A Piece of QAICCC: Towards a Countermeasure Against Crosstalk Attacks in Quantum Servers

Quantum computing, while allowing for processing information exponentially faster than classical computing, is far from becoming a personal commodity. Indeed, because of cost and needs for ultra-cold temperature, shielded environment, and complex wiring for control, access to quantum computers is likely to be provided remotely, through quantum servers. Sharing quantum hardware between multiple users enables the efficient use of quantum resources, but makes some security threats possible. For instance, previous studies demonstrated that crosstalk between attacker and victim's qubits can be exploited to mount security attacks. In this work, we address the problem of securing user circuits submitted to quantum servers. We propose the Qubit Allocation for Inter-Circuit Crosstalk Countermeasure (QAICCC), which aims to maximize qubit usage, reduce inter-circuit crosstalk as well as intra-circuit noise. QAICCC performs (1) a crosstalk analysis of the targeted quantum processor to determine qubits involved in crosstalk with the largest intensity; (2) the allocation of qubits in the safest possible way; and (3) the application of existing techniques to further reduce crosstalk between circuits and noise in user circuits. The main contribution is the allocation algorithm, which aims to maximize qubit usage (including making unused qubits available for future usage) while minimizing the largest inter-circuit crosstalk error rate. Thus, QAICCC will support quantum computing adoption by securing the usage of quantum servers by a large number of actors.