arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1910.07548quant-phcond-mat.mes-hallcond-mat.supr-con
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高保真$n$位Toffoli门的单步实现

Single-step implementation of high fidelity $n$-bit Toffoli gate

S. E. Rasmussen, K. Groenland, R. Gerritsma, K. Schoutens, N. T. Zinner

摘要:

$n$ -位Toffoli门的家族,以两位Toffoli门作为名义头,在量子信息中引起极大的兴趣,因为它们可以用作通用门和量子纠错等。我们提出了一个单步实现的任意$n$ -位Toffoli门(直到一个本地的基础变化),基于共振驱动一个单一的量子位,具有较强的伊辛耦合到$n$其他量子位。两个量子比特的情况下的设置结果与通用巴伦科门相同。理论上,门时间和误差与控制量子比特的数量无关,比传统的电路分解更好地缩放。我们注意到,我们的假设,即强耦合$n+1$量子位和与$n$成比例的驱动频率,可能会在大型系统中崩溃。尽管如此,我们的协议可以提高中等规模的量子计算机的能力,我们讨论了实施我们的协议对被困离子,里德伯原子和超导电路的前景。后一个平台的模拟表明,具有两个控制位的Toffoli门即使在存在退相干的情况下也能达到0.98以上的精度。我们还展示了如何类似的想法可以用来使一系列的控制- \textsc{not} -门在一个单一的步骤。我们展示了如何这些可以加快量子纠错码的实现,我们模拟的编码步骤的三个量子位的位翻转码和七个量子位的Steane码。

英文摘要:

The family of $n$-bit Toffoli gates, with the two-bit Toffoli gate as the figurehead, are of great interest in quantum information as they can be used as universal gates and in quantum error correction, among other things. We present a single-step implementation of arbitrary $n$-bit Toffoli gates (up to a local change of basis), based on resonantly driving a single qubit that has a strong Ising coupling to $n$ other qubits. The setup in the two-qubit case turns out to be identical to the universal Barenco gate. The gate time and error are, in theory, independent of the number of control qubits, scaling better than conventional circuit decompositions. We note that our assumptions, namely strongly coupling $n+1$ qubits and a driving frequency that scales with $n$, may break down for large systems. Still, our protocol could enhance the capabilities of intermediate scale quantum computers, and we discuss the prospects of implementing our protocol on trapped ions, Rydberg atoms, and on superconducting circuits. Simulations of the latter platform show that the Toffoli gate with two control bits attains fidelities of above 0.98 even in the presence of decoherence. We also show how similar ideas can be used to make a series of controlled-\textsc{not}-gates in a single step. We show how these can speed up the implementation of quantum error correcting codes and we simulate the encoding steps of the three-qubit bit-flip code and the seven-qubit Steane code.

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