Abstract
Superconducting artificial atoms are remarkably attractive to study quantum optics phenomena. The artificial atoms are nanoscale electronic circuits that can be fabricated using wellestablished techniques and can therefore be easily scaled up to larger systems. Their energy levels can be engineered as desired, and strong coupling can be achieved with resonators and transmission lines. This greater control of parameters is a huge advantage over natural atoms and allows to reach regimes that would otherwise be unattainable.
In this thesis, we report on quantum optics phenomena on chip and their emerging devices for present and future applications with a focus on quantum wave mixing (QWM) effects.
First, we study continuous wave mixing on a quantum object and observe a symmetric spectrum with an infinite number of side peaks. Then, we investigate two regimes of QWM: Coherent wave mixing and quantum wave mixing with nonclassical superposed states. In the former, two pulsed waves with frequencies slightly detuned from each other are scattered on the single artificial atom resulting in a symmetric spectrum with an infinite number of side peaks. The amplitude of each of these peaks oscillates in time according to Bessel functions with the orders determined by the number of interacting photons. In the latter regime, a time delay between the two pulses is introduced causing a striking difference in the spectrum, which now exhibits a finite number of narrow coherent emission peaks. Furthermore, the spectrum in the latter regime is asymmetric with the number of positive frequency peaks (due to stimulated emission) always exceeding by one compared to the negative frequency peaks (due to absorption).
Then, we investigate a coherent frequency conversion scheme with a single threelevel artificial atom. The scheme is based on threewave mixing, which utilises the quantised energy levels of the artificial atom. We drive the threelevel atom with two continuous drives corresponding to two transition frequencies of the atom and measure the coherent emission at the sum or difference frequency.
The device may be used as a quantum router, coherently interconnecting quantum channels, in prospective quantum networks.
Another part of the thesis addresses the challenge of measuring the absolute power of a microwave signal in a transmission line at cryogenic temperatures which is critical for applications in quantum optics, quantum computing and quantum information.
We demonstrate that a twolevel system strongly coupled to the open space can act as a quantum sensor of absolute power. We realise the quantum sensor using a superconducting flux qubit that is strongly coupled to the environment. The quantum sensor is independent of dephasing of the twolevel system.
In this thesis, we report on quantum optics phenomena on chip and their emerging devices for present and future applications with a focus on quantum wave mixing (QWM) effects.
First, we study continuous wave mixing on a quantum object and observe a symmetric spectrum with an infinite number of side peaks. Then, we investigate two regimes of QWM: Coherent wave mixing and quantum wave mixing with nonclassical superposed states. In the former, two pulsed waves with frequencies slightly detuned from each other are scattered on the single artificial atom resulting in a symmetric spectrum with an infinite number of side peaks. The amplitude of each of these peaks oscillates in time according to Bessel functions with the orders determined by the number of interacting photons. In the latter regime, a time delay between the two pulses is introduced causing a striking difference in the spectrum, which now exhibits a finite number of narrow coherent emission peaks. Furthermore, the spectrum in the latter regime is asymmetric with the number of positive frequency peaks (due to stimulated emission) always exceeding by one compared to the negative frequency peaks (due to absorption).
Then, we investigate a coherent frequency conversion scheme with a single threelevel artificial atom. The scheme is based on threewave mixing, which utilises the quantised energy levels of the artificial atom. We drive the threelevel atom with two continuous drives corresponding to two transition frequencies of the atom and measure the coherent emission at the sum or difference frequency.
The device may be used as a quantum router, coherently interconnecting quantum channels, in prospective quantum networks.
Another part of the thesis addresses the challenge of measuring the absolute power of a microwave signal in a transmission line at cryogenic temperatures which is critical for applications in quantum optics, quantum computing and quantum information.
We demonstrate that a twolevel system strongly coupled to the open space can act as a quantum sensor of absolute power. We realise the quantum sensor using a superconducting flux qubit that is strongly coupled to the environment. The quantum sensor is independent of dephasing of the twolevel system.
Original language  English 

Qualification  Ph.D. 
Awarding Institution 

Supervisors/Advisors 

Thesis sponsors  
Award date  1 Jun 2018 
Publication status  Unpublished  1 Mar 2018 