50.4ARMay 31
Linear Complexity Fermionic Simulation on Quantum Devices with Hardware Connectivity ConstraintsXiangyu Gao, Winston Li, Jiakang Li et al.
Simulating fermionic systems on quantum hardware requires compiling fermionic Hamiltonians into executable quantum circuits. Existing approaches treat each compilation stage independently, applying heuristics with localized objectives that produce circuits with superquartic gate count and depth scaling and compilation times reaching several hours for large instances. We present Accordion, an end-to-end framework that co-designs the fermion-to-qubit mapping with circuit synthesis and hardware routing. Accordion fixes the Jordan Wigner mapping, which despite its higher Pauli weight produces Pauli operators with structural regularity that enables provably efficient circuit generation. For full-rank all-to-all electronic structure Hamiltonians, we prove O(N^4) gate count and circuit depth, matching the information-theoretic lower bound imposed by the Theta(N^4) second excitation terms. On linear, IBM heavy-hex, and square-grid architectures, Accordion reduces gate count by up to 79% and circuit depth by up to 77% relative to the best baseline.
CLDec 16, 2021
Goal-Directed Story Generation: Augmenting Generative Language Models with Reinforcement LearningAmal Alabdulkarim, Winston Li, Lara J. Martin et al.
The advent of large pre-trained generative language models has provided a common framework for AI story generation via sampling the model to create sequences that continue the story. However, sampling alone is insufficient for story generation. In particular, it is hard to direct a language model to create stories to reach a specific goal event. We present two automated techniques grounded in deep reinforcement learning and reward shaping to control the plot of computer-generated stories. The first utilizes proximal policy optimization to fine-tune an existing transformer-based language model to generate text continuations but also be goal-seeking. The second extracts a knowledge graph from the unfolding story, which is used by a policy network with graph attention to select a candidate continuation generated by a language model. We report on automated metrics pertaining to how often stories achieve a given goal event as well as human participant rankings of coherence and overall story quality compared to baselines and ablations.