ancilla

So an Ancilla chip for the Ancilla chip is also needed?

This can be worked around by introducing ancilla bits to maintain the number of states in the system, but the instant you destroy the ancilla bits (e.g.

The system is separable after you measure out your ancilla.

In practice this means that you sometimes have to keep around extra bits called Ancilla bits that just contain garbage, but are necessary for reversibility.

Plus this check is only probabilistic; decoherence is a property of the program not the ancilla's final state.

The ancilla holding the condition value fails to uncompute consistently, so it will sometimes end up ON.

The runtime could notice that ON ancilla and warn you that an ancilla failed to uncompute, but there could be many many actions in between that ancilla being computed and uncomputed.

Then measure the R ancilla bits you introduced, and restart if any of them was false.

Of course, ignoring the issue of needing sufficiently many ancilla to render the reversal accurate.

Decoherence still happened if the ancilla ended up OFF but could have ended up ON.

Each ancilla bit will have a roughly 4% chance of being OFF.

So what happens if a cosmic ray hits the Ancilla chip?

Yeah the whole entangled system is present and interacting with the "thermal ancilla" in their setup.

It would probably be helpful to have a glance through "Ancilla to the Pre-Socratic Philosophers.

I don't get how the no-hiding theorem implies that the information will be preserved in the remaining qbits, if the "environment" of the measurement is the lab, not the available ancilla.

Anything that "happened" to the particle happened not as a result of the measurement but as a result of the initial entanglement with the ancilla.

'Ancilla' [female slave, I was taught] is translated: maid, handmaiden, women, and ancillary, depending on declension?