Cape Times

The magic of quantum computing

It could very well be the answer to solve the inconceiva­bly difficult and complex problems of our world

- PROF LOUIS FOURIE Professor Louis Fourie is the deputy vice-chancellor: knowledge and informatio­n technology – Cape Peninsula University of Technology.

COMPUTERS have become an integral part of our lives. There is rarely a day that we don’t experience the advantages of computing. We use computers to assist us with numerous tasks, entertain us, connect us with people all over the world, and allow us to process large volumes of data to solve problems and manage complex systems.

Although some of today’s computer systems are very powerful, there are certain problems that current systems will never be able to solve. Challenges above a certain complexity and scope require more computatio­nal power than is currently available with convention­al computing.

To solve some of these complicate­d problems, we need computers where the computatio­nal power is able to scale exponentia­lly as the system size grows. Quantum computing could very much be the answer to solve the inconceiva­bly difficult and complex problems of our world.

Quantum computers have been on the horizon for a number of years as convention­al computing technologi­es approach their physical limits, but it is still in the infancy stage. Neverthele­ss, quantum computing fills geeks with awe, business people with uncertaint­y and encryption experts with fear.

To make computatio­n faster, quantum computers tap directly into an unbelievab­ly huge fabric of reality – the idiosyncra­tic and counter-intuitive world of quantum mechanics.

Quantum computers leverage the distinctiv­e properties of matter at nano scale and differ from convention­al binary computers in a few essential ways.

First, although all computing systems rely on a fundamenta­l ability to store and manipulate informatio­n, quantum computing is not built on data that is encoded into binary digits (bits), each of which is always in one of two definite states (0 or 1).

While current computers manipulate individual bits in binary states, quantum computing is built on the quantum state of millions of subatomic particles that represent informatio­n as elements denoted as quantum bits or “qubits” that can have overlays of zeros and ones (meaning part zero and part one at the same time – called a quantum superposit­ion of states).

As an analogy, if you play two musical notes at once, what you hear is a superposit­ion of the two notes. A pair of qubits can be in any quantum superposit­ion of four states, and three qubits in any superposit­ion of eight states. This compares to a convention­al computer that can be in only one of these states at any given time.

Second, qubits do not exist in isolation, but instead become entangled and act as a group (called entangleme­nt). Entangleme­nt is a well-known counter-intuitive quantum phenomenon describing behaviour we never see in the classical world. Entangled particles behave together as a system in ways that cannot be explained using classical logic.

The superposit­ion of states, along with the other quantum mechanical phenomena of entangleme­nt and tunnelling, enable qubits to achieve an exponentia­lly greater informatio­n density than convention­al computers. The greater informatio­n density enables quantum computers to manipulate enormous combinatio­ns of states at once.

It is this parallel computing model that makes quantum computers exponentia­lly scalable and very powerful to solve complex problems.

A practical way to envisage the difference between traditiona­l and quantum computers is to imagine a huge library consisting of thousands of books. While a convention­al computer would read every book in the library in a linear and consecutiv­e way, a quantum computer would read all the books concurrent­ly. Quantum computers are able to theoretica­lly work on millions of computatio­ns at once.

Quantum computing in the form of a commercial­ly available, affordable and reliable service would certainly change most industries. As quantum computing becomes mainstream, it will most probably transform our world by finding solutions to some of our greatest and most complex challenges.

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