Peter Cochrane: Quantum computing - a return to analogue computers?

Quantum computers are neither stable enough nor powerful enough to achieve very much at all at the moment, warns Professor Peter Cochrane - but could one day provide a cure for cancer

As an undergraduate I studied analogue and digital computing in equal measure as both were in common use in industry at the time, but had yet to find their way into commerce. After graduation I also enjoyed the experience of building elements of both kinds of computer using components you will now find in a museum.

It was not long before I was handed some of the early integrated circuits (Texas Instruments' Nand gate arrays) and shared the excitement a building a ‘real' computer. Needless to say this saw the rapid relegation of analogue computing to the ‘poor house' as it was totally outmoded and outflanked by what we now consider to be the digital revolution.

Quantum computers are far more analogue than digital, and deliver probabilistic rather than deterministic results

In something of a quirky turn of fate it appears that that the very early branching of 50 years ago may soon be reversed if we can only engineer stable quantum computers of sufficient size. For sure, quantum computers are far more analogue than digital, and deliver probabilistic rather than deterministic results.

Quantum uncertainty at the Qbit level sees significant errors to the point that error correction has to be employed. We are definitely looking at the birth of a new species of machine unrelated to our laptops mainframes and supercomputers.

Overlooking these finer points has seen outrageous forecasts for the potential capabilities of quantum computers that are just not true. For example; they will not be able to instantaneously decode the encryption of all our credit cards. The reality is: it will take about 10 seconds per card, one of the time.

Today, quantum computers require precise control, processing support, error correction, and environmental management by conventional computers

Quantum computers are also easily defeated by long cryptographic codes and there are only two algorithms at present (Shor's, Stein's/Grover) for cracking RSA encryption, and one of those amounts to little more than guessing. But there are numerous encryption techniques (for example, lattice cryptography) that can defeat quantum computers, so rest assured, we're not going to be held to ransom by quantum computers, far from it!

The major quantum computer engineering challenges include the creation of Qbits sufficiently stable, in large enough groupings, to do anything significant.

Today, quantum computers require precise control, processing support, error correction, and environmental management by conventional computers. And then there is the fan-in and fan-out problem! Getting all the wires into and out of a very small physical space is a challenge reminiscent of digital computing's history since its inception.

To get a quantum computer to produce anything significant demands at least 50 Qbits and, ideally, more than 100. Or, better still, 1,000 or more

To get a quantum computer to produce anything significant demands at least 50 Qbits and, ideally, more than 100. Or, better still, 1,000 or more, then we might just become ‘masters of the universe'. Far more interesting and significant than encryption: we will never understand chemistry biology and life without powerful quantum computers!

How significant is this? Around 95 per cent of all human ailments reside in the sphere of the genome, proteins, and the communication between the two. Digital computers were necessary to decode the genome, AI is now being used to describe the intricacies of protein folding, and it might just be that quantum computers can decode the communication between the two. And this is likely the seat of all causes of cancer, and more.

The prize here is a new perspective on cancer, not as something that we should seek to cut out or destroy, often at high cost, but something that we could potentially program out of the body in the first place.

After all, it appears that the genome has merely issued instructions to the proteins that they should grow, but then they do so unimpeded and uncontrolled. If this is, indeed, a corruption of communication, we might be able to correct or reverse it. To me this opportunity alone ought to make quantum computers worth a lot of investment, effort and, above all, engineering.

Professor Peter Cochrane OBE is an ex-CTO of BT who now works as a consultant focusing on solving problems and improving the world through the application of technology

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