I saw that qiskit was just incorporated in a trapped ion device.

I transpiled my circuit to 2 backends: ibm superconducting device and aqt trapped ion device. I noticed that for ibm, the $X$ gate is transpiled into $U_3(\pi,0,\pi)$, whereas for aqt it is $R_x(-\pi)$.

Since both objectives of them are to take $0$ to $1$, why do they use a different quantum gate to do that?

By the way, for the aqt device, $H$ gate $= R_y(\pi/2)R_x(\pi)$. I was wondering, why are the two representations equal?


A particular gate's implementation is intrinsically tied to the underlying architecture. A U3 gate on IBM's superconducting backends is just a combination of 3 rotations alternatively around just two axes (for example rotate around X-axis, then Y-axis and then again X-axis; there are several other combinations to choose from). In fact this is the most general way in which you could take one point on a bloch sphere to any other point on it. In essence, that's what a U3 gate's signature means.

Now, to answer why this implementation of rotation varies on different backengs, here are my thoughts:

  1. We'd like to keep the noise minimal while making any of those rotations. You might want to read more about how a Z gate is implemented on IBM's superconducting systems (It's virtually free of any noise). I'm not so well-wersed with Trapped-Ion device's transpiled code so can't comment on it's optimality.
  2. I believe it could also have something to do with keeping gate abstractions intuitive enough for programmers which might give rise to different signatures for different backends.
|improve this answer|||||

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.