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Two-Photon Walk a Giant Leap For Quantum Computing
ElectricSteve writes "Research conducted at the University of Bristol means a number of quantum computing algorithms may soon be able to execute calculations of a complexity far beyond what today's computers allow us to do. The breakthrough involves the use of a specially designed optical chip to perform what's known as a 'quantum walk' with two particles ... and it suggests the era of quantum computing may be approaching faster than the scientific establishment had predicted. A random walk – a mathematical concept with useful applications in computer science – is the trajectory of an object taking successive steps in a random direction, be it over a line (with only two possible directions) or over a multi-dimensional space. A quantum walk is the same concept, but translated to the world of quantum computing, a field in which randomness plays a central role. Quantum walks form an essential part of many of the algorithms that make this new kind of computation so promising, including search algorithms that will perform exponentially faster than the ones we use today."
According to the quantum computing video from a while ago (I think it was 90 minutes or something, I just watched 20), a quantum computer is designed for the problem it solves- they aren't general purpose like the processors in use today. As far as I understood from the video*, quantum computers are mostly just useful for doing calculations related to quantum physics.
*If I'm wrong/misleading, please correct me.
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I just can't comprehend quantum computing and quantum mechanics in general.
What absolutely derails me is the talk about randomness, probability and statistics inherent with this field. The word chance gets mentioned a lot and that just stops me in my tracks.
In programming there is simply no room for chance. Algorithm must always return the same result given same parameters. 1 + 1 must always return an exact, perfect value of 2 no matter how many times it is executed.
But from what I read, in quantum world you can only say that this particular action will result in probability of 0.99999999999 (Number of nines vary per setup) of returning that particular result. Very large amount of nines sounds reassuring, but given the speed of CPU's processing an instructions billions of times per millisecond, give enough execution time and eventually you will hit that one time when the result will not be what is expected.
And one wrong result will put the entire program into an undefined state.
When every instruction has a chance (VERY minute but still) of failing how do you even start to approach an issue of debugging. In order to plan my program flow I need the stability of my assumptions. And this is even before we start talking about the really weird parts of quantum mechanics (Superposition of states, etc).
Perhaps I just don't understand the field of probability and statistics. Quantum computation is a reality thus randomness is not an insurmountable hurdle that my mind makes it to be. I would really appreciate if someone with some knowledge in the area would try to explain (Or provide me with a link that directly addresses this issue) how the chances of particle states get converted into solid 100% reliable predictability.