There are no reliable ways to distinguish text written by a human from text written by an large language model. OpenAI writes:

Do AI detectors work?

• In short, no. While some (including OpenAI) have released tools that purport to detect AI-generated content, none of these have proven to reliably distinguish between AI-generated and human-generated content.
• Additionally, ChatGPT has no “knowledge” of what content could be AI-generated. It will sometimes make up responses to questions like “did you write this [essay]?” or “could this have been written by AI?” These responses are random and have no basis in fact.
• To elaborate on our research into the shortcomings of detectors, one of our key findings was that these tools sometimes suggest that human-written content was generated by AI.
  • When we at OpenAI tried to train an AI-generated content detector, we found that it labeled human-written text like Shakespeare and the Declaration of Independence as AI-generated.
  • There were also indications that it could disproportionately impact students who had learned or were learning English as a second language and students whose writing was particularly formulaic or concise.
• Even if these tools could accurately identify AI-generated content (which they cannot yet), students can make small edits to evade detection.

There is some good research in watermarking LLM-generated text, but the watermarks are not generally robust.

I don’t think the detectors are going to win this arms race.