科学家观测量子状态实现新的芯片冷却方案

科学家们在连续观测过程中尽量不扰乱量子态相干。以色列和德国科学家近期展开合作，将通过对量子态进行观测来控制热力学（温度）和熵（沉降）这项技术的开发提上日程。

科学家们声称在一个二能级量子系统（像那些用于表征量子比特(q-bits)的量子系统）中，可通过改变量子系统的测量频率来控制温度和熵，从而可以实现新兴的冷却方案以及原子、分子和固态器件的瞬时沉降。

以色列魏兹曼科学研究所和德国波茨坦大学的科学家们声称，控制热力学和熵的常量是用于观测其量子态的频率。通过采用这种方式可以在更短时间内实现冷却和量子态纯化，速度较通过控制环实现热平衡、冷却或反馈要快很多。

据Gershon Kurizki（教授）、Noam Erez（博士后）和Goren Gordon（在读博士）称，量子观测是存在干扰的。他们与德国波茨坦大学的研究员Mathias Nest协同展开研究工作。

典型的量测不会干扰被测试的系统。然而，若某个量子系统正在进行某项特定测量，则其与另外特定系统的连接会暂时受到此量测的影响。

据这些科学家称，量子力学的不确定性可被用作一种新的芯片级冷却和量子计算方法。工程师们通常根据冷却芯片所需散热器的尺寸来计算热量损失。而研究人员称，超快速量测会加速或延缓热效应，从而使之与散热器的尺寸无关。

通过调节光温度量测的速率，研究人员发现温度本身也是可以被调节的。

研究人员称，采用连续测量还可以改变系统熵或下降时间（下降到最低能量态的所需时间）。通过调整系统熵，未来的量子计算机可以更快速度得到中间结果，各个计算之间的复原时间也将加速。

相关英文原文：

Measuring quantum states could yield new chip-cooling scheme

Scientists take great pains not to disturb the coherence of quantum states through constant measurements. Israeli and German scientists recently collaborated to turn this technique on its head, using the measurement of quantum states to control thermodynamics (temperature) and entropy (settling).

The scientists claim that in two-level quantum systems--like those used to represent quantum bits (q-bits)--the frequency used to measure them controls both temperature and entropy. The approach could enable novel cooling schemes as well as instant-settling for atomic, molecular and solid-state devices.

The scientists at the Weizmann Institute (Rehovot, Israel) and Potsdam University in Germany claim that the constant that controls thermodynamics and entropy is the frequency used to measure their quantum states. Both cooling and state purification, they claim, can be made to occur much more quickly than the normal time typically needed to achieve thermal equilibrium, cooling or feedback around a control loop.

Quantum measurements are intrusive, according to professor Gershon Kurizki, postdoctoral fellow Noam Erez and doctoral candidate Goren Gordon at the Wiesmann Institute. They worked in cooperation with researcher Mathias Nest at Potsdam University.

Classical measurements do not interfere with the system being measured. When a specific measurement is made in a quantum system, however, the coupling to other specific systems is temporarily interrupted by the measurement.

This odd characteristic of quantum mechanics can be harnessed, according to these scientists, as a new method of chip-scale cooling and quantum computing. Engineers usually measure heat loss in terms of the size of the heat sink needed to cool a chip. But the researchers claim that ultra-fast measurements can speed up or slow down thermal effects independent of the size of the heat sink.

By adjusting the rate at which optical temperature measurements were made, the researchers found that the temperature itself could be adjusted.

Taking frequent measurements also changed the system entropy or relaxation time--the time needed to reach the lowest energy state. By adjusting system entropy, future quantum computers could tilt toward faster settling of intermediate results and faster resetting between calculations, the researchers said.