论文标题

在仅随机测量的Kitaev模型中,拓扑,关键性和动态生成的Qubit

Topology, criticality, and dynamically generated qubits in a stochastic measurement-only Kitaev model

论文作者

Sriram, Adithya, Rakovszky, Tibor, Khemani, Vedika, Ippoliti, Matteo

论文摘要

我们考虑了在两个维度上的拓扑顺序的范式可解的模型,Kitaev的Honeycomb Hamiltonian,并将其转变为仅测量的动力学,该动力学由两量键键操作员的随机测量组成。我们发现一个纠缠相位图在某些方面与哈密顿问题的相似,而在其他方面却在质量上有所不同。当一种主要测量一种类型的键时,我们发现区域法纠缠的相位,可以在系统大小的时间指数上保护两个拓扑Qubit(在圆环上)。这概括了最近所提供的浮雕代码的想法,其中逻辑量子位是由时间周期性测量计划动态生成的,它是随机设置的。当所有类型的债券以可比的频率测量时,我们发现一个临界阶段,对对数违反了区域法则,该阶段将其与哈密顿量对应物进行了巨大区别。临界阶段具有与三方互助诊断的相同的拓扑Qubit,但仅在系统大小的时间多项式中保护它们。此外,我们观察到了混合状态的动态纯化的异常行为,在后期的特征是动态指数$ z = 1/2 $ - 一种通过测量实现的超球动力学。

We consider a paradigmatic solvable model of topological order in two dimensions, Kitaev's honeycomb Hamiltonian, and turn it into a measurement-only dynamics consisting of stochastic measurements of two-qubit bond operators. We find an entanglement phase diagram that resembles that of the Hamiltonian problem in some ways, while being qualitatively different in others. When one type of bond is dominantly measured, we find area-law entangled phases that protect two topological qubits (on a torus) for a time exponential in system size. This generalizes the recently-proposed idea of Floquet codes, where logical qubits are dynamically generated by a time-periodic measurement schedule, to a stochastic setting. When all types of bonds are measured with comparable frequency, we find a critical phase with a logarithmic violation of the area-law, which sharply distinguishes it from its Hamiltonian counterpart. The critical phase has the same set of topological qubits, as diagnosed by the tripartite mutual information, but protects them only for a time polynomial in system size. Furthermore, we observe an unusual behavior for the dynamical purification of mixed states, characterized at late times by the dynamical exponent $z = 1/2$ -- a super-ballistic dynamics made possible by measurements.

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