Merge pull request #689 from qiboteam/snz

Simplify and refactor SNZ pulse

src/qibolab/pulses.py

@@ -468,41 +468,43 @@ class SNZ(PulseShape):
     """
     Sudden variant Net Zero.
     https://arxiv.org/abs/2008.07411
+    (Supplementary materials: FIG. S1.)
 
     """
 
-    def __init__(self, t_half_flux_pulse=None, b_amplitude=1):
+    def __init__(self, t_idling, b_amplitude=None):
         self.name = "SNZ"
         self.pulse: Pulse = None
-        self.t_half_flux_pulse: float = t_half_flux_pulse
-        self.b_amplitude: float = b_amplitude
+        self.t_idling: float = t_idling
+        self.b_amplitude = b_amplitude
 
     def __eq__(self, item) -> bool:
         """Overloads == operator"""
         if super().__eq__(item):
-            return self.t_half_flux_pulse == item.t_half_flux_pulse and self.b_amplitude == item.b_amplitude
+            return self.t_idling == item.t_idling and self.b_amplitude == item.b_amplitude
         return False
 
     @property
     def envelope_waveform_i(self) -> Waveform:
         """The envelope waveform of the i component of the pulse."""
 
         if self.pulse:
-            if not self.t_half_flux_pulse:
-                self.t_half_flux_pulse = self.pulse.duration / 2
-            elif 2 * self.t_half_flux_pulse > self.pulse.duration:
-                raise ValueError("Pulse shape parameter error: pulse.t_half_flux_pulse <= pulse.duration")
+            if self.t_idling > self.pulse.duration:
+                raise ValueError(f"Cannot put idling time {self.t_idling} higher than duration {self.pulse.duration}.")
+            if self.b_amplitude is None:
+                self.b_amplitude = self.pulse.amplitude / 2
             num_samples = int(np.rint(self.pulse.duration / 1e9 * PulseShape.SAMPLING_RATE))
-            half_flux_pulse_samples = int(np.rint(num_samples * self.t_half_flux_pulse / self.pulse.duration))
-            iding_samples = num_samples - 2 * half_flux_pulse_samples
+            half_pulse_duration = (self.pulse.duration - self.t_idling) / 2
+            half_flux_pulse_samples = int(np.rint(num_samples * half_pulse_duration / self.pulse.duration))
+            idling_samples = num_samples - 2 * half_flux_pulse_samples
             waveform = Waveform(
                 np.concatenate(
                     (
                         self.pulse.amplitude * np.ones(half_flux_pulse_samples - 1),
-                        np.array([self.pulse.amplitude * self.b_amplitude]),
-                        np.zeros(iding_samples),
-                        -1 * np.array([self.pulse.amplitude * self.b_amplitude]),
-                        -1 * self.pulse.amplitude * np.ones(half_flux_pulse_samples - 1),
+                        np.array([self.b_amplitude]),
+                        np.zeros(idling_samples),
+                        -np.array([self.b_amplitude]),
+                        -self.pulse.amplitude * np.ones(half_flux_pulse_samples - 1),
                     )
                 )
             )
@@ -522,7 +524,7 @@ def envelope_waveform_q(self) -> Waveform:
         raise ShapeInitError
 
     def __repr__(self):
-        return f"{self.name}({self.t_half_flux_pulse}, {self.b_amplitude})"
+        return f"{self.name}({self.t_idling})"
 
 
 class eCap(PulseShape):

tests/test_instruments_zhinst.py

@@ -31,7 +31,7 @@ def test_zhpulse(shape):
     if shape == "Drag":
         pulse = Pulse(0, 40, 0.05, int(3e9), 0.0, Drag(5, 0.4), "ch0", qubit=0)
     if shape == "SNZ":
-        pulse = Pulse(0, 40, 0.05, int(3e9), 0.0, SNZ(10, 0.4), "ch0", qubit=0)
+        pulse = Pulse(0, 40, 0.05, int(3e9), 0.0, SNZ(10, 0.01), "ch0", qubit=0)
     if shape == "IIR":
         pulse = Pulse(0, 40, 0.05, int(3e9), 0.0, IIR([10, 1], [0.4, 1], target=Gaussian(5)), "ch0", qubit=0)
 

tests/test_pulses.py

@@ -34,7 +34,7 @@ def test_pulses_plot_functions():
     p1 = Pulse(0, 40, 0.9, 50e6, 0, Gaussian(5), 0, PulseType.DRIVE, 2)
     p2 = Pulse(0, 40, 0.9, 50e6, 0, Drag(5, 2), 0, PulseType.DRIVE, 200)
     p3 = FluxPulse(0, 40, 0.9, IIR([-0.5, 2], [1], Rectangular()), 0, 200)
-    p4 = FluxPulse(0, 40, 0.9, SNZ(t_half_flux_pulse=17, b_amplitude=0.8), 0, 200)
+    p4 = FluxPulse(0, 40, 0.9, SNZ(t_idling=10), 0, 200)
     p5 = Pulse(0, 40, 0.9, 400e6, 0, eCap(alpha=2), 0, PulseType.DRIVE)
     p6 = SplitPulse(p5, window_start=10, window_finish=30)
     ps = p0 + p1 + p2 + p3 + p4 + p5 + p6
@@ -155,7 +155,7 @@ def test_pulses_pulse_init():
     p8 = Pulse(0, 40, 0.9, 50e6, 0, Gaussian(5), 0, PulseType.DRIVE, 2)
     p9 = Pulse(0, 40, 0.9, 50e6, 0, Drag(5, 2), 0, PulseType.DRIVE, 200)
     p10 = FluxPulse(0, 40, 0.9, IIR([-1, 1], [-0.1, 0.1001], Rectangular()), 0, 200)
-    p11 = FluxPulse(0, 40, 0.9, SNZ(t_half_flux_pulse=17, b_amplitude=0.8), 0, 200)
+    p11 = FluxPulse(0, 40, 0.9, SNZ(t_idling=10, b_amplitude=0.5), 0, 200)
     p11 = Pulse(0, 40, 0.9, 400e6, 0, eCap(alpha=2), 0, PulseType.DRIVE)
 
     # initialisation with float duration and start
@@ -364,7 +364,7 @@ def test_raise_shapeiniterror():
     with pytest.raises(ShapeInitError):
         shape.envelope_waveform_q
 
-    shape = SNZ(0, 0)
+    shape = SNZ(0)
     with pytest.raises(ShapeInitError):
         shape.envelope_waveform_i
     with pytest.raises(ShapeInitError):
@@ -924,11 +924,11 @@ def test_pulses_pulseshape_eq():
     assert not shape1 == shape5
     assert not shape1 == shape6
 
-    shape1 = SNZ(17, 0.8)
-    shape2 = SNZ(17, 0.8)
-    shape3 = SNZ(18, 0.8)
-    shape4 = SNZ(17, 0.9)
-    shape5 = SNZ(18, 0.9)
+    shape1 = SNZ(5)
+    shape2 = SNZ(5)
+    shape3 = SNZ(2)
+    shape4 = SNZ(2, 0.1)
+    shape5 = SNZ(2, 0.1)
     assert shape1 == shape2
     assert not shape1 == shape3
     assert not shape1 == shape4