Intensive temperature and quantum correlations for refined quantum measurements
Intensive temperature and quantum correlations for refined quantum measurements
复制标题
用于精细量子测量的密集温度和量子相关性
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
A. Acín
中科院分区：
文献类型：
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作者：
A. Ferraro;A. García;A. Acín
我们考虑的温度的概念，在设置超出标准热力学处方。也就是说，而不是限制到标准的粗粒度测量，我们认为观察者能够掌握任何可能的量子测量-一个场景，可能是相关的纳米尺度。在这种情况下，我们专注于耦合谐振子的量子系统，并研究温度是否是一个密集的量的问题，在这个意义上，一块热态可以近似为一个有效的热态在相同的温度作为整个系统。使用量子保真度作为品质因数，我们确定的情况下，这种近似是无效的，因为块状态和参考热状态是可区分的精细测量。实际上，存在这种可扩展性甚至随着块大小而增加的情况。然而，我们也表明，这两种状态变得不太区分与粗粒度测量的块大小-从而恢复标准图片。然后，我们进一步构建一个有效的热态，它提供了一个很好的近似的块状态的任何可观的和大小。最后，我们指出，纠缠在这种情况下发挥的作用，表明，在一般情况下，热力学范式的本地密集温度适用于纠缠不存在于系统中。
We consider the concept of temperature in a setting beyond the standard thermodynamics prescriptions. Namely, rather than restricting to standard coarse-grained measurements, we consider observers able to master any possible quantum measurement —a scenario that might be relevant at nanoscopic scales. In this setting, we focus on quantum systems of coupled harmonic oscillators and study the question of whether the temperature is an intensive quantity, in the sense that a block of a thermal state can be approximated by an effective thermal state at the same temperature as the whole system. Using the quantum fidelity as figure of merit, we identify instances in which this approximation is not valid, as the block state and the reference thermal state are distinguishable for refined measurements. Actually, there are situations in which this distinguishability even increases with the block size. However, we also show that the two states do become less distinguishable with the block size for coarse-grained measurements —thus recovering the standard picture. We then go further and construct an effective thermal state which provides a good approximation of the block state for any observables and sizes. Finally, we point out the role that entanglement plays in this scenario by showing that, in general, the thermodynamic paradigm of local intensive temperature applies whenever entanglement is not present in the system.