Download Towards edge states in Optical Quasicrystals Supervisors: Dr. Ulrich

Towards edge states in Optical Quasicrystals
Supervisors: Dr. Ulrich Schneider (Cambridge), Dr. Ryan Barnett (Imperial)
Project Background: Understanding and engineering collective effects in interacting many-body quantum systems constitutes
one of the major challenges of modern physics. Ultracold atoms in optical lattices have been established as very versatile
and powerful Quantum Simulators to study quantum many-body physics, as they provide a flexible and clean test bed in
which various important model Hamiltonians can be faithfully implemented.
Experimentally, they combine the rich many-body physics encountered in e.g. condensed matter physics with the unique
manipulation and observation capabilities of quantum optics. In the past, we have successfully used these systems to study
quantum phase-transitions and the out-of-equilibrium dynamics of strongly correlated systems and to observes quantum
thermodynamics of small systems. Highlights include the first observation of fermionic Mott insulators with ultracold atoms,
the creation of negative absolute temperatures and the dynamical quasi-condensation of hard-core bosons—all manifest
quantum phenomena.
Two new developments have recently extended the realm of ultracold atoms towards microscopically controlled quantum
dynamics with individually addressable quantum systems: The development of quantum gas microscopes has enabled
unprecedented manipulation and readout on individual lattice sites, and the observation of many-body localization in
interacting disordered systems promises a route to systems where quantum information can be retained locally for long
times.
Project – We are currently setting up a novel experiment in Cambridge where we will load
both Bose-Einstein condensates and degenerate Fermi gases into novel, non-periodic optical
lattices—an optical Quasicrystal. Quasicrystals are a novel form of condensed matter that is
non-periodic, but long-range ordered. They have first been observed in the 1980s by Dan
Shechtman in diffraction experiments and their fundamental importance was recognized by
the Nobel Prize in Chemistry in 2011. Their structure was found to be given by aperiodic tilings
with more than one unit cell, such as the celebrated Penrose tiling. Aperiodic tilings represent
an interesting middle ground between periodic and disordered systems and contain fascinating
properties, such as topologically protected edge states similarly to topological insulators and
quantum Hall systems. In this project we aim to combine a quasi-periodic potential with a
quantum gas microscope in order to controllably and individually address these edge states
and study their properties and potential for controlled quantum dynamics.
First year project – The first year project is split roughly equally between experimental work in Cambridge, where you will
design and analyze the imaging and addressing setup used to controllably and selectively address the edge states, and a
theoretical/numerical part, where the expected edge states will be characterized and first addressing protocols be studied
numerically with the aim of demonstrating their potential for controlled quantum dynamics.
PhD project – During the PhD we will load atoms into the quasi-periodic potential and
study the resulting many-body physics using different experimental techniques. At the
same time, we will implement the microscope required to microscopically address and
manipulate parts of the system. We will analyse numerically/theoretically several
potential techniques to individually address and manipulate the edge states of this system
and to probe their topological properties. Towards the end of the PhD, we might detect
edge states experimentally and demonstrate their topological character. In a second
stream, we will also investigate the localization properties of these quasiperiodic
Part of the required laser system
potentials and try to establish the transport properties of localized excitations and to assess
their potential for quantum information purposes. During this second phase, you will be primarily based in Cambridge and
the supervision is envisioned to be 80-20% experiment/theory, which is however flexible depending on your interest.
Desired Student Background – We seek a talented and highly-motivated physics student to pursue this project in quantum
simulation of many-body quantum systems. Most of the necessary background will be obtained through the courses CDT
students take during the MRes programme. For instance, the formalism of quantised fields, as developed in the Quantum
and Nonlinear Optics methods lectures, is foundational to the theoretical aspects of the project. Advanced techniques in
quantum many-body theory will be developed as necessary in parallel with the project. The lectures on Quantum Physics
and Chemistry of Cold Matter will comprise essential background for the experimental aspects of the project. Understanding
the resilience of the expected controlled quantum dynamics in the context of external noise will draw heavily on the
formalisms developed in the Quantum Information lectures, such as decoherence theory and Master equations.
http://www.manybody.phy.cam.ac.uk
http://wwwf.imperial.ac.uk/~rlbarnet/