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This research establishes a graph-state framework to analyze monitored random Clifford circuits, revealing how emergent dense subgraphs explain the error-correcting capabilities of volume-law phases during measurement-induced phase transitions. By mapping stabilizer states to Erdős–Rényi ensembles, the study provides analytical solutions for GHZ entanglement content and precisely locates critical points that align with numerical simulations. These findings offer new theoretical tools for understanding non-equilibrium quantum dynamics and fault tolerance in scalable quantum architectures.
Typical Output States of Monitored Random Clifford Circuits: A Graph-Theoretic Approach
arXiv:2608.03102v1 Announce Type: new Abstract: Monitored random Clifford circuit is a paradigmatic platform for exploring non-equilibrium quantum many-body dynamics using quantum-information methods. It is well-known for exhibiting a measurement-induced phase transition (MIPT) between volume-law and area-law phases of bipartite entanglement. In this Article, we develop a graph-state based framework that grants direct access to the typical output states of monitored random Clifford circuits. We first show that, in the large-$N$ limit, where $N$ denotes qubit number, the graph representations of random stabilizer states converge to the Erd\H{o}s--R\'{e}nyi random graph ensemble $G(N,1/2)$. This observation allows us to resolve the open problem of Greenberger--Horne--Zeilinger (GHZ) entanglement in random stabilizer states. We derive analytically the mean GHZ content, $\langle g_3\rangle=1.204$ for even $N$ and $1.325$ for odd $N$. For monitored one dimensional (1D) circuits in the volume-law phase, we uncover an emergent dense subgraph of the form $G(N_{\mathrm{sub}},1/2)$ in the output-state graphs. This implies that the output state of a monitored circuit is equivalent to an output of a unitary circuit on $N_{\mathrm{sub}}$ qubits, weakly perturbed by the remaining $N-N_{\mathrm{sub}}$ qubits carrying little entanglement. This result directly accounts for the quantum error-correcting capability of the volume-law phase. We further identify a clustering effect in the spatial distribution of the dense subgraph along the 1D qubit chain, and reproduce it with an infection-recovery toy model that exhibits a measurement-induced absorbing-state phase transition. Finally, we locate the critical point of the MIPT at $p_c = 0.1608$ through a mean-field argument on the graph, in excellent agreement with the numerical result $p_c\approx 0.16$.
Abstract:Monitored random Clifford circuit is a paradigmatic platform for exploring non-equilibrium quantum many-body dynamics using quantum-information methods. It is well-known for exhibiting a measurement-induced phase transition (MIPT) between volume-law and area-law phases of bipartite entanglement. In this Article, we develop a graph-state based framework that grants direct access to the typical output states of monitored random Clifford circuits. We first show that, in the large-$N$ limit, where $N$ denotes qubit number, the graph representations of random stabilizer states converge to the Erdős--Rényi random graph ensemble $G(N,1/2)$. This observation allows us to resolve the open problem of Greenberger--Horne--Zeilinger (GHZ) entanglement in random stabilizer states. We derive analytically the mean GHZ content, $\langle g_3\rangle=1.204$ for even $N$ and $1.325$ for odd $N$. For monitored one dimensional (1D) circuits in the volume-law phase, we uncover an emergent dense subgraph of the form $G(N_{\mathrm{sub}},1/2)$ in the output-state graphs. This implies that the output state of a monitored circuit is equivalent to an output of a unitary circuit on $N_{\mathrm{sub}}$ qubits, weakly perturbed by the remaining $N-N_{\mathrm{sub}}$ qubits carrying little entanglement. This result directly accounts for the quantum error-correcting capability of the volume-law phase. We further identify a clustering effect in the spatial distribution of the dense subgraph along the 1D qubit chain, and reproduce it with an infection-recovery toy model that exhibits a measurement-induced absorbing-state phase transition. Finally, we locate the critical point of the MIPT at $p_c = 0.1608$ through a mean-field argument on the graph, in excellent agreement with the numerical result $p_c\approx 0.16$.
Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech)
arXiv:2608.03102 [quant-ph]
(or arXiv:2608.03102v1 [quant-ph] for this version)
https://doi.org/10.48550/arXiv.2608.03102 Focus to learn more arXiv-issued DOI via DataCite (pending registration)
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