Photon-assisted tunneling arises under an ac bias, with the drive frequency setting the photon energy. The excess photon-assisted noise is defined as the difference between the shot noise under a combined dc and ac bias and that under a dc bias alone. We investigate this quantity in tunneling into the Majorana or Andreev bound states, which are of great interest in the search for topological superconductors. Under a harmonic bias $V\left(t\right)=V_{\mathrm{dc}}[1-cos\left(\mathrm{\Omega }t\right)]$, the excess photon-assisted noise exhibits distinct behaviors: for Majorana or quasi-Majorana bound states, it undergoes multiple sign reversals as $V_{\mathrm{dc}}$ increases and vanishes at nonzero integer values of $e{V}_{\mathrm{dc}}/\mathrm{\Omega }$ (with $e$ the elementary charge), whereas for zero-energy Andreev bound states—particularly those producing nearly quantized zero-bias conductance peaks—it remains strictly negative over the entire $V_{\mathrm{dc}}$ range.

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• Andreev bound states
• Majorana bound states
• Quantum transport
• Shot noise
• Topological superconductors
• Bogoliubov-de Gennes equations
• S-matrix method in transport