Cat, Bits and Quantum Computers

28 November 2017 | Maryana Kartashevska | About a 3 minute read
Tags: computing, Digital, experiment, mechanics, quantum computing, Schrodinger, Schrodinger's Cat, tech

Quantum computing has been an area of interest to me for some time. In this series of short blog articles, I explore the weird and wonderful world of quantum mechanics and how quantum computers will eventually revolutionise the world as we know it.


Quantum computers rely on the phenomenon in quantum mechanics known as quantum superposition – an ability of small particles to exist in different states simultaneously. Think of the famed Schrodinger’s Cat thought experiment, where the animal in a sealed box is both alive and dead at the same time; a state that persists until it is observed, at which point only one of the alternatives is true.


The background to the experiment – very much hypothetical I should note – was a cat placed in a steel chamber with a flask of poison, a radioactive substance and a Geiger counter. If a radioactive atom were to decay during the course of an hour, as measured by the Geiger counter, a hammer would shatter the flask, releasing the lethal poison and killing the cat. If not, the cat lived. The catch was the tiny size of the radioactive substance, which made decay impossible to predict. As such, Schrodinger postulated that during the time allotted and until an outcome was observed, the cat was alive, dead or indeed both.


Counterintuitive at first glance and very much at odds with our day-to-day experience of the world – how can something exist in two contradictory states at the same time – yet scientifically sound. For the more mathematically inclined, Schrodinger’s paradox is a linear equation, which means a combination of its linear solutions is also a solution. In simpler terms, if ‘alive’ is a valid outcome and independently ‘dead’ is a valid outcome, algebraic theory dictates that ‘alive plus dead’ should also be a valid outcome.


Impossible, because we only ever observe things in their definitive state? Scientists themselves struggle to agree on how this phenomenon comes about. Opinions range from collapsing waves, where a particle “decides” to assume a particular state at the point at which it is observed, to many worlds, where the particle is just as real in its alternative state but exists in a parallel universe.


Which essentially means that the coffee a colleague dropped off at my desk this morning was hot, cold or both at the same time, until I picked up the cup and realised it was cold, though content in the belief that somewhere in a parallel universe its temperature was just right. But I digress.


So how does this relate to computing and information processing? Whereas in a conventional computer a bit – the basic unit of information – is a binary digit that can have only one logical value of 0 or 1 at a time, a quantum bit aka qubit can represent 0, 1 or both simultaneously. Theoretically, this allows a quantum computer to run calculations much-much faster by exploring multiple solutions to a problem at the same time, rather than having to go through them sequentially.


Therefore, by exploiting the principle of quantum superposition, a quantum computer is able to solve the capacity limitations of modern machines and the pressures of big data, promising enormous computational speedups and technological progress.


In the next blog, I’ll explore how scientists around the world are making quantum computing a reality and the real-life implications of any advancements. In the meantime, feel free to reach out and we can have a more detailed discussion over a cup of coffee – hot, cold or possibly both.


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