Step 1. Get yourself a quantum random generator (i.e.

https://qrng.anu.edu.au/)

Step 2. Perform a measurement to get a random number (0 or 1)

Step 3. Now, according to the Many Worlds interpretation of quantum mechanics (

https://en.wikipedia.org/wiki/Many-worlds_interpretation), both possibilities of 0 and 1 measurements actually did happen. There are now two of 'you' that exist in parallel universes each having measured 0 and 1. Every new version of 'you' repeats Step 2. 255 more times. (then 4 'you's, then 8 'you's, etc)

Step 4. After 256 repetitions, there are now 2^256 versions of you in parallel universes. But ONE of you will have the right private key that corresponds to the target bitcoin address! All of 'you' perform the test and one gets it right. (These 256 repetitions and test can happen in less than a fraction of a second.)

Step 5. Now, all the winning 'you' has to do (and I admit this is the tricky part) is transmit your winning combination back to the other 2^256-1 parallel universes and everyone wins! (Since 'you' were able to cash out millions, you should have the resources to fund an inter-parallel universe communications device easy!)

I'm still working on the last step