Quantum supremacy is when a quantum computing algorithm offers significant speedup compared to the best possible algorithm on a classical computer, and this speedup is demonstrated on a quantum computer. When quantum supremacy is achieved over a given classical algorithm, it then makes sense to run the algorithm on a quantum computer instead of a classical computer as the quantum computer will be more efficient. At the time of writing this book, there are a variety of areas which offer the promise of quantum supremacy, but no areas which have convincingly demonstrated it yet. These areas include machine learning and artificial intelligence, cryptography and computer security, searching, sampling and optimization, quantum chemistry and quantum dynamics, and more. But, because no area has demonstrated quantum supremacy as of the writing of this book, at present, it makes more sense to run algorithms on a classical computer instead of a quantum computer.
Quantum supremacy can provide the building blocks to power innovations and disruptions in medicine, finance and business processes, and more. As of the writing of this book, quantum supremacy has not been clearly demonstrated in any area on any machine, although engineers and scientists have a variety algorithms to offer the potential, quantum hardware still needs to improve before this potential is realized. These hardware improvements necessary to enable quantum supremacy may include, for example, making more qubits available, making the qubits more stable, and increasing the error correction of those qubits. Google, IBM, and others expect to demonstrate quantum supremacy in the near future because they expect to be able to make these improvements.
Why is quantum computing important? There's no one reason that outshines the others, but here are some comments from experts in the field highlighting why they work on it:
- Harnessing quantum computation is a worthy challenge that pushes humanity to be its best
- Quantum computing is needed because digital (classic) computing is running into the limits of its capability and quantum computing is the next frontier
- The universe is a quantum world, so to understand it we need quantum computation
- Quantum computers will help us tackle problems too difficult for a classic computer
- Developing new hardware based on new physics has historically helped progress in technology quantum computation should be no different
- Quantum computers will let us do things we can't do today