Computational Modelling of Ultrafast Chiral-light Matter Interactions (funded)

This theoretical/computational PhD project aims to investigate how the so-called “chiral” molecules – the ones that are not identical to their mirror images – can be detected using tailored femto- and attosecond laser pulses with orders of magnitude higher sensitivity than currently possible.

The successful candidate will use and further develop advanced quantum mechanical many-body computational tools to model, design and interpret the pioneering experiments on chiral light-matter interaction within the Extreme Light Consortium (XLC) of Imperial College Blackett Laboratory, see e.g. [1-3]. Specifically, the many-body quantum mechanical approach called B-spline algebraic diagrammatic construction (B-spline ADC) [4-6], developed at the XLC, will be employed to simulate the response of electrons within a chiral molecule to irradiation with tailored femto- and attosecond laser pulses.

Traditional chiro-optical methods rely on the electronic response of matter to both the electric and magnetic components of a circularly polarised wave, i.e. on the chiral molecule “sensing” the helix of the fields’ vectors evolution in space. However, the micron-scale pitch of this helix is way too large compared to the angstrom- or nanometre-scale size of the molecules, leading to extremely weak chiro-optical effects (usually below 0.1%).

In our work, we will bypass this fundamental limitation by tailoring the polarisation of the laser field in time, in a way that the chiral response of the molecules does not rely on the helical trajectories of the electric and magnetic field vectors of circularly polarised light. Our control over the temporal structure of the optical field enables the highest possible degree of control over the chiral response of chiral matter: quenching it in one chiral molecule while maximising it in its mirror twin [7-9]. High-precision quantum mechanical modelling [4-6] of the quantum many-electron wavepacket evolution that is behind the chiral molecular response is essential to determine the optimal shape of the probing light.

Applicants should hold a MSc in Physics, Chemistry, Mathematics, Computational Science, or a closely related subject by the start of the studentship and have a strong interest in theoretical and computational methods for atomic, molecular, and optical physics. Funding includes a tax-free stipend, conference travel, consumables, and tuition fees for students who are eligible for ‘home’ fees, see https://www.imperial.ac.uk/study/fees-and-funding/tuition-fees/fee-status/

For informal inquiries about the project, the team, or the application process, please contact Dr David Ayuso and/or Prof Vitali Averbukh.

[1] D. Schwickert et al, Sci. Adv. 8, eabn6848 (2022)
[2] T. Barillot et al, Phys. Rev. X 11, 031048 (2021)
[3] Li et al, Science 375, 285-290 (2022)
[4] M. Ruberti et al, Phys. Chem. Chem. Phys. 24, 19673-19686 (2022)
[5] M. Ruberti et al, Phys. Chem. Chem. Phys. 20, 8311-8325 (2018)
[6] M. Ruberti et al, J. Chem. Theory Comput. 14, 10, 4991-5000 (2018)
[7] D. Ayuso et al, Nat. Photonics 13, 866-871 (2019)
[8] D. Ayuso et al, Nat. Commun. 12, 3951 (2021)
[9] D. Ayuso et al, Optica 8, 10, 1243-1246 (2021)

 

Understanding electronic excitation and charge separation in photovoltaics using ultrafast x-ray spectroscopy (funded)

The next generation of solar energy materials need to be still more efficient, cheap and environmentally robust. We are pioneering the use of ultrafast x-ray spectroscopy to understand the quantum level processes at the core of optimising performance including exciton formation, delocalisation and localisation and the formation of other excitations or trapping of excitons that inhibits the eventual charge separation essential to photovoltaic function.

Our research uses our unique laser based HHG source to generate attosecond pulses of soft-x-rays and few-femtosecond optical pump sources designed to target exciton formation in key organic semiconductors. It is also intended to extend the measurements to probing a wider range of atomic sites by using x-ray free electron laser (XFEL) facilities in the USA, Switzerland and Germany.

Through this project you will:

• Learn about ultrafast lasers, non-linear optics and attosecond technology
• Participate in the full measurement process gaining skills in sample preparation, measurement and diagnostics, data analysis and data interpretation (using time-dependent density functional theory TDDFT)
• Participate in experiments at x-ray free electron lasers around the world, including Stanford, USA (LCLS II), Switzerland (Swiss FEL) and Germany (European XFEL). This will develop knowledge of XFEL science, and skills in experimental planning, teamwork and delivery
• Learn about the physics, chemistry and function of light harvesting materials
• Participate in a range of time-resolved x-ray spectroscopy measurements exploring various aspects of photochemistry and photophysics at the ultrafast timescale gaining skills in experimental design and ultrafast measurement techniques and developing independent scientific thinking

For further information please contact Prof Jon Marangos and/or Dr Mary Matthews

 

Dark matter detection with an electron in a Penning trap (funded)

In this project you will build a new quantum sensor to help detect the very weak microwave signals from dark matter. We plan to use an electron in a Penning trap as this quantum sensor. The orbits of the trapped electron will be monitored for changes caused by dark matter. These include both direct collisions with dark matter and absorption of single microwave photons from dark matter decays. As well as potentially detecting dark matter, we expect this new single microwave photon counter will have broader applications in fundamental and applied physics.

Amongst other things, you’ll get to:

• Design and assemble a Penning trap electrode stack that can be cooled to 4 K
• Build ultra-sensitive detections systems to read out the trapped frequencies
• Make low noise electronics for use at cryogenic temperatures
• Learn all the skills of trapping individual particles including loading, cooling, trap optimisation and image current frequency detection
• Detect single microwave photons using a trapped electrons
• Search for hints of dark matter by measuring the electron heating rates

For further information please contact Dr Jack Devlin.

 

A high quality factor Fabry-Perot cavity to convert dark matter axions into microwave photons (funded)

Dark matter makes up 84% universe but we do not know what it is. The goal of this project is to develop a new way to efficiently convert one type of dark matter, the axion, into microwave photons. The method we will use is the well-established cavity haloscope technique, but in our case using a radically new geometry – a Fabry Perot (FP) cavity operating in its fundamental TEM₀₀₁ mode. This geometry gives us sufficient sensitivity to convert axions into microwave photons with a reasonable count rate, making it possible to detect axions with masses above 0.12 meV.  This cavity geometry also can be sensitive to other types of dark matter.   

You’ll have a chance to:

• Learn how to design and test microwave components
• Simulate the performance of various cavity geometries
• Research high-Q mirror coatings and characterise their behaviour in a strong magnetic field
• Design a system to align the cavity and vary its resonant frequency
• Build a working prototype that can be cooled to cryogenic temperature
• Measure the noise spectrum of the cavity and use this to place limits on different types of dark matter

For further information please contact Dr Jack Devlin.

 

Quantum networks of atoms and molecules (funded)

An array of laser-cooled polar molecules interacting with Rydberg atoms is a promising hybrid system for scalable quantum computation.

Quantum information is stored in long-lived hyperfine or rotational states of molecules which interact indirectly through resonant dipole-dipole interactions with Rydberg atoms.

During this project you will:

• Join a team comprised of students, postdocs, and academics developing innovative quantum technologies
• Learn how to use precisely controlled lasers to cool atoms and molecules to ultracold temperatures
• Load the particles into traps formed by tightly focussed laser beams (optical tweezers)
• Rearrange the atoms and molecules into regular arrays and study their coherent interactions
• Implement a two-qubit gate between the molecules mediated by their strong interaction with a highly polar Rydberg atom
• Become an expert in vacuum and laser science, optics and imaging, 3Dmodelling, computer automation and interfacing, numerical modelling, and statistics and data analysis

For further information please contact Prof Mike Tarbutt

 

Testing fundamental physics with molecules in a lattice (funded)

An array of laser-cooled heavy polar molecules can be used for precision tests of fundamental physics beyond the Standard Model of Particle Physics.

The low-energy table-top experiments open a window to high-energy physics and allow us to explore new physics at energies beyond the reach of particle accelerators such as CERN.

During this project you will:

• Join a team comprised of students, postdocs, and academics developing innovative quantum technologies
• Learn how to use precisely controlled lasers to manipulate a beam of molecules and slow the molecules using radiation pressure
• Use a combination of magnetic and laser fields to trap and cool the molecules
• Arrange the molecules into a regular array by loading them into an optical lattice
• Implement a measurement protocol to search for small energy shifts induced by the electric dipole moment of the electron
• Become an expert in vacuum and laser science, optics and imaging, 3Dmodelling, computer automation and interfacing, numerical modelling, and statistics and data analysis

For further information please contact Dr Jongseok Lim.

 

Cooling atoms and molecules with deep ultraviolet lasers (funded)

Ultracold molecules are the next frontier in ultracold quantum science. We develop new powerful lasers in the deep ultraviolet to manipulate stable gas-phase molecules and to cool them to ultracold temperatures in the microkelvin regime.

Molecules cooled to such low temperatures offer many new possibilities in quantum information, simulation, and computation and for precise tests of fundamental physics.

During this project you will:

• Design and build lasers to produce high-power continuous radiation in the deep UV
• Stabilise and precisely control the frequencyof these lasers
• Produce gas-phase, polar molecules in a high vacuum environment and cool them using cryogenic helium
• Use radiation pressure to slow a molecular beam and trap the molecules in a magneto-optical trap, where they can be cooled to microkelvin temperatures
• Study collisions in the quantum regime and perform precision measurements to test new physics
• Use the strong dipolar interactions between the molecules to encode quantum information and simulation protocols

For further information please contact Dr Stefan Truppe.

 

Atom interferometry for inertial sensing (2 studentships - funded)

Our atom interferometers use laser light to prepare the internal and motional states of a cloud of laser-cooled rubidium atoms. This device can be extremely sensitive - for example the instrument in our laboratory can sense changes of a few billionths of the acceleration due to gravity.

The sensitivity and accuracy of such a device will enable navigation without the use of external signals such as Sonar or Satellite communications.

During this project you will:

• Join a team comprised of students, postdocs, and academics that is developing innovative quantum technologies.
• Laser-cool rubidium atoms to a few tens of microkelvin.
• Use the laser-cooled atoms to measure accelerations with high precision and accuracy.
• Advance current technology in collaboration with industry to build a more compact and reliable system that can be used in field trials.
• Test and characterise the performance of the system in field trials on the tube, ships and submarines.
• Become an expert in vacuum and laser science, optics and imaging, 3D modelling, computer automation and interfacing, numerical modelling, and statistics and data analysis.

For further information please contact Dr Joe Cotter.