I think this is a question of algorithm agility. Bitcoin has a mechanism to change its implementation[1], so it's possible to upgrade.
On the mining side, miners would pick a new algorithm, vote, and then cut over when approved. Although, if a post-quantum technique allowed faster mining, a change to the mining algorithm may not be needed. Bitcoin would notice the faster hashrate and increase the difficulty, miners would rush to buy quantum hardware. As long as quantum hardware is generally available for purchase, we'd still have decentralized mining.
On the wallet side, we'd need miners to vote for and approve quantum safe wallet operations. Users would need to update their software and their wallets. I'd expect some stuck wallets (like the initial blocks, lost keys) could get spent. This is sort of like someone recovering gold from a sunken ship.
I agree this seems like an existential threat, but there is an update path. Unless there's a sudden onset where no-one has time to react, I suspect the miners would reach consensus. Some users may be slow to update their wallets, and may suffer losses.
I think we'd eventually see recovery of the coins from the mining of the initial blocks, which are generally believed to lost/stuck. This would sort of be like recovery of gold from a sunken ship. I've heard that recovery of those coins would destabilize Bitcoin value, due to the large value. However, unless they are all unexpectedly recovered at once, I'd expect the market to "price that in" gradually as recovery begins.
I'd expect many cryptocurrencies not to survive the transition, although I'm a crypto skeptic and I don't expect hype/scam coins to survive anyway.
On the mining side, miners would pick a new algorithm, vote, and then cut over when approved. Although, if a post-quantum technique allowed faster mining, a change to the mining algorithm may not be needed. Bitcoin would notice the faster hashrate and increase the difficulty, miners would rush to buy quantum hardware. As long as quantum hardware is generally available for purchase, we'd still have decentralized mining.
On the wallet side, we'd need miners to vote for and approve quantum safe wallet operations. Users would need to update their software and their wallets. I'd expect some stuck wallets (like the initial blocks, lost keys) could get spent. This is sort of like someone recovering gold from a sunken ship.
I agree this seems like an existential threat, but there is an update path. Unless there's a sudden onset where no-one has time to react, I suspect the miners would reach consensus. Some users may be slow to update their wallets, and may suffer losses.
I think we'd eventually see recovery of the coins from the mining of the initial blocks, which are generally believed to lost/stuck. This would sort of be like recovery of gold from a sunken ship. I've heard that recovery of those coins would destabilize Bitcoin value, due to the large value. However, unless they are all unexpectedly recovered at once, I'd expect the market to "price that in" gradually as recovery begins.
I'd expect many cryptocurrencies not to survive the transition, although I'm a crypto skeptic and I don't expect hype/scam coins to survive anyway.
[1] https://blog.coinbase.com/bitcoin-s-elegant-upgrade-mechanis...