start from figure 2, turn the half mirror at D round so it faces the other way, now E will light up instead of F. Since his explanation doesn’t allow for that we’ve just proved his explanation is wrong.
Anyone know if that’s right? EDIT: seems clear to me both detectors must light up if you do this. EDIT2: it turns out that by “turn around” he means through 180 degrees, which should surely mean no change.
Can you clarify the question? Do you mean turning the mirror by a quarter-turn from its current orientation, so it’s diagonal in the other direction? I compute that if you do that it should work out with 1⁄4 chance of E, 1⁄4 chance of F, and 1⁄2 chance of neither (if it’s reflected back towards B or C it will never reach either). Exactly like the classical case, actually...
Edited to clarify—I agree re quarter turn, but it turns out he means half turn. I think our thought-experiment half-silvered mirrors are unchanged by a half turn.
A friend comments:
Anyone know if that’s right? EDIT: seems clear to me both detectors must light up if you do this. EDIT2: it turns out that by “turn around” he means through 180 degrees, which should surely mean no change.
It turns out he was referring to this error; see How accurate is the quantum physics sequence?
Can you clarify the question? Do you mean turning the mirror by a quarter-turn from its current orientation, so it’s diagonal in the other direction? I compute that if you do that it should work out with 1⁄4 chance of E, 1⁄4 chance of F, and 1⁄2 chance of neither (if it’s reflected back towards B or C it will never reach either). Exactly like the classical case, actually...
Edited to clarify—I agree re quarter turn, but it turns out he means half turn. I think our thought-experiment half-silvered mirrors are unchanged by a half turn.