Quantum physics with the benefit of hindsight Escaping from quantum weirdness by playing cards Quantum physics can be seen as a victory for common sense. Surely it is worth discarding the old ideas that make people think the opposite. A quantum card trick Many card games, if played fairly, are simply games of chance, of probabilities. Quantum physics usually gives results in terms of probabilities, but these are given exotic names like wavefunctions and superpositions, and are presented as things beyond our everyday experience. Are the probabilities we find in quantum physics anything like the ones we find playing cards? The answer is yes, but only after a small trick has been played. We need to be clear with what we mean here by shuffling, in case you worry later on that it is open to sleight of hand. Shuffling here just means reordering the pack in a way that, for practical purposes, is unpredictable. If you like, you can imagine a machine that blows the cards around in turbulent air for a few minutes before collecting them together again as a pack. Common sense tells us that the identity of the first card in a shuffled pack is already settled before the card is dealt, as a result of the shuffle – it is just that we don’t know what it is until we see it. This is a classical or “local hidden variables” view of the probability. | |
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