Correlated Quantum Dephasometry: Symmetry-Resolved Noise Spectroscopy of Two-Dimensional Superconductors and Altermagnets

TL;DR

The paper introduces correlated quantum dephasometry, a novel method for symmetry-resolved noise spectroscopy at the nanoscale and low frequencies, capable of distinguishing different symmetry classes in 2D quantum materials.

Contribution

It proposes a new quantum noise spectroscopy technique using correlated dephasing of spin qubits, enabling symmetry resolution beyond single qubit methods.

Findings

Discriminates s-, d-, and g-wave superconducting gaps in 2D superconductors.

Resolves symmetry in 2D antiferromagnets and altermagnets.

Operates effectively at low frequencies (~MHz) and nanoscale dimensions.

Abstract

Symmetry-resolved spectroscopies, such as angle-resolved photoemission spectroscopy and polarization-resolved Raman, are central for quantum material characterization, yet remain challenging at nanoscale dimensions and low frequencies. Here, we propose correlated quantum dephasometry, which enables symmetry resolved quantum noise spectroscopy of materials at nanoscale and low ($\sim$MHz) frequencies via correlated dephasing of two spin qubits near materials. Our approach leverages the finite-range spatial structures of nonlocal near-field noise correlations to isolate rotational symmetry of the material response in momentum space beyond single qubit capabilities. We apply our approach to two-dimensional (2D) superconductors, and predict clear fingerprints that discriminate s-, d-, and g-wave symmetry of the superconducting gap. To highlight the generality, we further show that the same framework resolves 2D s-wave antiferromagnets and d-wave altermagnets. Our results establish correlated quantum dephasometry as a nanoscale, low-frequency complement for symmetry-resolved spectroscopy applicable to a broad class of quantum materials.