Universal Collective Quantum Dephasing Due to Electromagnetic Fluctuations near Material Interfaces

One major obstacle for current quantum applications is decoherence. In a multiqubit system, coherence can be significantly limited by the collective dephasing (CD) processes. Current spin-qubit-based quantum information technologies (QIT) feature the proximity of spin qubits to different materials, including ferrimagnets, normal conductors, and superconductors. Previous studies largely focus on relaxation dynamics, single-photon emission, and Casimir-Polder effects induced by electromagnetic (EM) fluctuations near those material interfaces (MIs), but neglecting the CD effects. Here, we present a theory applicable to spin qubits' CD dynamics induced by EM fluctuations near general MIs. Our theory shows the universal behavior of EM fluctuations-induced pure dephasing and multiqubit decoherence through a comprehensive analysis of various MIs. We reveal distinct single-qubit and collective dephasing profiles related to microscopic dynamics in different MIs. We find that EM fluctuations-induced CD exhibits universal long-range behavior different from other noise sources. We identify three universal regimes for multiqubit decoherence in a two-dimensional spin qubit array associated with EM fluctuations. Furthermore, we introduce a nanophotonic approach to engineer CD with hyperbolic meta-structures. Our work establishes the foundation for studying CD dynamics near general MIs and paves the way for controlling CD effects in QIT.