Quantum Error Correction with Quantum States of Light

量子计算机正迅速成为一种变革性技术，有望彻底改变量子化学、机器学习或密码学等许多领域。然而，到目前为止，还没有人完成了经典计算机无法完成的有用的量子计算。这是因为目前的量子计算机是由少量量子比特（量子位）组成的，这些量子位是嘈杂的物体，只能在有限的时间内保持量子信息。最终，量子的真正力量将通过纠错的通用量子计算机释放出来，但这种机器所需的硬件开销是巨大的。一个特别具有挑战性的要求是，量子计算机应该是容错的，在这种情况下，计算被保护免受系统任何单个部分的错误。在我的研究中，我计划开发一种基于光量子态的容错量子计算架构。然后，利用在量子计算背景下获得的知识，我将开发用于量子增强传感的新型设备。量子计算机的传统方法是在物理两级系统（物理量子比特）中对信息进行编码，例如超导量子比特。为了纠正错误，人们使用量子纠错码并在物理量子比特的集合中加密逻辑量子比特。在这种方法中，对容错计算的要求是令人生畏的，需要数百万个量子位才能有效地实现肖尔分解算法。相反，另一种方法是使用玻色子编码在谐振子模式（如微波腔）中对信息进行编码。这种方法的硬件效率更高，因为物理量子比特的大集合被单个组件取代，谐波振荡器模式可以制成比物理量子比特更长寿的对象。由于这些原因，玻色子代码是构建容错量子计算机最有希望的选择之一。在我的研究中，我将开发它们的实际实现方法，并研究如何将单个玻色子代码组合成一个完整的量子计算机。总而言之：构建量子计算机是一项艰巨的挑战，我的研究目标是在我们可以设计的最高质量元素谐波振荡器上设计其架构的构建块。除了量子计算，玻色子代码也可以成为量子增强传感的强大资源。我还计划利用玻色子编码的进展，并将其应用于其他领域，例如量子计量学，这将有助于寻找暗物质。更广泛地说，玻色子编码可以在各种实验平台上实现，这一事实为量子传感提供了巨大的潜力，我的研究旨在开发新型量子增强传感器。

Quantum computers are rapidly emerging as a transformative technology, with the promise of revolutionizing many areas such as quantum chemistry, machine learning or cryptography. However, to date, no one has performed a useful quantum computation that could not have otherwise been done on a classical computer. This is because current quantum computers are composed of a small number of quantum bits (qubits), and these qubits are noisy objects that can only maintain quantum information for a finite amount of time. Ultimately, the true power of quantum will be unleashed through error-corrected, universal quantum computers, but the hardware overhead required for such machines is enormous. One particularly challenging requirement is that quantum computers should be fault-tolerant, in which case the computation is protected from errors in any single part of the system. In my research, I plan to develop a fault-tolerant quantum computing architecture based on quantum states of light. Then, leveraging the knowledge acquired in the context of quantum computing, I will develop novel devices for quantum-enhanced sensing. The traditional approach to quantum computers is to encode the information in physical two-level systems (physical qubits), for example superconducting qubits. In order to correct errors, one uses a quantum error-correction code and encrypts logical qubits in ensembles of physical qubits. In this approach, the requirements for fault-tolerant computations are daunting, with millions of qubits required for a useful implementation of Shor's factorization algorithm. Instead, an alternative approach is to use a bosonic code to encode the information in harmonic oscillator modes such as microwave cavities. This approach is more hardware-efficient because large ensembles of physical qubits are replaced by a single component, and harmonic oscillator modes can be made into longer-lived objects than physical qubits. For these reasons, bosonic codes constitute one of the most promising options to build a fault-tolerant quantum computer. In my research, I will develop methods for their practical implementation, and study how to combine individual bosonic codes to form a full quantum computer. To summarize: building a quantum computer is a formidable challenge, and my research aims at designing the building blocks of its architecture on the highest-quality elements we can engineer, harmonic oscillators. Beyond quantum computing, bosonic codes could also be a powerful resource for quantum-enhanced sensing. I also plan to leverage the advances made on bosonic codes and apply them to other areas such as quantum metrology, which for example would help in the search for dark matter. More broadly, the fact that the bosonic codes can be implemented in various experimental platforms holds great potential for quantum sensing, and my research aims at developing novel quantum-enhanced sensors.