Mind the gaps: The fraught road to quantum advantage

TL;DR

The article argues that delivering broadly useful quantum computing requires overcoming four intertwined gaps on the path from NISQ to FASQ: advancing from error mitigation to active error detection/correction, from basic error correction to scalable fault tolerance, from early heuristics to mature verifiable algorithms, and from exploratory quantum simulation to credible quantum advantage. It outlines a two-stage roadmap emphasizing near-term QEM-enabled growth and long-term fault-tolerant architectures, while comparing multiple hardware modalities and the substantial overheads involved. It then analyzes near-term algorithms, the potential for advantage in variational schemes, and the prospects for credible quantum advantage in quantum simulation, highlighting both theoretical limits and practical co-design needs. The outlook stresses gradual, regionally diversified progress across hardware, codes, decoders, and algorithms, with applications materializing across mega-, giga-, and teraquop regimes and evolving from scientific discovery toward broader societal impact.

Abstract

Quantum computing is advancing rapidly, yet substantial gaps separate today's noisy intermediate-scale quantum (NISQ) devices from tomorrow's fault-tolerant application-scale quantum (FASQ) machines. We identify four related hurdles along the road ahead: (i) from error mitigation to active error detection and correction, (ii) from rudimentary error correction to scalable fault tolerance, (iii) from early heuristics to mature, verifiable algorithms, and (iv) from exploratory simulators to credible advantage in quantum simulation. Targeting these transitions will accelerate progress toward broadly useful quantum computing.