论文标题
恒定深度量子电路的容忍量子加速
Fault-tolerant quantum speedup from constant depth quantum circuits
论文作者
论文摘要
量子计算领域中的一个定义功能是量子设备的潜力,即在特定的计算任务上优于其经典对应物。到目前为止,存在一些建议,表明某些采样问题可以有效地量化,但在复杂性理论中强烈持有的猜想是有效的,因此不可能有效地进行经典。一个称为量子加速的功能。但是,噪声对这些提案的影响一般尚不清楚,在某些情况下,众所周知,简单的噪声会破坏量子加速。 在这里,我们开发了一个容忍的这些抽样问题的家庭,我们可以使用恒定深度的量子电路来实现。我们提出了两个结构,每个结构都采用$ poly(n)$物理量子,其中一些是在嘈杂的魔术状态下准备的。我们的第一个构造是一个恒定的深度量子电路,该电路由四个维度的单个和两分的邻居Clifford门组成。该电路在最终测量之前与经典计算机具有一层交互。我们的第二个结构是一个恒定的深度量子电路,具有三个维度的单个和两小时的邻居克利福德门,但在最终测量之前与经典计算机进行了两层相互作用。 对于这些结构中的每一种,我们都表明,没有经典的算法可以根据其在$ poly(poly(n)$时间的输出分布进行采样,假设存在两个标准的复杂性理论猜想。我们假设的噪声模型是所谓的局部随机量子噪声。一路上,我们引入了各种新概念,例如恒定深度魔术状态蒸馏(MSD)和恒定深度输出路由,这些路由在基于测量的量子计算(MBQC)中自然出现,但在电路模型中没有恒定深度类似物。
A defining feature in the field of quantum computing is the potential of a quantum device to outperform its classical counterpart for a specific computational task. By now, several proposals exist showing that certain sampling problems can be done efficiently quantumly, but are not possible efficiently classically, assuming strongly held conjectures in complexity theory. A feature dubbed quantum speedup. However, the effect of noise on these proposals is not well understood in general, and in certain cases it is known that simple noise can destroy the quantum speedup. Here we develop a fault-tolerant version of one family of these sampling problems, which we show can be implemented using quantum circuits of constant depth. We present two constructions, each taking $poly(n)$ physical qubits, some of which are prepared in noisy magic states. The first of our constructions is a constant depth quantum circuit composed of single and two-qubit nearest neighbour Clifford gates in four dimensions. This circuit has one layer of interaction with a classical computer before final measurements. Our second construction is a constant depth quantum circuit with single and two-qubit nearest neighbour Clifford gates in three dimensions, but with two layers of interaction with a classical computer before the final measurements. For each of these constructions, we show that there is no classical algorithm which can sample according to its output distribution in $poly(n)$ time, assuming two standard complexity theoretic conjectures hold. The noise model we assume is the so-called local stochastic quantum noise. Along the way, we introduce various new concepts such as constant depth magic state distillation (MSD), and constant depth output routing, which arise naturally in measurement based quantum computation (MBQC), but have no constant-depth analogue in the circuit model.