09:00-09:30
Quantum many-body physics with arrays of single Rydberg atoms
Dr Thierry Lahaye, Institut d’Optique, CNRS, France
Abstract
This talk will present recent progress in the use of arrays of single atoms held in optical tweezers, and interacting strongly with each other when excited to Rydberg states. This platform provides an almost arbitrary control over the geometry of single-atom assemblies in 1, 2 and 3 dimensions, with up to about 100 atoms, and is ideal to realise quantum spin models with various types of interactions, such as the Ising or the XY models.
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Dr Thierry Lahaye, Institut d’Optique, CNRS, France
Dr Thierry Lahaye, Institut d’Optique, CNRS, France
Thierry Lahaye studied Physics at Ecole Normale Superieure in Paris. He then did his PhD at Laboratoire Kastler Brossel, under the supervision of Jean Dalibard, working on the evaporative cooling of a magnetically guided atomic beam. In 2006 he joined Tilman Pfau’s group in Stuttgart, Germany, as a post-doctoral researcher, and there he studied dipolar quantum gases of Chromium atoms. He was hired by CNRS as a researcher in 2008, and since 2012 he has been working at Institut d’Optique in Palaiseau, France, in the group led by Antoine Browaeys, on quantum simulation experiments using arrays of individual Rydberg atoms.
09:45-10:15
Quantum dots for quantum simulations
Dr Ruth Oulton, University of Bristol, UK
Abstract
Quantum dots, quantum emitters in a semiconductor matrix, are most often proposed as a bright and efficient source of single photons for many quantum technologies. And, as Professor Ruth Oulton has demonstrated previously, a near-perfect single photon source goes hand-in-hand with potentially deterministic interactions with input photons. However, it is the spin degree of freedom in their ground state which gives them the greatest scope for quantum simulations. Photons input into a QD device can be entangled with the long coherence time spin system, and protocols to produce entangle chains of photons (1D cluster states) have already been demonstrated. Professor Oulton will discuss how one may entangle very long coherence time photons with the spin. Reflecting the long photon from a quantum dot spin precessing in a magnetic field results in a phase modulation of the photon wave function in time, with periodic entanglement resulting. Professor Oulton will discuss the potential of spin-photon entangled states as building blocks for analogue and digital quantum simulations.
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Dr Ruth Oulton, University of Bristol, UK
Dr Ruth Oulton, University of Bristol, UK
Ruth Oulton’s field of research involves the study of nanoscale semiconductor devices that enable the exchange of “quantum” information between a single electron and a single photon. The idea is that they can use the rules of quantum mechanics to perform computing and measurements in a completely new way. She take ideas from quantum theory and information science, bring them together with what we are beginning to understand about semiconductors on the nanoscale, and to make working quantum devices that engineers will use as part of their everyday toolkit. In her recent work she studies single electron spins in atomic-like systems, and studies how the angular momentum of the photon and spin exchange information, and how photonic design can influence this. In other interdisciplinary side projects she studies the role of photonic structures in plants such as seaweed and begonias.
11:00-11:30
Quantum annealing with superconducting flux qubits
Professor Paul Warburton, University College London, UK
Abstract
Quantum annealing makes less stringent demands on qubit coherence than gate-based approaches, thereby enabling proof-of-principle demonstrations of annealers with around 2000 superconducting flux qubits. Furthermore by capacitively shunting the flux qubit and reducing the circulating current one can achieve both high coherence and low leakage, making the flux qubit an excellent approximation to a two-level quantum system. Nevertheless most measurements on experimental annealers are plagued by noise, and the role of coherence in quantum annealing is not currently understood. Professor Paul Warburton will describe his group’s experimental and analytical work on both understanding coherence in flux qubit annealers and how to optimise their use for real-world applications in the presence of noise. They have used the Schrieffer-Wolf transformation to extract the Pauli coefficients from quantum circuit models and developed this technique to investigate non-stoquastic Hamiltonians arising from simultaneous inductive and capacitive qubit interactions. They have analysed the extent to which Landau-Zener-Stückelberg oscillations can be used as a coherence metric in the context of quantum annealing. The group has also developed a new method for embedding real-world problems with high qubit connectivity onto hardware graphs of limited degree and show experimentally that this method outperforms rival embedding techniques for annealers in the presence of noise. The research is based upon work supported by EPSRC (grant reference EP/R020159/1) and the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA), via the US Army Research Office contract W911NF-17-C-0050. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the ODNI, IARPA, or the US Government.
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Professor Paul Warburton, University College London, UK
Professor Paul Warburton, University College London, UK
Paul Warburton is Professor of Nanoelectronics at the London Centre for Nanotechnology and the Department of Electronic and Electrical Engineering at University College London. He is interested in both experimental implementations and applications of quantum annealing using superconducting devices. He is involved in designing novel Hamiltonians which reveal the underlying quantumness of small systems of annealed qubits and/or which can be exploited for applications. His group gave the first demonstration of maximum-entropy inference using an experimental quantum annealer, confirming that information can be extracted from the excited states. He is part of the US-government-funded collaboration 'Quantum Enhanced Optimization'.
11:45-12:15
Energy-landscape shaping for quantum simulation with cold atoms and in semiconductors
Dr Sophie Shermer, Swansea University, UK
Abstract
Energy landscape shaping is a way to alter the natural evolution of a quantum system to achieve certain objectives utilising the continuous evolution of the system instead of applying discrete quantum gates and dynamic control. Using spin networks as an abstract model system Dr Sophie Shermer will discuss how to design energy landscapes to control information flow between nodes in various networks. Energy landscape design will be formulated as an optimal control problem and in terms of linear feedback control systems. Various solutions to the optimal control problems arising will be examined in terms of robustness. Robustness of the evolution with regard to uncertainty in system parameters, initial conditions and environmental effects such as decoherence is crucial, and the development of better tools inspired by classical engineering is essential for robust quantum technology. Dr Shermer will discuss classical engineering approaches to robustness and the challenges in applying them to quantum systems, as well as some promising results suggesting that classical limits on robustness need not apply to the latter. Possible implementations of energy landscape control using cold atoms trapped in optical lattices as experimental testbeds for pseudo-spin networks will also be considered.
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Dr Sophie Shermer, Swansea University, UK
Dr Sophie Shermer, Swansea University, UK
Sophie Shermer is an Associate Professor of Physics at Swansea University, UK. She previously held positions as a Cambridge-MIT (CMI) Research Fellow and Advanced Research Fellow of the UK Engineering and Physical Sciences Research Council (EPSRC) at the University of Cambridge, as a Marie Curie Visiting Professor at Kuopio University, Finland, as well as positions at the Open University and the University of Oregon. Sophie’s research interests range from nano-science at the quantum edge and quantum engineering, especially the design, modelling and characterisation of quantum devices and new paradigms for optimal and robust control, to medical physics and imaging.