Invited Speakers

Harnessing optical interfaces to spins in molecules 

Optically addressable spins are a promising platform for quantum technologies due to their ability to be readily prepared, coherently controlled, and read out—exemplified by remarkable demonstrations with solid-state defects. Molecular materials are also attractive for hosting optical-spin interfaces as chemical techniques can be used to tailor their properties and integrate them with other systems. Such properties could be beneficial for quantum sensing where, for example, precise spatial control between sensor and target is desired. In this talk, I will outline molecular spin systems which can be optically initialised, coherently controlled with microwaves, and optically read out, and how these systems offer promise as chemically synthesised quantum sensors. 

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A single electronic spin in a nuclear-spin full environment with room-temperature spin coherence

Colour centres in two-dimensional hexagonal boron nitride (hBN) are a promising 2D spin-photon interface candidate, offering the advantage of room-temperature single-photon emission combined with integration into scalable and compact hardware. Via optical and microwave spectroscopy at room temperature, we investigate the ground-state spin Hamiltonian of individual emitters related to carbon clusters in hBN. We identify a spin-triplet electronic ground state with zero-field coherences that survive up to microseconds at room temperature, and unravel how the symmetry of the spin-Hamiltonian protects the electronic-spin from decoherence processes in the near-zero-field regime. Our results place these defects in hBN as a unique platform for quantum technologies, enabling room-temperature and zero-field operation in a versatile host material.

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State engineering of a mesoscopic spin system (in a quantum dot)

Controllable quantum many-body systems are platforms for fundamental investigations into the nature of entanglement and promise to deliver computational speed-up for a broad class of algorithms and simulations. In particular, engineering entanglement within a dense spin ensemble can turn it into a robust quantum memory or a computational platform. Recent experimental progress in dense central spin systems, particularly semiconductor quantum dots, motivates the design of control protocols that use a central-spin qubit as a convenient proxy to engineer both classical and quantum resource states of a mesoscopic spin system. In this talk, I will give a brief introduction to the relevant physics and cover some of the successes and challenges that lie ahead.

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From small to large exciton-polaritons: the road towards the single-particle nonlinearity

Exciton-polaritons within semiconductor microcavities have emerged as versatile interfaces bridging the realms of light and matter, catalyzing remarkable advancements in both fundamental science and technology. These developments span from the observation of high-temperature Bose-Einstein condensation and the exploration of topological states to prospective applications encompassing photonic simulators and devices. In experiments, exciton-exciton interactions have been harnessed to unveil optical nonlinearities and unveil non-classical effects under intense illumination. However, the current frontier lies in realizing strong and controllable interactions in the single particle limit, which represents a crucial step towards quantum applications. High-lying excitonic Rydberg states hold the potential for such interactions, with cuprous oxide (Cu2O) standing out as a well-suited material boasting giant Rydberg excitons of ~1 μm diameter, resulting in strong blockade effects. Nonetheless, harnessing these interactions for practical applications remains challenging due to the relatively weak coupling between light and matter in this particular material. In this presentation, I will highlight recent advancements in the coupling of Rydberg excitons with light, offering insights into the ongoing efforts to unlock their potential.

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Atoms as material simulators: a brief introduction 

Quantum systems based on cold and ultracold atoms offer a unique playground for the study of interesting quantum phenomena due to their diversity and controllability. Placing these atoms in the periodic lattice potentials offered by sets of interfering laser beams allows for the study of statics, dynamics, and phase transitions so-called quantum simulators that can mimic, among other things, material systems. The advent of quantum gas microscopes capable of measuring the atoms’ positions in these lattices to within a single lattice site has opened the playground of possible studies even wider. 

This tutorial cannot cover the wide range of experiments done around the world using these incredible systems. My goal is, rather, to teach you what you need to know to understand the research done in the field. That is, I will briefly cover how one cools and traps atoms in light fields before describing the basics of quantum gas microscopy, as well as some of the limitations and challenges of microscopy-based quantum simulators. The last bit of the tutorial will comprise a whirlwind overview of some of the recent work being done on the study of systems relevant to quantum materials, giving the interested reader the foundation needed to learn more and some relevant literature with which to start. 

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Understanding the impact of phonon processes in solid-state quantum emitters

Quantum emitters (QEs) in condensed matter systems naturally interact strongly with phonon modes of their host material. This degrades quantum effects that are crucial for quantum technology applications, including photon indistinguishability and the coherence between electronic states. It is therefore important to accurately describe the impact of electron-phonon interactions on both dynamical and optical properties of a QE if we are to assess their viability as scalable quantum technologies. In this talk I will outline how methods from open quantum systems theory can be applied to model the impact of phonon processes in QEs. In particular, I will discuss how electron-phonon interactions are modified in the presence of photonic structures and strong light-matter coupling. These methods will be considered in the context of two exemplary QEs: semiconductor quantum dots and defects in 2D materials.

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Spin centres in SiC for quantum networking

In this talk, I will describe the opportunities of spin-photon interfaces associated to quantum emitters in SiC towards the development of quantum networking devices. SiC is a material widely used in power electronics applications, with high-purity wafers up to 200mm commercially available,  and established doping and micro-device fabrication recipes. It additionally features excellent optical and spintronic properties. I will also briefly describe our current work in investigating the application of telecom-wavelength single vanadium centres with ultra-narrow inhomogeneous broadening, and in developing SiC photonic devices. Finally, I will briefly outline the future challenges we need to tackle in creating novel quantum devices integrating electronics, photonics and spintronics functionalities on a single SiC chip.

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Room-temperature masers: from the laboratory to the field

Masers – the microwave analogue of lasers – can be operated as amplifiers and oscillators with quantum-limited noise performance. While conventional masers require high vacuums and cryogenic temperatures to operate, recent demonstrations of masers capable of operating in ambient conditions using pentacene-doped para-terphenyl and later nitrogen-vacancy centres in diamond have sparked renewed interest in the use of masers for quantum sensing.

In this talk, I will outline the basic physics of room-temperature maser devices and identify criteria for promising maser gain medium materials. I will conclude by discussing how optimised maser materials will allow the next generation of room-temperature masers to break out of the lab to address challenges in the real world.

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Strategies and challenges for integrated photonic quantum memories using rare earth doped crystals

The coherent interaction between photons and atoms lays the bases of quantum information science. It is crucial, for example, for the realisation of quantum memories for quantum communication and computing. The first proof of principle demonstrations were carried out in ensembles of atomic gases, but solid-state systems have emerged as a promising alternative, unleashing prospects for integration. The implementation of quantum memory protocols in waveguide has the potential of opening further avenues towards scalable quantum information protocols using complex quantum photonic circuits on chip. In this contribution, I will present strategies to develop integrated quantum devices using rare earth doped crystals, which offer very promising properties for quantum light generation and storage. I will report on the demonstration of a novel platform for quantum light storage based on laser written waveguides in a new writing regime that enables improved confining capabilities compared to previous demonstrations, compatibility with fibre cords and 3D capability, and opens the way for multiplexing in several degrees of freedom.

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