Which method is used to measure the state of a qubit?

The method used to measure the state of a qubit is known as measurement collapse. When a qubit, which can exist in a superposition of states, is measured, the act of measurement causes the qubit to collapse from its quantum state into one of the possible classical states, typically represented as 0 or 1. This transition is fundamental to quantum mechanics and is crucial in quantum computing, as it allows the retrieval of information about the qubit's state.

Measurement collapse signifies that prior to measurement, the qubit holds multiple potential values due to its quantum nature. Once a measurement is performed, this inherent uncertainty is resolved into a definite outcome. This behavior is a stark contrast to classical bits, where the state is clearly defined at all times.

Other methods mentioned, like decoding, initialization, and quantum computing, play roles in various processes involving qubits but do not directly pertain to the act of measuring a qubit's state. Initialization refers to setting a qubit to a specific state at the beginning of a quantum computation, while decoding relates to interpreting outputs from quantum operations. Quantum computing is the overarching field that utilizes these principles, but measurement collapse specifically addresses the mechanism that determines the result of measuring a qubit.