Could a photon activate multiple photomultipliers at once?

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Discussion Overview

The discussion explores whether a single photon can activate multiple photomultipliers (PMTs) simultaneously, examining the nature of light as both a particle and a wave, and the implications for detection mechanisms in experimental setups.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions if a photon emitted in a room could trigger both PMTs simultaneously, suggesting a probabilistic nature similar to electrons.
  • Another participant asserts that the measurement states indicate only one PMT can be triggered, and both cannot be activated at once.
  • A different viewpoint introduces the concept of superposition for the PMTs, suggesting that while both detectors can exist in a superposition state, the outcome remains that only one can be triggered.
  • One participant argues that light is a quantum object that exhibits both particle and wave properties, emphasizing that detection relates to particle-like behavior.
  • Another participant proposes that a virtual photon could potentially trigger multiple lasing cascades, raising a hypothetical scenario involving evanescent waves.
  • Several participants discuss the use of scintillation crystals to convert a high-energy photon into multiple lower-energy photons, which can then trigger multiple PMTs, noting this is a common practice in PET and SPECT applications.
  • One participant clarifies that while scintillation can lead to multiple detections, it does not mean the original photon hit two detectors; rather, it is the secondary photons that do so.
  • Another participant agrees that the triggering of multiple PMTs from secondary photons is often a nuisance, as the focus is on the original photon.

Areas of Agreement / Disagreement

Participants express differing views on whether a single photon can trigger multiple PMTs, with some arguing it cannot while others suggest mechanisms that allow for multiple activations through secondary photons. The discussion remains unresolved regarding the original photon's role in triggering multiple detectors.

Contextual Notes

Participants note limitations in their arguments, including the dependence on definitions of photon behavior and the specific configurations of detectors and scintillation materials. There is also mention of decoherence effects in photomultipliers that may influence outcomes.

Who May Find This Useful

This discussion may be of interest to those studying quantum mechanics, experimental physics, or anyone involved in detector technology and applications in medical imaging.

Ghostcrown
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At the risk of making my inexperience in quantum mechanics plainly obvious, I have a question to ask. Say you emit a photon from one side of a room. As I've come to learn, light is not only a particle, but a wave. Say there are two photomultipliers, both encompassed within the wave of light. Would that trigger both photomultipliers, or would it act like an electron does and "roll the quantum mechanical dice" so to speak, and hit one or the other out of pure probability?
 
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The measurement states are one or the other photo-multiplier is triggered, but not both. Both being triggered is not in the set of outcomes.

Edit: I want to add that the photo-multipliers themselves can be in superpostion. In the Dirac notation we might call this ##a\mid1,0 \rangle +b\mid0,1 \rangle ## where the first number is 1 if the 1st detector is triggered and so on. So these two seemingly mutually exclusive things can exist side by side, which might happen if the wave was incident on the two detectors but the detectors themselves were sufficiently isolated. But there is no ##|1,1> ## state essentially.
 
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Ghostcrown said:
As I've come to learn, light is not only a particle, but a wave.
Light is neither. It is a quantum object, that can show particle or wave properties sometimes. The detection of a photon is related to particle-like behavior, only one detector can detect it.

MisterX said:
So these two seemingly mutually exclusive things can exist side by side, which might happen if the wave was incident on the two detectors but the detectors themselves were sufficiently isolated.
Photomultipliers lead to decoherence within nanoseconds (or maybe even faster).
 
It is possible for a virtual photon to trigger a lasing cascade. I wonder if a prepared (in the manner of MisterX) evanescent wave of a single photon could trigger two lasing cascades.
 
If you want a single photon to trigger more than one PMT then the usual approach is to put a scintillation crystal in front. The high energy photon will hit the crystal and turn into a shower of lower energy photons and those secondary photons can trigger multiple PMTs. This is how most PET and SPECT is done.
 
DaleSpam said:
If you want a single photon to trigger more than one PMT then the usual approach is to put a scintillation crystal in front. The high energy photon will hit the crystal and turn into a shower of lower energy photons and those secondary photons can trigger multiple PMTs. This is how most PET and SPECT is done.

Indeed, and if the photon doesn't deposit its full energy in the crystal (e.g. compton scattering followed by escape), you can create signals in multiple scintillation crystals too. (This is basically also how Compton suppression works as well - use a scintillator crystal surrounding your detector as a veto)
 
Okay, but I would not call that "the photon hit two detectors" because the original photon got converted to multiple new photons and only those hit the detectors.
 
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Agreed.

As a practical matter this is often important because PMT tubes are relatively transparent to high energy photons so we need the crystals to detect enough photons at all. But we are interested in the first photon and not the shower of lower energy photons. So the triggering of multiple PMTs is somewhat of a nuisance.
 
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