The rapid advances in computing technologies since the second half of the 20th century have completely changed every aspect of our lives. There seems to be no limit to the capabilities of modern computers. But did you know that there are still several mathematical and computational tasks that even the most powerful computers available today cannot handle? Even if they become much faster in the future, such problems will remain beyond the scope of computers based on current classical technologies.
That’s where ‘quantum computers’ can show the way forward — and with the launch of the National Quantum Mission two weeks ago, India is pursuing this in a big way.
But first, what is quantum computing and why do we need it today?
The ABC of quantum computing
Multiplying two prime numbers, A and B, to find the product C is a trivial task for any computer. But given C, the reverse problem of finding A and B is a lot more complicated. And this problem becomes impossible to solve once A and B become very large. The complexity of this problem forms the basis of how we protect sensitive data like our credit card numbers from being stolen when used for online transactions. Another important example is connected to quantum mechanics (QM), the branch of physics that studies nature at the microscopic scale of atoms and electrons.
With the help of a computer, we can easily solve QM equations for a hydrogen atom, which contains one proton and one electron, or a hydrogen molecule, which contains two hydrogen atoms. But if we go to a somewhat more complex molecule, say that of the medicine Aspirin, which has 9 carbon atoms, 8 hydrogen atoms, and 4 oxygen atoms, the QM equations are impossible to solve even if we use the most powerful computer available today.
Can we ever solve such problems that clearly have significant implications for society as a whole? The answer is yes, but we must change the rules and build computing machines that follow the strange and counterintuitive laws of QM for storing and processing information. Such a machine is called a quantum computer, where the fundamental unit of information is called a quantum bit or qubit.
Unlike classical bits in conventional digital computers that can take the values 0 or 1, qubits can be prepared in arbitrary combinations of 0 and 1. Such a combination is called a superposition state. As we go from one qubit to many, the number of such available quantum states grows rapidly — 2 states for 1 qubit, 4 states for 2 qubits, and 1024 states for 10 qubits. The number of such states in a modest quantum computer with, say, 300 qubits, becomes larger than the number of atoms in the entire visible universe! One can now create a superposition that is a combination of all those states and manipulate it.
The ability to create and manipulate such a large number of states is one of the key factors that make quantum computers extremely powerful compared to conventional computers when solving certain kinds of problems. The power doesn’t come from doing the task faster but by doing it in a completely different way — a sort of quantum shortcut! In the 1990s, Peter Shor, a scientist working at Bell Labs, US, showed that if one uses these new rules, they can actually solve the prime factorisation problem explained earlier. Lov Grover, also from Bell Labs, showed that a certain type of search problem can be solved with much fewer steps. And thus began the race to build quantum computers.
The goals
The National Quantum Mission, approved by the Union Cabinet with a budget of Rs 6,000 crore, will focus on several aspects of quantum technologies and is broadly divided into four verticals — quantum computing & simulations, quantum communications, quantum sensing & metrology, and quantum materials & devices. Each of these verticals will be coordinated by a thematic hub (T-Hub), which will be set up as a Section 8 company to provide more freedom and flexibility, compared to conventional funding models.
All the relevant stakeholders are expected to come together to form a cohesive team to bid for the T-Hubs via an open call. In addition, hubs will also carry out translational research, incubate start-ups, create links with industries, foster international collaboration, run an outreach programme, and also develop a comprehensive human resource development initiative to create the workforce needed to execute this mission.
There are several competing approaches to build quantum computing hardware. Since it is not yet clear which method is likely to yield a practical quantum computer, the National Quantum Mission will focus on key hardware platforms such as trapped ion, superconducting, semiconducting, photonic and neutral atom qubits, while keeping a close eye on any new emerging platforms. The goal is to develop quantum computers with 50-100 qubits in about 5 years and accelerate to 1,000 qubits and beyond in 8 years across several hardware platforms.
Today’s qubits are still unstable and only retain information for a short time — of the order of milliseconds or less. Hence, a strong emphasis will be given to the development of methods to stabilise these qubits using quantum error correction and improve the accuracy of the computers. There will also be a focus on developing quantum software for applications relevant to India’s needs. The mission will create an ecosystem that will enable start-ups to develop and provide component technologies for quantum computers and also create sound business cases in the long run.
The challenges
While ample funding is important, it is the setting up of systems and processes that will be key to the National Quantum Mission’s success. This will need to include aggressive hiring of new talent, intensive training programmes, industry engagement to create future opportunities for the workforce, and practices to attract and retain good talent. By reducing delays in the disbursal of funds and eliminating restrictions on the import of critical enabling technologies, we will be able to progress rapidly and prevent wastage of time and resources. The mission will generate several indigenously developed technologies, but in an increasingly globalised world, a careful balance must be struck between a push for self-reliance and quick access to much-needed (and easily available) global resources. With several breakthroughs still needed to make quantum computers practical and useful, the mission should aim to create the right conditions for these advancements to take place in India.
Quantum computing and other quantum technologies are being aggressively pursued by many countries in the world. The National Quantum Mission offers a tremendous opportunity for India to contribute significantly in this area with many factors and conditions in its favour such as a large and young talent pool and a rapidly accelerating infrastructure for high-tech R&D. However, it will require dedicated teamwork with smart and efficient execution from all the stakeholders. An optimal mix of basic, applied and translational R&D, with a continuous and effective evaluation programme, is needed to keep India relevant in this highly critical area of science and technology and set the stage for taking a leadership position in the 21st century.
Prof. R. Vijayaraghavan is an Associate Professor of Physics at the Tata Institute of Fundamental Research, Mumbai and is an expert on superconducting quantum processors. Views are personal.
(Edited by Humra Laeeq)