Abstract

Our phenomenal color experience has very particular properties. There are six elementary colors, that is, colors that are not perceived as being composed of a combination of other colors: white, black, red, yellow, green, and blue. Noticeably, the six elementary colors are divided into two phenomenally distinct groups—achromatic and chromatic. Furthermore, the six elementary colors result from the outputs of three independent opponent processes: a white–black process, a red–green process, and a yellow–blue process. Any color percept can be described as a three-dimensional vector whose components are the output levels of these opponent processes. What brings about these properties of color experience? Here I point out that the phenomenal properties of color percepts have exact analogs in the mathematical properties of Bloch vectors reconstructed through qubit quantum state tomography. Such parallelism between phenomenal and physical states is exactly what dual-aspect theories of phenomenal consciousness predict. I therefore hypothesize that color experience is the phenomenal dual aspect of qubit quantum state tomography taking place somewhere in the brain. I show that a testable prediction of this hypothesis is that a color’s combined level of whiteness and blackness should be proportional to its perceived luminance. A natural generalization of the suggested relationship between color experience and qubits is that other types of phenomenal experience (e.g., odor, taste) result from quantum state tomography of systems with higher dimensionalities than a qubit. From the analysis of this generalization I derive a testable prediction regarding the dimensionality of odor space.