Where is my Quantum computer laptop?

While there are no encouraging signs that our flying hover board or jet packs are on the horizon, we have seen computing power progressively make yesterday’s computers hard rubbish. 

Computing has skyrocketed from kilobytes to terabytes, from bulky grey boxes to mobiles, from software to updates, from highways to clouds, changing devices more often than our wardrobes. 

Around fifty years ago Gordon Moore, co-founder of the Intel Corporation, predicted technological and social changes ahead as he noted that the number of silicon-based transistors on microprocessor chips doubled every two years. Following on from that, chip performance would in fact double every 18 months. 

That’s roughly what happened, but recently this growth rate has reached a limit. Industry professionals suggest we reached the turning point in 2013, as we are still growing but at a now slower rate as we approach the physical limits of silicon chips.

We have heard on the grapevine that physicists, mathematicians and engineers are exploring a whole new paradigm in computing at the ‘quantum’ level. Its touted as smaller and faster computing that is just around the corner, but according to quantum researchers this scenario is not quite right.

“There are a lot of public misconceptions about quantum computing, suggesting that it is much faster and much smaller but both of those things are actually false,” says Dr Austin Fowler, a physicist who divides his time between the University of Melbourne and the University of California Santa Barbara.

“At the moment the experimental models of quantum computers actually run significantly slower than a conventional computer and they are currently bigger in size too, but they run in a very different way. 

“Your current classical computers process numbers quickly but one at a time, however with a quantum computer that has different hardware you can process many things simultaneously. So this new device will allow us eventually to solve complex research problems, in a way that no current computer or future computer with silicon chip technology could do. You are not going to run windows on this type of computer.

“Classical computers use ‘bits’ which are ones and zeros, whereas quantum computers manipulate special quantum bits (qubits) that can be both one and zero at the same time. A register containing 32 qubits can represent over 4 billion different binary numbers, and this number doubles each time you add a qubit. Each operation in a quantum computer is slower but it changes the value of every number in the register. This type of parallel computing would be very useful for breaking encryption.”

Dr Fowler suggests to keep in mind that scientists are still trying to build a quantum computer: we’re not there yet.

“We have small prototypes and people are often surprised there are many physical technologies because there are different approaches under investigation. There are two leading technologies. One is superconducting circuits. The other is ion traps where you have single atoms minus one or two electrons suspended in an electromagnetic field and manipulated by laser beams or microwaves. They build on atomic clock technology.

“My colleagues and I look at superconducting technology. Our quantum bit technology can be a fraction of a millimetre or sometimes even a centimetre in size, which is quite big, and they operate at no more than 100MHz. 

“It just goes to show that the popular misconception that quantum must mean small and fast is not true as we actually want our quantum mechanical system to be large so we can get the wiring in, and the physics sets speed limits that are hard to break. 

Dr Fowler says the current experimental research challenges are to build more quantum bits (qubits) and make them more reliable. 

“On the theory side, I have a mathematics student working on using fewer qubits to compute, which turns out to be the problem of compressing a particular 3D structure to the smallest possible volume. 

“I have another student who is looking at qubits that vanish, for example light (photons) that can get absorbed, so we are working on software that can handle that phenomenon and still achieve reliable computation. 

“My UCSB colleagues are working on different aspects of implementing superconducting devices, from quantum amplifiers, to superconducting magnetic shields, to control electronics, to better isolation of qubits, to enable more to go on one chip.

“Its an exciting time in quantum physics as its still not clear which combination of technology, or exotic design will allow us to produce this exciting new device. But we are making quantum leaps, pun intended.”

www.physics.unimelb.edu.au