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Jack Woehr

Dr. Dobb's Bloggers

Quantum Probability : Snow in July

July 29, 2009

Talk about probability-based models of reality! The tiniest, most fine and delicate crystals of ice precipitated on my automobile's winshield last night in Colorado. Meanwhile, there's a 100+ (38 C°) heatwave in the Pacific Northwest. Which got me thinking about quantum computing and its underpinnings in quantum mechanics ...

Having been sorting through quantum computing trying to make sense of it all, a few things about QC in relation to quantum mechanics now seem apparent to me. (Please feel free to post comments challenging any foolishness.)

QM expresses subatomic reality in much the same way we computer programmers approach abstract problem spaces: QM virtualizes, conceptualizes.

There are moments in time and space wherein the observer latches state. There are transitions in state between observations. QM offers a conceptual mathematical model of the transitions we can't observe. If you sum the transitions per the recipe book, if you walk the virtualized state map, there is a statistical likelihood you will find the event you observe in the state predicted by the model.

EPR's challenge to QM and QM as it is studied today are not mutually contradictory. We'd like things to be simple, but they're not. EPR wanted a theory that explained things. QM doesn't really explain what's happening "down there": it merely offers a mathematical model which works, with a statistical likelihood of success, at predicting the outcome of certain events.

Today's problem domain of quantum computing is two-fold:

  1. Figure out theoretically how quantum circuits could do useful work.
  2. Build some real machines embodying the theoretical design.

Folks are describing computations that can be performed as useful side-effects of quantum interactions and drawing them up as quantum gates, in a fashion analogous to the invention of the digital adder, albeit vastly more subtle and difficult to construct.

One might picture the field of quantum computing in light of an interesting paper, A History of Semiconductor Research (Nathan Alan Teichhotz, MIT, 1967). It seems to me that in our present era, QC is about at a step analogous to where they built the first transistors of production quality.

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