Engineering quantum state with light
<p>Controlling the states of quantum systems is a subject of major interest for both fundamental science and technological development. In this thesis, we carry out theoretical studies on how this can be achieved using light, both of classical and of quantum mechanical nature. </p> <...
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| Other Authors: | |
| Format: | Thesis |
| Language: | English |
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2021
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| _version_ | 1797106495496650752 |
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| author | Gao, H |
| author2 | Jaksch, D |
| author_facet | Jaksch, D Gao, H |
| author_sort | Gao, H |
| collection | OXFORD |
| description | <p>Controlling the states of quantum systems is a subject of major interest for both fundamental science and technological development.
In this thesis, we carry out theoretical studies on how this can be achieved using light, both of classical and of quantum mechanical nature. </p>
<p>We study a driven cavity system, where the driving field is classical and the cavity field is quantum mechanical.
We demonstrate how virtual scattering of driving photons inside the cavity via two-photon processes can induce controllable long-range electron interactions in two-dimensional materials. We show that both the strength and the sign of the interactions can be tuned by the driving parameters and that the interactions are not screened effectively except at very low frequencies. For realistic cavity parameters, driving-induced heating of the electrons by inelastic photon scattering is suppressed and coherent electron interactions dominate. When the interactions are attractive, they cause an instability in the Cooper channel at a temperature proportional
to the square root of the driving intensity.
Our results open up a new avenue for engineering quantum materials on-demand and the possibility of studying the effect of long-range interactions in condensed matter systems. </p>
<p>Following that, we take a more general approach to investigate the effect of long-range density-density electron attractive interactions on a superconductor.
We show that the low-lying excitations of a 2D conventional superconductor can be significantly altered by these long-range interactions.
Using BCS theory, we find that these interactions combine non-linearly with the intrinsic local attractions of the superconductor to increase the Bogoliubov quasiparticle excitation energies, thus enlarging the superconducting gap.
Moreover, we show how the long-range nature of the driven-cavity-induced attractions qualitatively changes the collective excitations of the superconductor. Specifically, they lead to the appearance of additional collective excitations of the excitonic modes.
They further push the Higgs mode "in gap": it lies below the Bogoliubov quasiparticle continuum such that it cannot decay through the quasiparticle excitations. </p> |
| first_indexed | 2024-03-07T07:03:20Z |
| format | Thesis |
| id | oxford-uuid:7eb6654b-eab0-4bee-a9b9-d072c896d97c |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T07:03:20Z |
| publishDate | 2021 |
| record_format | dspace |
| spelling | oxford-uuid:7eb6654b-eab0-4bee-a9b9-d072c896d97c2022-04-05T13:13:33ZEngineering quantum state with lightThesishttp://purl.org/coar/resource_type/c_db06uuid:7eb6654b-eab0-4bee-a9b9-d072c896d97cPhysicsEnglishHyrax Deposit2021Gao, HJaksch, D<p>Controlling the states of quantum systems is a subject of major interest for both fundamental science and technological development. In this thesis, we carry out theoretical studies on how this can be achieved using light, both of classical and of quantum mechanical nature. </p> <p>We study a driven cavity system, where the driving field is classical and the cavity field is quantum mechanical. We demonstrate how virtual scattering of driving photons inside the cavity via two-photon processes can induce controllable long-range electron interactions in two-dimensional materials. We show that both the strength and the sign of the interactions can be tuned by the driving parameters and that the interactions are not screened effectively except at very low frequencies. For realistic cavity parameters, driving-induced heating of the electrons by inelastic photon scattering is suppressed and coherent electron interactions dominate. When the interactions are attractive, they cause an instability in the Cooper channel at a temperature proportional to the square root of the driving intensity. Our results open up a new avenue for engineering quantum materials on-demand and the possibility of studying the effect of long-range interactions in condensed matter systems. </p> <p>Following that, we take a more general approach to investigate the effect of long-range density-density electron attractive interactions on a superconductor. We show that the low-lying excitations of a 2D conventional superconductor can be significantly altered by these long-range interactions. Using BCS theory, we find that these interactions combine non-linearly with the intrinsic local attractions of the superconductor to increase the Bogoliubov quasiparticle excitation energies, thus enlarging the superconducting gap. Moreover, we show how the long-range nature of the driven-cavity-induced attractions qualitatively changes the collective excitations of the superconductor. Specifically, they lead to the appearance of additional collective excitations of the excitonic modes. They further push the Higgs mode "in gap": it lies below the Bogoliubov quasiparticle continuum such that it cannot decay through the quasiparticle excitations. </p> |
| spellingShingle | Physics Gao, H Engineering quantum state with light |
| title | Engineering quantum state with light |
| title_full | Engineering quantum state with light |
| title_fullStr | Engineering quantum state with light |
| title_full_unstemmed | Engineering quantum state with light |
| title_short | Engineering quantum state with light |
| title_sort | engineering quantum state with light |
| topic | Physics |
| work_keys_str_mv | AT gaoh engineeringquantumstatewithlight |