Understanding Side-Channel Vulnerabilities in Superconducting Qubit Readout Architectures

TL;DR

This paper investigates how frequency-multiplexed superconducting qubit readout architectures, while scalable, introduce crosstalk vulnerabilities that can be exploited for information leakage, highlighting security concerns beyond measurement errors.

Contribution

It reveals the security implications of readout crosstalk in superconducting qubit systems, a previously overlooked aspect in quantum hardware design.

Findings

Readout crosstalk causes correlated errors.

Vulnerabilities enable attackers to predict qubit states.

Security risks increase with system sharing.

Abstract

Frequency-multiplexing is an effective method to achieve resource-efficient superconducting qubit readout. Allowing multiple resonators to share a common feedline, the number of cables and passive components involved in the readout of a qubit can be drastically reduced. However, this improvement in scalability comes at the price of a crucial non-ideality -- an increased readout crosstalk. Prior works have targeted building better devices and discriminators to reduce its effects, as readout-crosstalk-induced qubit measurement errors are detrimental to the reliability of a quantum computer. However, in this work, we show that beyond the reliability of a system, readout crosstalk can introduce vulnerabilities in a system being shared among multiple users. These vulnerabilities are directly related to correlated errors due to readout crosstalk. These correlated errors can be exploited by nefarious attackers to predict the state of the victim qubits, resulting in information leakage.