Hyperledger Fabric uses elliptic curve cryptography for digitally signing that transactions. The elliptic curve cryptography relies on mathematical techniques which can be sped up using quantum computing (https://en.wikipedia.org/wiki/Post-quantum_cryptography). However, Hyperledger Fabric provides a pluggable cryptographic provider, which allows replacing these algorithms for digital signatures with others. Moreover, per the director of Information Technology Lab at NIST, the impact of quantum computing on the security of blockchain systems is at least 15 to 30 years from becoming a reality (https://www.coindesk.com/dc-blockchain-hearing-sees-call-for-congressional-commission/).