The Decoherence of Measurement
Uploaded by palma on Oct 09, 2000
Sam Vaknin's Psychology, Philosophy, Economics and Foreign Affairs Web Sites
Arguably the most onerous philosophical question attached to Quantum Mechanics (QM) is that of Measurement. The accepted (a.k.a. Copenhagen) Interpretation of QM says that our very act of conscious, intelligent, observable measurement – determines the outcome of the measurement in the quantum (microcosmic) realm. The wave function (which describes the co-existing, superpositioned, states of the system) collapses following a measurement. It seems that just by knowing the results of a measurement – we determine its outcome, determine the state of the system and, by implication, the state of the Universe as a whole. This notion is so counter-intuitive that it fostered a raging debate which has been on going for more than 7 decades now.
But, could we have turned the question (and, inevitably, the answer) on its head? Is it the measurement that brings about the collapse – or, maybe, we are capable of measuring only collapsed results? Maybe our very ability to measure, to design measurement methods and instrumentation, to conceptualize measurement and so on – are thus limited as to yield only the collapse solutions of the wave function?
Superpositions are notoriously unstable. Even in the quantum realm they should last but an infinitely split moment of time. Our measurement apparatus is not as refined as to capture a superposition long enough to justify the title of “measurement” or “observation”. By contrast, collapses are sufficiently stable to last, to be observed and measured. This is why we measure collapses.
But in which sense (excluding longevity which, anyhow, is a dubious matter in the quantum world) are collapse events measurable, what makes them so? Collapse events are not the most highly probable – some of them are associated with low probabilities and still they occur and are measured. Ex definitio, the more probable states will tend to be measured more (the wave function will collapse more often into high probability states). But this does not exclude the less probable states of the quantum system from materializing upon measurement.
The other possibility is that the collapse events are carefully “selected” for some purpose, within a certain pattern and in a certain sequence. What could that purpose be? Probably, the extension and enhancement of order in the Universe. That this is so can be easily substantiated: it is so. Order increases all the time. This is doubly true if we...