Qualia (クオリア, kuoria?) is the term used in the Ciel world (the EXA_PICO universe) to refer to the viewpoint that each individual soul has, or in other words, to the Static Hymmno Waves that carry the personality and memories of every single individual. Likewise, the Qualia could also be defined as the wall that separates every soul from each other, allowing the formation of individuality for each person, making it into the natural equivalent of the Boundary Gates that partition the Cosmospheres of each individual Reyvateil in Ar Ciel.
As can be surmised from this, the Qualia doesn't exist in the physical plane, and instead it exists on the same ethereal plane where feelings and souls are located. This plane is the Sixth Axis or Qualia Dimension, with the word aru-yan being used to refer to it in the Emotional Song Pact language, and it is inextricably linked to the Fifth Axis or Possibility Dimension due to the fact that every possibility is different from each other, so they won't share the same Qualia due to their inhabitants having experienced different lives in varying degrees.
Therefore, we could say the Qualia have as much impact as the physical laws when it comes to shaping the world, as all changes are directed either by the movements all objects in the universe carry out following the physical laws, or because they follow the will that their own Qualia represents, which is in turn finally directed by the overall Qualia of the universe itself: EXA_PICO.
Additionally, if it was possible to move across the Sixth Axis, it would be seen as a straight line, with the consequence that taking even a single step outside of that line would greatly change that person's own personality and memories. This is because said line is the limit between Qualia, serving the same purpose a country border would have in tridimensional space. Additionally, it is a common occurrence among novice users of the Oversight to step out of that line, or strictly speaking, being unable to observe the center of their own Qualia: the Qualia Core; due to their inexperience in wielding that power.
The Qualia concept also exists in our world, but it has a different definition: it means the characteristics that are intrinsic to every object in the universe, as well as the subjective perception of every being.