Research projects

Research projects for October 2019 can be found below.

Dr Sam Vinko

Data-driven Discovery Science of Matter in Extreme Conditions, January 2019 start

Fully funded by The Royal Society & EPSRC (UK student)
Starting: January 2019, 3.5 years duration

Applications are invited for a 3.5-year fully-funded PhD studentship in the Physics Department of the University of Oxford.

The project will be in the field of high-energy-density physics (HEDP), and will focus on applying techniques from data science and machine learning to the design and interpretation of experimental results from large-scale plasma physics experiments. In particular, the work will focus on experiments fielded on x-ray free-electron lasers (XFELs: https://lcls.slac.stanford.edu, https://www.xfel.eu) and on the National Ignition Facility (NIF: https://lasers.llnl.gov).

Large-scale experiments in HEDP relevant to inertial confident fusion and astrophysical research rely on complex, computationally-intensive modelling in high-dimensionality parameter spaces to interpret experimental results. These spaces are often too large to be investigated comprehensively, making the modelling subject to a host of inverse problem instabilities, which in turn lead to difficulties and uncertainty in the interpretation of data. In this project we will design and investigate x-ray scattering and spectroscopy experiments using novel machine learning techniques from data science with the aim of maximising the knowledge that can be extracted from large-scale experimental efforts. Experiments at the Linac Coherent Light Source XFEL and at the NIF will form a key part of this project bridging plasma physics and computer science, and the candidate will have ample opportunities to engage in a range of experimental, theoretical and computational work.

This project will be conducted in collaboration with several partners from the EU and the US. The successful student will be required to travel to Germany and California, and will have the opportunity to spend a significant portion of their time at partner institutions.

Eligibility: A full funding package (including all College and University fees, a monthly stipend, and travel and research funds) is available to UK students. Non-UK students interested in applying should contact Dr Vinko for further information (see below). Candidates will be expected to have obtained (or expect to obtain) a first class degree in Physics, Engineering, Computer Science or related discipline. Applicants should have an interest and solid background in plasma physics, programming and high performance computing. Experience in machine learning will be an advantage. Applications will be considered until the position is filled.

Enquiries and requests for additional information for this position should be made to Dr Sam Vinko (sam.vinko@physics.ox.ac.uk).

Email
sam.vinko@physics.ox.ac.uk

Dr Robert Smith

Single Impurity in a dipolar Bose-Einstein Condensate

A single impurity interacting with a quantum bath is a simple (to state) yet rich many-body paradigm that is relevant across a wide sweep of fields from condensed matter physics to quantum information theory to particle physics. The aim of this project is to create a highly controllable setting in which to study this physics. This starting point for this project will be our existing Erbium cold-atom machine. The special feature of Erbium atoms is their large magnetic dipole moments which result in long-range and anisotropic dipole-dipole interactions in addition to the short-range contact interactions more normally seen in cold atom systems. This project will involve adding a second atomic species to the experiment and using the resulting system to study a range of topics from polaron physics to information flow in open quantum systems.

For more details please contact Dr Smith:

Email
robert.smith@physics.ox.ac.uk

Professor Alexander Lvovsky

Machine learning with optical quantum tools and their simulators.

Machine learning has made enormous progress during recent years, entering almost all spheres of technology, economy and our everyday life. Machines perform comparably to, or even surpass humans in playing board and computer games, driving cars, recognizing images, reading and comprehension. It is probably fair to say that a modern machine will perform better than a human in any environment it has complete knowledge of. These developments however impose growing demand on our computing capabilities, including both the size of neural networks and the processing rate. This is particularly concerning in view of the decline of Moore’s law.

It is widely believed that quantum computers will be helpful in addressing this challenge. While fault-tolerant quantum computing is a matter of the future, modern “quantum annealers” – devices capable of finding the ground states of Ising-type Hamiltonians, show significant promise in this context. One of the most promising approaches to annealing is the optical one, involving squeezing combined with quadrature measurements and classical electronic processing. The vision of the research is to develop optical annealers further and apply them to train neural networks. This includes:
- Simulating the optical annealer on a classical computer and using it for practical machine learning and many-body physics;
- Developing experimentally a conceptually new version of the optical annealer with a significantly higher computational speed

For more details please contact Professor Lvovsky:

Email
alex.lvovsky@physics.ox.ac.uk

Dr Patrick Baird

DPhil Research Opportunity on Ultra-High-Q Microresonators for Optical Frequency Comb Generation

Ultra-High-Q microresonators are extremely powerful devices that allow confining enormous amounts of light into tiny micron-scale mode volumes. This enables the observation of nonlinear optical effects at low threshold powers, making microresonators ideal components for future integrated photonic circuits and for the next generation of optical computing.

A key application that utilizes nonlinear optics in microresonators is the generation of optical frequency combs. Optical frequency combs have been first developed 15 years ago and have become ubiquitous tools for spectroscopy, precision metrology and optical clocks. In 2005 optical frequency combs have been awarded with the Nobel Prize in Physics. Microresonators have recently shown to be promising candidates for shrinking optical frequency comb generators into chip-based devices for out-of-the-lab use [1]. However, the underlying physics of optical comb generation in microresonators is far from being fully understood and fundamentally different from conventional mode-locked laser comb generators [2].

There is opportunity for an Oxford D.Phil student to join a recently established research team at the National Physical Laboratory (NPL) to work on microresonator-based frequency comb generation. At present there are several research projects available both on the applied side of frequency comb generation in microresonators as well as on the fundamental research side with the goal of understanding the physics of the underlying comb generation process.

NPL provides an ideal environment for research on optical frequency combs with an existing infrastructure of optical atomic clocks and conventional frequency combs that can be used for future experiments.

[1] Del'Haye et.al, Optical frequency comb generation from a monolithic microresonator
Nature 450, 1214-1217 (2007)
[2] Kippenberg, Holzwarth, Diddams, Microresonator-Based Optical Frequency Combs
Science 332, 555-559, (2011)

For further information please contact either Dr Patrick Baird or Dr Pascal Del'Haye. There is funding for a least one studentship on this project.

Email
p.baird1@physics.ox.ac.uk
pascal.delhaye@npl.co.uk

Professor Paolo Radaelli & Professor Andrea Cavalleri

Breaking symmetry with light: ultra-fast ferroelectricity and magnetism from non-linear phononics

A collaboration between Prof. Paolo G. Radaelli and Prof. Andrea Cavalleri, who holds a joint appointment between
the Clarendon Laboratory and the Max Planck Institute for the Structure and Dynamics of Matter, (Hamburg).

Radaelli Cavalleri non linear graphic_0.png

Figure 1: schematic representation of non-linear photo-ferroicity. THz or far-IR ‘pump’ photons excite an IR-active mode (right), which is coherently coupled with a Raman mode (left). The rectified component of the Raman mode transiently generates ferromagnetism or ferroelectricity, which is probed coherently with a near-IR or visible light beam (top left).

The use of light to control the structural, electronic and magnetic properties of solids is emerging as one of the most exciting areas of condensed matter physics. One promising field of research, known as femto-magnetism, has developed from the early demonstration that magnetic ‘bits’ in certain materials can be ‘written’ at ultra-fast speeds with light in the visible or IR range [1]. More radically, it has been shown that fundamental materials properties such as superconductivity can be ‘switched on’ transiently under intense illumination [2]. Recently, the possibilities of manipulating materials by light have been greatly expanded by the demonstration of mode-selective optical control, whereby pumping a single infrared-active phonon mode results in a structural/electronic distortion along the coordinates of a second, anharmonically coupled Raman mode – a mechanism that was termed ‘nonlinear phononics’. Crucially, the Raman distortion is partially rectified, meaning that it oscillates around a different equilibrium position than in the absence of illumination. Very recently, it was realised that, under appropriate conditions, the rectified Raman distortion can transiently break the structural and/or magnetic symmetry of the crystal. Such symmetry breaking persist for a time corresponding to the carrier envelope of the pump, which can be less than a picosecond, and can give rise to the ultra-fast emergence of ferroic properties such as ferromagnetism and ferroelectricity. Through symmetry analysis and first-principle calculations, we have identified several promising ‘photo-ferroic’ materials that should display these effects, with potential applications in ultra-low-power information storage, ultra-fast electronics and many more.

This DPhil project will give the successful candidate the opportunity to pioneer this new field of research. Initial experiments on the candidate ‘photo-ferroic’ materials that we have already identified will be performed at the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, Germany. As a mode-selective pump, we will employ coherent laser radiation in the THz or far-IR range with sub-ps carrier envelopes, while the transient emergence of the ferroic properties will be probed with second-harmonic generation (SHG) and/or Faraday rotation of near-infra-red light. Later on in the project, changes in the crystal and magnetic structures of the materials will be probed with X-rays at free electron laser sources such as the European XFEL in Hamburg. Meanwhile, the candidate will develop search strategies for new classes of ‘photo-ferroic’ materials, based on symmetry and density functional theory calculations. He/she will develop the materials specifications in collaborations with crystal growers in Oxford and elsewhere, and will be involved hands on in all aspects of the design and realisation of the experiments and the data analysis.

The experimental part of this project will be predominantly based in Hamburg, so it is essential for the candidate to be willing and able to be based in Germany for extended periods during the DPhil.

[1] Femtomagnetism: Magnetism in step with light. Uwe Bovensiepen, Nature Physics 5, 461 - 463 (2009) abstract pdf
[2] See for example M. Mitrano,et al., ‘Possible light-induced superconductivity in K3C60 at high temperature’, Nature, 530, 461–464 (2016). [more at this link].
[3] Nonlinear phononics as an ultrafast route to lattice control, M. Först et. al., Nature Physics, 7, 854–856 (2011).

Professor Christopher Foot

1. Laser-cooled ion optical clocks for fundamental physics and redefinition of the second

Location: NPL Teddington and University of Oxford

This is an experimental project, working with one of the UK’s best atomic clocks at the National Physical Laboratory (NPL), based on measuring the frequency of an optical transition between two internal energy levels within ions confined in an rf trap. The aim is to develop optical clocks that can achieve fractional frequency uncertainties as low as 1 part in 1018 (approximately two orders of magnitude better than the current caesium microwave primary standards) as a precursor to an optical redefinition of the second. However, it must be shown that the frequencies derived from such optical clocks in different institutions (and countries) all agree, by means of comparison of these clocks in real time with others across Europe via optical fibre links, and across the globe via the Atomic Clock Ensemble in Space. These comparisons must be carried out at the highest levels of accuracy, with individual optical clocks operating close to their limits.

Techniques

Experimental techniques will involve quantum state manipulation of trapped single ions or linear strings of ions, which are laser-cooled close to the motional quantum ground state in the trap. Interrogation of a “forbidden” optical clock transition is by means of an ultra-stable laser. Critical to clock performance is the evaluation of frequency shifts due to perturbations of the clock ion(s) associated with interactions within their environment. Optical frequencies will be compared between different clocks both locally and internationally.

Impact

Atomic clocks and frequency standards have become an important resource for emerging quantum technologies. In addition to the role in providing the future SI second, the ability to measure optical frequencies with accuracies at the few parts in 1018 opens up possibilities to test fundamental physics at unprecedented levels. Measurements with the NPL ytterbium ion optical clock over the last few years have revealed new constraints on levels of violation of the Einstein Equivalence Principle by means of time-variation of fundamental constants. Optical atomic clock frequency sensitivities at these levels also point to applications in “relativistic geodesy”, where ultra-precise clocks sense the general relativistic gravitational redshift (with application to oil and mineral exploration, and climate research), and in future space science and satellite navigation and synchronisation of high speed communication networks.

Eligibility

This studentship is an EPSRC ICASE award, intended for Home and EU students.

Applicants should have a first or upper second class UK honours degree or equivalent in physics or engineering.

For more information, please contact:

Rachel Godun at NPL (rachel.godun@npl.co.uk) OR Christopher Foot at the University of Oxford (christopher.foot@physics.ox.ac.uk).

2. Development of cold-atom sources for quantum technologies

This project is suitable for those with an interest in developing new apparatus that will be applied to practical devices. We have developed a compact source of cold rubidium atoms based on a novel (patented) design of magneto-optical trap and we are collaborating with a laser company based in Scotland (M Squared Lasers) to commercialise this work. In this project we will develop a compact source of laser-cooled strontium atoms working with that company and other interested parties. Strontium requires a considerably different approach to that used for rubidium and developing the experimental methods into a robust and reliable system is the primary task.

We anticipate that there will be considerable demand for sources of cold strontium since they are necessary for clocks that use atoms in optical lattices (strontium clocks are currently the world-leading technology), matter-wave interferometers (for which one of the strontium isotopes is very suitable), as well as more fundamental research work on ultracold molecules and quantum gases. In summary, strontium has considerable advantages for quantum technology but it is not (yet) used so widely as rubidium because it requires more complicated apparatus. The technical issues will be addressed in this project and the cold-atom source will be demonstrated by building a matter-wave interferometer. Collaborations with other research teams to demonstrate other applications are likely.

It is expected that this project will be fully supported by a studentship for 4 years. Further information is available from Professor Foot.

Email
c.foot1@physics.ox.ac.uk

3. Experiments with ultracold atoms and Bose-Einstein condensates

Professor Foot’s research group investigate the fascinating properties on ultracold quantum gases at temperatures of a few tens of nanokelvin. The samples are produced using laser light to cool atoms from room temperature and then confining them in a magnetic trap where evaporation leads to further cooling. These processes increase the phase-space density by many orders of magnitude to reach quantum degeneracy (Bose-Einstein condensate for atoms with integer spin). The research group in Oxford has pioneered new methods of trapping ultracold atoms using a combination of radiofrequency and static magnetic fields that enables the investigation of the properties of 2D quantum systems. We are setting up experiments to work with multiple atoms species, e.g. two isotopes of Rb, or Rb and K atoms, in which atoms of one species act as ‘quantum probes’ of the surrounding gas. This will enable us to read out the quantum information from these systems and investigate new aspects of quantum thermodynamics and statistical physics. This work on understanding the fundamental quantum physics of many-body system has important implications for quantum devices and technology based on them. We also plan to carry out experiments on the transport properties in 1D quantum systems. Experiments with cold atoms allow single particles to be imaged and their properties measured thus providing deep insights that are complementary to work on quantum matter in Condensed Matter.

Email
c.foot1@physics.ox.ac.uk

Professor Gianluca Gregori

High Energy Density Laboratory Astrophysics - Scaling the Cosmos to the Laboratory

We are looking for DPhil experimental/theoretical positions to study and simulate in the laboratory extreme astrophysical conditions. The research is focussed on the following themes:

1. Investigation of the equation of state of ultra dense matter as the one occurring in the core of giant planets (such as Jupiter and many exoplanets). The experimental work involves using high power laser facilities to compress the matter to densities above solid and then applying x-ray techniques to probe its microscopic state. Interested students can also focus their work onto theoretical topics involving strongly coupled and partially degenerate plasmas - which are particularly relevant for describing white dwarf structure.

2. The understanding of the generation and amplification of magnetic fields in the Universe. We are particularly interested at the role of turbulence (and dynamo) in producing the present day values of magnetic fields in cluster of galaxies. Experiments on large laser facilities are planned in order to simulate in the laboratory intra-cluster turbulence and measure the resultant magnetic field generation and amplification by dynamo.

3. Quantum gravity with high power lasers. The idea is to use high intensity lasers to drive electrons to very high accelerations and then observe effects connected to the Unhruh-Hawking radiation. The ideal candidate is expected to work in defining the required experimental parameters and the proposal for a future experiment.
Our group has access to several laser facilities (including the National Ignition Facility, the largest laser system in the world). Students will also have access to a laser laboratory on campus (currently hosting the largest laser system in the department), where initial experiments can be fielded. Further details can be found by browsing our research web-page http://www.physics.ox.ac.uk/users/gregorig/

Prospective candidates are encouraged to contact Prof Gregori for further information.

Email
g.gregori1@physics.ox.ac.uk

Professor Simon Hooker

Plasma accelerators

In a laser wakefield accelerator an intense laser pulse propagating through a plasma excites a trailing plasma wave via the action of the ponderomotive force, which acts to expel electrons from the region of the laser pulse. The longitudinal electric field in this plasma wakefield can be as high as 100 GV / m, more than three orders of magnitude larger than that found in conventional RF accelerators such as those used at CERN. Particles injected into the correct phase of the plasma wave can therefore be accelerated to energies of order 1 GeV in only a few tens of millimetres.

Theoretical and experimental work on plasma accelerators in Oxford is undertaken by a collaboration of research groups in the sub-departments of Particle Physics and Atomic & Laser Physics.

Please note that applications to work in this area should be made to the sub-department of Particle Physics, as explained at https://lpax.web.ox.ac.uk/opportunities-graduate-research ; this page also gives further information on DPhil projects which are available in this area.

Further details from Prof Simon Hooker.

Email
s.hooker1@physics.ox.ac.uk

Dr Axel Kuhn

1. Hybrid quantum processing with atoms & photons in photonic networks

This project is aiming at the combination of integrated optics with single photons from strongly coupled atom-cavity systems. Besides demonstrating linear-optical quantum gates, multi-mode interferometers and photonic quantum walks, the idea of this new project is to investigate the usefulness of time-bin encoding within photons and to exploit atom-photon entanglement in the photon-emission process. The challenge will be to combine our existing single-photon emitters and the superconductive nanowire single- photon detectors with silica-on-silicon photonic chips carrying the LOQC networks. For doing so, a photonic switchyard consisting of electro-optic devices and fibre delay lines will be used to route the photons into the desired channels with the correct timing. Photon-photon correlation experiments are then going to be used to verify and demonstrate quantum supremacy of the networks under investigation. Furthermore we plan to investigate the feasibility of applying these photonic processing schemes in nano-scale light-matter interaction using plasmon-atom coupled system and near field nano-optics in collaboration with our project partners at the Université de Bourgogne.

2. Quantum entanglement of trapped neutral atoms

We propose two schemes for entangling remote atoms. In a probabilistic scheme, two distant atoms emit photons into high-finesse cavities that are eventually combined at a beamsplitter. Photon detections in different outputs then project the atoms into an entangled state. In a deterministic scheme, an atom emits a single cavity photon, which is reabsorbed by a second atom in a distant cavity. In doing so, the state of the first atom is entangled with that of the second. In both schemes, a high- finesse cavity is used to enhance the light-atom interactions. Currently, we have two optical cavity experiments with random atom loading. The first phase of the project will be to build a trap that permanently holds single atoms in the cavities. The second phase will be to generate and quantify the entanglement between two remote atoms using full Bell-state tomography. This project is based on three key technologies that we recently explored in our group, namely the trapping and manipulation of individual atoms in optical tweezers, high-finesse fibre-tip optical cavities and the quantum-controlled single-photon emission from coupled atom-cavity systems. Furthermore we plan to investigate how to apply this scheme to trapped ions with our project partner at the University of Sussex.

Person specification: These are highly challenging experimental projects which will push the limits of laser and optical technology. They would suit students with experience in atomic and laser physics and a keen interest in exploring quantum phenomena experimentally.

Please also see a global advert - see http://admin.euraxess.org/jobs/268354

Our research team at the University of Oxford offers positions for two doctoral students for a period of up to three years with an attractive salary. Both PhD projects are funded by a European Union Innovative Training Network (ITN). The aim of such ITNs is to provide structured, high quality, doctoral-level training in an academic collaborative network with strong involvement of industrial partners. Besides working on internationally competitive research projects in our laboratories, the successful applicants will attend ITN schools and workshops, have access to a professional skills training and development programme, and receive further scientific training at academic and industry partners in the network. The projects are embedded in the MSCA ITN “Light-Matter Interfaces for Quantum Enhanced Technology” (LIMQUET).

Given that the positions are funded by the European Commission on a H2020-MSCA-ITN, eligibility restrictions apply:
• Experience: Early-Stage Researchers (ESRs) shall, at the time of recruitment by the host organisation, be in the first four years (full-time equivalent research experience) of their research careers and not yet have been awarded a doctoral degree. Full-time equivalent research experience is measured from the date when a researcher obtained the degree which would formally entitle him or her to embark on a doctorate, either in the country in which the degree was obtained or in the country in which the researcher is recruited.
• Mobility Rule: at the time of recruitment by the host organisation, researchers must not have resided or carried out their main activity (work, studies, etc.) in the country of their host organisation for more than 12 months in the 3 years immediately prior to the reference date. Compulsory national service and/or short stays such as holidays are not taken into account.
• Each ESR will be supported by the project for a maximum of 36 months.
• All ESRs will take part in a secondment to another project partner for up to 30% of their appointment period.
• Mobility Allowances and Family Allowances (dependant on family circumstances) are payable to ESRs.

Work environment: The research team of Prof Kuhn does encompass two postdocs and four graduate students which operate three laboratories dedicated to cavity-qed and atom-photon coupling in cavities at the physics department of the University of Oxford. The work space is well equipped, comprising four vacuum chambers for studying atom-photon coupling in cavities, a large number of ECDL and fibre lasers for atom manipulation, a frequency comb for synchronously stabilising all laser and cavity frequencies, and a large battery of single-photon counters. The two projects build on the current work by other graduate students in our group, atom-cavity coupling and strong cavity coupling.
The new students will directly contribute towards achieving hybrid quantum processing with photons and atoms, and explore new schemes for cavity-mediated atomic entanglement. The projects will be pursued in close collaboration with our LIMQUET project partners in Dijon and Brighton. All necessary equipment is available, including high-finesse cavities, vacuum chambers, and the lasers for trapping and driving the photon production process. Close support on a day-to-day basis will be provided by at least one Oxford-based post-doctoral research assistant for the duration of the project.

3. Demonstration of a cavity-based photonic entangler

Entanglement, in which two quantum systems can exhibit correlations that are greater than the limit allowed by classical physics, is one of the most intriguing predictions of quantum mechanics. Entanglement between remote atoms or ions is a key resource for quantum computing, and plays a central role in the proposed NQIT Q20:20 machine.

We propose two schemes for entangling remote atoms: one probabilistic and one deterministic. In the probabilistic scheme, two distant atoms each emit a photon which are combined at the two input ports of a 50:50 beamsplitter. If the photons are detected at different output ports, then the atoms are projected into an entangled state. In place of a simple beam splitter, we also anticipate using more complex photonic networks [A. Holleczek, PRL 117, 023602 (2016)] in combination with active optical photon switching and routing. In the deterministic scheme, an atom emits a single photon which is reabsorbed by a second atom by running the emission process in reverse [J. Dilley, PRA 85, 023834 (2012)]. In doing so, the state of the first atom is entangled with that of the second. In both schemes, a high-finesse optical cavity is used to enhance the light-atom interactions.

Currently, we have two optical cavity experiments with random atom loading. The first phase of the project will be to build an optical dipole trap to permanently hold single atoms in the cavities. The feasibility of this approach has recently been demonstrated [D. Stuart, arXiv:1708.06672], and suitable fibre-tip and FIB-milled cavity mirrors are at present under development. The second phase will be to generate and quantify the entanglement between the two remote atoms using full Bell-state tomography.

Person specification

This is a highly challenging experimental project which will push the limits of laser and optical technology. It would suit a student with experience in atomic and laser physics and a keen interest in exploring quantum phenomena experimentally. EPSRC eligibility criteria apply for this project, therefore only UK students witha funding status of "Home" are eligible for the position.

Work environment

The research team of Dr Kuhn does encompass two postdocs and four graduate students which operate three laboratories dedicated to cavity-qed and atom-photon coupling in cavities at the Physics department of the University of Oxford. The work space is well equipped, comprising four vacuum chambers for studying atom-photon coupling in cavities, a large number of ECDL and fibre lasers for atom manipulation, a frequency comb for synchronously stabilising all laser and cavity frequencies, and a large battery of single-photon counters. The project builds on the current work by other graduate students in our group, atom-cavity coupling and strong cavity coupling.

The new student will directly contribute towards achieving cavity-mediated remote entanglement. The deterministic entanglement scheme will be done in close collaboration with Almut Beige’s theory group in Leeds, who have developed a complete quantum description of the field inside a cavity, as well as devised cavity-cavity coupling protocols. All necessary apparatus exists within NQIT, including high-finesse cavities, vacuum chambers, and all necessary lasers for trapping and driving the photon production process. Close support on a day-to-day basis will be provided by at least one Oxford PDRA for the duration of the project.

This project is RCUK funded and so there are eligibility restrictions on the funding.

Further details from Dr Axel Kuhn.

Email
A.Kuhn@physics.ox.ac.uk

Professor David Lucas

Entangling gates with performance close to fundamental limits

The Oxford and NIST Boulder ion trap groups have both demonstrated two-qubit entangling gates with world-record 99.9% fidelity, significantly higher than in any other qubit platform [Ballance et al. Phys.Rev.Lett. 2016, Gaebler et al., Phys.Rev.Lett. 2016]. However, the error is still about one order of magnitude above the quasi-fundamental limit set by Raman photon scattering. Oxford have also recently achieved the fastest (480ns) entangling gate in ion traps [Schäfer et al., Nature 2018] which is similar in speed to the recently-demonstrated two-qubit gates in silicon devices. This project will have the ambitious goal of minimizing the remaining technical errors, to push the best fidelity closer to the photon scattering limit of 99.99%. The student will also investigate the practicality of demonstrating new ideas for accelerating the gate speed further by control of the optical phase of the laser field that drives the gate, and/or reduction of the Lamb-Dicke parameter.

We are looking for a highly motivated first-class student to join these world-leading projects. For further information, please see our web page at www.physics.ox.ac.uk/users/iontrap or email Professor Lucas:

Email
d.lucas1@physics.ox.ac.uk

Professor David Lucas and Professor Andrew Steane

Ion trap optical cavities for next-generation quantum networking

The NQIT vision of quantum computing (see www.nqit.org) using distributed modular processors (network “nodes”) is limited by low entanglement rates between different nodes. The current state-of-the-art is <10Hz; we are aiming for ~1kHz average rate, but this is close to the limit imposed by the collection efficiency of the largest NA lens (NA 0.6) that is practical for photon collection. The long-term intention has always been to use optical cavities, which can in principle increase the photon collection probability close to unity, which would offer MHz entanglement rates between nodes. The technical challenges of integrating optical cavities and ion traps are formidable, hence cavities do not form part of the “Q20:20 machine” first-generation design. However, we would like to explore methods of combining cavities with microfabricated ion traps, and colleagues at Southampton have already undertaken some exploratory fabrication tests in this direction. The goal of this project will be to design and fabricate a simple ion trap / cavity system, in collaboration with microfabrication experts Southampton, and test it at Oxford. The use of cavities will be a critical research strand of our planned “phase 2” UK Quantum Technology “Hub” project, a ~£30M cross-disciplinary effort which, if awarded, will begin in Dec 2019.

We are looking for a highly motivated first-class student to join these world-leading projects. For further information, please see our web page at www.physics.ox.ac.uk/users/iontrap or email Professor Lucas:

Email
d.lucas1@physics.ox.ac.uk

Professor Dieter Jaksch

Solving non-linear PDEs on a quantum computer

This project is concerned with solving non-linear partial differential equations (PDEs) on a quantum computer. Recently, it has been shown that an exponential speedup in conventional multigrid (MG) methods for solving non-linear PDEs on a classical computer can be obtained via MG renormalization (MGR) methods [Journal of Computational Physics 372, 587 (2018)]. In this project, the DPhil student will implement MGR methods on a quantum computer focussing on industrially relevant problems in fluid dynamics. Based on current timetables for the future availability of quantum hardware (e.g. through our partnership with IBM), we expect our quantum algorithms to outperform classical computers within the next 3 – 5 years. Since non-linear PDEs are ubiquitous in all areas of science and technology, our method has the potential to leverage the use of quantum-enhanced algorithms in a broad range of real-world applications. The main tasks are:

(i) developing optimized implementations of algorithms for solving non-linear PDEs on existing quantum devices aiming to achieve an exponential speedup. This entails developing platform-specific algorithms mitigating their individual weaknesses such that a quantum advantage can be obtained. The student will consider quantum devices based on trapped ions and in particular the Q20:20 machine, as well as devices on IBM’s quantum computing network.

(ii) identifying industrially relevant applications where MGR methods on a quantum computer could help solving outstanding problems or improve the quality of existing solutions. This part of the project will be carried out in close collaboration with BAE Systems, who are interested in solving complex fluid dynamics problems that are modelled by non-linear PDEs.

For more information, please contact Professor Jaksch:

Email
d.jaksch1@physics.ox.ac.uk

Professor Peter Norreys

Laser-Plasma Interaction Physics for Inertial Fusion and Extreme Field Science

Intense lasers have extraordinary properties. They can deliver enormous energy densities to target, creating states of matter in the laboratory that are otherwise only found in exotic astrophysical phenomena, such as the interiors of stars and planets, the atmospheres of white dwarfs and neutron stars, and in supernovae. The behaviour of matter under these extreme conditions of density and temperature is a fascinating area of study, not only for understanding of fundamental processes that are, in most cases, highly non-linear and often turbulent, but also for their potential applications for other areas of the natural sciences. My team is working on:

• Inertial confinement fusion - applications include energy generation and the transition to a carbon-free economy and the development of the brightest possible thermal source for neutron scattering science
• New high power optical and X-ray lasers using non-linear optical properties in plasma
• Novel particle accelerators via laser and beam-driven wakefields - including the AWAKE project at CERN, as a potential route for a TeV e-e+ collider
• Unique ultra-bright X-ray sources

The understanding of these physical processes requires a combination of observation, experiment and high performance computing models on the latest supercomputers. My team is versatile, combining experiment, theory and computational modelling, including applications of machine learning. I can offer projects in all of these areas – please contact me to discuss your interests and let’s take it from there.

Email
p.norreys1@physics.ox.ac.uk

Professor Justin Wark

Studying High Pressure Matter with X-Ray Lasers

An opportunity exists for a DPhil project in the Physics Department at the University of Oxford to use the brightest X-ray source on the planet to study the response of matter to pressures normally only found towards the centre of planets. The student will work under the supervision of Professor Justin Wark in the sub-department of Atomic and Laser Physics. The project, funded by Lawrence Livermore National Laboratory in California, will entail both an experimental and theoretical study of matter under extreme conditions. On the experimental side, the student will use intense optical lasers to subject matter to many millions of atmospheres for timescales in the sub-nanosecond regime. In conjunction, the most intense x-ray laser on earth - the Linac Coherent Light Source at SLAC, will be used to obtain few-femtosecond single-shot diffraction images as the matter deforms or forms new phases. The experiments will be complemented by both classical molecular dynamics simulations, and by ab initio density functional theory calculations. The work builds on previous successful research recently published at the highest level (Science, 342, 220 [2013]). Full funding exists (fees and stipend) for successful UK or EU candidates for a period of 3.5 years. Interested candidates should have a upper-second or first class degree (or equivalent) in Physics, be interested in both experimental and theoretical physics, and be willing to spend some short periods in the US for experiments and collaborations. Enquiries can be made to Professor Justin Wark.

Email
j.wark1@physics.ox.ac.uk