Sensors—systems that help detect magnetic fields, electric fields, sensitive rotation and acceleration, measure time and picture biological systems with unprecedented accuracies, are an inevitable part of essentials like healthcare, security, environmental monitoring today, making them indispensable forday to day life.
The National Quantum Mission (NQM) launched by the Department of Science and Technology - Government of India, aims to boost and catapult the efforts across the nation to utilize and engineer the delicate quantum features of photons and atomic particles to build suchrevolutionary sensors that will be the ultimate solutions for a sustainable and greener development of the planet.
Classical sensors that have been traditionally used are based on principles that are familiar to us in the normal world – the intuitive way. For example, in medical diagnostics sensing of very delicate and feeble signals emitted by nucleons of atoms play a central role in detecting diseases by allowing imaging of the tissues. Sensing of extremely feeble magnetic fields generated by neurons allow for mapping the activity of the brain to detect neurological illnesses at an early stage. When it comes to navigation, the Global Positioning System (GPS) is the key to advancement in space research, enabling transportation and logistics etc. Without the ability of accurate measurement of time, the GPS would not work at all.
When one pushes the limits of these ‘classical’ sensors by going to atomic scales, one enters into the realm of sensitivities that lets us leap-frog into new domains of game changing applications.
One such example is the use of ‘squeezed states’ of light that overcome the standard limit of detection posed when using light for detection of physical phenomena. The fundamental principles of quantum mechanics lead to a situation that two particular properties (for instance position and momentum of photons, the basic carriers of light) cannot be measured simultaneously if one wants to measure them accurately. There is a natural limit on how accurately one can measure intensity of light when it is reflected from or absorbed by objects, or when the phase of light changes. This can be overcome by reducing the fluctuations in the measured parameter while decreasing the accuracy of unmeasured parameters. Quantum mechanics dictates that the product of the uncertainty of any twoconjugate variables (for e.g. Phase and Intensity of light, position and momentum of particles, Time and Energy etc.) has a minimum value of half of the reduced Planck’s constant. One can reduce the uncertainty in one of the parameters that is measured, while the uncertainty of the parameter that is not measured increases and does not have any relevance to the measurement process.
Quantum mechanics works counter intuitive to our experiences in physical world. What makes quantum mechanics counter intuitive is the way systems behave at atomic and sub-atomic level. They are based on properties such as superpositions (similar to two circular waves adding up in water when two pebbles are thrown), entanglement (a characteristic that lead to knowing the properties of two distant particles instantaneously), wave-particle duality (particles behaving as waves and vice versa) and tunnelling (particles finding their way into a physical wall even though there is a barrier), to name a few.
Electron microscope is another example where property of wave-particle duality is used. Standard optical microscope uses visible light as the medium of imaging. The electron microscope beats the resolution of standard optical microscope by choosing electrons instead of visible light. The wavelength electrons (considered as waves) can be reduced to a limit where nano-meter sized objects can be imaged – a task impossible with visible light.
The results of quantum mechanics have not been limited to sensors. The journey of putting the scientific principles of quantum mechanics has led to the discovery of semiconducting devices like transistors, superconductors as well as the understanding of the forces between atoms in molecules. It had led to the boom in semiconductor technology, clean energy, novel drugs, and so on. In the 21st century scientists across the world have been able to control and harness the delicate quantum mechanical features to build systems and devices that can take a leap forward into a completely new paradigm leading to the second quantum revolution, or Quantum 2.0. It can address humankind’s need for faster transportation, faster and secure communication, short lead times in designing drugs, securing borders, exploration of deep space, etc.
India has so far seen scattered and small-scale efforts by various scientists across Indian academia, government laboratories in defence, space and other laboratories in the domain. These scattered efforts have led to restricted capacity in the field with limited translation into useful products. The NQM mission is going to boost these efforts through co-ordinated efforts to consolidate existing knowhow into a larger scale to create a nationwide knowledge generation, translation into products and indigenisation.
As far as Quantum sensing is concerned, the National Quantum Mission is going to focus upon research and technology development in building a plethora of devices and systems. These include:
1. Magnetic sensors that can sense magnetic fields that are a million times smaller than the earth's magnetic field– virtual atoms trapped in diamonds, atoms cooled and trapped at near absolute zero temperature and collection of atoms at room temperature etc.
2. Precise clocks that will lose less than a 1 second in more than 300 billion years, allowing one to develop better navigation devices that are more than 1000 times accurate than the existing precision and also allow for study of the origin of universe that still remains elusive
3. Navigation devices that can be autonomous without the need for GPS signals – an important characteristic for future autonomous driving systems, deep space navigation
4. Affordable sensors for detecting the anatomical changes within human bodies with minimal intervention
NQM will help attain these at a cost that is affordable and scalable for wide range of applications.
