Measurement-enhanced entanglement in a monitored superconducting chain

• URL: http://arxiv.org/abs/2604.04375v1
• Date: Mon, 06 Apr 2026 02:52:53 GMT
• Title: Measurement-enhanced entanglement in a monitored superconducting chain
• Abstract summary: A common view in monitored quantum dynamics is that local measurements suppress entanglement growth.<n>We show that this intuition can fail in a one-dimensional spinful fermionic chain governed by a BCS Hamiltonian with pairing strength $$.<n>Using free-fermion simulations and quasiparticle analysis, we show that pairing suppresses entanglement growth, while measurements suppress pairing.
• Score: 2.2940141855172036
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: A common view in monitored quantum dynamics is that local measurements suppress entanglement growth. We show that this intuition can fail in a one-dimensional spinful fermionic chain governed by a BCS Hamiltonian with pairing strength $Δ$ and subject to continuous, on-site, spin-resolved charge measurements at rate $γ$. Using free-fermion simulations and quasiparticle analysis, we show that pairing suppresses entanglement growth, while measurements suppress pairing. Their competition yields measurement-enhanced entanglement: for $Δ>0$, the steady-state entanglement $S_s$ increases with $γ$ over a finite interval $0<γ<γ_{\rm peak}$. This occurs because stronger measurements suppress pairing correlations, which would otherwise suppress entanglement growth. Using a nonlinear sigma-model calculation and free-fermion simulations, we provide evidence that for $Δ>0$ and small but finite $γ$, the steady-state entanglement scales as $S_s\sim \ln^2 L$. This implies that, in this setting, measurement-enhanced entanglement does not persist in the thermodynamic limit.

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