The magnetic tweezer is a single molecule instrument that can measure the extension of biomolecules by tracking tethered probe particles. Due to its experimental simplicity and ability to apply a constant external force to probe particles, the magnetic tweezer is ideally suited to measuring single molecule dynamics under applied tension. In this thesis, I push the resolution of magnetic tweezers to angstrom spatial resolution by using a high-speed camera which can achieve more than 10 kHz temporal resolution.

I investigate the fundamental limits to magnetic tweezer resolution from basic principles, and investigate different types of light coherence to arrive on a new choice of light source for the magnetic tweezer: the superluminescent diode. I explore Langevin dynamics of tethered probe particles using the Allan variance, a more intuitive take on thermal fluctuations than the Power Spectral Density. I push the achievable resolution limits by using smaller beads, introduce higher gradient magnets to apply biologically relevant forces on these smaller beads, and introduce a Fourier filter system to achieve higher spatial resolution.