Photo: Reuters
Photo: Reuters

OPINION: The magic of quantum computing

By Louis Fourie Time of article published Feb 15, 2019

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JOHANNESBURG - 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 manipu- late individual bits in binary states, quantum computing is built on the quantum state of millions of sub- atomic 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 en- ables 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.

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


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