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arXiv 2409.08375quant-phcond-mat.str-el
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基于测量的子空间冷却型高维量子比特(qudit)量子制冷机

Measurement-based qudit quantum refrigerator with subspace cooling

Debkanta Ghosh, Tanoy Kanti Konar, Aditi Sen De

AI总结:

本研究提出子空间冷却方法,借助辅助系统、相互作用和任意秩投影测量实现高维自旋系统从高温热态到低能本征态的转变,验证了开链构型下的单位保真度效果及抗退相干能力。

摘要:

我们提出了一种方法,可将一组高维自旋系统从局部自旋s哈密顿量对应的极高温热态,转变为同一哈密顿量的低能本征态。该过程借助一个辅助系统、所有系统间的相互作用,以及对辅助系统执行的任意秩投影测量来实现,我们将这一过程称为子空间冷却(subspace cooling)。我们通过确定目标态与输出态的保真度,以及获得目标态的成功概率来评估该协议的性能。分析过程中,我们采用自旋s XXZ模型和双线性双二次(bilinear biquadratic)模型作为演化哈密顿量。研究表明,在两种模型场景下,当所有系统按开链排列时,经过合理次数的重复测量和有限时长的演化后可达到单位保真度;但当自旋间相互作用遵循星型构型时,该方法无法实现这一效果。我们发现,在维度固定的情况下,成功概率随测量中投影算符的秩增大而提升;且对于每个维度,都存在一个相互作用强度和演化周期的取值范围,可使保真度达到最大值。即便部分子系统与热浴接触,该方法也表现出抗退相干的特性。

英文摘要:

We develop a method to transform a collection of higher-dimensional spin systems from the thermal state with a very high temperature of a local spin-s Hamiltonian to a low-lying energy eigenstate of the same. The procedure utilizes an auxiliary system, interactions between all systems, and appropriate projective measurements of arbitrary rank performed on the auxiliary system. We refer to this process as subspace cooling. The performance of the protocol is assessed by determining the fidelity of the target state with the output one and the success probability of achieving the resulting state. For this analysis, spin-s XXZ and bilinear biquadratic models are employed as the evolving Hamiltonian. We demonstrate that in both scenarios, unit fidelity can be attained after a reasonable number of repeated measurements and a finite amount of evolution time when all the systems are aligned in an open chain, but it fails when the interactions between the spin follow the star configuration. We report that the success probability increases with the rank of the projectors in the measurement for a fixed dimension and that for each dimension, there exists a range of interaction strength and evolution period for which the fidelity gets maximized. Even when some subsystems are in contact with the thermal bath, the method proves to be resistant to decoherence.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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