# All posts by Hans

# My Ethereum address

0x5956b01f46593d8b71f680ffc7dadb87abb60b2f

# Curriculum Vitae

My Curriculum vitae is available here: CV-HansHarhoffAndersen2015.

See also my LinkedIn profile.

# PhD thesis: Cooling and Manipulating Ions in Traps with Integrated Optical Cavities

I have submitted and defended my PhD thesis in Ion trap physics.

The thesis is available here:

Cooling and manipulating ions in traps with integrated optical cavities

# Installing qutip on Windows

I had some problems installing Qutip on Windows.

I solved them by adding the MinGW32-xy path to the Windows path environment.

See details here.

# Getting started with Python

I’ve written a short introduction to getting started with Python including IPython and how to set a default search path.

It is mostly targeted Ubuntu users.

Link to guide on Google Docs.

# Ubuntu 14.04: Making it useful

sudo apt-get update && sudo apt-get dist-upgrade -y && sudo apt-get autoremove

sudo apt-get install ipython-notebook htop vim flashplugin-installer nautilus-open-terminal spyder tortoisehg-nautilus network-manager-openconnect ssh

# Total differentials

Total differentials are useful but how do you technically go from them to differentials of functions. Let’s define $f(x)$ as a continuous function.

Then

$$ df= \frac{\partial f}{\partial x} dx,$$

where df is called the total differential. If x(t) is a function t then how do we get this explicit dependence?

$$ f = \int df = \int \frac{\partial f}{\partial x} dx, $$

where we have used the fundamental theorem of calculus. Now we can perform a change of variables using the total differential of x ie. $dx=dx/dt dt$:

$$ f = \int \frac{\partial f}{\partial x} dx = \int \frac{\partial f}{\partial x} \frac{dx}{dt} dt,$$

which can be differentiated with respect to time to give

$$ \frac{df}{dt} =\frac{\partial f}{\partial x} \frac{dx}{dt}. $$

Here we changed the variables of the integrals (so be careful of the integral limits)

# Getting the newest version of Octave for Ubuntu/Debian

If you want the newest version of Octave (3.8 as of the time of writing) you will need to compile it yourself.

Do

sudo apt-get build-dep octave sudo apt-get install libqscintilla2-9 libqscintilla2-dev wget ftp://ftp.gnu.org/gnu/octave/octave-3.8.0.tar.bz2 tar -xvf octave-3.8.0.tar.bz2 cd octave-3.8.0 ./configure make make check sudo make install

when this is done Octave should work for you. Keep an eye out for warnings though. This was tested on Ubuntu 13.04 64 bit. If you use Debian you will need *libqscintilla2-8* instead of 9. I am actually not sure if you only need the dev package. On Debian you will also need to install *libxft2-dev* since this is not installed by default.

To run Octave with the GUI enabled run

octave –force-gui

this enables the GUI. The GUI is still in beta though so it might be a bit rough.

# Fase-skift i øvelse 5

Det kan være svært at fitte til arctan i forbindelse med målingen af fasen i øvelse 5 i Mekanik og Termodynamik. Her er en lille forklaring og et udtryk med cosinus man kan bruge i stedet: