How can I protect my bitcoin against quantum computing?

If quantum computing makes technological leaps, it could theoretically impact the cryptography that is currently used to secure many critical global systems: financial, military, government, even the bitcoin protocol. However, whether or not quantum computing technology will make those leaps on any particular time frame is speculative and debatable.

Can I do anything to prepare for an unexpected leap in quantum computing technology?

The bitcoin balances that are most vulnerable to a theoretical quantum threat (Shor's algorithm) are balances with exposed public keys. To prevent your bitcoin balances from having exposed public keys, you can do two things:

1. Use bitcoin wallets built with specific address types. 
   There are several address (or script) types in bitcoin, and some have exposed public keys by default. Those are P2PK, P2MS, and P2TR. Modern bitcoin wallets avoid P2PK and P2MS which are considered obsolete. However, P2TR (a taproot address) is a newer address type that happens to be less quantum resistant.
   
   Addresses that do not have exposed public keys by default are P2PKH, P2WPKH, P2SH, and P2WSH. All Unchained products are built with P2SH or P2WSH, so if you use an Unchained vault or loan, you are using a good address type from a quantum resistance perspective. P2WSH is also the best address type to defend against a lesser quantum threat affecting hash functions (Grover's algorithm). If you have a legacy vault using P2SH, you can easily upgrade to P2WSH.
2. Avoid holding bitcoin in an address that has been spent out of.
   All address types have exposed public keys once they've been spent out of. Therefore, whenever you spend bitcoin out of an address, the address should be emptied completely, moving any remaining balance to a new change address for your wallet. When you spend bitcoin out of an Unchained vault using our platform, this happens automatically.
   
   Additionally, once an address has been spent out of and emptied, avoid depositing more bitcoin to that address. Most bitcoin wallets can generate practically unlimited addresses so that you never have to reuse an address to operate the wallet. Unchained vaults automatically generate a new address for each deposit. You'll want to avoid "whitelisting" your addresses with an exchange or mining pool to repeatedly receive bitcoin, because if you don't update your whitelisted address after you spend bitcoin, you may end up receiving bitcoin to an address that's already been spent out of.
   
   If you currently hold bitcoin on an address that's been spent out of, you can simply move the bitcoin to a new, fresh deposit address within the same wallet.