5: Dirac Notation
- Page ID
- 56757
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- 5.1: The State of a System
- The state of a system means the collection of all properties that that system may have. For example, consider an electron. If you wanted to specify the state of that electron as completely as possible, you’d have to specify where it is and its momentum, as well as how well determined its momentum is. You would also have to specify the state of its angular momentum.
- 5.2: The Ket Vector
- To represent the state of a quantum particle, or a quantum system, we introduce the “ket vector”. This is just an abstract mathematical notation, a compact way of saying “the state of this particle”. The name “ket” is the latter half of the word “braket”, a misspelling of bracket.