Which one of the following is the context in which the term "qubit" is mentioned ?

(a) Cloud Services
(b) Quantum Computing ✓ UPSC's answer
(c) Visible Light Communication Technologies
(d) Wireless Communication Technologies

Why the answer is (b)

• A qubit (quantum bit) is the basic unit of information in quantum computing; unlike a classical bit fixed at 0 or 1, a qubit can exist in a superposition of both states and be entangled with other qubits — option (b).

• This lets quantum computers explore many possibilities at once, promising advantages in cryptography, materials simulation and optimisation.

• Qubits are realised with superconducting circuits, trapped ions or photons; India's National Quantum Mission aims at 50–1000-qubit machines.

• Cloud services, visible-light communication and wireless technologies use classical bits.

• Hence option (b).

Why the other options are wrong

(a) Cloud Services: Cloud services run on classical computing.
(c) Visible Light Communication Technologies: Visible light communication uses classical signals, not qubits.
(d) Wireless Communication Technologies: Wireless communication uses classical bits.

Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2022, held on 5 June 2022. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.