Wasn't expecting my question to hit top of HN. I guess I'll give some context for why I asked it.
I work in quantum error correction, and was trying to collect interesting and quantitative examples of repetition codes being used implicitly in classical systems. Stuff like DRAM storing a 0 or 1 via the presence or absence of 40K electrons [1], undersea cables sending X photons per bit (don't know that one yet), some kind of number for a transistor switching (haven't even decided on the number for that one yet), etc.
A key reason quantum computing is so hard is that by default repetition makes things worse instead of better, because every repetition is another chance for an unintended measurement. So protecting a qubit tends to require special physical properties, like the energy gap of a superconductor, or complex error correction strategies like surface codes. A surface code can easily use 1000 physical qubits to store 1 logical qubit [2], and I wanted to contrast that with the sizes of implicit repetition codes used in classical computing.
I work in quantum error correction, and was trying to collect interesting and quantitative examples of repetition codes being used implicitly in classical systems. Stuff like DRAM storing a 0 or 1 via the presence or absence of 40K electrons [1], undersea cables sending X photons per bit (don't know that one yet), some kind of number for a transistor switching (haven't even decided on the number for that one yet), etc.
A key reason quantum computing is so hard is that by default repetition makes things worse instead of better, because every repetition is another chance for an unintended measurement. So protecting a qubit tends to require special physical properties, like the energy gap of a superconductor, or complex error correction strategies like surface codes. A surface code can easily use 1000 physical qubits to store 1 logical qubit [2], and I wanted to contrast that with the sizes of implicit repetition codes used in classical computing.
1: https://web.mit.edu/rec/www/dramfaq/DRAMFAQ.html
2: https://arxiv.org/abs/1208.0928