Multi-Path Interference

Quantum mechanics is one of the most successful theories in physics, governing practically all processes in the microscopic world and even affecting many phenomena on a mesoscopic scale. Its predictions have been in excellent agreement with all experimental observations made throughout what has been almost an entire century.

In this Austrian-German collaboration, we are combining complementary experimental and theoretical knowhow towards testing the boundaries of quantum mechanics. To this end, we are working on possible generalizations of quantum mechanics involving higher dimensional systems and sensitive experimental tests that look for possible deviations from the expected quantum mechanical behavior. For example, in quantum mechanics all interference is due to pairs of paths, whereas in a generalized theory direct higher-order interference could exist.

Concretely we are using multi-path interferometers to achieve new, tighter limits on possible higher-order interference. Further, we are testing the limits of our current knowledge about the possibility of hypercomplex, e.g. quaternion, representations of quantum mechanics. These are precision tests that require the highest possible interference contrast and stability.

Our current free-space interferometers are limited in their interference contrast and only integrated optical solutions promise better performance. Based on our expertise in laser-written glass waveguides, we will create ultra-stable monolithic interferometers with on-chip shutters to perform the most decisive tests of higher-order interferences to date.

Five-Path Interferometer