Quantum Theory had been studied for 80 years before it was shown that there is a quantum equivalent of the model of computing that our systems rely on.

In the 1980s, the idea of a computer based on circuits using Quantum Logic gates was proposed. For the next couple of decades, people studied the theory of Quantum Computing, and some very interesting Quantum Algorithms were developed, but there were no actual Quantum Computers on which to run them.

These theorised Quantum Computers used a quantum version of the bits that store information in our everyday machines. A bit can only store one simple item of information: 0 or 1, and all of the complexity of our data processing is based on vast numbers of these 0s and 1s.

When people talk about their machines and software being 32 bit or 64 bit, they don't mean that their machines contain only 32 or 64 bits, they mean that the units of information (words) are made from blocks of 32 or 64 bits - 32 or 64 0s and 1s, and computer programs will operate on millions of bits of information.

So, it may be a shock to learn that, as of 2020, the largest quantum processor chip built by IBM has a mere 65 of these quantum bits, or qubits, slightly behind their rival Google which can place 72 qubits on a chip.

You might ask: why are so many people excited about Quantum Computers if they have such a tiny capacity? Well, companies building Quantum Computers using quantum circuits are aiming for several thousand qubits in the near future. The Canadian company D-Wave has created a form of Quantum Computer that uses a different model of computing and their systems boast around 5000 qubits.

Even so, it seems there's no competition: how could a Quantum Computer do anything useful with only a few thousand qubits of information? Well, quantum bits aren't restricted to holding a 0 or a 1: during the operation of a Quantum Computer, each of its qubits can be in a mixture of 0 and 1, and, unlike the isolated bits of a conventional computer, qubits can "co-operate" via quantum entanglement.

One important consequence of this is that, while a conventional system made from, say, 3 bits only needs 3 numbers to describe it, a Quantum Computer with 3 qubits requires 2 x 2 x 2 = 8 numbers to describe it. Now, scale that up to several thousand qubits and you begin to see the potential of a Quantum Computer.

When we have Quantum Computers with thousands of qubits arranged in circuits, many currently intractable problems will become solvable.

What can be acheived right now? Two things. First, D-Wave's systems do not employ quantum circuits, instead arranging their qubits in topologies suitable for a process called quantum annealing. The good news is that quantum annealing supports the solution of various types of optimisation problem, which directly impacts many real-world computational issues. So, it's possible to use the power of Quantum Computing today.

The second thing which any business can do is to become quantum ready : by understanding the potential of Quantum Computing, even though it may not be practical now, a business can position itself to take advantage of the technology when (and it is a case of when not if) it becomes commercially available and affordable. It is possible to buy time on the limited form of circuit-based Quantum Computers, and large businesses are already doing that: preparing their staff for the likely revolution that is to come shortly.