New Linear-Optical Approach to Quantum Information Processing and Quantum Simulation

Linear optical networks formed from beam splitters and phase shifters have been shown capable of carrying out all quantum information processing tasks, but at the cost of rapid growth in resources as the complexity of the task increases. Here, we show that the use of recently introduced directionally unbiased optical multiports (N≥3), where input ports can double as output ports, can achieve results with much more compact setups and with substantial savings in resources. The behavior of such multiports is highly flexible, with a variety of possible behaviors being controlled by a set of parameters that can be changed or tuned in real time. Here we give an overview of the properties and potential applications of these multiports. Applications include their use as high-dimensional coins and lattice sites for quantum walks, new type of logical gates for two-photon entangled states, and elements of optical simulators for solid state systems. We illustrate that the band structures and electronic behavior of a variety of solid state systems, including those with nontrivial topological behavior, can be simulated using relatively compact linear-optical systems based on such directionally unbiased multiports.