DRDO signs TDF agreement with Zero mK India for indigenous 20 mK dilution refrigerator

On September 24, 2026, the Defence Research and Development Organisation (DRDO) marked a major milestone in India's deep-tech engineering landscape by signing its inaugural high-value project agreement under the revised Technology Development Fund (TDF) scheme. The contract, executed in New Delhi between the Director of TDF and representatives from Rajasthan-based startup Zero mK India Private Limited, focuses on the collaborative design, fabrication, and experimental validation of an indigenous 20 millikelvin (20 mK) dilution refrigerator. This specialized cryogenic platform is engineered to create sub-kelvin thermal environments essential for operating, characterising, and testing advanced quantum computing hardware, quantum sensors, and secure communication systems.

The agreement represents the first high-value deep-tech allocation disbursed from the enhanced ₹500 crore TDF corpus, which was previously sanctioned by Defence Minister Rajnath Singh to support high-risk, cutting-edge technological developments across domestic industry and start-ups. Commending the initiative, Union Defence Minister Rajnath Singh emphasized that the collaborative partnership establishes a vital precedent for future public-private R&D frameworks in emerging strategic domains. Defence Secretary and DRDO Chairman Rajesh Kumar Singh, alongside senior leadership from the Directorate General of Micro Electronic Devices & Computational Systems and Cyber Security (DG MCC), the Directorate General of Technology Management (DG TM), and the Solid State Physics Laboratory (SSPL) in Delhi, also extended their congratulations to the joint project teams.

Strategic Push for Indigenous Sub-Kelvin Cryogenic Infrastructure

The development of an indigenous 20 mK-class dilution refrigerator addresses a longstanding vulnerability within India's scientific and defence research infrastructure. Sub-kelvin cryogenic hardware has historically been sourced exclusively from a limited number of overseas manufacturers in Europe and North America. Procurement of these specialized systems often entails long lead times, stringent export control regulations, restrictive licensing frameworks, and high capital costs. By establishing domestic capabilities to design, assemble, and certify millikelvin cryogenic test environments, the initiative provides a resilient backbone for national deep-tech programs.

The project is closely aligned with the objectives of India's National Quantum Mission, which seeks to establish self-reliant capabilities across quantum computing, quantum communications, quantum sensing, and quantum metrology. Operating quantum processors requires an environment where thermal energy is nearly eliminated, as even minimal thermal excitation can cause decoherence, destroying fragile quantum states. A 20 mK operating environment—translating to a temperature just 0.02 Kelvin above absolute zero—provides the required thermal stability to preserve phase coherence in solid-state quantum devices such as superconducting qubits, quantum dot spin architectures, and ultra-precise atomic sensors.

Thermodynamics and Sub-Kelvin Engineering Challenges

Engineering a dilution refrigerator capable of reaching and maintaining stable temperatures at 20 mK presents extraordinary mechanical, thermal, and fluid dynamics challenges. Unlike conventional mechanical cryocoolers or standard liquid helium cryostats that operate at 4.2 K, sub-kelvin dilution systems rely on the unique quantum thermodynamic properties of a mixture of two helium isotopes: stable Helium-4 and the rare light isotope Helium-3.

When a mixture of Helium-3 and Helium-4 is cooled below a critical phase-separation temperature of approximately 0.8 Kelvin, it spontaneously separates into two distinct liquid phases: a concentrated phase consisting almost entirely of pure liquid Helium-3 floating above a dilute phase consisting of Helium-3 dissolved in superfluid Helium-4. Because the enthalpy of Helium-3 in the dilute phase is higher than in the concentrated phase, forcing Helium-3 atoms to cross the phase boundary from the concentrated phase into the dilute phase absorbs heat from the surrounding mixing chamber. This endothermic process, known as phase dilution, provides continuous cooling down to temperatures below 10 millikelvin.

To sustain this continuous cooling cycle, the system incorporates specialized multi-stage heat exchangers, ultra-low-pressure turbomolecular and sorption pumps, and sophisticated gas handling manifolds that circulate Helium-3 while isolating the mixing chamber from external thermal radiation. The engineering requirements for such a system are exceptionally demanding:

• Ultra-High Vacuum and Hermetic Integrity: The outer cryostat vacuum vessels and internal vacuum chambers must maintain ultra-high vacuum levels down to 10^-8 mbar or better to eliminate convective gas heat leaks.
• Multi-Stage Thermal Shielding: Interlocking copper and aluminum radiation shields operating at intermediate temperatures (such as 50 K, 4 K, and 0.7 K) reflect blackbody thermal radiation away from the central mixing chamber.
• Precision Vibration Isolation: Mechanical vibrations generated by room-temperature backing pumps or pulse-tube pre-coolers can introduce parasitic thermal energy via micro-frictional damping. Advanced mechanical damping and flexible thermal links are required to decouple vibrations from the sub-kelvin cold stage.
• Custom Attenuated Signal Wiring: Routing electrical interconnects, microwave coaxial cables, and DC measurement lines from room-temperature instrumentation down to the 20 mK mixing chamber requires specialized beryllium-copper and superconducting niobium-titanium cables fitted with inline attenuators to block thermal radiation while preserving signal integrity.

The TDF Ecosystem and Deep-Tech Manufacturing Framework

The execution of this project under DRDO's Technology Development Fund highlights an evolving paradigm in India's defence R&D ecosystem. The TDF scheme is designed to fund Indian Micro, Small, and Medium Enterprises (MSMEs), start-ups, and private industry partners up to 90% of total project costs, encouraging private firms to undertake high-risk technological development that would otherwise be cost-prohibitive.

Under this agreement, the Alwar-based start-up Zero mK India Private Limited will leverage technical mentorship, testing infrastructure, and peer review support from DRDO laboratories, specifically the Solid State Physics Laboratory (SSPL) in Delhi. SSPL researchers will assist in evaluating prototype sub-assemblies, validating sub-kelvin thermometry calibration, and conducting rigorous operational testing of the dilution refrigerator under realistic experimental conditions. This collaborative framework accelerates the transition of advanced physics concepts from academic laboratories into commercially viable industrial products.

Building a domestic supply chain for dilution refrigerators requires establishing specialized manufacturing capabilities in precision machining of high-purity oxygen-free high-conductivity copper, electron-beam welding of thin-walled stainless steel pressure boundary components, and fabrication of sintered silver heat exchangers with surface areas spanning hundreds of square meters. Establishing these manufacturing workflows within India strengthens the broader precision engineering ecosystem, creating spillover benefits for aerospace, nuclear, and cryogenic process industries.

Strategic Impact and Long-Term Engineering Outlook

As quantum technologies transition from theoretical physics into defense, cryptography, signal intelligence, and high-performance computing, sovereign control over the underlying test and operational infrastructure becomes imperative. Developing indigenous dilution refrigerators ensures that Indian defence labs and private technology firms can benchmark, qualify, and iterate quantum chips without depending on foreign hardware maintenance schedules or restrictive export clearance procedures.

Furthermore, the sub-kelvin testing capability developed through this TDF initiative lays the groundwork for modular quantum test chambers, high-density coaxial signal routing interfaces, and automated cryogenic monitoring systems. These capabilities will support testing of advanced superconducting electronics, low-noise amplifiers, single-photon detectors, and strategic sensor packages under extreme thermal constraints.

The successful execution of the 20 mK dilution refrigerator project under DRDO's TDF framework highlights the pivotal role of advanced thermal and fluid testing infrastructure in securing India's technological sovereignty. For specialized engineering and test rig manufacturers such as Neometrix Defence Limited, these advances reinforce the critical necessity of high-precision gas distribution networks, automated pressure testing benches, and custom cryogenic test solutions that validate mission-critical components under extreme environmental conditions.