Quantum Dot Dissipation in Microwave Resonators : Toward High Bandwidth Charge Readout
(2025)- Abstract
- Detecting a single elementary charge has become an important task to achieve as applications within quantum
technologies such as for qubit readout, nanothermodynamics or single shot photodetection rely on the location
of single electrons. The use of microwave resonators as the readout method for the charge sensitive single electron
devices, such as quantum dots, has been extensively used to achieve high-speed charge readout. By matching the
input impedance of the resonator to the high impedance of the quantum dot, this yields a large signal with a
bandwidth set by the dissipation rate of the resonator. Most implementations of these systems use an external
inductance which together with the parasitic capacitance of... (More) - Detecting a single elementary charge has become an important task to achieve as applications within quantum
technologies such as for qubit readout, nanothermodynamics or single shot photodetection rely on the location
of single electrons. The use of microwave resonators as the readout method for the charge sensitive single electron
devices, such as quantum dots, has been extensively used to achieve high-speed charge readout. By matching the
input impedance of the resonator to the high impedance of the quantum dot, this yields a large signal with a
bandwidth set by the dissipation rate of the resonator. Most implementations of these systems use an external
inductance which together with the parasitic capacitance of the input line forms a resonant circuit. This limits the
resonance frequency and impedance of the resonator which sets an upper limit to the bandwidth of the resonator,
limiting the maximum readout speed. By instead using the resonators typically employed in circuit quantum
electrodynamics for this readout, this limit can be bypassed.
In Paper I, we study the dissipation in the quantum dot at these increased frequencies enabled by a coplanar
waveguide resonator. Here, as the energy of the microwave photons is no longer negligible compared to the
temperature of the sensor, additional transport in the QD becomes enabled. This results in increased dissipation
for asymmetric QDs, and the appearance of spin-dependent dissipation. Additionally, we show that the photon
energy broadens the linewidth of the quantum dot as seen by the microwave resonator, decreasing the maximum
sensitivity of the sensor.
In Paper II, we use a high impedance Josephson junction (JJ) array resonator to further increase the readout
bandwidth. We find here that by operating the resonator in the nonlinear regime, the added dissipation from
the quantum dot sensor qualitatively changes the signal, enabling a frequency shift along the steep edge of the
response. This leads to a near-unity signal without the need to satisfy the impedance matching condition imposed
upon a linear resonator. By avoiding this matching condition we show that the bandwidth of the resonator can
be further increased, allowing faster maximum readout speeds in the resonator. Finally, we discuss further benefits
and limits to a high-impedance device operating in the nonlinear regime. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/2cd61817-85f8-47f1-b3d2-327ddf9cd5b5
- author
- Havir, Harald LU
- supervisor
-
- Ville Maisi LU
- Peter Samuelsson LU
- opponent
-
- Ass. Prof. Ares, Natalia, University of Oxford, United Kingdom.
- organization
- publishing date
- 2025
- type
- Thesis
- publication status
- published
- subject
- keywords
- Circuit Quantum Electrodynamics, Low-Dimensional Transport, Microwave Resonators, Quantum Dots, Charge Sensing, Nonlinearities
- pages
- 138 pages
- publisher
- Department of Physics, Lund University
- defense location
- Lecture Hall Rydbergsalen, Department of Physics, Professorsgatan 1, Faculty of Engineering LTH, Lund University, Lund. The dissertation will be live streamed, but part of the premises is to be excluded from the live stream.
- defense date
- 2025-10-10 09:15:00
- ISBN
- 978-91-8104-647-2
- 978-91-8104-646-5
- language
- English
- LU publication?
- yes
- id
- 2cd61817-85f8-47f1-b3d2-327ddf9cd5b5
- date added to LUP
- 2025-09-08 11:07:07
- date last changed
- 2025-10-02 08:09:15
@phdthesis{2cd61817-85f8-47f1-b3d2-327ddf9cd5b5,
abstract = {{Detecting a single elementary charge has become an important task to achieve as applications within quantum<br/>technologies such as for qubit readout, nanothermodynamics or single shot photodetection rely on the location<br/>of single electrons. The use of microwave resonators as the readout method for the charge sensitive single electron<br/>devices, such as quantum dots, has been extensively used to achieve high-speed charge readout. By matching the<br/>input impedance of the resonator to the high impedance of the quantum dot, this yields a large signal with a<br/>bandwidth set by the dissipation rate of the resonator. Most implementations of these systems use an external<br/>inductance which together with the parasitic capacitance of the input line forms a resonant circuit. This limits the<br/>resonance frequency and impedance of the resonator which sets an upper limit to the bandwidth of the resonator,<br/>limiting the maximum readout speed. By instead using the resonators typically employed in circuit quantum<br/>electrodynamics for this readout, this limit can be bypassed.<br/>In Paper I, we study the dissipation in the quantum dot at these increased frequencies enabled by a coplanar<br/>waveguide resonator. Here, as the energy of the microwave photons is no longer negligible compared to the<br/>temperature of the sensor, additional transport in the QD becomes enabled. This results in increased dissipation<br/>for asymmetric QDs, and the appearance of spin-dependent dissipation. Additionally, we show that the photon<br/>energy broadens the linewidth of the quantum dot as seen by the microwave resonator, decreasing the maximum<br/>sensitivity of the sensor.<br/>In Paper II, we use a high impedance Josephson junction (JJ) array resonator to further increase the readout<br/>bandwidth. We find here that by operating the resonator in the nonlinear regime, the added dissipation from<br/>the quantum dot sensor qualitatively changes the signal, enabling a frequency shift along the steep edge of the<br/>response. This leads to a near-unity signal without the need to satisfy the impedance matching condition imposed<br/>upon a linear resonator. By avoiding this matching condition we show that the bandwidth of the resonator can<br/>be further increased, allowing faster maximum readout speeds in the resonator. Finally, we discuss further benefits<br/>and limits to a high-impedance device operating in the nonlinear regime.}},
author = {{Havir, Harald}},
isbn = {{978-91-8104-647-2}},
keywords = {{Circuit Quantum Electrodynamics; Low-Dimensional Transport; Microwave Resonators; Quantum Dots; Charge Sensing; Nonlinearities}},
language = {{eng}},
publisher = {{Department of Physics, Lund University}},
school = {{Lund University}},
title = {{Quantum Dot Dissipation in Microwave Resonators : Toward High Bandwidth Charge Readout}},
url = {{https://lup.lub.lu.se/search/files/227220671/kappa_LUCRIS.pdf}},
year = {{2025}},
}