The year 2025 marked a century of quantum mechanics, observed as the International Year of Quantum Science and Technology. A hundred years after the physics was settled, the engineering has finally become a national strategic question, and quantum technology now sits alongside semiconductors and artificial intelligence in the small set of capabilities that determine long-run technological standing.
Quantum technology uses the principles of quantum mechanics to build systems for computing, communication, sensing, metrology and materials, exploiting properties that have no classical analogue.
The Four Principles
- Superposition: a quantum particle can exist in multiple states simultaneously until measured, which lets a quantum computer explore many possibilities at once
- Entanglement: two particles remain connected across distance, so a change in one affects the other’s state, which is the basis of quantum communication and the future quantum internet
- Quantum tunnelling: a particle passes through an energy barrier that classical physics forbids, a principle already central to semiconductors
- Quantisation: energy is absorbed or emitted in discrete packets rather than continuously
Where a classical bit is 0 or 1, a qubit can be a combination of both.
The Four Application Domains
Quantum computing. Qubits solve certain problems far faster than classical machines. The realistic near-term targets are drug discovery, financial modelling, climate modelling, quantum chemistry, material design, and logistics and supply-chain optimisation. Note the word certain: quantum computers are not faster at everything, only at specific problem classes.
Quantum communication. Quantum Key Distribution exchanges cryptographic keys using quantum states. Its security is physical: if a third party observes the state, the observation disturbs the system and alerts the users. The quantum internet, built on entanglement, quantum memories and quantum repeaters, would enable ultra-secure communication, distributed quantum computing and networked sensors.
Quantum sensing and metrology. Sensors measuring physical quantities with extreme precision: magnetic-field detection, gravity measurement, atomic-clock timekeeping, navigation in GPS-denied environments, mineral and oil exploration, earthquake and volcanic monitoring, medical diagnostics, brain imaging, and submarine detection.
Quantum simulation. Specialised systems modelling complex quantum behaviour to study molecular interactions, new drugs, battery materials, superconductors, catalysts, high-energy physics and novel materials.
The National Quantum Mission
Approved in 2023 with an outlay of over Rs 6,000 crore for eight years, from 2023-24 to 2030-31, built around four verticals: quantum computing, quantum communication, quantum sensing and metrology, and quantum materials and devices.
The four-vertical structure is a deliberate hedge. A mission betting only on quantum computing would be betting on the hardest and slowest of the four.
Where Quantum Lands First
This is the part most coverage gets wrong. Quantum sensors are likely to become useful well before large-scale universal quantum computers, because they need far fewer qubits and are much closer to deployment.
That has direct strategic consequences for India. Navigation in GPS-denied environments, submarine detection, and gravity-based mineral exploration are near-term military and resource capabilities, not distant possibilities. A country that treats quantum purely as a computing race will underinvest in the part that pays off first.
The Security Problem Nobody Can Defer
Sufficiently capable quantum computers would break the public-key cryptography that currently secures banking, government communication, digital identity and payments. This is not speculative; it is a matter of timing.
The threat arrives before the machine does, through harvest-now-decrypt-later: an adversary can record encrypted traffic today and decrypt it once the capability exists. For a country running digital public infrastructure at India’s scale, migration to post-quantum cryptography is a present-tense problem with a future-tense trigger.
The Honest Constraints
- Talent. The binding constraint is people, not money. Quantum physicists and cryogenic engineers cannot be produced on a mission timeline.
- Hardware supply chains. Dilution refrigerators, control electronics, specialised lasers and ultra-pure materials are mostly imported from a handful of suppliers.
- Error correction. Current qubits are noisy, and the overhead needed for fault tolerance is enormous. Announcements of qubit counts are not announcements of usable capability.
- Commercial uncertainty. No one can currently state with confidence when a quantum computer will produce commercially decisive advantage.
The Way Forward
- Prioritise the sensing vertical for near-term strategic returns.
- Begin post-quantum cryptography migration for critical infrastructure now, not when a machine appears.
- Fund doctoral and postdoctoral pipelines aggressively, since talent has the longest lead time.
- Build domestic capacity in enabling hardware, particularly cryogenics and control electronics.
- Keep the four-vertical hedge intact, resisting pressure to concentrate everything on computing.
Quantum technology is not a race to a single machine. It is four separate races, and India’s realistic wins are in the ones that get less attention.
Frequently Asked Questions
What is quantum technology?
Technology that uses the principles of quantum mechanics to build advanced systems for computing, communication, sensing, metrology and materials. It exploits quantum properties such as superposition, entanglement, tunnelling and quantisation, which have no classical equivalent.
What is a qubit?
The quantum equivalent of a classical bit. A classical bit is either 0 or 1. A qubit can exist in a combination of 0 and 1 at the same time through superposition, which is what allows a quantum computer to explore many possibilities simultaneously.
What are the four principles used in quantum technology?
Superposition, where a particle exists in multiple states at once until measured; entanglement, where two particles remain connected even when far apart so that a change in one affects the other; quantum tunnelling, where a particle passes through an energy barrier that classical physics forbids; and quantisation, where energy is absorbed or emitted in discrete packets.
What is Quantum Key Distribution?
A secure communication method that uses quantum mechanics to create and distribute cryptographic keys between two parties. Its security is physical rather than mathematical: if a third party observes the quantum state, the act of observation disturbs the system and alerts the users.
What is the National Quantum Mission?
Approved in 2023 with an outlay of over Rs 6,000 crore for eight years from 2023-24 to 2030-31. It has four verticals: quantum computing, quantum communication, quantum sensing and metrology, and quantum materials and devices.
Why will quantum sensing be deployed before quantum computing?
Because quantum sensors need far fewer qubits and are much closer to practical deployment than a large-scale universal quantum computer. They are the near-term commercial and strategic payoff of quantum research, while general-purpose quantum computing remains a longer horizon.
What are the applications of quantum sensing?
Magnetic-field detection, gravity measurement, timekeeping through atomic clocks, navigation in GPS-denied environments, mineral and oil exploration, earthquake and volcanic monitoring, medical diagnostics, brain imaging, and submarine detection and defence sensing.
What was the International Year of Quantum Science and Technology?
2025 was observed as the International Year of Quantum Science and Technology, marking 100 years since the development of quantum mechanics and recognising its growing strategic importance.
Practice Questions
Prelims MCQs
- A qubit differs from a classical bit because it
(a) Stores more data per unit area
(b) Can exist in a superposition of 0 and 1
(c) Operates at higher temperature
(d) Uses optical rather than electronic signals
Answer: (b) Superposition allows a qubit to represent a combination of states, which is the basis of quantum parallelism. - Quantum Key Distribution derives its security from
(a) The difficulty of factoring large numbers
(b) The fact that observation disturbs the quantum state
(c) The length of the encryption key
(d) Distributed ledger verification
Answer: (b) Any interception alters the quantum state and is therefore detectable, which makes the security physical rather than computational. - India's National Quantum Mission was approved in
(a) 2019
(b) 2021
(c) 2023
(d) 2025
Answer: (c) The Mission was approved in 2023 for eight years, from 2023-24 to 2030-31. - Which of the following is not one of the four verticals of the National Quantum Mission?
(a) Quantum computing
(b) Quantum communication
(c) Quantum sensing and metrology
(d) Quantum cryptocurrency
Answer: (d) The fourth vertical is quantum materials and devices; cryptocurrency is not part of the Mission. - Quantum tunnelling is best described as
(a) Two particles remaining linked across distance
(b) A particle passing through an energy barrier classical physics forbids
(c) Energy being emitted in discrete packets
(d) A particle occupying multiple states at once
Answer: (b) Tunnelling is the passage through a barrier that would be insurmountable classically, and it underpins semiconductor behaviour.
Mains Questions
- Quantum technology is a strategic capability rather than a commercial one in the near term. Examine with reference to India's National Quantum Mission. (250 words)
- Quantum computing threatens existing cryptographic systems. Discuss the implications for India's digital infrastructure and the responses available. (250 words)
- Quantum sensing is likely to deliver practical benefits before quantum computing. Explain why, with applications. (150 words)
- Discuss the role of quantum communication in securing critical national infrastructure. (150 words)
- Evaluate India's institutional and human-capital readiness for the National Quantum Mission. (250 words)
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