Physlib

PhyslibAlpha.ProbabilisticTheory.Measurement.Binary

Binary measurements

i. Overview

Every effect of an Archimedean system defines a yes/no measurement: the outcome `true` has the effect itself, the outcome `false` its complement.

ii. Key results

  • `Effect.binaryMeasurement` : the binary measurement associated to an effect.

iii. Table of contents

  • A. Binary measurements

A. Binary measurements

5 declarations

definition

Effect of outcome bb for the binary measurement of ee

For an effect ee in an ordered additive commutative group EE with unit 11, and a boolean value b∈{true,false}b \in \{\text{true}, \text{false}\}, this function returns ee if b=trueb = \text{true} and the complement 1−e1 - e if b=falseb = \text{false}.

theorem

∑b∈BoolbinaryAtom(e,b)=1\sum_{b \in \text{Bool}} \text{binaryAtom}(e, b) = 1

Let EE be an ordered additive commutative group with a unit element 11. For any effect e∈Ee \in E (where 0≤e≤10 \le e \le 1), the sum of its binary atoms over all boolean outcomes b∈{true,false}b \in \{\text{true}, \text{false}\} is equal to the unit element 11. That is, ∑b∈{true,false}binaryAtom(e,b)=1\sum_{b \in \{\text{true}, \text{false}\}} \text{binaryAtom}(e, b) = 1.

definition

Binary measurement of an effect ee

Given an effect ee in an ordered additive commutative group FF with unit 11 (meaning e∈Fe \in F such that 0≤e≤10 \le e \le 1), the binary measurement associated with ee is a measurement on the boolean outcome space {true,false}\{\text{true}, \text{false}\}. This measurement is defined such that the effect corresponding to the outcome true\text{true} is ee, and the effect corresponding to the outcome false\text{false} is the complement 1−e1 - e.

theorem

The outcome {true}\{\text{true}\} of binaryMeasurement(e)\text{binaryMeasurement}(e) is ee

Let FF be an ordered additive commutative group with unit 11. For any effect e∈Fe \in F (where 0≤e≤10 \le e \le 1), let binaryMeasurement(e)\text{binaryMeasurement}(e) be the measurement on the outcome space {true,false}\{\text{true}, \text{false}\} associated with ee. Then, the effect corresponding to the measurable set {true}\{\text{true}\} under this measurement is equal to ee. That is, binaryMeasurement(e)({true})=e\text{binaryMeasurement}(e)(\{\text{true}\}) = e.

theorem

The binary measurement of {false}\{\text{false}\} is the complement 1−e1 - e

For any effect ee (an element satisfying 0≤e≤10 \le e \le 1) in an ordered additive commutative group FF with unit 11, the binary measurement associated with ee assigns the complement effect 1−e1 - e to the measurable set containing the outcome {false}\{\text{false}\}.