Markus Hiekkamäki, phD student in Robert Fickler’s group in Tampere University
Since classical interference has become ubiquitous in our modern optical devices and experiments, it is reasonable to assume that its quantum counterparts could become as prevalent in the next wave of technologies. The first signs of this can already be seen in the plethora of potential quantum technological applications that heavily rely on non-classical multi-photon interference effects. One degree of freedom where multi-photon interference has not been extensively studied yet is the transverse-spatial degree of freedom. This lack of studies is surprising when considering the potential benefits this degree of freedom has demonstrated in many other technological applications. Hence, our work aimed to increase our understanding of quantum interference in transverse spatial modes. We do this by investigating two-photon interference effects in this degree of freedom and by exploring some of their applications in metrology. The quantum interference experiments we performed utilized arbitrary unitary devices built using multi-plane light conversion devices and a simplified system that allowed us to create single-beam N00N states.