology: (1) Reverberation simulation in music production: all music is composed to be heard in a reverberant environment, whether a concert hall or an algorithm designed to simulate an optimal reverberant field. (2) Architectural Acoustics: where a building is simulated and auditioned before construction/renovation to determine the resulting acoustic quality and identify any changes that might be appropriate. (3) Virtual environment modelling: e.g. computer games, virtual reality applications and film/television postproduction, where various sound-sources are placed in and around a virtual environment with the potential for allowing interaction with the space. Although research at both York and Aalto encompasses standard room acoustics simulation methods based on geometric acoustic techniques (where sound is assumed to behave as a ray of light with the associated limitations involved with making such an assumption) most of our interests and efforts are focused on approaches that solve the acoustic wave equation directly, that therefore offer the potential for a full, complete and accurate simulation of the soundfield within an enclosed space. Recent research has included optimal grid-sampling schemes, frequency dependent diffusing boundaries, spatial encoding for receivers and source excitation strategies. Directional source encoding and real-time auralisation have also been explored, taking the best aspects of wave based and geometric approaches, and offering significant and real potential for both further research and commercial exploitation. Hence, solutions now exist for the main constituent features of any simulation - source excitation and directivity, wave propagation, boundary interaction, and receiver encoding. This is coupled with new modelling methods and the possibility of using Graphical Processing Units to speed up calculation times. Much of this work to date has been validated using simple, easy to measure objective metrics such as room mode analysis, reverberation time, polar directivity plots, boundary characteristics, etc. It therefore now seems appropriate to tackle more demanding simulations with a view to validating this approach for a broader range of problems. A number of options will be explored including simple, analytically trivial shoebox-shaped rooms, previously published data that formed the basis for a round robin study on room acoustics measurement and simulation, as well as the study of new, complex spaces based on their direct measurement, both physical and acoustic. The aim of this visit is to facilitate a benchmark study in the use and testing of new room acoustic prediction and auralisation methods for a number of specific ideal and real-world scenarios. This therefore leads to the following objectives: (1) Consolidation of code into an appropriate framework for carrying out this benchmark study; (2) design, carry out and write up testing of new room acoustic prediction and auralisation methods; (3) organise and present results at the first York-Aalto Auralisation Workshop. The project will result in a consolidation of our research codebase to more easily facilitate both this and future studies, at least one major journal publication and a workshop between York and Aalto to allow initial dissemination and feedback on our results, as well as further encourage the ongoing collaboration between our two groups.

Macroscopic quantum systems such as superfluids, superconductors, and atomic gas condensates bring quantum physics to scales observable by the naked eye. These quantum-coherent phenomena originated in the laboratory but are now either already used for commercial applications (for example superconductors) or being actively developed with technological applications in mind (for example Bose condensates). At the same time the edges of our knowledge about these systems keep being extended, revealing unprecedented phenomena: a good example is the recent discovery of time crystals that bend the categorical impossibility of perpetual motion machines. The proposed research programme will explore the edges of macroscopic quantum order in superfluid 3He. Superfluid 3He is a macroscopic quantum system with extremely rich phenomenology, touching seemingly distant fields such as high-energy physics and cosmology. The most famous example is the Higgs mechanism, which was originally discovered in a superconductor (-fluid) system and later become a part of the Standard Model of particle physics. Another example is the Kibble-Zurek mechanism, originally a cosmological speculation, which was discovered in superfluid 3He and now forms a cornerstone of modern laboratory physics. The right way to understand low-temperature superfluid 3He from a mechanical perspective is to think about a vacuum where a rod can be moved around as if the superfluid is not there in the first place. Only if the probing exceeds an intrinsic threshold of the vacuum, such as a minimum size set by the Cooper pair size or a maximum velocity set by the superfluid energy gap, will the quantum nature of the vacuum be revealed. This means that the vacuum ceases to be a background and starts interacting with the probe. For example, a probe that is small enough will reveal the intrinsic structure of the vacuum which is hidden from large probes. An unexpected corollary of the intrinsic structure is that the surfaces of the superfluid form a two-dimensional system nearly detached from the three-dimensional bulk: move a rod near the surface and any energy released will be stuck to the surface. The magnetic properties of the superfluid are largely determined by the dynamics of magnetic particles emerging from the bulk vacuum. These particles can form a time crystal, a dynamic phase of matter in permanent repeating motion. Other "time phases" such as disordered time liquids can be created with a similar approach and explained by harnessing the toolbox of equilibrium physics to explore dynamic systems. This fellowship will explore the quantum vacuum mechanically and magnetically: 1. I will lead the exploration of the surface-bound fermions by carrying out a series of transport experiments in the few hundred nanometre thick surface layer of superfluid 3He. In practice this means heating the surface layer at one point and observing how the heat flows along the surface by measuring temperature at another point on the surface. The technology commissioned for this project will also allow revealing the superfluid vacuum's intrinsic structure by moving a tiny rod in the bulk of the superfluid where the interaction with the vacuum dramatically changes at scales smaller than Cooper pair radius. 1. My team will create a new bosonic phase of matter which spontaneously becomes incoherent - a time liquid - by melting a quantum time crystal. The melting process is initiated by increasing the particle density. Mapping the phase diagram of the "time phases" in the superfluid vacuum will cement this new field of study. This project is backed by leading technical, experimental and theoretical collaborators in the Host Institution and internationally. Discoveries delivered by this fellowship will lead new fields of research with academic and technological implications spanning from two-dimensional physics of bound fermions to magnon-based room temperature quantum devices.

Heat engines are the motors of our industrialised society. By converting thermal energy into mechanical work, they set cars, airplanes and ships in motion and drive the generators that deliver electricity to our computers and smartphones. None of these modern applications would be possible without one fundamental theory that emerged 200 years ago and has ever since enabled engineers to develop more and more powerful and efficient machines: thermodynamics. Equipped with only a few elementary concepts and laws, this theory lays down the basic rules that govern the performance of James Watt's 18th century steam engine and today's car engines alike. During the past two decades, a new era has begun, in which scientists are exploring miniaturisation as a novel design principle for thermal engines. In a series of landmark experiments, smaller and smaller engines have been built and successfully operated. In 2016, this fascinating development led to the realisation of a functional heat engine with only one atom. Objects this tiny are no longer bound by the mechanical rules of our classical world; they can occupy two places at the same time, tunnel through barriers or influence each other at a distance without direct interaction. These counterintuitive phenomena are manifestations of the quantum laws of motion that govern the world at atomic scales. Heat engines operating in this realm can be equipped with features that no classical engineer could have imagined. The scientific discipline that describes this new type of machine and tries to harness their technological potential is still in its infancy and has been dubbed quantum thermodynamics. Although likely able to overcome classical performance limits, quantum engines are still far from practical applications, not least due to their minuscule energy output; to move a car, one would need roughly as many single-atom engines as there are molecules in one liter of water. This number is absurdly large, mainly because it compares objects at radically different scales. Still, it is clear that, even to be useful for technologies on their own scale, quantum engines need to grow. But how can their size be increased when smallness is precisely the property that makes them quantum? Quantum mechanics provides a solution to this dilemma: collective behaviour. Due to a strange interaction without a classical counterpart, objects like atoms can act in a coordinated way, like birds in a flock. This remarkable phenomenon has fascinated scientist for decades. Here, we propose to utilise it for the next generation of quantum machines. Imagine an engine working with a collective quantum gas containing millions of atoms instead of just one. Such a device could benefit from quantum effects while still producing significant power output. Moreover, the pistons of this engine could be perfectly synchronized with all the atoms they move around. Thus, an enormous level of control could be achieved, which would be impossible to realise with an ordinary gas, whose atoms follow unpredictable trajectories. Such unique features make collective quantum machines a fascinating yet unexplored subject of quantum engineering. Laying down the conceptual foundations for the design and implementation of this new type of device is the major goal of this project. The theory we will develop at the University of Nottingham will be the counterpart of thermodynamics in the world of collective quantum phenomena: collective quantum thermodynamics. Quantum technologies are widely expected to shape our century in a similar way as the industrial revolution changed 19th and 20th century. Collective quantum machines have the potential to become the steam engines of this development. They will not move our future cars, but they might well provide the power for our quantum computers and encryption devices.

Recent progress in quantum technologies is underpinning significant advances across many sectors including defence, healthcare, and communication. At the same time, several challenges emerge as scientists strive to manipulate quantum states for signal enhancement, noise reduction, and ultimately quantum computing. A paradigmatic example is the recent demonstration of noise mitigation on a 127-qubit chip, but this has highlighted the limitations of coherence time, gate fidelity, and error suppression, as well as the challenge of connecting large numbers of physically separate qubits. Therefore, whilst improvements on established technologies remain crucial for scaling them up, the search for alternative routes towards quantum computing remains a most promising pathway towards useful quantum supremacy. Quantum Information with Mechanical Systems (QuIMS) explores the potential of mechanical resonators as a novel computing platform, both in support of existing qubit technologies (e.g., for quantum memories) and as a stand-alone qubit technology. To this end, we will build mechanical resonators with ultra-high coherence times that are manipulated with extreme precision by means of light fields. In this opto-mechanical system, we will attempt for the first time to embed several qubits in a single mechanical resonator, removing the need for cumbersome connecting wires that impedes, for instance, spin qubit devices. These mechanical qubits are expected to offer exciting opportunities to implement multi-qubit gates directly on a single resonator, which can greatly suppress the main sources of errors encountered in current platforms. The core novelty on which QuIMS leverages is the quadratic opto-mechanical coupling, which is needed for mechanical quantum computing but has so far been out of reach. We will design new devices that exploit symmetry and phononic crystals to suppress detrimental contributions such as heating of the mechanical resonators. We will work with graphene and carbon nanotubes that are uniquely suited to achieve the quadratic regime owing to their extremely low mass and strong interaction with radio-frequency light. The synergy of our complementary state-of-the-art facilities and of experimental and theoretical expertise at the Universities of Exeter and Lancaster are ideally suited to nurture the ambitious aims of this proposal. Upon demonstrating the quadratic opto-mechanical interaction, in collaboration with project partners including the National Quantum Computing Centre, we will explore the potential of our devices for applications such as signal enhancement, noise reduction, mechanical signal processing, filtering, and transduction. Hence, we will benchmark the performance of our opto-mechanical quantum systems against that of other known platforms such as superconducting, photonic, Rydberg and ion devices. Finally, we will investigate how our platforms can be combined with existing technologies, to be employed, e.g., as highly coherent memories (due to the extreme quality factors attainable by mechanical resonators).

FITNESS is a Doctoral Network at the intersection of electric power distribution networks optimization, electricity markets, communications, and control systems. The project will develop new methodologies for active distribution networks services in the era of smart grids. FITNESS is the first training network dedicated to this challenge and involves 5 Beneficiaries and 5 Associated Partners from 7 EU countries, guaranteeing a pan-European approach in a multi-sectoral context (universities, research centres, and SMEs). FITNESS will train a new generation of scientific professionals who can transition between disciplines and between the public and private sectors based on (i) Recruited Researcher (RR) projects; (ii) courses and workshops, with the emphasis on hands-on, collaborative learning and attention to transferable skills; (iii) mobility, knowledge transfer, all within a training network that includes some of Europe's finest researchers.