Wave Function Terminology - Are these synonyms?

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Discussion Overview

The discussion revolves around the terminology used in quantum mechanics, specifically whether "probability amplitude" and "probability density" are synonymous terms. The scope includes conceptual clarification and technical explanation related to quantum wave functions.

Discussion Character

  • Conceptual clarification, Technical explanation

Main Points Raised

  • Some participants assert that "probability amplitude" and "probability density" are not interchangeable terms, highlighting that the former is complex while the latter is real.
  • It is noted that the probability density can be derived by taking the modulus of the probability amplitude and squaring it.
  • One participant suggests that it is reasonable to refer to a complex wave function as a probability amplitude, with its modulus squared representing the probability density, contingent on the wave function being a solution to Schrödinger's equation.
  • Another participant confirms that the notation ##\Psi## represents a probability amplitude and ##\Psi^*\Psi## represents the corresponding probability density, assuming normalization of the wave function.

Areas of Agreement / Disagreement

Participants generally agree that "probability amplitude" and "probability density" are distinct concepts, but there is some variation in how these terms are applied and understood in context.

Contextual Notes

There are assumptions regarding the normalization of the wave function and its status as a solution to Schrödinger's equation that are not fully explored in the discussion.

shanepitts
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Are the quantum mechanical terms "probability amplitude" and "probability density" used interchangeably?
 
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shanepitts said:
Are the quantum mechanical terms "probability amplitude" and "probability density" used interchangeably?

No.

The probability amplitude is complex.
The probability density is real.

Take the modulus of the probability amplitude and square it to get the probability density.
 
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craigi said:
No.

The probability amplitude is complex.
The probability density is real.

Take the modulus of the probability amplitude and square it to get the probability density.

Thanks.

So is it safe to say that a complex wave function is a probability amplitude and that its modulus squared is a probability density?
 
Safe enough for all practical purposes, provided that the complex wave function in question is a solution to Schrödinger's equation.
 
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Yes. ##\Psi## is a probability amplitude and ##\Psi^*\Psi## is the corresponding probability density, assuming that ##\Psi## has been normalized so that
$$\int^{+\infty}_{-\infty}{\Psi^*\Psi dx} = 1$$
 
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