FTQC Can't Be Achieved With Constant Overhead

Interesting paper from UMD. They prove that we can not have one universal constant spacetime overhead that works for arbitrarily long quantum computations of arbitrary width. The more interesting result is that they show that this cost can be shared across multiple qubits. This works in the favor of algorithms like Shor but is troublesome for thing like iterative phase estimation with large amounts of qubit reuse. We knew about the overall width vs. duration vs. reliability but nevertheless I think this is a nice way to frame it. submitted by /u/sinanspd [link] [comments]