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Lesson 10

Superposition and entanglement


To discover that groups of particles in the same superposition of states at the same time are said to be entangled. 


Revisit the ideas about the Observer Effect studied in Lesson 9.

The Observer Effect involves objects, on a quantum scale, becoming something different, depending on whether and when they are observed. In Lesson 9, the example studied involved electrons acting as waves until they were observed, or interacted with the screen in Young’s Experiment, during which they reverted to behaving as particles.

Reflect on your ideas about the Observer Effect pair up with another student, and either describe the principle, or give an example. 


Watch the video:

(2 min)


View slides 3-4 (Schrodinger's Cat) from the Superposition & Entanglement presentation, and summarise in your workbook.

Watch the video:

Schrodinger's Cat (4 min)

Answer the questions:

Schrodinger's cat is inside a box with 50% chance of dying from poisonous gas.

3. What is happening to the cat when we are not observing it?

4. What does it mean when the narrator says "It's our observation that forces nature to collapse"?


Working in small groups, come up with a thought experiment, or example, to explain superposition. Document the group's idea, including an explanation and representation of superposition.

e.g. Superposition of a substitute teacher.

A substitute teacher does not know what subject he or she will teach in a particular day because it is impossible to know in advance who will call in sick in the morning. That substitute teacher might be teaching Maths, Science, English, Drama, etc, with each subject representing a quantum state. Before the teacher goes into the school to find out what they are teaching, they are in a superposition of all the available subjects. Once they go into the school, the superposition collapses to just one particular state corresponding to the class they will teach.


Watch the video:

View slides 5-6 of Superposition & Entanglement, summarise the slides in your workbook, and answer the question:

5. How did Einstein describe entanglement?

6. What does it mean for two particles to be entangled?

7. Two particles are entangled. If you measure one particle, what happens to the second one?


Working in the same groups, come up with a thought experiment, or example, to explain entanglement. Document your idea, including an explanation and representation of superposition and entanglement.

e.g. Entanglement at a distance:

Two cards (Ace of Hearts and Ace of Spades) are given to two students in a sealed envelope. If one of the students opens his or her envelope and checks the card, it is automatically automatically obvious what card the second student has, even if that student is in another room. Prior to opening the envelope. we can say the Ace of hearts and Spades is in superposition in both envelopes until we check.


(4 min)

As a group,you will report back to the class with a quick summary presentation of your thought experiments, addressing the two key ideas of superposition and entanglement.

With your teacher, summarise the main findings of the class.


(30 min)

Superposition & Entanglement Activities on qCraft.

Watch the videos:

Log into qCraft on a computer with the qCraft Curriculum map loaded (see the How to install qCraft with MinecraftEdu section on the Appendix of the Teacher Guide). Complete the PLAY and REFLECT activities from either Lesson 2 or Lesson 3 in the qCraft Teacher guide.