Towards Quantum Computing for Audio and Music Expression

A partial version of Chapter 2 has been published as a book chapter: Itaboraí, P.V., Miranda, E.R. (2022). Quantum Representations of Sound: From Mechanical Waves to Quantum Circuits. In: Miranda, E.R. (eds) Quantum Computer Music. Springer, Cham. https://doi.org/10.1007/978-3-031-13909-3_10 - However, the "Quantum Computer Music" book version and this Thesis' chapter 2 have some noticeable differences in their content, due to the rapid development of this field.This research delves into the initial approaches of the use of emerging Quantum Computing technologies in music practice, anchored on preliminary studies on Quantum Representation of Audio (QRA). The approach is interdisciplinary, and attempts to explore the object - QRA - both from a technical scope and an artistic scope. A systematic review unifies diverse QRA techniques, spotlighting the need to bring accessibility to these techniques and terminologies (dense in theoretical physics formalism) for a computer music and/or artistic audiences, in a didactic manner. In this review, some additional techniques initially only discussed for representing images are translated into audio. An improved classification system is proposed to better organise the QRA field. This led to the observation of a pair of strategies that can be converted into each other with the use of a single quantum gate, sparking ideas for future Quantum Audio Conversion algorithms. To bridge theory and practice, a Python package named 'quantumaudio' was prototyped, enabling a flexible use of quantum audio encoding and decoding schemes for three QRA strategies. Demonstrations of simple workflows with 'quantumaudio' underlined their potential to generate constituent sound materials for electronic music, on account of a simple digital musical interface prototype that maps quantum signals to wavetable oscillators. The journey culminated with one of the demonstrations - "Geiger-Counter Effect" (GCE) - being integrated into two artistic processes, which explored the juxtaposition of quantum measurements with early analog music aesthetics. The first became an acousmatic study, "Rasgar, Saber", whereas the second materialised in the form of "Rever", a design/improvisation process of crafting a hybrid quantum-digital-analog musical instrument, inspired by the work of Walter Smetak. This study hopes to lay foundations and examples for the dawning approaches in Quantum Computer Music, starting from the essence of organised sound