Dynamics and entanglement in open quantum systems with long-range interactions
Lead Research Organisation:
University of Nottingham
Department Name: Sch of Physics & Astronomy
Abstract
Nowadays quantum mechanics is used not only to predict physical behaviour, but also to exploit quantum resources in paradigm changing applications such as quantum communication and computation. During the last couple of decades we have witnessed a revolution in the experimental realisation of these quantum systems. Ultracold atomic gases are nowadays routinely created and used for the study of complex many-body phenomena such as quantum phase transitions shedding light on open problems in condensed-matter physics. Considering this appealing landscape, the present PhD project aims at studying a novel platform -- atomic gases excited to low lying states -- where long-range interactions arise due to the exchange of virtual photons among the atoms. Here, the dissipation (emission of photons into the surrounding electromagnetic field) can acquire a collective character. The aims of this project include:
I) The study of the dynamics of excitations in a system with long range interactions with particular emphasis in situations relevant to quantum information processing, such as a one dimensional chain of atoms.
II) The analysis of the effect that the collective character of the dissipation has in the system, i.e. making an excitation extremely long-lived due to many-body effects only.
III) The consideration of an induced "blockade effect" due to the presence of long range strong interactions, which could then be applied, e.g. for quantum information protocols. It can also be considered in specific systems such as strontium atoms as a limiting factor of the precision of atomic clocks.
IV) The investigation of schemes for creating and accessing entangled many-body states either coherently, e.g. via adiabatic transfer, or as stationary states of collective dissipation. These can form a resource for highly sensitive interferometry and precise clocks, with applications ranging from satellite navigation to energy and mineral exploration.
In summary, this is a theoretical project that is located at the interface of cold atoms, non-equilibrium physics and quantum optics and that, if successful, will open new perspectives in quantum technologies and quantum information. Moreover, from a more fundamental perspective, it will provide new insights into our understanding of physical phenomena emerging in quantum systems far from equilibrium.
I) The study of the dynamics of excitations in a system with long range interactions with particular emphasis in situations relevant to quantum information processing, such as a one dimensional chain of atoms.
II) The analysis of the effect that the collective character of the dissipation has in the system, i.e. making an excitation extremely long-lived due to many-body effects only.
III) The consideration of an induced "blockade effect" due to the presence of long range strong interactions, which could then be applied, e.g. for quantum information protocols. It can also be considered in specific systems such as strontium atoms as a limiting factor of the precision of atomic clocks.
IV) The investigation of schemes for creating and accessing entangled many-body states either coherently, e.g. via adiabatic transfer, or as stationary states of collective dissipation. These can form a resource for highly sensitive interferometry and precise clocks, with applications ranging from satellite navigation to energy and mineral exploration.
In summary, this is a theoretical project that is located at the interface of cold atoms, non-equilibrium physics and quantum optics and that, if successful, will open new perspectives in quantum technologies and quantum information. Moreover, from a more fundamental perspective, it will provide new insights into our understanding of physical phenomena emerging in quantum systems far from equilibrium.
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/N50970X/1 | 01/10/2016 | 30/09/2021 | |||
| 1794541 | Studentship | EP/N50970X/1 | 01/10/2016 | 31/03/2020 | Jemma Needham |
| Description | We have explored the nature of collective behaviour in 1D atomic lattices. We have studied the time evolution of a simple excited state (which can be prepared, experimentally, through laser driving) and found that such a system enters a subradiant state. The excitation remains within the system for much longer than expected for a single atom. By investigating controllable parameters in our set-up, we developed a storage protocol which allows the excitation to be held within the chain for even longer times. This is achieved by applying an external magnetic field to the system for the atoms to align to, and then adiabatically rotating this field, to alter the form of the coupling between atoms. A report of these results is currently being written for publication. The results have also been presented in the form of posters and presentations at local and international conferences. EDIT: We investigated further into the preparation of a subradiant state by exploring the spectrum of decay modes and the corresponding energies. We found that by exciting a Gaussian wave packet, we could prepare a state that is more subradiant, and travels coherently with a constant group velocity. This project has since been published. Additionally, we are currently investigating the dynamics of atomic gases with non-zero temperature (the atomic velocities are accounted for). We have derived equations of motion for the system, and we have started exploring the scattering properties and collective behaviour of an atomic gas, such as an atomic ring with rotation. EDIT: We re-evaluated the methods used above to derive the dynamics of a many body atomic system with motion, and performed a derivation from first principles which treats the motion as part of the bath dynamics (included with the radiation field that encompasses the atoms). In this way, we are able to treat distinguishable atoms with a quantum mechanical description of uncertainty in their positions. We compared this to the results for atoms with classically described disorder. This project is being written for publication. |
| Exploitation Route | The second project is in collaboration with the group of Robin Kaiser at INPHYNI (Universite Cote D'azur). I visited the group for 1 week where we had discussions on the progress and possible directions of the project. We will soon be writing up results for this project for publication. Elements from both of these projects was presented at an international workshop which led to a collaboration with the group of Igor Ferrier-Barbut at Institut d'Optique in Palaiseau, France. We ran simulations for the laser driving of 1D atomic chains to help determine appropriate regimes for them to explore experimentally in order to observe features of collective behaviour. This collaboration may be continued following experimental investigations and could potentially lead to publications. |
| Sectors | Other |
| Description | Motional effects on cooperative behaviour in an atomic gas |
| Organisation | University of Côte d'Azur |
| Country | France |
| Sector | Academic/University |
| PI Contribution | We have started a project together and I am currently performing the calculations that will give rise to a common publication. |
| Collaborator Contribution | They hosted me for a week and we had fruitful discussions that led to advances in the understanding of the project. |
| Impact | I am giving a presentation about the results we have gotten so far next week in the DAMOP section of the DPG march meeting in Rostock, Germany. The results will be soon written in a paper and sent for publication to a peer-reviewed journal. |
| Start Year | 2018 |