The Quantum Leap: Quantum Technologies and the National Quantum Mission

Quantum technology is the use of the laws of quantum mechanics, the physics of atoms and subatomic particles, to build machines that compute, communicate and measure in ways classical physics cannot. Where classical technology treats matter as continuous and predictable, quantum technology exploits strange behaviours such as superposition, entanglement and tunnelling that appear only at atomic scales. For UPSC, quantum technology sits at the intersection of science, national security and strategic autonomy, which is why the Union Cabinet approved the National Quantum Mission in April 2023 with an outlay of ₹6,003.65 crore spread over eight years.

The field got a global spotlight when the United Nations designated 2025 as the International Year of Quantum Science and Technology, marking 100 years since Werner Heisenberg's 1925 paper that laid the foundations of quantum mechanics.

The rulebook of the quantum world

A quantum is the smallest discrete unit of energy or matter behaviour; a photon, for instance, is the quantum of light. Quantum mechanics is the branch of physics that describes how such particles behave at atomic and subatomic scales, where everyday intuition breaks down. Classical bits in a computer are either 0 or 1, but a qubit, the basic unit of quantum information, can exist in a combination of 0 and 1 at the same time. This difference is the seed of everything quantum technology promises.

Superposition is the principle that a quantum particle can exist in multiple states at once until it is measured. It lets a quantum computer explore many possible solutions to a problem simultaneously, which is why superposition matters for optimisation, drug discovery and artificial intelligence. Entanglement is the phenomenon in which two quantum particles become linked so that the state of one instantly affects the other, no matter how far apart they are. It is the foundation of quantum communication and of Quantum Key Distribution. Interference means quantum states can combine so that correct answers are amplified and wrong ones cancelled, a property exploited by quantum algorithms. Tunnelling is the ability of a quantum particle to pass through an energy barrier that classical physics says it should not cross, and it is used in quantum devices, sensors and advanced electronics. Decoherence is the loss of quantum behaviour when a quantum system interacts with its environment; because qubits are disturbed by heat, noise and vibration, decoherence is the biggest engineering challenge in building stable quantum computers, which is why they need extreme isolation and near-absolute-zero temperatures.

Four families of quantum technology

Quantum computing uses qubits and quantum phenomena to solve problems that are practically impossible for classical supercomputers, such as simulating molecules for drug design or optimising large logistics networks. Quantum computers are not simply faster laptops; they are special-purpose machines suited to particular classes of problems. Quantum communication uses quantum principles, especially entanglement, to share information securely. Its flagship application is Quantum Key Distribution (QKD), a method by which two parties create and share a secret encryption key; because any attempt to observe a quantum state disturbs it, an eavesdropper trying to intercept the key reveals their presence. QKD does not transmit the message itself; it secures only the key used to encrypt it, and it matters for defence communication, banking networks, diplomatic channels and critical infrastructure.

Quantum sensing and metrology use quantum effects to measure physical quantities with extraordinary precision. Quantum sensors can detect minute changes in magnetic fields, gravity and time, with applications in submarine detection, mineral exploration, satellite-free navigation and medical imaging; India has developed an indigenous Quantum Diamond Microscope for magnetic-field imaging. Quantum materials and devices is the effort to engineer new materials, such as superconductors and single-photon sources, and the hardware, cryogenic systems, lasers and photonics, on which the other three families depend.

Why quantum keeps security planners awake

Much of the world's digital security rests on public-key encryption such as RSA, the Rivest-Shamir-Adleman algorithm, whose safety depends on the fact that classical computers cannot factor very large numbers in reasonable time. A sufficiently powerful quantum computer running Shor's algorithm, a quantum algorithm that factors large numbers exponentially faster than classical methods, could break RSA and similar schemes, exposing banking systems, government databases and digital public infrastructure. This has created the threat known as Harvest Now, Decrypt Later, in which adversaries store encrypted data today and plan to decrypt it once quantum computers mature. The defensive answer is post-quantum cryptography, new encryption algorithms designed to resist quantum attacks, together with a planned national migration of vulnerable systems to quantum-safe standards.

Quantum cryptography, also called quantum encryption or Quantum Key Distribution, refers to various cybersecurity methods for encrypting and transmitting secure data based on the naturally occurring and immutable laws of quantum mechanics. Its guarantees are physical, not mathematical: if a third party tries to read the encoded data, the quantum state changes, altering the expected outcome and revealing the eavesdropper.

India's quantum journey so far

India's quantum effort began in research laboratories and has steadily moved toward demonstration and mission mode. The Ministry of Electronics and Information Technology launched QSim, the Quantum Computer Simulator Toolkit developed with IIT Roorkee, IISc Bengaluru and C-DAC, which lets researchers and students write, test and debug quantum algorithms without access to scarce and expensive real quantum hardware. In quantum communication, IIT Delhi and the Defence Research and Development Organisation (DRDO) demonstrated Quantum Key Distribution over 1 km of free space, a first for the country, while the Department of Space demonstrated free-space QKD over 300 metres with real-time processing. The Ministry of Electronics and Information Technology has deployed the Metro Area Quantum Access Network (MAQAN) in Chennai as a secure quantum communication testbed.

On hardware, the DRDO developed a 6-qubit quantum processor based on superconducting circuits in collaboration with the Tata Institute of Fundamental Research (TIFR), and Bengaluru-based start-up QpiAI has unveiled QpiAI-Indus, a 25-qubit superconducting quantum computer launched on World Quantum Day in April 2025. These are modest by global standards, but they mark India's entry into indigenous quantum hardware development rather than mere research dependence.

The two-laboratory milestone came earlier: in December 2020 DRDO demonstrated Quantum Key Distribution between its DRDL and RCI laboratories in Hyderabad using a time-bin QKD scheme, the country's first inter-laboratory quantum communication link.

The National Quantum Mission

The National Quantum Mission (NQM) is India's flagship programme for quantum technology, approved by the Union Cabinet in April 2023 with an outlay of ₹6,003.65 crore for eight years, from 2023-24 to 2030-31. Implemented by the Department of Science and Technology (DST), it aims to build a complete ecosystem of research, start-ups, skilled manpower, testbeds and industry participation across four verticals: quantum computing, quantum communication, quantum sensing and metrology, and quantum materials and devices.

The mission runs on a Hub-Spoke-Spike model through four Thematic Hubs: quantum computing at the Indian Institute of Science, Bengaluru; quantum communication at the Indian Institute of Technology Madras in association with the Centre for Development of Telematics (C-DOT); quantum sensing and metrology at IIT Bombay; and quantum materials and devices at IIT Delhi. Together the hubs anchor 14 technical groups and 17 project teams, bringing together 152 researchers from 43 institutions across 17 states and 2 Union Territories.

The mission's computing targets are staged: 20 to 50 physical qubits in three years, 50 to 100 in five years, and 50 to 1,000 in eight years. In communication, the goals are satellite-based secure quantum communication over long distances and inter-city QKD networks, which matter for secure defence, government and banking communication. Start-ups are part of the design: guidelines to support quantum start-ups have been formulated under the mission, and by 2026 support had expanded to 17 start-ups working on areas such as quantum biosensors, photon sensing, quantum positioning and precision electronics.

The communication targets are concrete: satellite-based secure quantum communication over 2,000 kilometres, within India and with other countries, alongside inter-city QKD networks. On hardware the mission backs both superconducting and photonic platforms, and in sensing it aims at high-sensitivity atomic magnetometers and atomic clocks for precision timing, communications and navigation.

The global quantum race and India's institutional map

The quantum race is geopolitical. The United States leads in quantum computing hardware through companies such as IBM and Google, China has invested heavily in quantum communication including the Micius satellite for space-based QKD, and the European Union runs the Quantum Flagship programme. For India, falling behind would mean dependence on foreign-controlled computing, communication and cryptographic infrastructure. The mission therefore spreads institutional roles: the Department of Science and Technology implements the National Quantum Mission, the Ministry of Electronics and Information Technology runs the MAQAN testbed and a Centre of Excellence in Quantum Technology, the DRDO pursues defence applications such as quantum communication and sensing, the Department of Space works on satellite-based QKD, and C-DOT partners IIT Madras on the communication hub.

This division of labour matters because quantum technology is not one industry but four: progress in computing means little without the cryogenics and photonics of the devices vertical, and secure communication needs both the physics and the telecom networks to carry it. The Hub-Spoke-Spike model is designed to keep these pieces connected, with start-ups and industry as the spokes that carry laboratory results toward deployment.

The DST's QuEST (Quantum Enabled Science and Technology) programme supports quantum capability building across institutions, complementing the mission-mode push of the NQM.

Challenges and the way forward

The road is steep. Qubits are fragile: heat, noise and vibration cause decoherence and errors, so quantum systems demand costly isolation and cryogenics. India still depends on imports for much of the hardware stack, including cryogenic systems, photonics, lasers, superconducting circuits and precision electronics. There is a skilled-manpower gap, because quantum technology needs interdisciplinary expertise across physics, computer science, electronics and materials science. Research also risks staying confined to laboratories unless it is connected with start-ups, defence, telecom, finance and manufacturing through testbeds and procurement.

The way forward is to implement the mission in true mission mode, with clear timelines, measurable outcomes and inter-ministerial coordination. India should build an indigenous hardware ecosystem in cryogenics, photonics, lasers and semiconductors; begin a quantum-safe cybersecurity transition through a national audit of vulnerable encryption and phased adoption of post-quantum cryptography; develop human resources through interdisciplinary courses and quantum labs; and prioritise near-term applications such as QKD, quantum sensors and quantum simulation instead of chasing only the universal quantum computer.

Nobel 2025: quantum goes macroscopic

The 2025 Nobel Prize in Physics went to John Clarke, Michel Devoret and John Martinis for demonstrating macroscopic quantum tunnelling and energy quantisation in superconducting circuits, the discovery that underpins modern quantum computing.

Quantum tunnelling is the phenomenon where particles pass through energy barriers that classical physics says are impassable, a consequence of wave-particle duality: the particle's wave function extends beyond the barrier, giving a probability of appearing on the other side. The laureates showed that billions of electron pairs (Cooper pairs) in a cooled superconducting circuit, joined through a Josephson junction, behave as a single collective quantum object that can tunnel between electrical states.

The significance is foundational: it proved quantum laws hold from electrons to circuits of billions of atoms when coherence is preserved, and provided the conceptual basis for superconducting qubits, the technology behind the quantum processors of Google, IBM and TIFR. It also enables quantum sensors, ultra-sensitive SQUIDs, precision metrology and microwave-to-optical conversion for quantum communication.

Test yourself with these prelims-style questions.

Key Terms

• Quantum technology: Quantum technology is any technology that exploits the rules of quantum mechanics, such as superposition, entanglement and tunnelling, to perform tasks impossible for classical devices. Its main branches are quantum computing, quantum communication, quantum sensing and metrology, and quantum materials and devices. India approved the National Quantum Mission in 2023, with a budget of Rs 6,003.65 crore for 2023-24 to 2030-31, to build capability in all four areas. Example: Quantum key distribution uses entangled photons to create encryption keys that reveal any eavesdropping, making interception detectable.
• quantum mechanics: Quantum mechanics is the branch of physics describing nature at the atomic and subatomic scale, where energy, momentum and other quantities come in discrete packets. Its core principles include superposition, the uncertainty principle and entanglement. Developed in the 1920s by figures such as Heisenberg, Schrodinger and Dirac, it underpins semiconductors, lasers and all quantum technologies. Example: The transistors in every smartphone work because quantum mechanics explains how electrons behave inside semiconductors.
• superposition: Superposition is the quantum-mechanical principle that a quantum system can exist in a combination of multiple states at once until it is measured. A qubit, for example, is not simply 0 or 1 but a superposition of both, which is what gives quantum computers their potential power. When measured, the system collapses into one definite state. Example: The National Quantum Mission aims to build intermediate-scale quantum computers (50 to 1000 qubits) that exploit superposition and entanglement.
• entanglement: Quantum entanglement is a phenomenon in which two or more particles become correlated so deeply that the quantum state of each cannot be described independently of the others, no matter how far apart they are. Measuring one entangled particle instantly determines the corresponding state of its partner, a connection Einstein called spooky action at a distance. It is a foundational resource for quantum computing, quantum communication and quantum cryptography. Example: Quantum key distribution, in which entangled photons are used to generate encryption keys that reveal any eavesdropping attempt.
• tunnelling: Quantum tunnelling is the phenomenon in which a particle passes through an energy barrier that it classically could not surmount, because its wave-like nature gives it a small probability of appearing on the other side. It is a direct consequence of the uncertainty principle and has no classical analogue. Tunnelling underlies phenomena from radioactive decay to the operation of scanning tunnelling microscopes and flash memory. Example: Quantum tunnelling is essential to nuclear fusion in the Sun, where protons fuse despite repelling each other electrically.
• National Quantum Mission: The National Quantum Mission is India's mission-mode programme for quantum science and technology, approved by the Union Cabinet on 19 April 2023 with an outlay of Rs 6,003.65 crore over eight years. Implemented by the Department of Science and Technology, it works through four verticals: quantum computing, quantum communication, quantum sensing and metrology, and quantum materials and devices. Its goals include building intermediate-scale quantum computers of 50 to 1,000 physical qubits and satellite-based secure quantum communication over 2,000 km within India. Example: Four thematic hubs in the mission's verticals were approved to be set up in consortia of academic institutions.
• quantum: In physics, a quantum (plural: quanta) is the smallest discrete unit of a physical property, such as a photon being the quantum of light. The quantum hypothesis, introduced by Max Planck in 1900 to explain black-body radiation, holds that energy is absorbed and emitted in indivisible packets rather than continuously. It is the founding idea of quantum mechanics and of the technologies grouped under quantum today. Example: A photon, the quantum of electromagnetic energy, underlies both solar cells and quantum communication systems.
• qubit: A qubit is the basic unit of quantum information, the quantum analogue of the classical bit. While a bit is either 0 or 1, a qubit can exist in a superposition of both states until measured, and multiple qubits can be entangled so their states are correlated. Physical realisations include superconducting circuits, trapped ions and photons. Example: The superconducting qubits used by IBM and Google, cooled to near absolute zero, form the processors in today's experimental quantum computers.
• Quantum Key Distribution: Quantum Key Distribution is a method of secure communication that uses quantum-mechanical properties of particles, typically photons, to share encryption keys between two parties. Because measuring a quantum system disturbs it, any eavesdropping attempt on the key exchange is immediately detectable, giving QKD security rooted in physics rather than computational difficulty. It is a leading application of quantum communication and a focus area of India's National Quantum Mission. Example: A bank using a QKD link to distribute encryption keys between two data centers with eavesdropping-proof security
• Interference: In quantum physics, the phenomenon in which the probability amplitudes of quantum states combine like waves, reinforcing or cancelling each other. Quantum interference is a core resource of quantum computation: quantum algorithms are designed so that the probability amplitudes of wrong answers cancel out while those of correct answers add up. Example: In a quantum computer, interference is engineered so that the desired computational outcome becomes far more likely to be measured than any other.
• Decoherence: Decoherence is the process by which a quantum system loses its quantum behaviour, such as superposition and entanglement, through interaction with its environment. Any stray vibration, heat, electromagnetic noise or measurement-like interaction collapses the delicate quantum state into an ordinary classical one, destroying the information the computation depends on. It is the central engineering challenge of quantum computing, since qubits must be isolated well enough to finish their calculations before decoherence sets in. Example: Superconducting qubits must operate in dilution refrigerators near absolute zero, largely to delay decoherence long enough to run quantum gates.
• quantum computing: Quantum computing is a computing paradigm that uses quantum bits (qubits), which exploit superposition and entanglement to process information in ways classical bits cannot. Certain problems, such as factoring large numbers or simulating molecules, could in principle be solved far faster than on classical machines. Practical machines remain noisy and small, and India's National Quantum Mission (approved in 2023) has quantum computing as a core focus. Example: Google's 2019 Sycamore processor performing a specific sampling task in 200 seconds, a task it claimed would take a leading supercomputer thousands of years.
• Quantum communication: Quantum communication is the use of quantum phenomena such as superposition and entanglement to transmit information with security or capabilities beyond classical communication. Its flagship application is Quantum Key Distribution, which makes eavesdropping detectable, and longer-term goals include quantum networks and a quantum internet linking quantum computers. It is one of the four verticals of India's National Quantum Mission, alongside computing, sensing, and materials. Example: Two institutions exchanging encryption keys over a QKD-secured optical fiber link, where any interception attempt would be detected
• Quantum sensing and metrology: Quantum sensing and metrology is the use of quantum phenomena such as superposition and entanglement to measure physical quantities with far greater precision than classical instruments allow. It is one of the four verticals of India's National Quantum Mission, alongside quantum computing, quantum communication, and quantum materials. Practical uses include atomic clocks that keep time to within a fraction of a second over millions of years, and gravimeters that detect underground mineral deposits or groundwater. Example: Atomic clocks used in navigation satellites rely on quantum transitions of atoms to maintain ultra-precise time.
• Quantum Diamond Microscope: The Quantum Diamond Microscope is India's first indigenous instrument for dynamic magnetic-field imaging, developed by the P-Quest Group at IIT Bombay under the National Quantum Mission and announced in November 2025. It is based on nitrogen-vacancy centers in diamond, atomic-scale defects that retain quantum coherence at room temperature and are extremely sensitive to magnetic variations, read out optically through a technique called optically detected magnetic resonance. It enables three-dimensional magnetic-field imaging at the nanoscale, with applications in neuroscience, materials research, and non-destructive evaluation of semiconductor chips. Example: Mapping buried current paths inside an encapsulated semiconductor chip in 3D without destroying it
• Quantum materials and devices: Quantum materials and devices is a research theme covering materials that exhibit pronounced quantum phenomena, such as superconductors and topological materials, and the devices built from them, including quantum sensors, magnetometers, and single-photon sources. Advances here underpin practical quantum technologies in sensing, metrology, and communication. It is one of the focus areas of India's National Quantum Mission. Example: The indigenous Quantum Diamond Microscope developed at IIT Bombay, a quantum sensing device for nanoscale magnetic-field imaging
• RSA: RSA, named after Rivest, Shamir and Adleman who published it in 1977, is a public-key encryption algorithm widely used to secure digital communication. Its security rests on the fact that classical computers cannot factor very large numbers into their prime factors within any practical time. A powerful enough quantum computer running Shor's algorithm could break it, which is why post-quantum cryptography is being developed. Example: RSA-2048 underpins the TLS certificates that secure HTTPS websites and online banking sessions.
• Shor's algorithm: Shor's algorithm, published by mathematician Peter Shor in 1994, is a quantum algorithm that factors large integers and solves discrete logarithms in polynomial time, problems that are infeasible for classical computers. A sufficiently powerful quantum computer running it could break RSA and elliptic-curve cryptography, which secure most of today's digital communication. It is the main reason governments and industry are migrating to post-quantum cryptography. Example: Factoring the large semiprimes underlying RSA-2048 encryption.
• Harvest Now, Decrypt Later: Harvest Now, Decrypt Later is a cybersecurity threat model in which adversaries intercept and store encrypted data today, planning to decrypt it once cryptographically relevant quantum computers can break current public-key algorithms such as RSA through Shor's algorithm. It creates urgency to migrate to post-quantum cryptography now, because secrets with a long shelf life (state communications, health and financial records) are already being harvested. This threat is a key justification for India's National Quantum Mission and global post-quantum standardisation. Example: Encrypted diplomatic cables or medical records stolen today could be decrypted years later by a future quantum computer, which is why agencies are adopting quantum-safe encryption in advance.
• post-quantum cryptography: Post-quantum cryptography is the development of encryption algorithms that remain secure against attacks by future quantum computers. Today's widely used public-key systems, like RSA and elliptic-curve cryptography, could be broken by Shor's algorithm running on a large enough quantum machine. Standardisation is led by the US National Institute of Standards and Technology, which finalised its first post-quantum standards in 2024. Example: The ML-KEM standard (based on CRYSTALS-Kyber), finalised by NIST in 2024 for key exchange that resists quantum attacks.
• QSim: QSim, the Quantum Computer Simulator Toolkit, is India's first indigenously developed quantum computing toolkit, launched by the Ministry of Electronics and Information Technology in 2021. Developed jointly by IISc Bengaluru, IIT Roorkee, and C-DAC, it lets researchers and students write, debug, and test quantum algorithms on classical computers in a cost-effective way, including simulating noisy quantum circuits to prepare for real hardware. It serves as an educational and research platform for building quantum programming skills. Example: A student testing and debugging Grover's search algorithm in QSim's graphical workbench before running it on an actual quantum processor
• IIT Delhi: The Indian Institute of Technology Delhi is one of India's premier engineering institutes, established in 1961. Under the National Quantum Mission it anchors the thematic hub on quantum materials and devices, and together with DRDO it demonstrated Quantum Key Distribution over 1 km of free space, a first for the country. Example: The IIT Delhi and DRDO demonstration of Quantum Key Distribution over 1 km of free space.
• Hub-Spoke-Spike model: The Hub-Spoke-Spike model is the implementation architecture of India's National Quantum Mission, approved in 2023 with an outlay of about Rs 6,003 crore. Four Thematic Hubs, covering quantum computing, quantum communication, quantum sensing and metrology, and quantum materials and devices, act as hubs coordinating research across the country. Partner institutions serve as spokes, while targeted, time-bound mission projects form the spikes that deliver specific technologies. Example: Under this model, a thematic hub on quantum communication works toward satellite-based quantum key distribution links between Indian cities.
• Thematic Hubs: The Thematic Hubs are the four research hubs through which India's National Quantum Mission (Rs 6,003.65 crore, 2023 to 2031) is executed under a hub-spoke-spike model. They cover quantum computing at IISc Bengaluru, quantum communication at IIT Madras with C-DOT, quantum sensing and metrology at IIT Bombay, and quantum materials and devices at IIT Delhi, with a target of building up to 1,000-qubit quantum computers in eight years. Each hub anchors a national network of researchers, startups and industry partners. Example: The quantum computing hub at IISc Bengaluru, tasked with developing intermediate-scale superconducting quantum computers.
• Indian Institute of Science, Bengaluru: India's premier research university, established in 1909 through the vision of Jamsetji Tata and located in Bengaluru, renowned for advanced research in science and engineering. It is consistently ranked among the country's top research institutions and plays a leading role in frontier technology research. Example: IISc Bengaluru hosts the Thematic Hub for Quantum Computing under the National Quantum Mission.
• Indian Institute of Technology Madras: One of India's premier engineering and research institutes, located in Chennai, Tamil Nadu, known for excellence in engineering education, research and technology development. It anchors major national research programmes and industry collaborations in emerging technologies. Example: IIT Madras hosts the Thematic Hub for Quantum Communication under the National Quantum Mission, in association with C-DoT.
• IIT Bombay: The Indian Institute of Technology Bombay is one of India's premier engineering and research institutes, established in 1958 in Mumbai. Under the National Quantum Mission it anchors the thematic hub on quantum sensing and metrology, and its incubation ecosystem produced ImmunoACT, the company behind NexCAR19, India's first indigenous CAR-T therapy. Example: IIT Bombay hosts the quantum sensing and metrology hub of the National Quantum Mission.
• Aspect: In UPSC answer writing, 'aspect' refers to one distinct dimension or facet of an issue, such as its economic, social, political, or environmental aspect. Questions demanding multiple perspectives expect answers structured aspect by aspect rather than as a single narrative. It matters as a basic analytical unit of GS answers and a cue to multi-dimensional analysis.
• Detail: In the UPSC context, detail refers to the specific, verifiable facts, figures, dates, committee names and case examples that support an argument in an answer. Examiners reward answers that move from a general claim to concrete detail, because it signals genuine knowledge rather than memorised headings. For UPSC it matters as an answer-writing skill: each value addition, such as a constitutional article number or a recent report's finding, earns marks in both prelims and mains.
• Department of Science and Technology: The Department of Science and Technology is the department under India's Ministry of Science and Technology that anchors national science policy, research funding and technology development. It runs flagship bodies and programmes including the Science and Engineering Research Board (SERB), the Technology Information, Forecasting and Assessment Council (TIFAC), and national missions on emerging technologies. It is the nodal department for the National Quantum Mission, approved in 2023 to build India's capabilities in quantum computing, communication and sensing. Example: The National Quantum Mission (2023-2031), implemented through this department, aims to develop quantum computers in the 50 to 1000 qubit range.
• Ministry of Electronics and Information Technology: The Ministry of Electronics and Information Technology is the Union ministry in charge of India's digital and electronics ecosystem, covering IT policy, digital infrastructure, electronics manufacturing, semiconductors, and cybersecurity coordination. It administers flagship programmes such as Digital India and the India Semiconductor Mission, and oversees agencies like CERT-In. It took its current form in 2016. Example: It administers the India Semiconductor Mission's incentive schemes for chip fabrication and design-linked projects.
• DRDO: The Defence Research and Development Organisation is India's premier military research agency, established in 1958 to design and develop indigenous weapons systems. It runs a network of laboratories working on missiles, radars, electronic warfare, and combat vehicles. For UPSC, its programmes, from the Agni and Prithvi missiles to the Tejas fighter's systems, anchor questions on defence indigenization and self-reliance. Example: The Integrated Guided Missile Development Programme, launched in 1983 under A.P.J. Abdul Kalam, produced the Agni and Prithvi missile families.
• Department of Space: The Department of Space (DoS) is the Government of India department, under the Prime Minister's Office, that oversees the country's space programme. It administers ISRO, and after the 2020 space-sector reforms it also oversees IN-SPACe (the regulator and promoter for private players) and NewSpace India Limited (the commercial arm). All national space policy, from launch authorisations to international cooperation, flows through this department. Example: The Indian Space Policy 2023, which opened the sector to private participation, was issued under the Department of Space.
• C-DOT: C-DOT, the Centre for Development of Telematics, is the Department of Telecommunications' research institution founded in 1984 to build indigenous digital switching technology. Under Sam Pitroda's leadership it developed low-cost rural exchanges that carried India's telecom revolution to the villages. For UPSC it is the flagship example of indigenous technology development and a key antecedent of the Digital India story in science and technology answers. Example: Its RAX rural automatic exchanges connected thousands of Indian villages in the 1990s.
• Key takeaways: Key takeaways is a quick-revision summary box placed at the end of each article, listing the most exam-relevant points in a short numbered list. It distils definitions, dates, figures, provisions and examples into a form suited for last-minute revision before Prelims and Mains. Together with the article's practice questions, it turns every topic into a self-contained study unit.
• QKD: QKD is the abbreviation for Quantum Key Distribution, a quantum communication technique for sharing encryption keys with security guaranteed by the laws of physics. Any attempt to eavesdrop on the key exchange disturbs the quantum states being transmitted and reveals the intrusion. See the full entry under Quantum Key Distribution (QKD). Example: A bank using a QKD link to distribute encryption keys between two data centers with eavesdropping-proof security
• Defence Research and Development Organisation (DRDO): The Defence Research and Development Organisation (DRDO) is the research and development wing of India's Ministry of Defence, established in 1958 and headquartered in New Delhi. It develops indigenous military technologies across missiles, radars, electronic warfare, combat vehicles, naval systems and life sciences through a network of more than fifty laboratories. Its stated mission is to make India self-reliant in critical defence technologies, a goal now tied to the Atmanirbhar Bharat push in defence production. Example: The Agni series of ballistic missiles and the Light Combat Aircraft Tejas are among DRDO's flagship programmes.
• Metro Area Quantum Access Network (MAQAN): India's first metro-area quantum communication testbed, a 15 km fibre network in Chennai built by a team from IIT Madras with SETS, ERNET and C-DAC. It provides a platform to experiment with quantum key distribution (QKD) protocols and lays down the requirements for future city-scale quantum-secure networks. It feeds into the National Quantum Mission's goal of satellite and inter-city quantum communication. Example: MAQAN demonstrated entanglement and QKD protocols over Chennai's metro fibre, a stepping stone to the planned 2,000 km inter-city quantum backbone.
• Tata Institute of Fundamental Research (TIFR): The Tata Institute of Fundamental Research is a premier public research institution in Mumbai, founded in 1945 by Homi J. Bhabha under the Department of Atomic Energy. It conducts fundamental research in physics, mathematics, chemistry, biology and computer science, and contributes to India's quantum computing efforts under the National Quantum Mission. Example: TIFR is among the institutions developing indigenous superconducting quantum computers under the National Quantum Mission.
• QpiAI-Indus: QpiAI-Indus is India's first full stack quantum computer, a 25 qubit superconducting system developed by the Bengaluru startup QpiAI and unveiled on World Quantum Day, 14 April 2025. It was developed with support from the National Quantum Mission (coordinated by the Department of Science and Technology) and integrates indigenous quantum hardware, control systems and software. Example: QpiAI followed it with Kaveri, a 64 qubit system, launched in November 2025.
• Centre for Development of Telematics: The Centre for Development of Telematics (C-DOT) is an autonomous telecom R&D body set up by the Government of India in 1984. Tasked with building indigenous digital switching and telecom technology, it developed India's own rural telephone exchanges, reducing dependence on imported equipment and extending connectivity to villages. It matters for UPSC for science-tech and governance questions on indigenous innovation and digital infrastructure.

• The International Year of Quantum Science and Technology was the UN's 2025 designation marking 100 years since Heisenberg's 1925 paper that laid the foundations of quantum mechanics.

• Quantum cryptography, also called quantum encryption or Quantum Key Distribution, refers to various cybersecurity methods for encrypting and transmitting secure data based on the naturally occurring and immutable laws of quantum mechanics.

• QuEST (Quantum Enabled Science and Technology) is the DST programme supporting quantum capability building across institutions, complementing the National Quantum Mission.

• An atomic clock is an ultra-precise timekeeper using atomic vibrations as its reference; the NQM targets high-sensitivity atomic clocks for precision timing, communications and navigation.

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