Core Ideas:

Quantum Mechanics – The theory that describes how matter and light behave at very small

scales, such as atoms and particles.

​Wave function – A mathematical description that encodes all the possible outcomes of a

quantum system and how likely each one is.

​Superposition – The idea that a quantum system can be described as being in multiple

possible states at the same time.

​

​

Measurement:

Measurement – The act of observing a quantum system, which produces a single definite

result.

Measurement Problem – The question of why measurements give one outcome when the

theory allows many possibilities.

Wave function Collapse – The idea that the wave function suddenly reduces to one outcome

when a measurement occurs.

​

Reality and Causation:

Determinism – The view that the present state of the universe completely determines its future.

Probability – A way of describing how likely different outcomes are.

Hidden variables – Hypothetical underlying features of reality that determine outcomes but are

not included in standard quantum mechanics.

​

Space and Connections:

Locality – The principle that objects can only be influenced by nearby events, not

instantaneously by distant ones.

Non-locality – The idea that distant systems can be connected in ways that cannot be

explained by local interactions alone.

Entanglement – A strong quantum connection between particles such that measuring one

affects the description of the other, even when they are far apart.

 

John Bell and Related Experiments:

Bell’s theorem – A result showing that no theory based on both locality and hidden variables

can reproduce all the predictions of quantum mechanics.

Bell inequalities – Mathematical limits that local hidden-variable theories must satisfy.

Bell test experiments – Experiments that test Bell’s inequalities; their violation supports

quantum mechanics and rules out many local hidden-variable theories.

 

Major Interpretations:

Copenhagen interpretation – Treats quantum mechanics as a theory about measurement

outcomes, not a direct description of microscopic reality.

Pilot-wave theory – An interpretation in which particles always have definite properties, guided

by a wave.

Many-Worlds interpretation – An interpretation in which all possible measurement outcomes

occur, each in a separate branch of the universe.

Transactional interpretation – An interpretation that explains quantum events using a time-

symmetric exchange between past and future.

 

Properties:

Local / Non-local – Whether influences are limited to nearby interactions or can act across

distance.

Deterministic / Indeterministic – Whether outcomes are fixed by prior states or involve

fundamental randomness.

Collapse / No collapse – Whether the wavefunction is assumed to collapse during

measurement.

Single-world / Many-world – Whether only one outcome occurs or all outcomes exist in

separate branches.

Observer-dependent / Observer-independent – Whether measurement plays a fundamental

role in defining reality.

​

​

​

​