Quantum Error Correction with Quantum States of Light

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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.