Qubits are inherently fragile and highly susceptible to environmental noise and perturbations, which can cause errors and the loss of information. This phenomenon, known as decoherence, is a fundamental challenge in building reliable quantum computers. Furthermore, the act of measuring a qubit’s state can affect or collapse its superposition, which is problematic because measurement is essential for computation.
To overcome these issues, significant research and engineering efforts are dedicated to quantum error correction and error mitigation. Error correction involves encoding quantum information across multiple physical qubits to protect against errors, creating more stable logical qubits. Error mitigation techniques aim to reduce the impact of noise on computation results without necessarily achieving full fault tolerance.
Making quantum error correction work is a key focus. Google is offering educational resources, including a Coursera course, to teach development for quantum error correction. This course provides hands-on experience with industry-standard software tools like Stim and Crumble.
Recent breakthroughs in error mitigation and correction by various players, including Alice & Bob, Amazon (AWS), IBM, QuEra, Microsoft, Quantinuum, and IonQ, promise to shorten timelines for achieving universal fault-tolerant quantum computers. For example, Microsoft’s topological approach aims for built-in error resistance at the hardware level. Quantinuum has demonstrated running experiments using their ion-trap hardware without a single error by leveraging qubit virtualization and error correction. Researchers using neutral atoms have also executed complex, error-corrected quantum algorithms.
Reducing the overhead required for quantum error correction remains a practical challenge. Google’s mission is to build quantum computing for otherwise unsolvable problems, and this often requires developing a large-scale, error-corrected quantum computer. Their latest chip, Willow, is presented as a significant step in this direction.
Developing a qubit that can be measured and controlled while still offering protection from environmental noise is an inherent challenge. The focus is on moving beyond the current Noisy Intermediate-Scale Quantum (NISQ) era towards resilient quantum computing where logical qubits are protected and can sustain longer computations.
