Four photon ‘shapes’ boost quantum network capacity

Researchers at The University of Tokyo and RIKEN have experimentally generated four orthogonal temporal modes of microwave photons, a technique that could significantly boost the capacity of quantum networks. The work demonstrates a method for encoding more quantum information within individual photons, using a fixed-frequency transmon qubit to shape the photons as they propagate along a waveguide. This photon-shaping allows for mode-selective absorption, with efficiencies exceeding 0.89 for matched modes and remaining below 0.13 for orthogonal ones. These results highlight the feasibility of temporal-mode engineering for constructing a higher-dimensional orthogonal basis. Generating single microwave photons shaped in four distinct ways now demonstrates a pathway to increasing the capacity of quantum networks, as a fixed-frequency transmon qubit proved instrumental in achieving this control. This photon-shaping technique allows for the creation of orthogonal temporal modes, essentially imprinting different characteristics onto individual photons propagating along a waveguide, and represents a step toward encoding more quantum information within each photon. The ability to precisely manipulate these temporal modes relies on…