Coherence is one of the most significant limitations of quantum computing

The statement is referring to one of the major challenges in quantum computing, which is maintaining coherence.

Quantum coherence is a fundamental principle in quantum mechanics where a quantum system can exist in multiple states simultaneously, a property known as superposition. This is what allows quantum computers to perform complex calculations at a much faster rate than classical computers.

However, maintaining this state of coherence is difficult. Interaction with the environment (known as decoherence) can cause the quantum system to lose its superposition and collapse into a single state. This is a significant limitation because once coherence is lost, the quantum computer loses its quantum computational advantage.

Therefore, a lot of research in quantum computing is focused on finding ways to increase the coherence time (the time that a quantum system can stay in superposition) and to correct errors that occur when decoherence happens. This includes developing new materials and technologies, as well as error correction algorithms.

In summary, while coherence is what makes quantum computing powerful, maintaining it is also one of its biggest challenges.