Very strange how history repeats itself. The Turing machine is Alan Turing's mathematical proof that a programmable digital computer was possible using nothing but George Bool's logic gates, however they had to wait for Tommy Flowers to invent a working vacuum tube logic gate. In 1985, David Deutsch described a quantum Turing machine using nothing but Richard Feynman's Qbits, or in other words a mathematical proof that a programmable quantum computer was possible. Now we are waiting on someone to invent a practical quantum logic gate. Just recently, a single atom transistor has been created (http://www.purdue.edu/newsroom/research/2012/120219KlimeckAtom.html). I wonder when this article will be repeated for the, as yet to be created, quantum Turing machine.
Like in the CERN lab effort, the smaller you digging into understand subparticles, the larger the forces required (The practical size of a magnetic field generator is not limited by the size but the COST and complexity of the structure).
Likewise, I infer by your comment Max, that there is a practical limit of economics.
The cool factor can only take you so far.