Arrasmith Andrew, Cincio Lukasz, Sornborger Andrew T, Zurek Wojciech H, Coles Patrick J
Theoretical Division, MS 213, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
Department of Physics, University of California Davis, Davis, CA, 95616, USA.
Nat Commun. 2019 Jul 31;10(1):3438. doi: 10.1038/s41467-019-11417-0.
Although quantum computers are predicted to have many commercial applications, less attention has been given to their potential for resolving foundational issues in quantum mechanics. Here we focus on quantum computers' utility for the Consistent Histories formalism, which has previously been employed to study quantum cosmology, quantum paradoxes, and the quantum-to-classical transition. We present a variational hybrid quantum-classical algorithm for finding consistent histories, which should revitalize interest in this formalism by allowing classically impossible calculations to be performed. In our algorithm, the quantum computer evaluates the decoherence functional (with exponential speedup in both the number of qubits and the number of times in the history) and a classical optimizer adjusts the history parameters to improve consistency. We implement our algorithm on a cloud quantum computer to find consistent histories for a spin in a magnetic field and on a simulator to observe the emergence of classicality for a chiral molecule.
尽管量子计算机预计会有许多商业应用，但人们对其解决量子力学基础问题的潜力关注较少。在这里，我们关注量子计算机在一致历史形式体系中的效用，该形式体系此前已被用于研究量子宇宙学、量子悖论以及量子到经典的转变。我们提出了一种用于寻找一致历史的变分混合量子 - 经典算法，该算法通过允许执行经典方式无法完成的计算，应该会重新激发人们对这种形式体系的兴趣。在我们的算法中，量子计算机评估退相干泛函（在量子比特数和历史中的次数方面都有指数加速），而经典优化器调整历史参数以提高一致性。我们在云量子计算机上实现我们的算法，以找到磁场中自旋的一致历史，并在模拟器上观察手性分子的经典性出现。
