Quantum heat engines as quantum computers

热机，如发动机和冰箱，自从200年前热力学的概念出现以来，一直是它的中心。对这类机器的更好理解的探索最终与创造具有更高功率输出和效率的性能更好的机器的目标联系在一起。由于热机器可以建立在越来越小的尺度上，很明显，它们将不可避免地达到量子力学的微观领域，而用宏观机器的（经典）热力学语言来描述它们已经不够了。这导致了量子热力学新理论的诞生，它试图将两种现有理论结合起来。近年来，量子热机的理论和实验研究都取得了很大的进展。引人注目的是，如今这些不再仅仅是理论概念，而是在实验中使用许多不同的物理平台，如金刚石中的氮空位中心，核磁共振装置，超冷原子和离子阱来实现。然而，量子热机的多功能性超越了它们作为热机、冰箱或热泵的直接用途。它们可以以新颖的方式应用于创造全新的有用设备，并作为将我们的热机知识应用于不同物理领域的桥梁。本着这种精神，本项目的主要目标是设计第一台可以执行量子计算算法的量子热机。这将把量子热力学与量子计算这个非常重要的领域联系起来。从这个新的热力学角度来看，量子计算机可以更好地理解和长期优化，这是量子计算机大规模应用不可或缺的关键一步。为此，我们有三个目标。首先，我们开始研究量子热机及其效率和功率的波动，如果量子相干存在于设置中。在此基础上，我们将开发利用量子热机的冲程实现量子门的协议。我们专注于简单的量子门，仅由一个或两个量子比特组成，作为任何量子计算算法的基本构建块。我们将从热力学和量子力学的角度充分研究这些协议，并评估它们的效率和保真度。最后，我们将详细阐述我们的引擎协议，通过考虑实验参数和场景使它们更加现实，这些协议可以在量子热力学和量子计算的现有实验平台上实现。

Thermal machines like engines and fridges have been a central point of thermodynamics since its conception 200 years ago. The search for a better understanding of such machines was ultimately linked to the goal of creating better-performing machines with higher power output and efficiency. As thermal machines could be built on increasingly smaller scales, it became clear that they would inevitably reach the microscopic domain of quantum mechanics, and it would no longer suffice to describe them in the language of the (classical) thermodynamics of macroscopic machines. This led to the creation of the new theory of quantum thermodynamics, which tries to combine the two existing theories. In recent years, great theoretical and experimental advancements have been made in the study of quantum thermal machines. Strikingly, nowadays these are no longer just theoretical concepts but are implement in experiments using many different physical platforms like nitrogen-vacancy centers in diamond, NMR setups, ultracold atoms, and ion traps. However, the versatility of quantum thermal machines goes beyond their direct usage as heat engines, refrigerators, or heat pumps. They can be applied in novel ways to create completely new useful devices and serve as a bridge to apply our knowledge of thermal machines to different physical fields.In this spirit, the main goal of this project is to design the very first quantum heat engine which can perform quantum computational algorithms. This will connect quantum thermodynamics to the highly important field of quantum computation. With this new thermodynamic perspective, quantum computers can be much better understood and long-term be optimized, which is an indispensable crucial step for any large-scale application of quantum computers. For this, we have three objectives. First, we begin with a study of quantum heat engines and their fluctuations of efficiency and power if quantum coherences are present in the setup. Based on this we will then develop protocols to implement quantum gates with the strokes of a quantum heat engine. We focus on simple quantum gates, consisting of only one or two qubits which serve as the basic building blocks of any quantum computational algorithm. We will fully study these protocols from a thermodynamic and quantum mechanical perspective and assess their efficiency and fidelity. Lastly, we will elaborate on our engine protocols by making them more realistic by taking into account experiment parameters and scenarios, which can be implemented on current experimental platforms in quantum thermodynamics and quantum computation.