1. The Wikipedia article on quantum computing describes a quantum computer as “a computer that exploits quantum -mechanical phenomena.” The rest of the article then tries to explain what these quantum-mechanical phenomena actually are.
Unfortunately, the article limits itself to the mainstream interpretation of these and, therefore, suffers from what I perceive to be logical and philosophical errors. Indeed, in the realistic interpretation of quantum mechanics that I have been developing, system wavefunctions are only useful to model our own uncertainty about the system. I subscribe to Hendrik Antoon Lorentz’s judgment at the last Solvay Conference under his leadership: there is no need whatsoever to elevate indeterminism to a philosophical principle. Not in science in general, and not in quantum mechanics in particular. I, therefore, think quantum mechanics cannot offer a substantially new computing paradigm.
Of course, one may argue that, for specific problems, some kind of three- or more-valued logic – rather than the binary or Boolean true/false dichotomy on which most logic circuits are based – may come in handy. However, such logic has already been worked out, and can be accessed using appropriate programming languages. Python and the powerful mathematical tools that come with it (Pandas, NumPy and SciPy) work great with ternary logic using a {true, false, unknown} or a {-1, 0, +1} set of logical values rather than the standard {0, 1} Boolean set. The Wikipedia article on three-valued logic is worth a read and, despite the rather arcane nature of the topic, much better written than the mentioned article: have a look at how operators are used on these three-valued sets in meaningful algebras or logical models, such as that of Kleene, Priest or Lukasiewicz.
2. One may, of course, argue that, even when there is probably no such thing as a new logical quantum computing model or logic, quantum technology may offer distinct advantages when it comes to storage of data about this or that state or, one day, lead to devices with faster clock and/or bus speeds. That appears to be a pipedream too:
- To keep, say, an electron in this or that spin state, one must create and steady an electromagnetic field – usually one does so in a superconducting environment, which makes actual mechanical devices used for quantum computing (qubits) look like the modern-day equivalent of Babbage’s analytical machine. In my not-so-humble view, such devices will never ever achieve the sheer material performance offered by current nanometer-scale MOSFETs.
- As for bus or transmission speeds, quantum theory does not come with a new theory of charge propagation and, most importantly, is fundamentally flawed in its analysis of how signals actually propagate in, say, a lattice structure. I refer to one of my papers here (on electron propagation in a lattice), in which I deconstruct Feynman’s analysis of the concept of the free and effective mass of an electron. Hence, for long-distance transmission of signals, optical fiber cannot be beaten. For short-distance transmission of signals (say, within an electrical circuit, I refer to the above-mentioned nano-technology which continues to revolutionize the chip industry.
Brussels, 4 July 2023
Reading Feynman 