# Quantum Mechanics

Curriculum Connections: Quantum Mechanics is part of the physics curriculm in Ontario, but often so much time is spent on the personalities and history of Quantum Mechanics that students don't really get a chance to understand the key concepts and how it is so radically different from classical mechanics. Curricula in many other places have almost no time alotted to Quantum Mechancs. This is a travesty when Quantum Mechanics is the basis of our understanding of chemistry, nuclear energy, computers, lasers, medical imaging etc. However, if you are teaching wave interference of springs, water and light, you can also throw in electrons. Radioactivity is often hidden in the curriculum somewhere. Why not take a bit of time to point out how truly strange its randomness is. Similariy, if you are teaching about polarized light as a wave phenomena, you can go a little further and discuss how a single photon can be polarized.

1) Interference
This lesson introduces students to some of the key concepts of quantum mechanics (wave-particle duality, randomness, uncertainty and the effect of measurement) through a simulation of electron interference. These ideas are reinforced with a 5-minute video of the real experiment and then data from a interference experiment involving buckminsterfullerene molecules - objects that are five orders of magnitude bigger! The question is examined further in the Quantum Eraser lesson.

This lesson was developed before the Perimeter Institute of Theoretical Physics developed their wonderful 25-minute video and Teachers Guide on the same subject called The Challenge of Quantum Reality. You should order your free copy (for teachers in Canada) today and use it instead of or in addition to the lesson here.

This lesson emphasizes one of the key concepts- randomness. The students explore a physical model using the pseudo-randomness of dice in small groups and then they examine intrinsic randomness of radioactivity using a computer simulation.

3) Quantum Polarization
This lesson starts with experimenting with polarizing filters and calcite and then analyses the results in terms of a wave model. A series of thought experiments around polarized photons has the students explore the meaning of quantization of states, the effect of measurement on reality and entanglement. Finally, games involving polarized photons in quantum cryptography and tic-tac-toe are introduced.

4) Bose-Einstein Condensates
Bose-Einstein condensates are a weird state of matter predicted by quantum physics, where millions of atoms are in the same place at the same time! There used to be a great lesson on the Physics 2000 site of the University of Colorado. IT IS NO LONGER THERE. :( . In addition to Bose-Einstein condensates it explains and uses the following topics: temperature, absolute zero, Big Bang, atomic spectra, lasers, Doppler shift, magnetic fields and Heisenberg’s Uncertainty Principle. This is a great way to tie together many standard concepts covered in your curriculum, while having your students learn some truly modern physics.

5) Heisenberg' Uncertainty Principal and Diffraction
This looks at the diffraction of light through a single slit using a really cheap hands-on demo, an experiment with slits of known width and a simulation. Diffraction is usually taught as classical wave behaviour, but light is made of photons, so the diffraction of light must be a quantum mechanical phenomena and it must have a quantum mechanical explanation. The explanation is Heisenberg's Uncertainty Principal.

6) Quantum Editor
This lesson looks closely at the perplexing question of how a single photon can interfere with itself. Which path does it take in a double slit experiment - one side, both or neither? It looks at a set of demonstrations which require a laser pointer, straight pin and a few polarizing filters.

7) Measuring Planck's Constant with LED's
This is one of the rare simple and cheap experiments you can do in quantum mechanics. It has been around for a while and keeps being rediscovered. Essentially it is conservation of energy with a quantum device. One electron liberates one photon and eV = hf. If you graph eV against f it looks like the graph for the photoelectric effect, because an LED is just the PE effect run backwards.

8) Quantum Information
This is a brief introduction to quantum cryptography and quantum computing. It requires that students are already familiar with wave-particle duality, quantum superposition and polarized light. It is a very difficult subject and has been kept very short, active and conceptual.

9) Quantum Uncertainty
This lesson joins lessons 1, 3, 5 and 6 in the common theme of quantum uncertainty. It is a summary of the wave model and how it must give way to quantum physics when the light is faint, much as Newtonian mechanics and gravity must give way to special and general relativity.

10) How to make a Laser
This lesson uses a great PhET simulation and a couple of short videos to fully involve the student in understanding what these ubiquitous tools are all about.