If I knew how to make my ranting more coherent, I'd be getting crank late night phone calls from Sweden ! IMHO, there is a necessary connection between quantum states & information. Quantum entanglement is "merely" the reduction in bits necessary to describe the world. The only really solid (nailed down) connection between information theory and physics which exists today is entropy and thermodynamics. Therefore, the only really persuasive argument for a physicist will be to start with physical entropy (taking cues from Maxwell, Boltzmann, Planck, Bekenstein) and derive quantum computation directly, bypassing all of "elementary" physics completely. I suspect that quantumness is a necessary property of everything in the universe, so worrying about the quantumness of every one of the distinct particles makes the problem needlessly complicated. I had hoped that Verlinde's approach would provide some progress along these lines, but I haven't heard anything more. There's a video of him discussing it which is worth while seeing http://homer.kitp.ucsb.edu/online/joint98/verlinde2/snd/Verlinde2_TheorySemi... 354MBytes, 93 minutes. The paper: http://arxiv.org/abs/1001.0785 Re quantum computation: I'm still extremely uneasy with Shor's quantum factoring algorithm. The problem isn't with his algorithm, per se, but with the basic quantum model on which it is based. Leaving aside the potentially unsolvable problem of achieving the amount of isolation from the environment required to factor a large number, I'm not so sure that the underlying physics can represent the quantum phases to the amount of precision required to factor very large numbers. I think that quantum theory has something very new to add to computer science, but I'm not sure that the current concept of a "qubit" is that item. Qubits are still stuck in the completely unrealistic Aleph_1 (=2^(Aleph_0) by the continuum hypothesis) world, and so can't really be said to be part of _computer science/information theory_ at all. We also need a new type of quantum gate that doesn't depend upon a "collapse of the wave function" in order to operate. Given the lack of progress in quantum computation/qubits in the last decade, I'd say it's way past time to move on and draw some new cards from the deck. At 08:47 AM 2/9/2013, Warren Smith wrote:
I'd be interested to here more ranting on the topic from H.Baker. (A bit more coherent preferably, he sounds like he's getting at something interesting, but what?)