Posts
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The Phase Vocoder, or: how to stretch without a catch
YouTube and podcast apps appear to be able to change the playback speed of an audio signal without (dramatically) changing the pitch. How does this work? And could it be useful for musicians looking to change the playback speed of a sample during a performance? A look at the phase vocoder. -
Sinterrandomness
PSA for those who participated in a Secret Santa-type game this year: you have unwittingly been approximating $e$ in what must be one of the most inane ways possible. -
Simple automatic error propagation in Python
Often when working with experimental data we run into the problem of having to propagate the uncertainty of a set of measurements into another (derived) quantity. For moderately complicated dependencies, the bookkeeping becomes arduous. By defining some basic rules, we can have a computer do most of the heavy lifting, without invoking any symbolic math. -
How we see the world
In which we try to figure out what bottlenose dolphins, black holes, and imaging systems have in common, whether it is possible to see without light, and what it means to 'see' something in the first place. -
How to bibliography
In which we discuss how to keep track of interesting references using ancient software, and use some Lisp to glue it all together, making life more pleasant altogether indeed. -
Earnshaw's Theorem, or: Why Frogs Can Float, but Magnets Won't
When thinking about trapping of magnetic particles such as atoms, we often say that particles that seek out strong magnetic fields (bar magnets, compass needles) cannot be trapped with stationary fields. Referred to as Earnshaw's theorem, it's usually encountered as its restatement that 'Magnetic field maxima are forbidden!' Samuel Earnshaw, however, wasn't in the business of messing around with magnets in his shed, no, he had greater ambitions. -
Protein Folding through Quantum Annealing
Some classical problems have such a large number of degrees of freedom that solving them is intractable on classical computers. It would simply take astronomical times to sample the full state space and find the solution. Even though these problems are classical in nature, quantum-assisted techniques may provide a way out by, as it were, probing all configurations in parallel, and following the optimal solution. Here we explore some of these ideas using the problem of protein folding. -
The Spin Mott Insulator
What happens to the Mott insulators when particles are given a spin degree of freedom? Or: a foray into quantum magnetism. -
Maxwell's demon and the limits of computation
What do messy rooms, information processing, and opening your fridge have in common? I'm not sure, but some aspects of the latter two are described by thermodynamics. Here we have a look at some of the bounds thermodynamics places on performing computations, and how a thought experiment from the mid-1800's got this ball rolling. -
Exploring the superfluid to Mott insulator phase transition
A lot of research in atomic physics and related areas deals with quantum simulation: using well-understood and well-controlled systems to mimic not so well-understood ones. This quantum mimicry is created first and foremost through an analogy. Here, we take a look at the ur-quantum simulation: the superfluid to Mott insulator phase transition. -
Plotting complex functions on a sphere using d3
A while ago, I wanted to plot a complex function that was defined on a sphere, and do it in such a way that both the magnitude and phase of the function would be made visible. Without resorting to complicated three-dimensional plotting methods, the most straightforward way of doing that is to use a colormap to display the phase, while the magnitude is used to set the transparency. (This makes it harder to read off the numerical value of the magnitude, but we'll have to stomach that for now.)
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