Quantum Spectral Authentication under Public Unitary Challenges

TL;DR

This paper proposes Quantum Spectral Authentication (QSA), a method for verifying remote quantum resources using public challenges and spectral analysis, with practical implementation and noise tolerance considerations.

Contribution

It introduces a novel quantum authentication primitive that verifies quantum secrets without revealing them, including a practical low-depth implementation and noise resilience analysis.

Findings

QSA effectively verifies quantum secrets using spectral features.

The symmetric verifier-driven unitary compiler is more noise tolerant.

Hardware experiments validate the practicality of the approach.

Abstract

We introduce Quantum Spectral Authentication (QSA), a primitive for verifying that a remote quantum endpoint still possesses a previously installed secret quantum resource, such as a hidden state or state-preparation capability, without revealing that secret. QSA uses fresh public unitary challenges and spectral features of the planted state to derive transcript-bound session material for explicit authentication. We analyse attack strategies including eigenstate propagation across challenges, repeated-session leakage, and direct online forgery. For practical implementation, we develop a symmetric verifier-driven unitary compiler compatible with low-depth quantum phase estimation. Simulations indicate that this symmetric fast-power construction is substantially more noise tolerant than an asymmetric alternative, and small-instance experiments on IBM ibm_fez provide a hardware sanity check. QSA therefore offers a plausible near-term authentication layer for quantum networks and control-plane applications.