---
_id: '10058'
abstract:
- lang: eng
text: 'Quantum information and computation has become a vast field paved with opportunities
for researchers and investors. As large multinational companies and international
funds are heavily investing in quantum technologies it is still a question which
platform is best suited for the task of realizing a scalable quantum processor.
In this work we investigate hole spins in Ge quantum wells. These hold great promise
as they possess several favorable properties: a small effective mass, a strong
spin-orbit coupling, long relaxation time and an inherent immunity to hyperfine
noise. All these characteristics helped Ge hole spin qubits to evolve from a single
qubit to a fully entangled four qubit processor in only 3 years. Here, we investigated
a qubit approach leveraging the large out-of-plane g-factors of heavy hole states
in Ge quantum dots. We found this qubit to be reproducibly operable at extremely
low magnetic field and at large speeds while maintaining coherence. This was possible
because large differences of g-factors in adjacent dots can be achieved in the
out-of-plane direction. In the in-plane direction the small g-factors, on the
other hand, can be altered very effectively by the confinement potentials. Here,
we found that this can even lead to a sign change of the g-factors. The resulting
g-factor difference alters the dynamics of the system drastically and produces
effects typically attributed to a spin-orbit induced spin-flip term. The investigations
carried out in this thesis give further insights into the possibilities of holes
in Ge and reveal new physical properties that need to be considered when designing
future spin qubit experiments.'
acknowledged_ssus:
- _id: M-Shop
- _id: NanoFab
acknowledgement: The author gratefully acknowledges support by the Austrian Science
Fund (FWF), grants No P30207, and the Nomis foundation.
alternative_title:
- ISTA Thesis
article_processing_charge: No
author:
- first_name: Daniel
full_name: Jirovec, Daniel
id: 4C473F58-F248-11E8-B48F-1D18A9856A87
last_name: Jirovec
orcid: 0000-0002-7197-4801
citation:
ama: Jirovec D. Singlet-Triplet qubits and spin-orbit interaction in 2-dimensional
Ge hole gases. 2021. doi:10.15479/at:ista:10058
apa: Jirovec, D. (2021). Singlet-Triplet qubits and spin-orbit interaction in
2-dimensional Ge hole gases. Institute of Science and Technology Austria.
https://doi.org/10.15479/at:ista:10058
chicago: Jirovec, Daniel. “Singlet-Triplet Qubits and Spin-Orbit Interaction in
2-Dimensional Ge Hole Gases.” Institute of Science and Technology Austria, 2021.
https://doi.org/10.15479/at:ista:10058.
ieee: D. Jirovec, “Singlet-Triplet qubits and spin-orbit interaction in 2-dimensional
Ge hole gases,” Institute of Science and Technology Austria, 2021.
ista: Jirovec D. 2021. Singlet-Triplet qubits and spin-orbit interaction in 2-dimensional
Ge hole gases. Institute of Science and Technology Austria.
mla: Jirovec, Daniel. Singlet-Triplet Qubits and Spin-Orbit Interaction in 2-Dimensional
Ge Hole Gases. Institute of Science and Technology Austria, 2021, doi:10.15479/at:ista:10058.
short: D. Jirovec, Singlet-Triplet Qubits and Spin-Orbit Interaction in 2-Dimensional
Ge Hole Gases, Institute of Science and Technology Austria, 2021.
date_created: 2021-09-30T07:53:49Z
date_published: 2021-10-05T00:00:00Z
date_updated: 2023-09-08T11:41:08Z
day: '05'
ddc:
- '621'
- '539'
degree_awarded: PhD
department:
- _id: GradSch
- _id: GeKa
doi: 10.15479/at:ista:10058
file:
- access_level: closed
checksum: ad6bcb24083ed7c02baaf1885c9ea3d5
content_type: application/x-zip-compressed
creator: djirovec
date_created: 2021-09-30T14:29:14Z
date_updated: 2022-12-20T23:30:07Z
embargo_to: open_access
file_id: '10061'
file_name: PHD_Thesis_Jirovec_Source.zip
file_size: 32397600
relation: source_file
- access_level: open_access
checksum: 5fbe08d4f66d1153e04c47971538fae8
content_type: application/pdf
creator: djirovec
date_created: 2021-10-05T07:56:49Z
date_updated: 2022-12-20T23:30:07Z
embargo: 2022-10-06
file_id: '10087'
file_name: PHD_Thesis_pdfa2b_1.pdf
file_size: 26910829
relation: main_file
file_date_updated: 2022-12-20T23:30:07Z
has_accepted_license: '1'
keyword:
- qubits
- quantum computing
- holes
language:
- iso: eng
month: '10'
oa: 1
oa_version: Published Version
page: '151'
project:
- _id: 2641CE5E-B435-11E9-9278-68D0E5697425
call_identifier: FWF
grant_number: P30207
name: Hole spin orbit qubits in Ge quantum wells
publication_identifier:
issn:
- 2663-337X
publication_status: published
publisher: Institute of Science and Technology Austria
related_material:
record:
- id: '8831'
relation: part_of_dissertation
status: public
- id: '10065'
relation: part_of_dissertation
status: public
- id: '10066'
relation: part_of_dissertation
status: public
- id: '8909'
relation: part_of_dissertation
status: public
- id: '5816'
relation: part_of_dissertation
status: public
status: public
supervisor:
- first_name: Georgios
full_name: Katsaros, Georgios
id: 38DB5788-F248-11E8-B48F-1D18A9856A87
last_name: Katsaros
orcid: 0000-0001-8342-202X
title: Singlet-Triplet qubits and spin-orbit interaction in 2-dimensional Ge hole
gases
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: dissertation
user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1
year: '2021'
...
---
_id: '11539'
abstract:
- lang: eng
text: 'Despite recent progress in understanding Ly α emitters (LAEs), relatively
little is known regarding their typical black hole activity across cosmic time.
Here, we study the X-ray and radio properties of ∼4000 LAEs at 2.2 < z < 6 from
the SC4K survey in the COSMOS field. We detect 254 (6.8per cent±0.4per cent)
LAEs individually in the X-rays (S/N > 3) with an average luminosity of 1044.31±0.01ergs−1
and average black hole accretion rate (BHAR) of 0.72±0.01 M⊙ yr−1, consistent
with moderate to high accreting active galactic neuclei (AGNs). We detect 120
sources in deep radio data (radio AGN fraction of 3.2per cent±0.3per cent). The
global AGN fraction (8.6per cent±0.4per cent) rises with Ly α luminosity and
declines with increasing redshift. For X-ray-detected LAEs, Ly α luminosities
correlate with the BHARs, suggesting that Ly α luminosity becomes a BHAR indicator.
Most LAEs (93.1per cent±0.6per cent) at 2 < z < 6 have no detectable X-ray emission
(BHARs < 0.017 M⊙ yr−1). The median star formation rate (SFR) of star-forming
LAEs from Ly α and radio luminosities is 7.6+6.6−2.8 M⊙ yr−1. The black hole to
galaxy growth ratio (BHAR/SFR) for LAEs is <0.0022, consistent with typical star-forming
galaxies and the local BHAR/SFR relation. We conclude that LAEs at 2 < z < 6 include
two different populations: an AGN population, where Ly α luminosity traces BHAR,
and another with low SFRs which remain undetected in even the deepest X-ray stacks
but is detected in the radio stacks.'
acknowledgement: JM acknowledges the support of a Huygens PhD fellowship from Leiden
University. We thank Camila Correa for help analysing snipshot merger trees. We
thank the anonymous referee for constructive comments. We also thank Jarle Brinchmann,
Rob Crain, Antonios Katsianis, Paola Popesso, and David Sobral for discussions and
suggestions. We also thank the participants of the Lorentz Center workshop ‘A Decade
of the Star-Forming Main Sequence’ held on 2017 September 4–8, for discussions and
ideas. We have benefited from the public available programming language PYTHON,
including the NUMPY, MATPLOTLIB, and SCIPY (Hunter 2007) packages and the TOPCAT
analysis tool (Taylor 2013).
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: João
full_name: Calhau, João
last_name: Calhau
- first_name: David
full_name: Sobral, David
last_name: Sobral
- first_name: Sérgio
full_name: Santos, Sérgio
last_name: Santos
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: Ana
full_name: Paulino-Afonso, Ana
last_name: Paulino-Afonso
- first_name: Andra
full_name: Stroe, Andra
last_name: Stroe
- first_name: Brooke
full_name: Simmons, Brooke
last_name: Simmons
- first_name: Cassandra
full_name: Barlow-Hall, Cassandra
last_name: Barlow-Hall
- first_name: Benjamin
full_name: Adams, Benjamin
last_name: Adams
citation:
ama: 'Calhau J, Sobral D, Santos S, et al. The X-ray and radio activity of typical
and luminous Ly α emitters from z ∼ 2 to z ∼ 6: Evidence for a diverse, evolving
population. Monthly Notices of the Royal Astronomical Society. 2020;493(3):3341-3362.
doi:10.1093/mnras/staa476'
apa: 'Calhau, J., Sobral, D., Santos, S., Matthee, J. J., Paulino-Afonso, A., Stroe,
A., … Adams, B. (2020). The X-ray and radio activity of typical and luminous Ly α
emitters from z ∼ 2 to z ∼ 6: Evidence for a diverse, evolving population. Monthly
Notices of the Royal Astronomical Society. Oxford University Press. https://doi.org/10.1093/mnras/staa476'
chicago: 'Calhau, João, David Sobral, Sérgio Santos, Jorryt J Matthee, Ana Paulino-Afonso,
Andra Stroe, Brooke Simmons, Cassandra Barlow-Hall, and Benjamin Adams. “The X-Ray
and Radio Activity of Typical and Luminous Ly α Emitters from z ∼ 2 to z ∼ 6:
Evidence for a Diverse, Evolving Population.” Monthly Notices of the Royal
Astronomical Society. Oxford University Press, 2020. https://doi.org/10.1093/mnras/staa476.'
ieee: 'J. Calhau et al., “The X-ray and radio activity of typical and luminous
Ly α emitters from z ∼ 2 to z ∼ 6: Evidence for a diverse, evolving population,”
Monthly Notices of the Royal Astronomical Society, vol. 493, no. 3. Oxford
University Press, pp. 3341–3362, 2020.'
ista: 'Calhau J, Sobral D, Santos S, Matthee JJ, Paulino-Afonso A, Stroe A, Simmons
B, Barlow-Hall C, Adams B. 2020. The X-ray and radio activity of typical and luminous
Ly α emitters from z ∼ 2 to z ∼ 6: Evidence for a diverse, evolving population.
Monthly Notices of the Royal Astronomical Society. 493(3), 3341–3362.'
mla: 'Calhau, João, et al. “The X-Ray and Radio Activity of Typical and Luminous
Ly α Emitters from z ∼ 2 to z ∼ 6: Evidence for a Diverse, Evolving Population.”
Monthly Notices of the Royal Astronomical Society, vol. 493, no. 3, Oxford
University Press, 2020, pp. 3341–62, doi:10.1093/mnras/staa476.'
short: J. Calhau, D. Sobral, S. Santos, J.J. Matthee, A. Paulino-Afonso, A. Stroe,
B. Simmons, C. Barlow-Hall, B. Adams, Monthly Notices of the Royal Astronomical
Society 493 (2020) 3341–3362.
date_created: 2022-07-08T07:34:10Z
date_published: 2020-04-01T00:00:00Z
date_updated: 2022-08-18T11:25:31Z
day: '01'
doi: 10.1093/mnras/staa476
extern: '1'
external_id:
arxiv:
- '1909.11672'
intvolume: ' 493'
issue: '3'
keyword:
- Space and Planetary Science
- Astronomy and Astrophysics
- 'galaxies: active'
- 'galaxies: evolution'
- 'galaxies: high-redshift'
- 'quasars: supermassive black holes'
- 'galaxies: star formation'
- 'cosmology: observations'
- 'X-rays: galaxies'
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://arxiv.org/abs/1909.11672
month: '04'
oa: 1
oa_version: Preprint
page: 3341-3362
publication: Monthly Notices of the Royal Astronomical Society
publication_identifier:
eissn:
- 1365-2966
issn:
- 0035-8711
publication_status: published
publisher: Oxford University Press
quality_controlled: '1'
scopus_import: '1'
status: public
title: 'The X-ray and radio activity of typical and luminous Ly α emitters from z
∼ 2 to z ∼ 6: Evidence for a diverse, evolving population'
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 493
year: '2020'
...