Jobs

Applications are invited to fill up to two postdoc positions to work with the Quantum Optics and Quantum Many-body Systems team at the University of Strathclyde, to work on two related PASQuanS tasks:

1) Benchmarking, certification, and applications of analogue quantum simulators, associated with the EU Flagship project on Programmable Large-Scale Atomic Quantum Simulators (http://www.pasquans.eu)

2) Software development for applications of quantum simulators, especially considering the mapping of solutions of partial differential equations onto quantum dynamics.

We are seeking highly motivated theoretical researchers who will be responsible for research on each of these projects, developing novel insight into many-body physics, new techniques to benchmark and verify quantum simulators, and applications relevant to other academic disciplines and industry. The successful applicants will be based in the Department of Physics under the supervision of Prof. Andrew Daley. Technical knowledge of computational methods, especially tensor network techniques for many-body dynamics, would be an advantage.

The applications are available online at http://www.strath.ac.uk/hr/workforus (vacancy reference 244690). For any more information, please contact Prof. Andrew Daley (andrew.daley@strath.ac.uk)

Professor Andrew Daley
Department of Physics
University of Strathclyde
John Anderson Building
107 Rottenrow East
Glasgow G4 0NG, UK

http://qoqms.phys.strath.ac.uk
http://cnqo.phys.strath.ac.uk

Dissipative quantum simulation with sub-wavelength atom arrays

Quantum Optics – Atoms group (https://atom-tweezers-io.org)
Laboratoire Charles Fabry, Institut d’Optique, Palaiseau, France

Proposal for a Master 2 thesis to be followed by a PhD (starting date: spring 2020).
Supervisors: Antoine Browaeys: antoine.browaeys@institutoptique.fr
Igor Ferrier-Barbut: igor.ferrier-barbut@institutoptique.fr
Internship allowance: Yes

The goal of this thesis project is to develop a quantum simulator for dissipative quantum-many problems, to emulate many-body ensembles with intrinsic collective dissipation and with external driving by a classical or quantum field. The platform we will develop during this internship, to be followed by a PhD, will be based on structured ensembles of atoms held in microscopic optical traps (tweezers), and interacting with near-resonant laser light. The light induced dipoles interact via the resonant dipole-dipole interaction mediated by the vacuum field.

The structuring of atomic arrays in optical tweezers creating a configurable quantum simulator has been invented by our group [1,2]. The collective effects will be here induced by the resonant dipole interactions between the atoms, which exhibits both a real and imaginary part, which signs a collective spontaneous emission.
The exchange of excitation that results from the interaction naturally implements an interacting spin system where the two atomic states are mapped onto the two states of a spin 1⁄2 (see figure). This system is thus a quantum simulator for dissipative spin systems. To reach strong interactions, the interparticle distance must be shorter than the wavelength of the transition between the two levels, here around l = 780nm for Rb atoms.

The project will take place on an existing cold rubidium setup, with
high-numerical-aperture lenses in vacuum. We will first explore situations where atoms are ordered in a chain and will target an interparticle distance smaller than l/2. In this situation long lived sub-radiant states should exist that we will seek to observe [3]. We will then generate an optical tweezer array with light close to a blue transition of Rb at 420nm in order to reduce the diffraction limit. Using a spatial light modulator (SLM) we will generate a configurable array with interparticle distance of a few hundred nm, thus shorter than the wavelength of the transition at 780nm. Such arrays have been predicted to exhibits perfect reflectivity [4,5]. During the PhD that will follow we will put the optical tweezer array in place on the experiment and implement the experimental protocol to deterministically fill it with single atoms. We will then perform the first experiments in the strongly interacting regime.

References
[1] D. Barredo et al., Science 354, 1021 (2016).
[2] D. Barredo et al., Nature 561, 79 (2018).
[3] R. Bettles et al., PRA 94, 043844 (2016).
[4] R. Bettles et al., PRL 116 103602 (2016).
[5] E. Shahmoon et al., PRL 116 103602 (2016).

Synthetic topological matter using arrays of single Rydberg atoms

Quantum Optics – Atoms group (https://atom-tweezers-io.org)
Laboratoire Charles Fabry, Institut d’Optique, Palaiseau, France

Proposal for a Master 2 thesis to be followed by a PhD (starting date: spring 2020).
Supervisors: Antoine Browaeys: antoine.browaeys@institutoptique.fr
Thierry Lahaye: thierry.lahaye@institutoptique.fr
Internship allowance: Yes

Over the past few years, our group has developed a very versatile experimental platform for quantum simulation of spin models, based on arrays of single atoms trapped in optical tweezers, and strongly interacting with each other when excited to Rydberg levels. We can generate defect-free atomic arrays of up to 70 atoms with almost full control of the geometry in one, two and three dimensions [1,2], as shown in the figure. Interactions between Rydberg atoms allow us to implement Ising [3,4] or XY spin Hamiltonians [5,6]. The latter is obtained using the resonant dipole-dipole interaction, which induces a coherent exchange of the Rydberg states (“spin”) of a pair of atoms. A spin excitation can thus “hop” from one atom to another, in perfect analogy with a
boson hopping from one site to another in a lattice. As an atom can host at most one spin excitation, those bosons have an infinite onsite interaction; one talks about “hard-core bosons”.
Recently, in collaboration with the theory group of H.P. Büchler in Stuttgart, we have used this platform to study topological matter in one dimension, by realising a bosonic version of the Su-Schrieffer-Heeger model where the hard-core interactions give rise to a new phase of mater, called a symmetry protected topological phase [6]. We now extend these studies to two-dimensional models, with the long-term goal of realizing a so far elusive phase, namely a bosonic fractional topological insulator. Following our proposal [7] we will first demonstrate, in a small array of a few atoms, that the dipole-dipole interaction can be used to create the spin-orbit coupling needed to reach this goal, and then try to observe chiral edge currents revealing the topological band structure. Finally, the many-body regime will be reached by adding several spin excitations in the system.
The project will comprise (1) the development of an upgraded system for addressing optically selected atoms in the arrays, using a spatial light modulator; and (2) data-taking and analysis for the demonstration of a spin-orbit coupling. It will be essentially experimental, but may include some modelling, in collaboration with our theory colleagues in Stuttgart.

References
[1] D. Barredo et al., Science 354, 1021 (2016).
[2] D. Barredo et al., Nature 561, 79 (2018).
[3] H. Labuhn et al., Nature 534, 667 (2016).
[4] V. Lienhard et al., Phys. Rev. X 8, 021070 (2018).
[5] S. de Léséleuc et al., Phys. Rev. Lett. 119, 053202 (2017).
[6] S. de Léséleuc et al., Science 365, 775 (2019).
[7] S. Weber et al., Quantum Sci. Technol. 3, 044001 (2018).