BitMEX Research proposes an alternative to quantum freeze: a "canary address" triggering mechanism.

CoinFeed reported on April 16th that, according to a research article published by BitMEX Research, in response to the quantum freeze scheme proposed in BIP-361 (which prohibits sending to quantum-fragile addresses for three years after activation and prohibits spending from quantum-fragile addresses after five years), the authors propose an alternative mechanism: instead of directly freezing after five years, the address enters a "canary observation state." This scheme establishes a special "canary fund" address, generated using a "sleeve digit" system to prove that no one knows the private key. Only when a valid spend occurs on-chain from this address is it proven that a quantum computer capable of stealing Bitcoin exists, at which point the freeze is immediately activated. If the canary is never triggered, quantum-fragile coins can be spent normally. Users can donate Bitcoin to the canary address as a quantum bounty, forming a 1-of-2 multisignature output, and investors can withdraw their Bitcoin at any time.