The first
part of this website on quantum mechanics arose from reading the book
"Quantum Mechanics: The Theoretical Minimum" by Leonard Susskind. It covers
the basics of quantum mechanics up to the harmonic oscillator, including the
necessary math.
Susskind's
website is at https://theoreticalminimum.com/
You find a dictionary of quantum mechanics at
beginners’ level here: quantum-abc.
A philosophical paper dealing with
(quantum)physics and the “real world” you find here.
The second part of this website deals with the
basics of quantum computing. It is under construction and constantly being
updated.
…errors, broken links? … please give me a hint
...
You can reach me via the email address dieter.kriesell (at) gmx.de
Dieter Kriesell
Quantum
mechanics:
The 2D-harmonic oscillator in
cartesian and polar coordinates. |
|
We calculate angular momentum in
spherical coordinates both classic and quantum. |
|
… with various basis vectors … |
|
Two examples for the chain rule
for partial derivatives. |
|
Two observables are simultaneously
measurable if and only if the respective matrices commutate. |
|
How to calculate commutators that
contain a function of one operator. |
|
Solving integrals containing sin
and cos by use of complex functions. |
|
This paper describes how a
continuous function can be quantized and how differentiation and integration
are expressed explicitly with matrices. |
|
A bunch of differential equations
in physical context. |
|
The Dirac |
|
This paper shows the
transformation process from discrete probability to continuous probability
density. It is a kind of reverse process compared with the paper above. |
|
A translation of the original
paper with some comments. |
|
From classical physics to quantum
mechanics via the Ehrenfest Theorem. |
|
Power series of exponentials
containing Pauli matrices. |
|
How to handle exponentials with
Pauli matrices. |
|
How to
solve the time-dependent Schrödinger equation (no potential)? |
|
How to
solve a wave packet in one dimension without potential by superposition of
plane waves? |
|
We have a
particle in a 3D-box. Within the box we have potential zero and infinity
outside. How to calculate the energy eigenvalues and the eigenfunctions? |
|
How to
Calculate energy values and eigenfunctions for the one-dimensional potential
well? |
|
How to
calculate energy values and eigenfunctions for the one-dimensional undamped
harmonic oscillator? |
|
How to
calculate the bouncing ball with quantum mechanics? |
|
Is there
an uncertainty relation in the classical harmonic oscillator? |
|
How to
perform a spin flip? |
|
The free particle and its wave
function. |
|
Basics for understanding Fourier
series |
|
Two worked through examples for
Fourier series. |
|
Proofs for some Gauss Integrals. |
|
About the use of Hadamard matrices
in error correction. |
|
An example that shows that a 2x2
Hermitian matrix can be transformed in diagonal form. |
|
We become acquainted with Hermite
polynomials and proof orthogonality. |
|
We start with a finite dimensional
Hilbert space and end up with the spin of an electron. |
|
This
paper shows the way from a (real) function |
|
We check the derivation rules with
cartesian and polar coordinates. |
|
This short paper describes the
Lorentz transformation in the simple case two systems moving away from each
other at constant speed on the x-axis. |
|
This is more or less an exercise
in complex arithmetic. |
|
A compilation of mathematics you
need if you want to start with quantum mechanics. |
|
Two ways to write a matrix in a
new basis. |
|
States with position and momentum
will be described with either position wave functions or momentum wave
functions. This paper presents both descriptions parallel. |
|
Uncertainty of momentum and
position Operator in momentum and position representation. |
|
We take a close look at the
harmonic oscillator and number operator, raising operator and lowering
operator. |
|
An illustration of the spin
problem and the tensor product. |
|
Partial derivatives in cartesian
and polar representation. |
|
We work with the 1D step barrier
problem and use the probability current to develop reflection and
transmission probability |
|
Time development and Schroedinger equation for constant and commutating time dependent Hamiltonians. |
|
Here you find a compilation of
keywords for quantum mechanics on a basic level. |
|
These are the exercises of the
book “Quantum Mechanics, The Theoretical Minimum” of Leonard Susskind &
Art Friedman. |
|
A traditional access to the
quantum mechanic oscillator and the Hermite
polynomials. |
|
We calculate the ratio of incoming
to outgoing wave. |
|
Time-independent vs.
time-dependent operators. |
|
Two ways to get time-dependent
Heisenberg operators out of time-independent Schroedinger
operators. |
|
We look at a spin ½ in a magnetic
field: -
constant in direction and strength, -
constant in direction but slowly changing its strength, -
rotating (NMR). |
|
The equations of motion by use of
density matrices. |
|
A precessing spin represents a
qubit, we calculate probabilities for spin-up and spin-down. |
|
We substitute the variable in a
polynomial and an exponential function and take a look at the derivatives. |
|
Tensor products, correlation, and
superposition. |
|
The trigonometric identities
resolved in exponential terms. |
|
We start from classic physics, use
de Broglie and arrive at the Schroedinger equation. |
|
The infinite potential well is
either presented by use of trigonometric or complex exponential functions.
This paper works simultaneously through both and shows the difference – in
the end all works fine. |
|
Unitarian matrices don’t change
the dot product, map orthonormal bases to orthonormal bases and play an
important role in the time development of quantum states. |
|
We calculate the speed of the
electron of the hydrogen atom by use of the quantum mechanical Viral theorem. |
|
Wave functions (normalized
polynomials) and matrices. |
Quantum
computing:
We examine a quantum circuit on
conceptual level and basic level. |
|
Four Bell states in detail. |
|
We work through a qubit-exercise,
measuring Bell-states on both conceptual and basic level. |
|
We construct the CNOT-gate and its
inverse. |
|
An alternative access to the
Deutsch-Jozsa algorithm for a 3-qubit input. |
|
A numerical example for applying
Grover’s algorithm. |
|
This is a detailed example of
applicating Grover’s algorithm to a SAT problem. |
|
This is the same example as above,
solved by Alessandro
Berti. The circuit
used is different, the result the same. |
|
List of combinations of |0>,
|1>, |+>, |->, |y+>, |y-> states with the Kronecker-product (tensor-product). |
|
A proof of the no cloning theorem |
|
Arithmetic with bras and kets of different dimension |
|
The quantum Fourier transformation
explicit for 1, 2, 3 and 4 qubits. |
|
An explicit and detailed
work-through the Deutsch algorithm. |
|
The Toffoli and the Fredkin
quantum gates. |
|
Practical application of Simon’s
problem from a programmer’s point of view. |
|
Application of Simon’s problem to
a four-bit and a two-bit function, more mathematical. |
|
If you are interested in how a
spin flip physically can be performed, you will find a description here. |
|
A short description of spin
states, the Hadamard Matrix, Bloch sphere and rotation. |
|
We work through an example of
quantum teleportation on both conceptual and basic level. |
|
A second example with Alice and
Bob |
Last
actualization March 2025