"Error-free" as in "perfect?" As in "written by God and the angels, not humans?" (we're speaking here of program-logic and maybe hardware-logic errors)
I can't say truthfully about even one single line of code that it is without error. That's because us humans, well, we can't prove no negative hypotheses!
The best I can say is that the probability of an error is a number between 0 and 1. I reach that number by way of well- or ill-defined and well- or ill-understood software development and testing principles; by a count of the source software lines in question; by an understanding of how well or poorly I candidate, poor mutt, applies those principles in producing those lines of code; and more.
And I can express that understanding only as a probability. So the term "logic-error-free" means close to nothing.
If I saw an ad for a software engineer who produced "error-free" code I'd either apply right away or I'd run right away: the company hasn't thought much about how it develops, tests, and delivers its software. So it'll be either a great opportunity or an endless nightmare.
That part's easy as pie. Anybody can do that.
Hey, good luck in your search :-)