swap sweepers carefully - not all frequency sweepers are the same

src/qibolab/instruments/zhinst/executor.py

@@ -13,7 +13,7 @@
 from qibolab.couplers import Coupler
 from qibolab.instruments.abstract import Controller
 from qibolab.instruments.port import Port
-from qibolab.pulses import FluxPulse, PulseSequence, PulseType
+from qibolab.pulses import DrivePulse, FluxPulse, PulseSequence, PulseType
 from qibolab.qubits import Qubit
 from qibolab.sweeper import Parameter, Sweeper
 from qibolab.unrolling import Bounds
@@ -701,11 +701,10 @@ def play_sweep(exp, channel_name, pulse):
     def rearrange_rt_sweepers(
         sweepers: list[Sweeper],
     ) -> tuple[Optional[tuple[int, int]], list[Sweeper]]:
-        """Rearranges list of real-time sweepers based on hardware limitations.
+        """Rearranges list of real-time sweepers based on heuristic
+        discoveries.
 
-        The only known limitation currently is that frequency sweepers must be applied before (on the outer loop) other
-        (e.g. amplitude) sweepers. Consequently, the only thing done here is to swap the frequency sweeper with the
-        first sweeper in the list.
+        The only thing this function currently does is either swap two sweeper or do nothing.
 
         Args:
             sweepers: Sweepers to rearrange.
@@ -718,12 +717,17 @@ def rearrange_rt_sweepers(
             iter(s for s in sweepers if s.parameter is Parameter.frequency), None
         )
         if freq_sweeper:
+            # If readout frequency sweep, swap it with the outermost loop
+            # If drive, swap it with the innermost sweep
+            swap_idx = 0
+            if any(isinstance(pulse.type, DrivePulse) for pulse in freq_sweeper.pulses):
+                swap_idx = len(sweepers) - 1
             sweepers_copy = sweepers.copy()
             freq_sweeper_idx = sweepers_copy.index(freq_sweeper)
-            sweepers_copy[freq_sweeper_idx] = sweepers_copy[0]
-            sweepers_copy[0] = freq_sweeper
+            sweepers_copy[freq_sweeper_idx] = sweepers_copy[swap_idx]
+            sweepers_copy[swap_idx] = freq_sweeper
             log.warning("Sweepers were reordered")
-            return (0, freq_sweeper_idx), sweepers_copy
+            return (swap_idx, freq_sweeper_idx), sweepers_copy
         return None, sweepers
 
     def sweep(self, qubits, couplers, sequence: PulseSequence, options, *sweepers):