Integrated Photonic Quantum Frequency Processor for High-Dimensional Quantum Information Processing

This program will focus on he development of a compact, robust, affordable, Quantum Frequency Processor (QFP) for High-Dimensional Quantum Information Processing (QIP). This advanced QFP device will help propel the US forward as a world leader in quantum technology.  Core capabilities enabled by distributed quantum information processing include not only quantum key distribution, but also critical areas like distributed quantum computing, entanglement-based quantum sensing, and blind quantum computing. All these applications will require quantum networks that can mediate communication and entanglement between physically separated systems. For some of the capabilities outlined above, physical separation is fundamental to the application itself. For example, quantum networks can enable interferometric telescopes with longer baselines and hence finer resolution than possible with classical techniques. In addition, quantum clocks connected over a quantum network could realize global timing with precision beyond the possibilities of isolated systems. In both these cases, the distance between devices is crucial to the application, which makes quantum networks a necessity.  While matter-based qubits are extremely fragile, photons experience virtually no decoherence and are the only realistic choice to carry quantum information over long distances. In recent years there has been progress in facilitating entanglement and communication between end nodes using satellite-based and terrestrial free space optical links. However, for dense and short reach communications, like local area and metropolitan area networks, these modes of communication are unrealistic given the need for line-of-sight links and relatively high optical loss over short distances. The tremendous bandwidth and low loss offered by optical fiber makes it a critical tool for interconnecting a large number of quantum resources for both computing and distributed sensing.  The same advantages of low loss and massive parallelization of communications channels in the spectral domain seen in fiber optic networks will be crucial for scaling up quantum networks. However, much of the previous work in quantum information has utilized photonic degrees of freedom which cannot be easily preserved in standard single-mode fiber. On the other hand, discrete variable frequency encoding provides natural stability in optical fiber, straightforward measurement with high-efficiency filters and detectors, and compatibility with wavelength-division multiplexing. By cascading electro-optic phase modulators (EOMs) and Fourier-transform pulse shapers, any frequency-bin quantum operation can be realized in a theoretically scalable fashion, defining the Quantum Frequency Processor (QFP) needed for implementation of a quantum network.