Which property allows a qubit to hold the values zero and one at the same time?

The correct answer is B, the Department of Science and Technology. The Union Cabinet approved the mission on 19 April 2023 and placed its implementation with that department, which runs it through four thematic hubs at leading academic institutions. Option A is wrong because the Department of Atomic Energy looks after nuclear power, nuclear research centres and related applications, and it is not the nodal agency here. Option C is wrong because the Department of Space, which runs the Indian Space Research Organisation, has demonstrated quantum key distribution of its own but does not implement the mission. Option D is wrong because the Ministry of Electronics and Information Technology runs programmes in semiconductors and artificial intelligence, a separate stream. Learn the pairing of each mission with its nodal department, since that is the usual question format.

The correct answer is B, 50 to 1,000 physical qubits. This is the headline target stated when the Cabinet approved the mission, and it is to be achieved on more than one hardware platform, including superconducting and photonic technology, rather than on a single design. The range is called intermediate scale because machines of this size are large enough to be useful for research but still too small to run error corrected algorithms at full strength. Option A is wrong because machines of a few dozen qubits already existed worldwide when the mission was framed, so that would be no target at all. Option C is wrong because a thousand is the upper and not the lower end of the stated range. Option D is wrong because no national programme has set a target of tens of thousands of physical qubits for eight years.

The correct answer is B, the Indian Institute of Science, Bengaluru. The mission divides the field among four thematic hubs, and quantum computing was assigned to the Indian Institute of Science. Option A is wrong because the Indian Institute of Technology Madras hosts the hub for quantum communication, which covers quantum key distribution over fibre and by satellite. Option C is wrong because the Indian Institute of Technology Bombay hosts the hub for quantum sensing and metrology, the branch that produces atomic clocks, magnetometers and gravimeters. Option D is wrong because the Indian Institute of Technology Delhi hosts the hub for quantum materials and devices, which builds the superconductors, topological materials and single photon sources the other three branches depend on. Learn the four as a set, since questions often swap two of them.

The correct answer is B, factoring large integers. Peter Shor published the algorithm in 1994, and it would let a sufficiently large quantum computer break the large number factorisation on which public key encryption such as the RSA system depends. That threat is the reason governments and standards bodies have begun work on post quantum cryptography. Option A is wrong because searching an unsorted database is the task of Grover's algorithm, published by Lov Grover in 1996, which gives a quadratic rather than an exponential speedup. Option C is wrong because sorting is not a problem on which quantum computers hold any celebrated advantage. Option D is wrong because image compression is a classical signal processing task with no quantum algorithm of this importance. Keep the pair clear: Shor factors, Grover searches.

The correct answer is B, an unknown quantum state cannot be copied and measuring it disturbs it. The no cloning theorem forbids an exact copy of an unknown state, and any measurement changes the state, so an eavesdropper on the channel inevitably leaves statistical traces that the two legitimate parties detect when they compare a sample of their key. The BB84 protocol of Charles Bennett and Gilles Brassard, proposed in 1984, is built on exactly this. Option A is wrong because double encryption is a classical measure and is not what makes the method secure. Option C is wrong because the speed of the signal has nothing to do with secrecy. Option D is wrong because quantum key distribution runs over ordinary optical fibre and free space links that any receiver can physically access; the security lies in physics, not in hiding the channel.