I’m not sure what you are trying to achieve with another PhD. Really. For one, living on a student salary is not something most people want to extend if they can avoid it.
There aren’t enough faculty (or even postdoc) positions in physics for every graduating PhD student, so why would you think your chances of landing such jobs will increase once you have spent another 4 years working on another similar degree? In other words, what are the odds that doing another PhD will improve your situation rather than simply delay your entry to the private sector, which is where the vast majority of physics jobs are?
Realistically you will not find a private sector job doing supersymmetry or string theory but the most recent available study (2015) of the American Society asked
(p)hysicists who worked in the private sector … to identify the most rewarding aspects of their jobs. They wrote that they found their jobs intellectually stimulating and challenging, and that they enjoyed regularly working with smart and interesting people
(t)he types of careers commonly pursued by physicists in the private sector involved solving complex problems, managing projects, and writing for a technical audience.
It is also the case that, in “hot” fields like quantum information, private companies can’t hire physics graduates fast enough. In Canada, a country which historically lacks the US in terms of private sector jobs for physicists, the federal government expects that private sector jobs in quantum technologies will increase 200-fold in the next 20 years or so. That’s 20000%, i.e. that’s really 200 times. I can’t find a similar document for the US but or Europe but the X-factor must be in the same range. Universities have difficulties attracting faculty in this area because they can’t match offers from … you guessed it: the private sector.
All of this to say that suggesting private sector jobs are “boring” is a bit of a broad exaggeration.
If you are hell-bent on doing another degree, consider instead a Masters in a cognate field (computer science or even an MBA) where the timelines are shorter and you can complement or highlight the skill set you picked up in your PhD.