The second quantum revolution aims beyond the understanding of basic science to its application in novel technologies. In this framework, the development of integrated quantum photonic processors (QPICs) holds the potential to make powerful quantum computation widely accessible. Particularly, photonics provides unique capabilities for quantum communications, sensing, simulation, and computing.
Compared to photonic circuits intended for classical information processing, quantum operation poses new challenges. Above all, photon losses must be minimized in quantum photonics, since information is irreversibly destroyed with each lost photon. Similarly, today’s quantum computers aren’t very good at handling mistakes, unlike regular computers, which can easily fix small errors in data. Near-term quantum computers are often classified as noisy intermediate-scale quantum (NISQ) devices. However, while numerous algorithms have been devised for a large, error-corrected quantum computers, practical applications for NISQ computers are lacking, leaving a chasm to be filled to promote a virtuous cycle of investment and continued development essential for a thriving quantum computing space. Fortunately, intermediate-scale quantum photonic devices offer the prospect of achieving quantum advantage over classical computers for specific tasks. While classical computers are fundamentally inefficient at handling complex quantum mechanical systems – such as the molecular quantum dynamics – engineering controllable quantum devices optimized to efficiently characterize quantum systems shows great promise. Although many different platforms for QPICs are being developed, none has shown the versatility of femtosecond laser writing (FLW) in realizing diverse quantum systems. For these reasons, QLASS aims at leveraging the capabilities of FLW to fabricate 3D photonic circuits with unprecedented number of modes within glass. Compared to other QPIC techniques, using glass yields extremely small interface losses – ideal for modular architectures connecting multiple chips – with speed, affordability, and optimization for end-user goals. Incorporating high-performance single-photon sources, superconducting nanowire single-photon detector, and electronics enabling reconfigurable state manipulation via control of an exceptionally large number of cryogenic-detector channels, we will create an end-to-end quantum photonics platform. Of particular interest is implementing Variational Quantum Algorithms (VQAs), which have emerged as leading candidates for near-term advantage, for which our platform is ideally suited. We will develop software for end users to translate VQAs into FLW circuits, with error mitigation methods to enhance QPIC performance.
