From 031785514fd0caff35419e29cdfd322de8a09c0b Mon Sep 17 00:00:00 2001 From: Maciej Topyla <m.m.topyla@student.tudelft.nl> Date: Sun, 4 Sep 2022 18:50:51 +0000 Subject: [PATCH] Update src/4_vector_spaces_QM.md --- src/4_vector_spaces_QM.md | 34 +++++++++++++++------------------- 1 file changed, 15 insertions(+), 19 deletions(-) diff --git a/src/4_vector_spaces_QM.md b/src/4_vector_spaces_QM.md index 72265c9..996b9d8 100644 --- a/src/4_vector_spaces_QM.md +++ b/src/4_vector_spaces_QM.md @@ -105,25 +105,21 @@ The inner product in quantum mechanics is the analog of the usual scalar product The inner product (probability amplitude) $\langle \psi | \phi \rangle$ exhibits the following properties: -!!! info "Complex conjugate:" - $$\langle \psi | \phi \rangle=\langle \phi | \psi \rangle^*$$ - -!!! info "Distributivity and associativity" - $$\langle \psi |\{c_1 |\phi_1\rangle+c_2 |\phi_2 \rangle\}=c_1\langle \psi | \phi_1\rangle+c_2\langle \psi | \phi_2\rangle$$ - -!!! info "Positivity" - $$\langle \psi | \psi \rangle\geq0$$. If $\langle \psi | \psi \rangle = 0$$ - then this implies that the state vector $|\psi\rangle=0$ is the null element of the Hilbert space. - -!!! info "Orthogonality" - Two states $|\psi \rangle$ and $|\phi \rangle$ are said to be *orthogonal* if - $$\langle \psi | \phi\rangle=0 \, .$$ - By analogy with regular vector spaces, we can think of these two state vectors $|\psi \rangle$ and $|\phi \rangle$ as being *perpendicular* to each other. Note that for a quantum system occupying a certain state, there is a vanishing probability of it being observed in a state orthogonal to it. - -!!! info "Norm:" - The quantity $\sqrt{\langle \psi | \psi \rangle}$ is known as the *length* or the *norm* of the state vector $|\psi\rangle$. You can see from the properties of complex algebra that this length must be a real number. - -A physically valid state $|\psi \rangle$ must be normalized to unity, that is $\langle \psi | \psi \rangle=1$. Note that a state that cannot be normalized to unity does not represent a physically acceptable state. +!!! info + 1. Complex conjugate: + $$\langle \psi | \phi \rangle=\langle \phi | \psi \rangle^*$$ + 2. Distributivity and associativity: + $$\langle \psi |\{c_1 |\phi_1\rangle+c_2 |\phi_2 \rangle\}=c_1\langle \psi | \phi_1\rangle+c_2\langle \psi | \phi_2\rangle$$ + 3. Positivity: + $$\langle \psi | \psi \rangle\geq0 \, .$$ + If $\langle \psi | \psi \rangle = 0$ then, this implies that the state vector $|\psi\rangle=0$ is the null element of the Hilbert space. + 4. Orthogonality: + Two states $|\psi \rangle$ and $|\phi \rangle$ are said to be *orthogonal* if + $$\langle \psi | \phi\rangle=0 \, .$$ + By analogy with regular vector spaces, we can think of these two state vectors $|\psi \rangle$ and $|\phi \rangle$ as being *perpendicular* to each other. Note that for a quantum system occupying a certain state, there is a vanishing probability of it being observed in a state orthogonal to it. + 5. Norm: + The quantity $\sqrt{\langle \psi | \psi \rangle}$ is known as the *length* or the *norm* of the state vector $|\psi\rangle$. + You can see from the properties of complex algebra that this length must be a real number. A physically valid state $|\psi \rangle$ must be normalized to unity, that is $\langle \psi | \psi \rangle=1$. Note that a state that cannot be normalized to unity does not represent a physically acceptable state. A set of orthonormal basis vectors $\{|\psi_i\rangle\text{;}\; i=1,2,3,...,n\}$ will have the property $\langle \psi_i |\psi_j \rangle=\delta_{ij}$ where $\delta_{ij}$ is a mathematical symbol known as the *Kronecker delta*, which equals unity if $i=j$ and zero if $i\neq j$. -- GitLab