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Quantum Electro- and Acoustodynamics in Waveguides
Doktorsavhandling, 2021

This thesis deals with the interaction between artificial atoms and quantum fields in one-dimensional waveguides. The waveguide represents a one-dimensional environment for the atom, which we use to study the properties of open quantum systems. All quantum systems are, in fact, open, and interactions between the system and its environment lead inevitably to a loss of energy and quantum coherence. A continuous loss of information into the environment is called a Markovian process. The work contained in this thesis indicates that deviations from a Markovian process can be detected in the steady state of driven systems. This could simplify the detection of non-Markovianity in open quantum systems, as no information about the system's transient dynamics would be necessary.

Specifically, this thesis considers both electromagnetic fields in microwave transmission lines and acoustic fields in the form of surface acoustic waves (SAWs) traveling on the surface of solids. The recent realization of artificial atoms interacting with acoustic waves has opened up a new research field called quantum acoustics. We have built a model of the interaction between atoms and SAWs that predicts the existence of a new regime where the atom forms its own cavity. Additionally, we have considered synthesizing electromagnetically induced transparency, a quantum optics phenomena in opaque media where the absorption of photons is canceled, in waveguides using multiple closely spaced two-level systems.

Some of the work in this thesis represents experimental work done in collaboration. In the first experiment, we studied the routing of acoustic waves at the quantum level. In the other experiment, we demonstrated electromagnetically induced transparency by creating an effective $\Lambda$ system using a giant artificial atom. This thesis reviews the numerical techniques used to model these experiments.

## Författare

### Andreas Josefsson Ask

Chalmers, Mikroteknologi och nanovetenskap (MC2), Tillämpad kvantfysik

### Cavity-free vacuum-Rabi splitting in circuit quantum acoustodynamics

PHYSICAL REVIEW A,; Vol. 99(2019)

**Artikel i vetenskaplig tidskrift**

### Towards phonon routing: controlling propagating acoustic waves in the quantum regime

New Journal of Physics,; Vol. 21(2019)

**Artikel i vetenskaplig tidskrift**

### Engineering the level structure of a giant artificial atom in waveguide quantum electrodynamics

PHYSICAL REVIEW A,; Vol. 103(2021)

**Artikel i vetenskaplig tidskrift**

### Ask, A., Fang, L., Kockum, A. F., Synthesizing electromagnetically induced transparency without a control field in waveguide QED using small and giant atoms

### Ask, A., Johansson, G., Non-Markovian steady states of a driven two-level system

In this thesis, we theoretically study the interaction of artificially made atoms with one-dimensional quantum fields. Artificial atoms have properties chosen by the engineer, unlike natural atoms, whose properties are selected by nature. Such powers in design have led to many novel demonstrations of fundamental quantum phenomena. These atoms also constitute the fundamental building blocks of a quantum information processor, and many of the systems and theoretical techniques discussed in this thesis have applications in this direction.

### Styrkeområden

Nanovetenskap och nanoteknik (SO 2010-2017, EI 2018-)

### Fundament

Grundläggande vetenskaper

### Ämneskategorier

Atom- och molekylfysik och optik

### ISBN

978-91-7905-462-5

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4929

### Utgivare

Chalmers tekniska högskola

Opponent: Klaus Møllmer, Aarhus University, Denmark