An optimal beam splitter layout for universal multiport interferometers
Programmable photonic circuits that can implement linear transformation between any number of input and output optical channels are used both for quantum computation in quantum optics and for signal processing in telecommunications. These “universal multiport interferometers” can be built using meshes of reconfigurable beam splitters, for example on an integrated photonic platform.
Oxford academics have developed a new method for implementing universal multiport interferometers, which uses a more compact mesh of beam splitters. This novel technology has many advantages over the current state of the art:
- circuits implementing the new layout occupy half as much physical space as previously, which minimises optical losses and on-chip resources
- they are more tolerant to optical losses than previous designs
This new design is demonstrably optimal in terms of compactness of the mesh of beam splitters and will be used to improve both quantum computation and signal processing capabilities.
As photonics research advances, there is increasing demand for fully programmable photonic devices that can perform a wide range of tasks. One such device with applications across several fields is the programmable universal multiport interferometer, which can be used to implement any linear transformation between any number of input and output optical channels.
In quantum optics, these devices are used to provide programmable quantum interference between photons, which is necessary for quantum information processing. In telecommunications, these devices provide a method for programmable photonic signal processing.
Universal multiport interferometers are typically built using a mesh of programmable beam splitters and phase shifters. These optical elements can be straightforwardly built on integrated photonic chips which can support a high density of optical components and process a large number of optical channels. The specific layout of the mesh of beam splitters is determined by the programming method that is used to translate the targeted overall transformation between all optical channels to individual beam splitter settings.
Oxford University academics have developed both a new layout of beam splitters for universal multiport interferometers and a new programming method that have several advantages over the current state of the art. This new layout is twice as compact as the previously best-known layout, and this compactness is demonstrably optimal. This increased compactness reduces optical losses and decreases the physical footprint of these devices. Furthermore, the transformation fidelity of this new layout is less sensitive to optical losses.
This new, improved layout and programming method for universal multiport interferometers, which can be scaled to any number of optical channels, will be used to enhance current capabilities in quantum optics and communications. The reduced losses and increased compactness enhance the accuracy of quantum computations on the one hand and of signal processing for telecommunications on the other.
Furthermore, other envisaged applications include the fields of laser technology and astrophysics, where photonic beam combining and processing are used, as well as next-generation microwave photonics where coherent manipulation of many optical channels will be required.
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