High-order homodyne correlation measurement

For Master's students / PhD students

This projects deals with the foundations optics. While quantum technology is a rapidly growing field, it uses mainly already known quantum optical concepts. Within this project a new detection scheme for the characterisation of a quantum state of light will be implemented. Roughly speaking: just like the number of pixels of a digital camera sets the resolution of the image taken, in a homodyne correlation measurement of a quantum light mode it is the number of detectors used, which determines the resolution of the quantum properties of the state.

Here a squeezed quantum state will be analysed with a homodyne detector with 8 or 16 elements. For this, a chip-scale 16-port linear quantum optical network, which we source from Alex. Szameits group, will be connected to a linear photo-detector with 16 elements. 

The student will build the detection electronics, assemble the optical elements and devel

Implementing an optical spring in an atomic force microscope

For Master's students / PhD students

We use laser radiation pressure rather than a traditional mechanical actuator in order to drive the oscillation of a micron sized cantilever as used in atomic force microscopy (AFM). This greatly reduces disturbances caused by sound waves when doing AFM in a fluid environment.

Creating an optical spring by using the AFM cantilever as one end mirror of a detuned optical resonator enables the in situ tuning of the resonance frequency and the damping of the opto-mechanical oscillator as needed when working with samples with large variations of the surface stiffness. Here the optical restoring force comes from the dependence of the optical power, and hence the radiation pressure force, in the resonator on the resonator detuning, and hence the position of the cantilever.

The student will implement the optical resonator, the optical coupling and readout. The parameter range in terms of oscillation frequency and quality factor will be explored. Knowledge on optical, opto-mechanical systems and AFMs will be acquired.

Building a Quantum Frequency Converter

For Master's students

Many branches of the emerging field of quantum technology, such as quantum communication, quantum simulation, quantum sensing and ultimately quantum computation rely on the interaction of quantum light with quantum states of matter. In our labs we can produce quantum light in a squeezed state reliably at the specific wavelength of 1064nm. While we can do a lot of interesting experiments with it, being fixed to a specific wavelength limits our ability to use squeezed light in scenarios requiring a different wavelength, such as coupling to atomic transitions, transmission through optical fibres, or detecting single photons efficiently with affordable avalanche detectors.

The goal of this project is to build a quantum frequency converter, transferring the quantum state of light at 1064nm onto a visible light field. This can be done via sum frequency generation in a second-order nonlinear crystal. For efficient operation the nonlinear crystal need to sit inside an optical resonator. The student will assemble the nonlinear resonator, control loops and the quantum state detection system at the visible wavelength. Knowledge of state-of-the-art quantum technology will be acquired. 

Building a student lab experiment on Pound-Drever-Hall laser stabilisation

For Bachelor's students or physics teachers-to-be

Laser stabilisation is common problem in the laboratory. This projects aim at building an experiment demonstrating the Pound-Drever-Hall laser stabilisation scheme, which is going to be used for the advanced Master's level lab courses.

Optimising electro-optical modulators

For Bachelor's students

The complexity of quantum optical experiments requires the active stabilisation of a great number of interferometric pathways on the optical table. In order to obtain information about the optical phase relation of different beams we use modulation/demodulations techniques. The requirements on the quality of electro-optical modulators for our purposes are beyond the commercially available devices. This project is about optimising our home made electro-optical modulators, i.e optimising the linearity, modulation depth and at the same time minimise residual amplitude modulation and RF-leakage.

An advanced read-out scheme for Foucault's pendulum

For physics teachers-to-be

Foucault's pendulum is supposed to work continuously. Hence it needs to be driven. The driving is done via the process of parametric amplification, which requires a precise timing of the driving motor with respect to the actual pendulum motion. At the moment the timing is derived from an electromechanical contact, which turns out to be unreliable. The task of this project is to implement a remote read-out scheme based on light barriers or some more sophisticated techniques. The student should not be afraid of a soldering iron and some basic computer programming.