论文标题

使用相对阶段Toffoli大门在随身携带的加法器上有效构建控制模块化加法器

Efficient Construction of a Control Modular Adder on a Carry-Lookahead Adder Using Relative-phase Toffoli Gates

论文作者

Oonishi, Kento, Tanaka, Tomoki, Uno, Shumpei, Satoh, Takahiko, Van Meter, Rodney, Kunihiro, Noboru

论文摘要

控制模块化添加是核心算术功能,我们必须考虑实际量子计算机实现有效实现的计算成本。为了在控制模块化加法器中达到低计算成本,我们专注于最小化KQ,这是由量子数和电路深度的乘积定义的。在本文中,我们通过在两种主要类型的量子计算机中使用相对相的toffoli门构建一个有效的控制模块化加法器:逻辑层上的耐断层量子计算机(FTQ)和嘈杂的中间尺度量子计算机(NISQ)。与货车仪和伊托(Itoh)相比,我们提供了更有效的结构,该结构是基于随身携带的加法器。在FTQ中,$ T $ GATES由于蒸馏而产生的巨额成本,该蒸馏件构成了Ancilla,以高精度运行$ T $ GATES,但消耗了很多专门准备的Ancilla Qubits和很多时间。因此,我们必须减少$ t $门的数量。我们提出了一个新的控制模块化加法器,该加法器仅使用原件的$ t $门数的20%。此外,当我们考虑蒸馏时,我们发现我们通过运行$θ\ left(n / \ sqrt {n / \ sqrt {\ log n} \ right)$ t $ t $ n $ t $ n $ t $ syultaney $θ\ left(n / \ sqrt {n / \ sqrt {n / \ sqrt {在NISQ中,CNOT门是主要的错误源。我们提出了一个新的控制模块化加法器,该加法器仅使用原件的CNOT门数的35%。此外,我们表明我们电路的$ \ text {kq} _ {\ text {cx}} $(量子数和cnot-depth的乘积)是原始电路的38%。因此,我们实现了有效的控制模块化加法器,从而改善了量子计算机中有效执行算术的前景。

Control modular addition is a core arithmetic function, and we must consider the computational cost for actual quantum computers to realize efficient implementation. To achieve a low computational cost in a control modular adder, we focus on minimizing KQ, defined by the product of the number of qubits and the depth of the circuit. In this paper, we construct an efficient control modular adder with small KQ by using relative-phase Toffoli gates in two major types of quantum computers: Fault-Tolerant Quantum Computers (FTQ) on the Logical layer and Noisy Intermediate-Scale Quantum Computers (NISQ). We give a more efficient construction compared to Van Meter and Itoh's, based on a carry-lookahead adder. In FTQ, $T$ gates incur heavy cost due to distillation, which fabricates ancilla for running $T$ gates with high accuracy but consumes a lot of specially prepared ancilla qubits and a lot of time. Thus, we must reduce the number of $T$ gates. We propose a new control modular adder that uses only 20% of the number of $T$ gates of the original. Moreover, when we take distillation into consideration, we find that we minimize $\text{KQ}_{T}$ (the product of the number of qubits and $T$-depth) by running $Θ\left(n / \sqrt{\log n} \right)$ $T$ gates simultaneously. In NISQ, CNOT gates are the major error source. We propose a new control modular adder that uses only 35% of the number of CNOT gates of the original. Moreover, we show that the $\text{KQ}_{\text{CX}}$ (the product of the number of qubits and CNOT-depth) of our circuit is 38% of the original. Thus, we realize an efficient control modular adder, improving prospects for the efficient execution of arithmetic in quantum computers.

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