Can Google’s Quantum Computer mine the remaining Bitcoin in 2 seconds?

3 Million Bitcoin in 2 Seconds: Google Quantum Computer

If Sycamore does a hit and run, the ASICs will not be able to handle the difficulty when the next difficulty adjustment occurs. You don’t care your mempool transaction won’t be confirmed and all the other mempool transactions clogging up the network… then you’re back to paying $25 tx fee just to get yours included when thousands if not tens of thousands of transactions need to be processed. Then, many Bitcoin nodes will crash because they won’t have the memory to keep all the transactions in the mempool. Right, who cares?

All you need is sycamore to start mining immediately after the last difficulty adjustment. Then it has two weeks to mine all the Bitcoins it wants. Leave the network when the next difficulty adjustment occurs. ASICs will then have a very difficult time trying to mine the subsequent blocks essentially halting all the mempool transactions and bringing Bitcoin down. This is a very big weakness in how Bitcoin’s Proof of Work (PoW) algorithm. There are a few like DASH’s Dark Gravity Wave (DGW) that change difficulty every block, so quantum computers mining would have difficulty adjust itself every block. You also have DigiShield (by DigiByte) and eHRC (by FeatherCoin) that also adjust difficulty per block. Even if quantum computers did a hit and run using the other algorithms, the blockchain can recover much more gracefully than how Bitcoin’s Proof of Work algorithm currently handles it.

I wrote some more on difficulty adjustment algorithms.