How many bits can a qubit hold?
It is possible to fully encode one bit in one qubit. However, a qubit can hold more information, e.g., up to two bits using superdense coding.
How big is a qubit?
about 0.2 millimeter across
Each qubit is about 0.2 millimeter across, big enough to be visible through an ordinary microscope.
Does a qubit have infinite values?
Contrary to the classical bit, a qubit can have an infinite number of values, those on the surface of the Bloch sphere (at least until it is measured), so: How do the availability of infinite values affect the computational power?