A crucial feature of quantum tunneling is that, like many other quantum phenomena, it depends on the spread-out wave-like nature of matter particles. But for a body made up of very many particles to tunnel it has to maintain the wave aspects of all its constituents marching in step, with peaks and troughs of waves coinciding, something we refer to as the system being coherent, or simply “in tune.” Decoherence describes the process whereby all the many quantum waves very rapidly get out of step with one another and wash away any overall coherent behavior, thus destroying the body’s ability to
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