Previous Year Question

A qubit, or quantum bit, is the fundamental unit of information in quantum computing. In classical computing, a bit exists in only one of two definite states—0 or 1. In contrast, a qubit can exist in a combined state of 0 and 1 because of quantum superposition.

The general state of a qubit is mathematically represented as

where α and β are probability amplitudes and ∣𝛼∣² + ∣𝛽∣² =1. When a measurement is performed, the qubit produces either 0 or 1 as the outcome.

Entanglement can also be established between qubits in quantum computers. By using superposition, entanglement and interference, a quantum computer can process multiple possibilities differently from a classical computer for certain specific problems.

Qubits can be created through different physical systems such as superconducting circuits, trapped ions, photons, neutral atoms or quantum dots. Qubits are extremely sensitive; the process through which environmental interaction destroys their quantum state is known as decoherence. Therefore, quantum error correction and highly controlled operating conditions are required.

Cloud services, visible-light communication and wireless communication also use advanced computing and communication technologies, but a ‘qubit’ is not their fundamental unit of information.