The perfect flaw: how a diamond defect is changing quantum physics

Quantum physics, a fascinating yet often counter-intuitive field, promises revolutionary advancements across various sectors. One of its persistent challenges has been maintaining 'quantum coherence' – the ability of quantum states to remain stable and interconnected – especially at room temperature. This is where the recent breakthrough involving Nitrogen-vacancy (NV) centres in diamonds becomes profoundly significant. These NV centres are not just mere impurities; they are specific atomic defects within the diamond's crystal lattice where two adjacent carbon atoms are replaced by a nitrogen atom and an empty lattice site (vacancy). This unique structural arrangement gives them extraordinary quantum properties.

Historically, the pursuit of quantum technologies has been hampered by the phenomenon of 'decoherence,' where fragile quantum states quickly lose their properties due to interaction with their environment. This often necessitates extremely cold temperatures or highly isolated environments, making practical applications difficult and expensive. The discovery and subsequent research into NV centres offered a glimmer of hope because they inherently possess the ability to maintain quantum spins in a coherent state even at room temperature. This intrinsic property makes diamonds with NV centres a 'perfect flaw' – a defect that is immensely valuable. Early research focused on individual or small clusters of NV centres for applications like ultrasmall magnetic field sensors, leveraging their sensitivity to external fields.

What happened in the recent research is a significant leap forward. Instead of isolating individual NV centres, scientists demonstrated that by densely packing trillions of these centres together, they could harness their 'noisy interactions' to create a 'superradiant maser.' A maser (Microwave Amplification by Stimulated Emission of Radiation) is the microwave equivalent of a laser, producing coherent microwave radiation. Superradiance is a quantum phenomenon where a collection of excited atoms or molecules collectively emit radiation much faster and more intensely than they would individually. This collective emission amplifies the signal and overcomes individual noise, leading to a powerful, coherent output at room temperature.

Key stakeholders in this research include academic institutions and national laboratories globally, such as those in the United States, Europe, and increasingly, India. Funding agencies like the Department of Science & Technology (DST) and the Science and Engineering Research Board (SERB) in India play a crucial role in supporting fundamental and applied research. Private industries in defence, healthcare, and quantum computing are also keen observers and potential investors, as this technology holds immense commercial potential.

For India, this development is particularly important given its ambitious National Quantum Mission (NQM), launched in 2023 with a substantial outlay of Rs 6003.65 crore (approximately $725 million) for the period 2023-2031. The NQM aims to nurture and scale up scientific and industrial R&D in quantum technologies. Developing expertise in NV centre technology aligns perfectly with the NQM's objectives of developing quantum computing, quantum communication, quantum sensing and metrology, and quantum materials. This can bolster India's strategic independence in critical technologies, reduce reliance on foreign imports, and foster a robust domestic ecosystem for quantum innovation. It contributes to the 'Make in India' and 'Atmanirbhar Bharat' initiatives by encouraging indigenous development and manufacturing of advanced sensors and quantum devices.

Historically, India has always recognized the importance of scientific temper, enshrined in Article 51A(h) of the Constitution as a fundamental duty. The Scientific Policy Resolution of 1958, championed by Prime Minister Jawaharlal Nehru, laid the foundation for scientific development. Today, advancements like NV centre technology contribute to broader themes of national security (e.g., highly sensitive defence sensors, secure quantum communication), economic growth (new industries, high-skilled jobs), and social welfare (advanced medical diagnostics). The future implications are vast: ultra-sensitive sensors for medical imaging, navigation systems that are impervious to GPS jamming, sophisticated materials characterization, and potentially even components for fault-tolerant quantum computers. This research pushes the boundaries of what's possible at room temperature, bringing practical quantum technologies closer to reality and positioning India to be a significant player in the global quantum race.