论文标题

让每个量子位选择其基础门

Let Each Quantum Bit Choose Its Basis Gates

论文作者

Lin, Sophia Fuhui, Sussman, Sara, Duckering, Casey, Mundada, Pranav S., Baker, Jonathan M., Kumar, Rohan S., Houck, Andrew A., Chong, Frederic T.

论文摘要

近期量子计算机主要受两个量子位(或Qubits)之间量子操作(或门)的错误限制。物理机器通常提供一组基闸门,其中包括可以在给定技术中实现的原始2 Q量(2q)和1 Quition(1Q)门。 2q纠缠大门,再加上一些1q门,允许通用量子计算。在超导技术中,目前的最新状态是在每对量子位之间实现相同的2Q门(通常是XX-或XY型门)。大型量子计算机中2Q门的严格硬件均匀性要求使实验室中的时间和资源密集型努力扩大了。我们提出了一个激进的想法 - 允许每对量子位之间的2q基栅极不同,选择可以在给定的量子对之间校准的最佳纠缠门。这项工作旨在使量子科学家能够使用并非完全统一的量子系统运行有意义的算法。科学家还将能够使用更广泛的新颖2Q大门进行量子计算。我们开发了一个理论框架,以识别与XX这样的“标准”轨迹偏离“标准”轨迹的“非标准”卡坦轨迹上的良好的2q基闸门。然后,我们引入了使用非标准2Q门进行校准和编译的实用方法,并讨论了改善编译的可能方法。为了在案例研究中证明我们的方法,我们使用具有遥不可及的Transmon量子的纠缠栅极体系结构模拟了标准的XY型轨迹和更快的非标准轨迹。我们在这些非标准轨迹上确定有效的2Q基闸门,并使用它们来编译许多标准基准电路,例如QFT和QAOA。我们的结果表明,相对于速度和相干限制的栅极保真度,基线2Q门的改善。

Near-term quantum computers are primarily limited by errors in quantum operations (or gates) between two quantum bits (or qubits). A physical machine typically provides a set of basis gates that include primitive 2-qubit (2Q) and 1-qubit (1Q) gates that can be implemented in a given technology. 2Q entangling gates, coupled with some 1Q gates, allow for universal quantum computation. In superconducting technologies, the current state of the art is to implement the same 2Q gate between every pair of qubits (typically an XX- or XY-type gate). This strict hardware uniformity requirement for 2Q gates in a large quantum computer has made scaling up a time and resource-intensive endeavor in the lab. We propose a radical idea -- allow the 2Q basis gate(s) to differ between every pair of qubits, selecting the best entangling gates that can be calibrated between given pairs of qubits. This work aims to give quantum scientists the ability to run meaningful algorithms with qubit systems that are not perfectly uniform. Scientists will also be able to use a much broader variety of novel 2Q gates for quantum computing. We develop a theoretical framework for identifying good 2Q basis gates on "nonstandard" Cartan trajectories that deviate from "standard" trajectories like XX. We then introduce practical methods for calibration and compilation with nonstandard 2Q gates, and discuss possible ways to improve the compilation. To demonstrate our methods in a case study, we simulated both standard XY-type trajectories and faster, nonstandard trajectories using an entangling gate architecture with far-detuned transmon qubits. We identify efficient 2Q basis gates on these nonstandard trajectories and use them to compile a number of standard benchmark circuits such as QFT and QAOA. Our results demonstrate an 8x improvement over the baseline 2Q gates with respect to speed and coherence-limited gate fidelity.

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