AI 中文总结
该研究探讨非理想QND能量测量下的恶魔式功提取协议，证明使用热浴时其恶魔式净增益非正，仅用幺正操作时可正，并以单量子比特为例分析性能。
AI 中文摘要
我们解决了在量子非破坏（QND）能量测量辅助下从量子系统提取功的问题。当可执行完美QND测量且存在辅助零温浴时，即使没有输入态的任何先验信息，原则上也可提取量子态的全部能量；由于零温浴的存在，该过程的测量本身无能量成本。相反，本文考虑同一协议在非理想场景下的情况，特别是当辅助浴具有有限温度时的情形。此时不仅无法提取系统的全部能量，测量策略还会产生非零能量成本，该成本包含系统与测量装置的相互作用以及对应的兰道尔擦除成本。我们从绝对量和明确包含测量能量成本的所谓恶魔式净增益两方面，定量评估这些功提取协议的性能。我们严格证明，当功提取协议可使用热浴时，对于任意温度的辅助浴，恶魔式净增益始终非正；反之，当仅考虑幺正操作时，恶魔式净增益可达到正值。我们还通过分析单量子比特系统的范例实例，进一步讨论这些不同的性能指标。
英文摘要
We address the problem of extracting work from a quantum system assisted by a quantum non-demolition (QND) energy measurement. When a perfect QND measurement can be performed and an auxiliary zero-temperature bath is available, the full energy of the quantum state can in principle be extracted even without any prior information on the input state. Owing to the presence of a zero-temperature bath, this is achieved at no energetic cost for the measurement process itself. On the contrary, here we consider what happens when the same protocol is implemented in non-ideal scenarios, specifically when the auxiliary bath has a finite temperature. In this case, not only is it impossible to extract the entire energy from the system, but the measurement strategy also acquires a non-zero energetic cost, accounting for both the interaction between system and measurement apparatus, and the corresponding Landauer erasure cost. We quantitatively assess the performance of these work-extraction protocols, both in absolute terms and through the so-called daemonic net gain, which explicitly includes the energetic cost of the measurement. We rigorously prove that, when access to a thermal bath is allowed in the extraction protocol, the daemonic net gain is always non-positive for any temperature of the auxiliary bath. Conversely, when only unitary operations are considered, the daemonic net gain can attain positive values. We further discuss these different figures of merit by analyzing a paradigmatic example for a single qubit system.
Comments13 pages, 3 figures
