Securing NISQ Quantum Computer Reset Operations Against Higher Energy State Attacks

Enabling the sharing of quantum computers among di erent users requires a secure reset operation that can reset the state of a qubit to ground state |0ð and prevent leakage of the state to a post-reset circuit. This work highlights that the existing reset operations available in superconducting qubit NISQ quantum computers are not fully secure. In particular, this work demonstrates for the rst time a new type of higher-energy state attack. Although NISQ quantum computers are typically abstracted as working with only energy states |0ð and |1ð, this work shows that it is possible for unprivileged users to set the qubit state to |2ð or |3ð. By breaking the abstraction of a two-level system, the new higher-energy state attack can be deployed to a ect the operation of circuits or for covert communication between circuits. This work shows that common reset protocols are ine ective in resetting a qubit from a higher-energy state. To provide a defense, this work proposes a new Cascading Secure Reset (CSR) operation. CSR, without hardware modi cations, is able to e ciently and reliably reset higher-energy states back to |0ð. CSR achieves a reduction in |3ð-initialized state leakage channel capacity by between 1 and 2 orders of magnitude, and does so with a 25x speedup compared with the default decoherence reset. CCS CONCEPTS • Security and privacy → Security in hardware; • Hardware → Quantum technologies.