Qubits, despite their name, are not inherently analog or digital in nature. The distinction between analog and digital usually refers to the representation and manipulation of continuous values versus discrete values, respectively. However, qubits in quantum computing operate based on the principles of quantum mechanics, which involve complex mathematical formulations.
While classical bits are inherently digital and represent discrete values (0 or 1), qubits can exist in superpositions of both 0 and 1 simultaneously. This property of superposition allows qubits to represent a continuum of states between 0 and 1, rather than being limited to discrete values. Mathematically, qubits are represented as vectors in a complex vector space.
However, when it comes to practical implementation and measurement of qubits, the readout process is usually discrete and digital. When a qubit is measured, it collapses into either the 0 state or the 1 state, providing a classical, discrete outcome. This measurement outcome is analogous to a classical bit.
Therefore, while the internal state of a qubit can be considered as existing in a superposition and is not purely digital, the measurement and output of a qubit are ultimately discrete and digital. It is this measurement outcome that can be used as the basis for classical computation or as an input to subsequent quantum operations.