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# Topic 4: The quantum version of probabilistic concepts
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> In mathematics, on often speaks of non-commutative instead of quantum constructions.
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## Section 1: Generalities about classical versus quantum systems
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In classical physics, we assume that a systema's properties have well-defined values regardless of how we choose to measure them.
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### Basic terminology
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#### Observables
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#### Set of states
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The preparation of a system builds a convex set of states as our initial condition for the system.
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For a collection of $N$ system. Let procedure $N_1=\lambda P_1$ be a preparation procedure for state $P_1$, and $N_2=(1-\lambda) P_2$ be a preparation procedure for state $P_2$. The state of the collection is $N=\lambda N_1+(1-\lambda) N_2$.
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#### Set of effects
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The set of effects is the set of all possible outcomes of a measurement. $\Omega=\{\omega_1, \omega_2, \ldots, \omega_n\}$. Where each $\omega_i$ is an associated effect, or some query problems regarding the system. (For example, is outcome $\omega_i$ observed?)
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#### Registration of outcomes
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A pair of state and effect determines a probability $E_i(P)=p(\omega_i|P)$. By the law of large numbers, this probability shall converge to $N(\omega_i)/N$ as $N$ increases.
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**Quantum states, observables, and effects can be represented mathematically by linear operators on a Hilbert space.**
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## Section 2: Examples of physical experiment in language of mathematics
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### Sten-Gernach experiment
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**State preparation:** Silver tams are emitted from a thermal source and collimated to form a beam.
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**Measurement:** Silver atoms interact with the field produced by the magnet and impinges on the class plate.
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**Registration:** The impression left on the glass pace by the condensed silver atoms.
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## Finite probability spaces in the language of Hilbert space and operators
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> Superposition is a linear combination of two or more states.
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A quantum coin can be represented mathematically by linear combination of $|0\rangle$ and $|1\rangle$.$\alpha|0\rangle+\beta|1\rangle\in\mathscr{H}\cong\mathbb{C}^2$.
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> For the rest of the material, we shall take the $\mathscr{H}$ to be vector space over $\mathbb{C}$.
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@@ -9,4 +9,5 @@ export default {
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Math401_T1: "Math 401, Topic 1: Probability under language of measure theory",
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Math401_T2: "Math 401, Topic 2: Finite-dimensional Hilbert spaces",
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Math401_T3: "Math 401, Topic 3: Separable Hilbert spaces",
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Math401_T4: "Math 401, Topic 4: The quantum version of probabilistic concepts",
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}
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