Experimental demonstration of a Grover-Michelson interferometer.

We present a low-resource and robust optical implementation of the four-dimensional Grover coin, a four-port linear-optical scatterer that augments the low dimensionality of a regular beam-splitter. While prior realizations of the Grover coin required a potentially unstable ring cavity to be formed, this version of the scatterer does not exhibit any internal interference. When this Grover coin is placed in another system, it can be used for interferometry with a higher-dimensional set of optical field modes.

Topological boundaries and bulk wavefunctions in the Su-Schreiffer-Heeger model.

Working in the context of the Su-Schreiffer-Heeger model, the effect of topological boundaries on the structure and properties of bulk position-space wavefunctions is studied for a particle undergoing a quantum walk in a one-dimensional lattice. In particular, we consider what happens when the wavefunction reaches a boundary at which the Hamiltonian changes suddenly from one topological phase to another and construct an exact solution for the wavefunction on both sides of the boundary. The reflection and transmission coefficients at the boundary are calculated as a function of the system's hopping parameters, and it is shown that for some parameter ranges the transmission coefficient can be made very small.

Experimental demonstration of a directionally-unbiased linear-optical multiport.

All existing optical quantum walk approaches are based on the use of beamsplitters and multiple paths to explore the multitude of unitary transformations of quantum amplitudes in a Hilbert space. The beamsplitter is naturally a directionally biased device: the photon cannot travel in the reverse direction. This causes rapid increases in the optical hardware resources required for complex quantum walk applications, since the number of options for the walking particle grows with each step.

Odd- and even-order dispersion cancellation in quantum interferometry.

We describe a novel effect involving odd-order dispersion cancellation. We demonstrate that odd- and even-order dispersion cancellation may be obtained in different regions of a single quantum interferogram using frequency-anticorrelated entangled photons and a new type of quantum interferometer. This offers new opportunities for quantum communication and metrology in dispersive media.