# The simplest quantum system | Summary and Q&A

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July 5, 2017
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MIT OpenCourseWare
The simplest quantum system

## TL;DR

The video discusses simplifying quantum mechanics by considering a system with only two possible states.

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### Q: What is the simplest quantum system according to the professor?

According to the professor, a particle in a box or a system with a delta function potential could be considered the simplest quantum system. However, both systems still have complexities due to the infinite number of states or scattering states involved.

### Q: Why is it important for the Hamiltonian (H) in quantum mechanics to be Hermitian?

The Hamiltonian is required to be Hermitian because complex numbers and energies are involved in quantum mechanics. Additionally, for probabilities to be conserved, the inner product of the wave function must exist, which requires the Hamiltonian to be Hermitian.

### Q: How does simplifying the system by considering only two points affect the mathematical representation?

Simplifying the system to only two possible points allows the wave function to be represented by a two-component vector. This vector contains the amplitudes for being at each point, with the squared magnitudes of these amplitudes representing the probabilities.

### Q: In what physical scenarios can the simplified system with two possible points be applied?

The simplified system with two possible points can be applied to scenarios such as a particle's position in a box with a partition or a particle's spin, where the particle can be in either an "up" or "down" state.

## Summary & Key Takeaways

• The video introduces the concept of simplifying quantum mechanics by focusing on a system with only two possible states.

• It explains that by considering a particle that can only exist at two points, we can simplify the mathematical representation of the system.

• This simplified system can be applied to physical scenarios such as a particle's position in a box or a particle's spin.