Zitat:
Zitat von JoAx
[...] Die Frage ist jetzt - relativ zu was?
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Ich bin davon ausgegangen Path 1 zu Path 2. Ansonsten kann ich mir die relative Länge des Weges nur noch im Zusammenhang mit den Spiegeln in jedem Weg vorstellen.
BTW:
Das "welche Phase - welcher Weg" - Informationsspiel hatte ich hier mal vorgestellt -->
http://www.quanten.de/forum/showthread.php5?t=2851
PS: Das Photon wird durch eine Wellenfunktion beschrieben AFAIK. Dann habe ich meinen Splitter (Polarisationsfilter (?))
und dahinter habe ich dann exakt die gleichen Verhältnisse in meinem Beispiel: relative Länge der Wege zueinander, und gleiche Anordnung der Spiegel. Dann kommt mein zweiter Splitter (?) und meine zwei Detektoren.
Logisch erscheint mir dann eben 50/50 --> statistisch nach einer großen Anzahl von Versuchen.
Dieses Verhalten von dem Quantenobjekt ist doch in diesem Beispiel vergleichbar mit anderem Verhalten von anderen Quantenobjekten. Z.B. einem Silberatom bei Stern-Gerlach.
Mich interessiert das so wie hier beschrieben:
http://scienceblogs.com/principles/2...d-decoherence/
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The only way to detect interference of a single photon is to repeat the experiment many times, each time sending only one photon in. You record which detector “clicked” for each photon, and slowly build up a measurement of the probability of finding it at each detector. You can also vary the relative path length, repeating the experiment many times at various different lengths, and
in this way you’ll trace out the probability distribution as a function of mirror position. If you’re dealing with wavefunctions, you’ll see an interference pattern ranging between 0% and 100% probability for each detector, and if you’re dealing with particles, you’ll find a constant 50% for each detector.
So what do you find if you do this? Well, if you’ve set your interferometer up properly, with short path lengths and stable mirror mounts and all that technical stuff, you should see an interference pattern. So, a beamsplitter gives us a wavefunction in a superposition of two states.
How does this turn into two photons that each take a single path, though? To see that, let’s think about making our interferometer huge:
...
The wavy lines (*in beiden Pfaden) indicate a really long distance, say, a hundred kilometers, passing through air the whole way. What do we see then?
Well, if we’re talking about a long distance in a turbid medium, there’s going to be a phase shift. If you think in terms of waves, there are going to be interactions along the way that slow down or speed up the waves on one path or the other. This will cause a shift in the interference pattern, depending on exactly what happened along the way. Those shifts are really tiny, but they add up. If you’re talking about a short interferometer in a controlled laboratory setting, there won’t be enough of a shift to do much, but if you’re talking about a really long interferometer, passing through many kilometers of atmosphere, it’ll build up to something pretty significant.
That phase shift changes the interference pattern.
If the probability of finding the photon at Detector 1 is 100% with no interactions, it could be, say, 25% with the right sort of interactions. Or 50%. Or 75%. Or 0%. The exact probability depends on exactly what happened to the piece of the wavefunction that traveled on each path.
And here’s the thing: that shift is also random. What you get depends on exactly what went on when you sent a particular photon in. A little gust of wind might result in a slightly higher air density, leading to a bigger phase shift. Another gust might lower the density, leading to a smaller phase shift. Every time you run the experiment, the shift will be slightly different.
So what happens to your interference pattern? Well, it goes away. The first photon may have a 100% chance of turning up at Detector 1,
but the second will have a 25% chance, the third a 73.2% chance, the fourth a 3.6% chance, and so on. As you repeat the experiment many times these all smear together, and you end up finding that half of the photons end up on Detector 1, and the other half end up on Detector 2. The interaction between the photon and the air destroys your interference pattern.
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ABER mit dem Unterschied:
Wie schaut es aus, wenn ich diese "really long distance, say, a hundred kilometers, passing through air the whole way" nur in einen Pfad einbaue?
Der andere Pfad aber immer noch wie im "1. Versuch" die kontrollierten Laborbedingungen hat.
Verliere ich auch die Interferenzeigenschaften? Messe ich das Photon dann am Detektor 1 öfters? Oder bekomme ich auch hier 50 / 50 ?