Though it doesn't answer the specific study he wanted, which was "Let's take a group of people with a known exposure to a positive case, isolate them for two weeks to prevent a second exposure, and conduct repeated PCR tests during this time to determine how long it takes for the first positive test to appear."
I haven't found any study to answer that particular question, but probably for good reason - it would be a waste of time and tests in pursuit of a point of information that is not really practically useful now. More important is to monitor time since infection and possible symptoms, rather than testing for the virus.
As to @biobook's assertion that such a study is a waste of time, that is beyond me. I would argue that it would be an extremely useful study, as it would enable improved accuracy of quarantine requirements, showing goodwill of kinds to people who are experiencing draconian measures, enabling more of a back-to-normal life, without any increased risk to public health. On the contrary, people are more likely to comply if they have a reasonable route to a quicker way out of it.
Maybe I'm still misunderstanding you.
Until now, if someone had been exposed to a positive case, they were told to isolate for 14 days, and you wanted to do more testing, so they could leave isolation earlier. But now the CDC okays leaving isolation on day 7 with a single test.
I don't see how further testing could get you out of isolation earlier.
Days 1-2 after exposure, a negative test just means that the virus hasn't yet multiplied enough to be measurable.
Days 3-4 a negative test could be you weren't infected, but could be a false negative and you were infected, so you need to wait to see if symptoms occur, which are most likely by day 5. If no symptoms on day 5, and a test is negative, you can leave isolation 2 days later. (In practice, it may take 2 days just to get the results of the test.) This hardly seems "draconian".
When do you think additional testing would be beneficial?