Question about measuring physcial observables

In summary, the conversation discusses the concept of measurement in quantum systems and the ability to predict eigenvalues. It also explains how quantum mechanics allows for the calculation of the average of all possible eigenvalues, known as the expectation value. The conversation ends with a question about defining physical observables and their relationship to nature.
  • #1
cragar
2,552
3
So my measurement of a quantum system is an eigenvalue of that operator.
And we are not able to predict what eigenvalue we will get, even if we knew the precise state vector before we make our measurement. But QM allows us to calculate the average of all these eigenvalues, if we made an infinite amount of measurements and then took the average. And we call this the expectation value. So the expectation value that we calculate might not even be a possible eigenvalue that we could measure?
Im just starting to learn QM. Any input will be much appreciated.
 
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  • #2
cragar said:
So the expectation value that we calculate might not even be a possible eigenvalue that we could measure?

Correct.
 
  • #3
ok thanks for your answer. Do we just define what physical observables are and then think of ways to measure these quantities that we defined. Or does nature have infinite amount of physical observables.
 

1. What is the definition of a physical observable?

A physical observable is a quantity or property of a physical system that can be measured or observed. It can be a fundamental physical quantity, such as mass or energy, or a derived quantity, such as velocity or temperature.

2. How are physical observables measured?

Physical observables are measured using various techniques and instruments, such as rulers, thermometers, scales, and voltmeters. These tools allow scientists to quantify and record the value of a physical observable in a precise and accurate manner.

3. What is the importance of measuring physical observables?

Measuring physical observables is crucial for understanding and describing the world around us. By quantifying and recording these properties, scientists can make predictions, test theories, and gain a deeper understanding of the laws and principles that govern the behavior of the physical world.

4. Can physical observables change over time?

Yes, physical observables can change over time. This is because physical observables are dependent on the state of a physical system, and the state of a system can change due to various factors, such as external forces, temperature, or chemical reactions.

5. How do scientists ensure the accuracy of measurements of physical observables?

Scientists use a variety of methods to ensure the accuracy of measurements of physical observables. This includes using precise and calibrated instruments, conducting multiple trials, and comparing results with other scientists' measurements. Additionally, scientists also take into account potential sources of error and use statistical analysis to evaluate the reliability of their measurements.

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