Who of the creators of the first bulky transistor could have imagined that their creation would change the world so dramatically in a span of only 50 years? Today, we are completely dependent on electronics, with an estimated 1,200 quintillion transistors being used in everything from our mobile phones to our washing machines. And our thirst for computational power only grows. In order to fit more and more transistors into our devices, we will have to make them smaller and smaller. In fact, soon our transistors will have to be the size of a few atoms and that means we will have to encroach on the world of quantum physics. And since we are here, why not explore the place a little?
The microscopic, quantum world is quite unlike our macroscopic, classical one. Well- defined objects such as particles become indiscriminate waves, while what we thought were continuous, smooth waves suddenly can be described in a discreet, divisible fashion. Particles can appear in two places at the same time until you actually look at them, when they instantaneously jump into one of the places, in fundamentally unpredictable fashion. Finally, in the quantum world two objects can become so deeply connected, or entangled, that even if they would be separated by the stretch of the Milky Way, one of them would instantaneously feel something happening to the other.
It is these strange properties of quantum objects requiring us to re-evaluate our very notion of reality, that have made theoretical physicists think whether we could also re-think the way we do computing, moving beyond simple models of 0’s or 1’s. Indeed, over the last 20 years, these physicists have come up with quantum algorithms that are more secure, much faster and more efficient than classical ones. In fact, in theory a quantum computer could almost instantaneously solve certain problems that would take a classical computer longer than the current age of the universe!
So can we actually build one of these? We need a few ingredients: a quantum physical object, some way of controlling it and making it interact with others of its kind, and a way of measuring it.
All this whilst isolating it from its classical surroundings, as most quantum objects are very sensitive and lose their quantum properties very easily – which is why we don’t see many quantum effects in our classical world. To this extent, we have quite a few options to choose from, but let us look at one of the simplest quantum systems, an entity whose weird wave- particle nature has for hundreds of years been perplexing the greatest minds of science such as Newton, Maxwell and Einstein: light, or a photon, as it is known by its particle name.
Light is already used in modern telecommunications to send information, in fact it has been used to send signals between ships going back hundreds of years ago. This is because light is very fast (it actually travels at the speed of light) and it is relatively easy to send it over long distances without much distortion. Even at the potentially sensitive quantum level. Photons are also quite easy to manipulate and measure.
The problem with photons though, is that it is really difficult to produce large numbers of pure, single photons, and make them interact with one another (unfortunately, lightsabers are still science-fiction).
But we are working on it. After all, the first electronic transistor was also the only one of its kind at the time and no one could dream that it would be miniaturised and mass-produced…
About the Author
Krzysztof “Kris” Kaczmarek is currently a third-year DPhil student in Atomic and Laser Physics at the University of Oxford. He is a member of the ultrafast quantum optics and optical metrology group headed by Prof. Ian Walmsley. Kris’ particular research interest are optical quantum memories, i.e. devices for storing quantum light. Kris has been involved in photonics, or the science of light, for the last 5 years, having started building “classical” lasers as an undergraduate in the Ultrafast Phenomena Lab at the University of Warsaw, Poland, where he is also from.