India is taking an important step towards next-generation secure communication technology. According to the Government of India’s reply to Lok Sabha Unstarred Question No. 3515, answered, the Defence Research and Development Organisation (DRDO) has completed a project demonstrating fibre-based secure quantum communication and successfully established a 200 km fibre-based Quantum Key Distribution (QKD) Proof of Concept (PoC).
DRDO, in collaboration with IIT Delhi, has also demonstrated free-space quantum-secure communication based on quantum entanglement. The government has further stated that a follow-up project to demonstrate Long Range Free Space Quantum Key Distribution is in the planning stage, with an expected project cost of ₹118 crore.
This development is significant for India’s defence modernisation, cybersecurity, military communications and the protection of sensitive information. However, it is important to understand what has already been demonstrated, what remains under development, and how quantum communication could change the future of defence communication systems.
Key Highlights of the Government’s Reply
200 km fibre-based QKD
DRDO has successfully established a Proof of Concept for secure quantum communication through optical fibre.
Free-space quantum communication
DRDO and IIT Delhi have demonstrated quantum-entanglement-based free-space quantum-secure communication.
Long-range development planned
A follow-up project for long-range free-space QKD is in the planning stage.
Expected project cost: ₹118 crore
This is the expected cost of the planned follow-up project, not a confirmed total expenditure for every stage of a nationwide defence quantum network.
1. Background: What Is Quantum Communication?
Quantum communication is an advanced method of transferring information or establishing secure cryptographic keys by using principles of quantum physics. Unlike conventional communication systems, which encode information in ordinary electrical or optical signals, quantum communication can use individual particles of light called photons and quantum properties such as superposition and entanglement.
Its most important security advantage is that certain quantum communication protocols can reveal attempts to intercept the quantum signals used to establish encryption keys.
Today, defence forces depend on digital communication for command and control, intelligence sharing, surveillance, logistics, air-defence coordination and battlefield operations. These systems require strong protection against interception, unauthorised access and cyberattacks.
Quantum communication is being developed to strengthen this security, particularly where highly sensitive information must remain protected against increasingly powerful computing technologies.
How is quantum communication different from conventional communication?
| Feature | Conventional secure communication | Quantum communication |
| Information security | Generally relies on cryptographic algorithms and secure key management | Can use quantum properties to establish keys and detect certain interception attempts |
| Data transmission | Electrical, radio, microwave or optical signals | Quantum states, often carried by photons |
| Interception detection | Depends on system monitoring and security controls | Certain QKD protocols can reveal disturbances caused by interception |
| Long-distance use | Established networks can cover extensive distances through repeaters and other infrastructure | Distance is challenging because quantum signals are fragile and losses accumulate |
| Current applications | Operational military, government and commercial networks | Specialised deployments, trials and developing quantum-secure networks |
Important distinction: Quantum communication does not mean that every message is automatically encrypted or impossible to hack. Quantum Key Distribution helps two parties establish shared secret keys. Those keys must then be used with suitable encryption, authenticated protocols and secure equipment to protect actual messages.
2. How Does Quantum Key Distribution (QKD) Work?
Quantum Key Distribution is one of the most important practical applications of quantum communication. It allows two authorised parties to establish a shared secret encryption key using quantum signals.
Suppose a military headquarters needs to communicate confidential operational information to a forward command centre. Before sending sensitive data, the two locations need a secure cryptographic key.
Military Headquarters
Generates and transmits quantum signals
Quantum channel: optical fibre or free-space optical link
Security checks identify excessive errors that may indicate interception
Forward Command Centre
Receives quantum signals and helps establish the shared key
Encrypted military communication
The established key is used with an appropriate encryption system to protect messages.
The process generally involves the following stages:
- Quantum signal generation: Specialised equipment generates quantum states, often using photons.
- Signal transmission: The photons travel through an optical fibre or a free-space optical link.
- Measurement and verification: The receiving system measures the signals. The sender and receiver compare suitable information over an authenticated conventional channel to estimate errors and assess security.
- Key establishment: They perform the required error correction and privacy amplification to obtain a shared secret key.
- Data encryption: The key is used with a suitable cryptographic system to secure the actual communication.
If the observed error rate or other security checks indicate a possible attack, the parties can reject the affected key rather than use it.
This is the central idea behind QKD: certain attempts to measure or intercept quantum signals can disturb them, allowing the communicating parties to detect potential eavesdropping. The degree of protection depends on the protocol, equipment, implementation and security assumptions.
3. Fibre-Based Quantum Communication: What Does the 200 km PoC Mean?
The Ministry of Defence has confirmed that DRDO completed a project demonstrating fibre-based secure quantum communication and established a Proof of Concept for 200 km fibre Quantum Key Distribution.
Optical fibre is already widely used in telecommunications because it can carry large volumes of data over long distances. Quantum communication uses specialised optical equipment and quantum signals over such infrastructure to establish secure keys.
A 200 km demonstration is an important technical milestone because quantum signals are fragile. As they travel through optical fibre, photons are lost through absorption, scattering and other imperfections. This reduces the number of useful quantum signals reaching the receiver.
However, a Proof of Concept is not the same as a fully deployed defence communication network.
The government’s answer does not specify:
- Whether the 200 km demonstration was conducted over existing commercial fibre, a dedicated fibre link or another experimental arrangement.
- The final operational key-generation rate, system availability or performance under field conditions.
- Whether the technology has been deployed across operational military formations.
- The number of defence locations that could eventually be connected.
- The cost of scaling the fibre-based system into a larger operational network.
These details would be important in assessing its practical military readiness.
Why is fibre-based QKD useful for defence?
Fibre-based systems could be particularly useful for securing communication between fixed installations, such as command headquarters, strategic facilities, defence research establishments and selected military data centres.
Such a network could provide an additional layer of cryptographic security for sensitive communications, provided that its equipment, key-management systems and network architecture meet defence requirements.
Nevertheless, fibre-based QKD does not automatically secure every device or network connected to it. Endpoints, authentication systems, computers and communication equipment must also be protected.
4. Free-Space Quantum Communication: Why Is It Important?
The second major achievement mentioned in the government’s reply is the demonstration of quantum-entanglement-based free-space quantum-secure communication by DRDO in collaboration with IIT Delhi.
Free-space communication transmits optical signals through the atmosphere rather than through a physical optical fibre. Depending on the system design, the communication link may be established between buildings, ground stations, aircraft or other suitable platforms.
This technology is important because military communication cannot always depend on a fixed fibre connection.
In a separate announcement dated 16 June 2025, the Press Information Bureau reported that DRDO and IIT Delhi had demonstrated quantum-entanglement-based free-space quantum-secure communication over more than one kilometre on the IIT Delhi campus. The experiment achieved a secure key rate of approximately 240 bits per second, with a quantum bit error rate below 7%.
These experimental results provide useful context for understanding the progress reported to Parliament in March 2026. However, the parliamentary reply does not explicitly state that the follow-up long-range project has already achieved a particular distance or operational performance.
What is quantum entanglement?
Quantum entanglement is a physical phenomenon in which quantum systems share correlations that cannot be explained by ordinary classical physics.
In appropriately designed quantum communication protocols, entangled quantum states can help establish shared cryptographic keys and test whether the expected quantum correlations are present.
Entanglement does not allow information to be transmitted instantaneously faster than light. Communication still requires a suitable physical channel and, for key-distribution protocols, conventional communication to complete the necessary checks.
How could free-space QKD support the Armed Forces?
Potential applications include:
- Secure links between selected ground stations and other optical communication platforms.
- Experimental links for future satellite-based quantum communication.
- Protection of selected military command-and-control communications.
- Secure communication between defence research facilities and strategic installations.
- Future quantum-network infrastructure connecting geographically separated nodes.
These are potential applications, not a confirmation that the demonstrated Indian system is already operational in all these roles.
5. Why Could Quantum Communication Be Revolutionary for India’s Defence System?
The strategic importance of quantum communication lies in the growing need to protect military information against interception, cyberattacks and future advances in computing.
Modern warfare depends not only on weapons and platforms but also on the secure exchange of information. A compromise of sensitive communications can expose operational plans, intelligence assessments, deployment details and command decisions.
The following are important areas in which quantum-secure communication could contribute to defence capability.
5.1 Secure command-and-control communication
Commanders require trusted channels to exchange orders, intelligence and operational updates. QKD could strengthen key distribution for selected high-security links, helping protect the confidentiality of sensitive information when integrated with appropriate encryption.
5.2 Protection against interception
Certain forms of eavesdropping on quantum signals can introduce detectable disturbances. This could help identify compromised key-establishment attempts and allow affected keys to be discarded.
5.3 Air defence and integrated military operations
Secure communication is essential when air-defence units, surveillance systems and command centres exchange sensitive information. Quantum-secure key distribution could become one component of the protection architecture for selected links.
5.4 Naval and maritime security
Future optical and satellite-assisted quantum networks could support secure links between suitable shore facilities, ships and other platforms. Practical deployment would depend on range, weather, platform movement and the availability of suitable optical terminals.
5.5 Strategic infrastructure and defence research
Defence laboratories, sensitive data centres and strategic installations could benefit from additional protection for cryptographic keys used to safeguard confidential information.
Will quantum communication make military networks impossible to hack?
No. That would be an exaggeration.
QKD can offer strong security properties for key establishment under defined assumptions, but it does not eliminate every cyber threat. Hackers may still target endpoint computers, poorly configured equipment, compromised credentials, software vulnerabilities, insiders or the conventional communication channel used by the protocol.
The realistic objective is to strengthen the security of selected communications and make certain interception attempts easier to detect, rather than to create a completely invulnerable network.
6. ₹118 Crore Project: What Has the Government Announced?
The financial information in the parliamentary reply relates to the planned follow-up project for demonstrating long-range free-space Quantum Key Distribution.
| Particular | Status as per the reply dated 13 March 2026 |
| Fibre-based secure quantum communication project | Completed |
| Fibre QKD demonstration | 200 km Proof of Concept established |
| Entanglement-based free-space quantum communication | Demonstrated by DRDO and IIT Delhi |
| Long-range free-space QKD project | In planning stage |
| Expected cost of follow-up project | ₹118 crore |
| Final operationalisation date | Not specified |
| Total cost of a nationwide operational quantum defence network | Not specified |
Does ₹118 crore mean the system will be operational soon?
Not necessarily. The amount is the expected cost of the planned follow-up project, not confirmation that the full system has been approved, funded, completed or deployed.
A development project of this kind may involve optical equipment, quantum photon sources and detectors, secure key-management infrastructure, communication terminals, experimental testing, integration and field validation. These are typical requirements for such systems; the parliamentary reply does not provide a project-wise expenditure breakdown.
Similarly, the reply does not give a specific deadline for operationalisation. It would therefore be incorrect to announce a confirmed deployment year on the basis of this answer alone.
7. Important Questions Raised in Parliament — and What Remains Unanswered
The question raised by Shri Shahu Shahaji Chhatrapati addressed four fundamental issues: the existence of a project, its details, the operationalisation timeline and the estimated expenditure.
The government has provided a clear response on the demonstrated technologies and the expected cost of the follow-up project. However, several questions remain relevant for understanding how the programme may progress.
Question 1: Is a quantum communication-based defence project under implementation?
Partly answered
The government confirmed that the fibre-based demonstration project had been completed and a 200 km fibre QKD Proof of Concept established. It also reported the free-space demonstration with IIT Delhi.
Question 2: What is the status of the next development stage?
Planning stage
The follow-up project for long-range free-space QKD was stated to be in the planning stage. The reply does not establish that the follow-up project has entered full-scale execution.
Question 3: When will the system become operational?
Not specified
No operationalisation date or deployment schedule was provided. Further official information would be required to establish the expected completion date and rollout stages.
Question 4: What is the estimated expenditure?
Partly answered
The expected cost of the long-range free-space QKD follow-up project is ₹118 crore. The reply does not disclose a detailed cost breakdown or the total future cost of an operational network.
Additional issues that deserve attention
For defence planners and technology researchers, the next important questions include:
- What operational distance and secure key-generation rate will the long-range system achieve?
- Will the system be designed for fixed installations, mobile platforms, satellite links or a combination of these?
- How will the technology perform under rain, fog, dust, atmospheric turbulence and other challenging conditions?
- What arrangements will ensure reliable communication if a quantum link fails?
- How will the system integrate with existing military communication infrastructure?
- What arrangements will protect the equipment and key-management systems from physical tampering and cyberattacks?
- Will the project involve Indian industry, research institutions and domestic component manufacturers?
- What milestones, testing criteria and operational acceptance requirements will apply?
These are relevant technical and policy questions. They should not be interpreted as evidence of any deficiency in the DRDO programme.
8. Quantum Communication vs Post-Quantum Cryptography: An Important Distinction
Quantum communication is often discussed alongside quantum computing and post-quantum cryptography, but these technologies serve different purposes.
| Technology | Main purpose | Relevance to defence |
| Quantum communication | Uses quantum states for communication-related tasks, including secure key distribution | Can help protect selected high-security communication links |
| Quantum computing | Uses quantum-mechanical systems to process information | May enable new scientific capabilities and threaten some existing cryptographic systems |
| Post-quantum cryptography (PQC) | Uses conventional computing with cryptographic algorithms designed to resist known quantum-computing attacks | Can protect software, digital communications and networks without requiring a quantum communication link |
The distinction matters because QKD and PQC are not necessarily competing solutions.
A defence network may use QKD for selected links while adopting post-quantum cryptographic algorithms across a much wider range of systems, including networks where installing specialised quantum equipment is impractical.
The US National Institute of Standards and Technology (NIST) explains that QKD has technical and implementation challenges and that post-quantum cryptography offers a different approach to protecting data against potential quantum-computing threats.
Why does this matter for India?
A comprehensive quantum-security strategy could require more than one technology. Potential priorities include:
- Developing indigenous quantum communication hardware.
- Evaluating post-quantum cryptographic algorithms for defence and government networks.
- Establishing secure key-management and authentication procedures.
- Protecting legacy communication systems during a gradual transition.
- Training scientists, engineers, cybersecurity professionals and defence personnel.
- Testing systems against realistic technical and operational threats.
A combination of appropriate cryptography, secure hardware, network monitoring and disciplined security procedures will remain important even as quantum technologies advance.
9. Major Technical Challenges Before Large-Scale Deployment
Although the reported demonstrations are significant, moving from an experimental link to a reliable military communication network involves several challenges.
A. Communication distance and signal loss
Photons can be lost during transmission, reducing the rate at which secret keys can be established. Long-distance systems need to overcome this limitation through suitable optical engineering, network architecture and other technical approaches.
B. Atmospheric conditions
Free-space optical links can be affected by clouds, fog, dust, turbulence and weather conditions. Military systems must be evaluated for availability and reliability in the environments where they are expected to operate.
C. Equipment reliability
Quantum systems require specialised sources, detectors, optical components and calibration procedures. The equipment must be reliable, tamper-resistant and suitable for deployment in demanding environments.
D. Mobility and field conditions
A fixed optical link is different from a link involving moving platforms or changing line-of-sight conditions. Practical military applications may require sophisticated tracking, pointing and acquisition systems.
E. Authentication and endpoint security
QKD alone does not establish that the other party is genuinely the intended recipient. Authentication must be implemented separately or integrated into the protocol. Endpoint computers and conventional network equipment must also be secured.
F. Cost and scalability
An experimental demonstration does not automatically establish the cost-effectiveness of a large network. Defence authorities would need to evaluate equipment costs, maintenance, training, key-management requirements, network availability and the security benefit compared with alternative approaches.
G. Integration with existing military systems
The technology must operate alongside established communication infrastructure. During any transition, operational continuity, interoperability and backup communication arrangements would be critical.
These challenges do not diminish the reported achievements. They explain why further research, testing and validation are needed before drawing conclusions about widespread operational use.
10. Other Potential Applications Beyond Defence
Quantum communication is a dual-use technology, meaning it may have applications in both military and civilian sectors.
Banking and financial services
Quantum-secure key distribution could be evaluated for protecting selected financial networks and sensitive transactions.
Government communications
Selected government departments could explore quantum-secure links for highly confidential information.
Telecommunications
Quantum networking research could support the development of specialised secure communication infrastructure.
Research and future quantum networks
Universities and research institutions could develop photonic technologies, quantum networking equipment and applications related to a future quantum internet.
These are possible areas of application, not confirmation that quantum communication has already been deployed throughout these sectors in India.
11. What Does This Development Mean for Defence Personnel and Veterans?
For serving personnel, veterans and defence-sector aspirants, the immediate significance is the expansion of India’s advanced defence research capabilities.
Potential longer-term implications include:
- Greater demand for specialists in quantum physics, photonics and optical engineering.
- New research opportunities in cybersecurity, communications engineering and quantum information science.
- Potential requirements for specialised technical training, system maintenance and secure network management.
- Opportunities for eligible Indian technology companies and research institutions to contribute to indigenous defence technology.
However, the parliamentary reply does not announce any specific recruitment, vacancies, training programmes or employment benefits for serving personnel or ex-servicemen. Any future opportunities would depend on official project requirements and recruitment notifications.
12. Frequently Asked Questions (FAQs)
1. What is India’s quantum communication-based defence project?
It is a DRDO-led effort to demonstrate secure quantum communication technologies. The Ministry of Defence has confirmed a completed fibre-based demonstration with a 200 km QKD Proof of Concept and a free-space quantum-entanglement-based demonstration conducted with IIT Delhi.
2. What is the expected cost of the next project?
The expected cost of the planned Long Range Free Space Quantum Key Distribution project is ₹118 crore, according to the government’s Lok Sabha reply dated 13 March 2026.
3. Has DRDO completed a 200 km quantum communication test?
The government has confirmed that a 200 km fibre-based QKD Proof of Concept was successfully established. This should not be confused with confirmation of a fully operational 200 km military network.
4. What is the difference between fibre-based and free-space QKD?
Fibre-based QKD uses optical fibre to carry quantum signals. Free-space QKD transmits optical signals through the atmosphere, potentially enabling links where laying fibre is difficult or where suitable optical terminals can be deployed.
5. When will India’s quantum defence communication system become operational?
The parliamentary reply does not specify an operationalisation date. It states that the follow-up long-range free-space QKD project is in the planning stage.
6. Can quantum communication prevent all hacking?
No. QKD can help establish cryptographic keys and detect certain interception attempts, but it cannot eliminate all cyberattacks, equipment vulnerabilities, identity-spoofing risks or endpoint compromises.
7. Is quantum communication the same as quantum computing?
No. Quantum communication uses quantum properties for communication-related purposes. Quantum computing uses quantum systems to perform computations. Post-quantum cryptography uses algorithms designed to resist attacks from sufficiently powerful quantum computers.
8. Will this technology replace existing military communication systems?
There is no such announcement in the parliamentary reply. Quantum-secure technologies are more likely to be evaluated for integration into selected systems, alongside conventional communication and cryptographic safeguards.
9. Does the ₹118 crore allocation cover the entire Indian quantum defence network?
The reply describes ₹118 crore as the expected cost of the follow-up long-range free-space QKD project. It does not establish that this amount covers a nationwide operational network or all future quantum communication expenditure.
10. What is the official source of this information?
The primary source is the Ministry of Defence’s answer to Lok Sabha Unstarred Question No. 3515, dated 13 March 2026. The earlier free-space demonstration was also reported by the Press Information Bureau on 16 June 2025.
Conclusion: A Significant Step Towards Future-Ready Defence Communication
India’s progress in quantum communication represents an important development in indigenous defence research. The completed fibre-based QKD Proof of Concept over 200 km, together with the free-space quantum-secure communication demonstration by DRDO and IIT Delhi, provides a foundation for further research into secure communication networks.
The proposed ₹118 crore follow-up project for long-range free-space QKD could help advance this work. Its ultimate significance will depend on technical performance, field testing, system reliability, integration with existing military infrastructure and the project’s eventual operational outcomes.
For now, the key takeaway is that India has demonstrated important quantum communication capabilities, while long-range free-space QKD remains at the planning stage according to the parliamentary reply. The next milestones to watch are official project approvals, development progress, performance demonstrations and any announcement of operational deployment.