Optimized stateful hash-based signatures can offer better trade-offs than the standard schemes available today. SHRINCS is live on the @Liquid Network in production today via Simplicity. Jonas Nick at OPNEXT on why this may allow Bitcoin to operate in a post-quantum world without betting on specific future software. Full technical writeup:

Blockstream

OP_CHECKSHRINCS: A Hash-Based Signature Opcode for Post-Quantum Bitcoin

OP_CHECKSHRINCS is a proposed Bitcoin opcode for post-quantum signatures whose security rests on SHA-256, the hash function Bitcoin already uses.