Simulating quantum mechanical systems is very difficult. This is not because we do not know the equations governing these systems but because the solutions to these equations do not scale well. What does that mean? Let's say we were to simulate a quantum mechanical system of 500 particles. Then, even if we made a computer with every atom in the universe as its bit, it would take more than the age of the universe to run the computation. The same task could potentially be done in a matter of days on a quantum computer.
Quantum computers are new kinds of computers that harness the power of quantum mechanics. Just as computers use bits as their fundamental entities, quantum computers use qubits. The possible states of a bit are 0 and 1. Qubits may not only be in states of 0 or 1 but also in superpositions of 0 and 1. Superposition is a quantum mechanical concept, which very roughly speaking, allows a qubit to be both 0 and 1 at the same time. Furthermore, with multiple qubits, quantum computers possess the property of entanglement, which allows for correlations not possible in classical settings. Both of these properties, along with many others, allow quantum computers to do certain tasks beyond the reach of classical computers.
One of the things that quantum computers can do efficiently is factor a very large number efficiently. This is important because the RSA encryption, which is one of the most widely used encryption systems on the internet, is based on the fact that classical computers cannot factor very large numbers efficiently. Thus, in the future, there is a very real threat of quantum computers breaking encryption protocols. This is one of the reasons that has contributed immensely to the “hype.” Big tech companies like, IBM, Google, and Microsoft have big programs in quantum computing. Countries around the world are starting to invest heavily to compete in what has been called the next “space race” by National Interest.
Very recently, it was reported by the Financial Times that Google has achieved quantum supremacy. Quantum supremacy refers to the point where quantum computers are demonstrably better at solving some specific problem than classical computers. This is a landmark result and has received a lot of attention.
Does that mean all the encryption schemes can be broken now? No. Here's the catch with quantum supremacy experiments: these experiments involve a very different problem than factoring. The qubits in present quantum computers are very noisy, and the quantum supremacy experiments are designed to take advantage of such setup. But solving factoring requires qubit with much less noise. And we are at least 15-20 years away from building quantum computers which will be powerful enough to break encryption. So encryption is a long term concern.
The Business Proposition
If the factoring application is in the future, what can we do now? A lot. Quantum mechanics provides the solution to the very thing it breaks: encryption. Quantum mechanics guarantees encryption from the laws of physics - the future of internet could be quantum. Another application of near term quantum computers will be simulating atoms and molecules. This could be useful for pharmaceutical companies and material science companies. A report from BCG estimated the size of the market for near term quantum computers to be $2 billion - $5 billion. As per the report, this size is expected to grow to $450 billion - $850 billion in the long term with applications including drug design and risk assessment for financial services firms. These estimates are for the applications we can foresee. But as quantum computing continues to develop over the coming decades, we may find that its applications exceed even the most optimistic estimates: after all, few foresaw the tremendous potential of classical computing during its advent in the 1960s and 1970s. We all should be curious and excited about quantum computing and its transformative potential.
Kanav Setia is a PhD candidate in physics at Dartmouth College. He works with Professor James Daniel Whitfield on quantum computation and quantum information. Before matriculating at Dartmouth, Mr. Setia worked for the Indian Space Research Organisation (ISRO). Mr. Setia holds a B. Tech. from the Indian Institute of Space Science and Technology.