论文标题
量子电路的通用跨界
A universal crossover in quantum circuits governed by a proximate classical error correction transition
论文作者
论文摘要
我们制定了一个半古典电路模型，以阐明量子纠缠在最近发现的量子回路中的编码相变的作用。作为起点，我们定义了一个随机电路模型，其最接近的邻居经典门被擦除错误中断。与量子设置类似，该系统以关键错误率进行纯化过渡，以高于输出状态中的经典信息熵消失。我们表明，这种相变位于定向的渗透普遍性类别中，这与零熵是动力学的吸收状态一致。该古典电路无法生成熵。在存在误差的情况下，添加任意小的量子门密度可以通过破坏吸收状态来消除过渡：量子门会产生内部纠缠，可以通过错误有效地转换为经典的熵。我们在半古典电路的有效模型中描述了这种不稳定性的普遍特性。我们的模型突出了经典电路和量子电路中信息动力学之间的关键差异。
We formulate a semi-classical circuit model to clarify the role of quantum entanglement in the recently discovered encoding phase transitions in quantum circuits with measurements. As a starting point we define a random circuit model with nearest neighbor classical gates interrupted by erasure errors. In analogy with the quantum setting, this system undergoes a purification transition at a critical error rate above which the classical information entropy in the output state vanishes. We show that this phase transition is in the directed percolation universality class, consistent with the fact that having zero entropy is an absorbing state of the dynamics; this classical circuit cannot generate entropy. Adding an arbitrarily small density of quantum gates in the presence of errors eliminates the transition by destroying the absorbing state: the quantum gates generate internal entanglement, which can be effectively converted to classical entropy by the errors. We describe the universal properties of this instability in an effective model of the semi-classical circuit. Our model highlights the crucial differences between information dynamics in classical and quantum circuits.
