Constructing a virtual two-qubit gate by sampling single-qubit operations
Constructing a virtual two-qubit gate by sampling single-qubit operations
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DOI：
10.1088/1367-2630/abd7bc
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发表时间：
2021-02-01
影响因子：
3.3
通讯作者：
Fujii, Keisuke
中科院分区：
文献类型：
--
作者：
Mitarai, Kosuke;Fujii, Keisuke
当量子电路的任务是计算观测值的期望值时，我们证明了某种非局域操作可以通过对一组具有准概率分布的局域操作进行采样来模拟。利用这个结果，我们描述了一种将两个量子比特门分解为一系列单量子比特操作的策略。所需的操作是量子位在泡利基中的投影测量，以及围绕x，y和z轴的pi/2旋转。在误差为0的情况下，获得目标观测值的期望值所需的采样次数大约为O（9（k）/1（2）），其中k是执行的“切割”次数。所提出的技术使得能够在一对遥远的量子位之间执行“虚拟”门，其中没有直接的相互作用，因此否则不可避免地会有许多交换门。它还可以用来改进具有小尺寸量子设备的大型量子计算机的模拟，这是Peng等人提出的想法（2019 arXiv：）。这项工作可以增强量子比特在近期噪声量子计算机上的连通性。
We show a certain kind of non-local operations can be simulated by sampling a set of local operations with a quasi-probability distribution when the task of a quantum circuit is to evaluate an expectation value of observables. Utilizing the result, we describe a strategy to decompose a two-qubit gate to a sequence of single-qubit operations. Required operations are projective measurement of a qubit in Pauli basis, and pi/2 rotation around x, y, and z axes. The required number of sampling to get an expectation value of a target observable within an error of epsilon is roughly O(9(k)/epsilon(2)), where k is the number of 'cuts' performed. The proposed technique enables to perform 'virtual' gates between a distant pair of qubits, where there is no direct interaction and thus a number of swap gates are inevitable otherwise. It can also be utilized to improve the simulation of a large quantum computer with a small-sized quantum device, which is an idea put forward by Peng et al (2019 arXiv:). This work can enhance the connectivity of qubits on near-term, noisy quantum computers.