My new paper on photonic quantum programmable gate arrays is now on arXiv! 🍾⚛️🎉 We describe an architecture for a nanophotonic integrated circuit which can be reprogrammed to perform any quantum computation. arxiv.org/pdf/1910.10141…
1/ Photonic systems have many unique advantages for quantum information processing, but deterministic multi-photon gates are difficult to implement, and complex quantum circuits can be prohibitively large to do with free-space optics since processing is done along the photon path
2/ In this theoretical paper, we present an architecture for a photonic integrated circuit which can be dynamically programmed to implement any quantum operation, in principle deterministically and with perfect fidelity.
3/ Our architecture consists of a lattice of beamsplitters and phase shifters, which perform rotations on path-encoded photonic qubits, and embedded quantum emitters, which use a two-photon scattering process to implement two-qubit controlled gates deterministically. 
4/ By appropriately setting phase shifts, the device can be programmed to implement any quantum circuit without hardware modifications.
5/ We show how to exactly prepare arbitrary quantum states and operators on the device, and we apply machine learning techniques to automatically implement highly compact approximations to important quantum circuits. Here's it learning to implement a quantum Fourier transform:
6/ Our design is the first (to our knowledge) to extend programmable integrated optics to the quantum domain in a manner which is both deterministic and spatially efficient (an N qubit state is encoded in O(N) waveguides).
7/7 There has been tremendous recent experimental progress in both of the key technologies required to realize this design: nanophotonic processors and waveguide-coupled quantum emitters. Ongoing advancements may allow for feasible near-future implementation of this device.
Supplementary materials and the #TensorFlow code for the circuit optimization section can be found at github.com/fancompute/qpga
Thanks to @sunilkpai and some of my labmates who aren't on Twitter for being helpful brainstorming buddies / rubber ducks for debugging, and shoutout to @InertialObservr for helping me debug the Mathematica animation in the first Tweet 😂
