Generation and characterization of microwave quantum states

Doctoral thesis, 2022

The theory of quantum mechanics started developing in the 1920s to account for certain phenomena involving light and radiation that could not be explained by classical physics, such as the spectra of light emitted by atoms. Over the last decades we have seen the emergence of quantum information science which addresses the question whether we can use the quantum behavior of light to create new technologies, and indeed, it turns out that quantum effects are useful for applications in cryptography, sensing, and computing.
Advances in engineering have also resulted in the ability to fabricate controllable quantum systems that can be utilized within those fields.
There are different platforms for quantum technologies, but superconducting circuits are seen as particularly promising and large companies such as Google and Amazon are investing in this.

The perhaps most important step in order to be able to take advantage of quantum effects is quantum state preparation. Microwaves are the natural frequency range for superconducting circuits, and in this thesis we demonstrate different ways to prepare useful microwave quantum states. Additionally, we characterize the states and their properties since it is also exceedingly important to verify which state was generated.