论文标题
用于捕获的离子量子计算机的航天飞机量子映射器
A Shuttle-Efficient Qubit Mapper for Trapped-Ion Quantum Computers
论文作者
论文摘要
被困的离子(Ti)量子计算机是先驱量子技术之一。但是,TI系统在单个陷阱中的数量可能有限。执行有意义的量子算法需要多个陷阱系统。在这样的系统中,计算可能经常涉及两个不同的陷阱的离子,必须将量子位在同一陷阱中共处,因此,其中一个离子需要在陷阱之间穿梭(移动),从而增加了振动能量,增加了保真度,并增加了程序执行时间。最初映射的选择会影响穿梭数量。现有的贪婪策略计算每对量子位之间发生的门数,并分配边缘重量。高边缘的量子位彼此靠近。但是,它忽略了门发生的程序的阶段。直觉上,晚期门对初始映射的贡献可能已经将离子穿梭到其他陷阱以满足其他门操作。在本文中,我们针对此差距,并提出一项新政策,尤其是针对量子数量相当大的计划(对实用规模的量子程序有效)。我们的政策是程序自适应,并优先考虑在该计划的初始阶段重新出现的大门,以期在后期发生的大门。我们的技术可用于120个随机电路的平均降低9%的航天飞机/计划(充其量为21.3%),并提高了3倍的程序保真度(平均为1.41倍)。
Trapped-ion (TI) quantum computer is one of the forerunner quantum technologies. However, TI systems can have a limited number of qubits in a single trap. Execution of meaningful quantum algorithms requires a multiple trap system. In such systems, the computation may frequently involve ions from two different traps for which the qubits must be co-located in the same trap, hence one of the ions needs to be shuttled (moved) between traps, increasing the vibrational energy, degrading fidelity, and increasing the program execution time. The choice of initial mapping influences the number of shuttles. The existing Greedy policy counts the number of gates occurring between each pair of qubits and assigns edge weight. The qubits with high edge weights are placed close to each other. However, it neglects the stage of the program at which the gate is occurring. Intuitively, the contribution of the late-occurring gates to the initial mapping reduces since the ions might have already shuttled to a different trap to satisfy other gate operations. In this paper, we target this gap and propose a new policy especially for programs with considerable depth and high number of qubits (valid for practical-scale quantum programs). Our policy is program adaptive and prioritizes the gates re-occurring at the initial stages of the program over late occurring gates. Our technique achieves an average reduction of 9% shuttles/program (with 21.3% at best) for 120 random circuits and enhances the program fidelity up to 3.3X (1.41X on average).