Fixes #7078: Change prefix of MemorySlot channel in Qasm Instructions (…

…#8166)

* Fixes #7078: Add is_schedulable property to qiskit.pulse.Channel and don't apply a delay to it if True

RegisterSlot and MemorySlot have this set to False. The default implementation in Channel sets it to True.

* Fixes #7078: Introduce ClassicalIOChannel as a subclass of pulse.Channel

RegisterSlot, MemorySlot and SnapshotChannel now derive from this class. There are some tests to fix.

* Fixes #7078: Make Acquire.channels only return the channel

* Fixes #7078: Execute black

* Fixes #7078: Put slots in new tuple in acquire

* Fixes #7078: Add is_schedulable property to qiskit.pulse.Channel and don't apply a delay to it if True

RegisterSlot and MemorySlot have this set to False. The default implementation in Channel sets it to True.

* Fixes #7078: Remove is_schedulable property from qiskit.pulse.channel

* Fixes #7078: Put checks in SetPhase, ShiftPhase and SetPhase. Remove check from Delay.

* Fixes #7078: Add unit tests for restrictions on Classical IO channels

* Fixes #7078: Add unit tests for abstract nature of ClassicalIOChannel

* Fixes #7078: Tidying after self-review.

* Fixes #7078: Add release note.

* Fixes #7078: remove typo

Co-authored-by: Naoki Kanazawa <nkanazawa1989@gmail.com>

qiskit/pulse/channels.py

@@ -165,6 +165,12 @@ class PulseChannel(Channel, metaclass=ABCMeta):
     pass
 
 
+class ClassicalIOChannel(Channel, metaclass=ABCMeta):
+    """Base class of classical IO channels. These cannot have instructions scheduled on them."""
+
+    pass
+
+
 class DriveChannel(PulseChannel):
     """Drive channels transmit signals to qubits which enact gate operations."""
 
@@ -192,7 +198,7 @@ class AcquireChannel(Channel):
     prefix = "a"
 
 
-class SnapshotChannel(Channel):
+class SnapshotChannel(ClassicalIOChannel):
     """Snapshot channels are used to specify instructions for simulators."""
 
     prefix = "s"
@@ -202,13 +208,13 @@ def __init__(self):
         super().__init__(0)
 
 
-class MemorySlot(Channel):
+class MemorySlot(ClassicalIOChannel):
     """Memory slot channels represent classical memory storage."""
 
     prefix = "m"
 
 
-class RegisterSlot(Channel):
+class RegisterSlot(ClassicalIOChannel):
     """Classical resister slot channels represent classical registers (low-latency classical
     memory).
     """

qiskit/pulse/instructions/frequency.py

@@ -16,7 +16,7 @@
 from typing import Optional, Union, Tuple
 
 from qiskit.circuit.parameterexpression import ParameterExpression
-from qiskit.pulse.channels import PulseChannel
+from qiskit.pulse.channels import PulseChannel, PulseError
 from qiskit.pulse.instructions.instruction import Instruction
 
 
@@ -46,7 +46,13 @@ def __init__(
             frequency: New frequency of the channel in Hz.
             channel: The channel this instruction operates on.
             name: Name of this set channel frequency instruction.
+        Raises:
+            PulseError: If channel is not a PulseChannel.
         """
+        if not isinstance(channel, PulseChannel):
+            raise PulseError(
+                "The `channel` argument to `SetFrequency` must be of type `channels.PulseChannel`."
+            )
         if not isinstance(frequency, ParameterExpression):
             frequency = float(frequency)
         super().__init__(operands=(frequency, channel), name=name)
@@ -93,9 +99,15 @@ def __init__(
             frequency: Frequency shift of the channel in Hz.
             channel: The channel this instruction operates on.
             name: Name of this set channel frequency instruction.
+        Raises:
+            PulseError: If channel is not a PulseChannel.
         """
         if not isinstance(frequency, ParameterExpression):
             frequency = float(frequency)
+        if not isinstance(channel, PulseChannel):
+            raise PulseError(
+                "The `channel` argument to `ShiftFrequency` must be of type `channels.PulseChannel`."
+            )
         super().__init__(operands=(frequency, channel), name=name)
 
     @property

qiskit/pulse/instructions/phase.py

@@ -18,7 +18,7 @@
 from typing import Optional, Union, Tuple
 
 from qiskit.circuit import ParameterExpression
-from qiskit.pulse.channels import PulseChannel
+from qiskit.pulse.channels import PulseChannel, PulseError
 from qiskit.pulse.instructions.instruction import Instruction
 
 
@@ -52,7 +52,14 @@ def __init__(
             phase: The rotation angle in radians.
             channel: The channel this instruction operates on.
             name: Display name for this instruction.
+
+        Raises:
+            PulseError: If channel is not a PulseChannel.
         """
+        if not isinstance(channel, PulseChannel):
+            raise PulseError(
+                "The `channel` argument to `ShiftPhase` must be of type `channels.PulseChannel`."
+            )
         super().__init__(operands=(phase, channel), name=name)
 
     @property
@@ -108,7 +115,13 @@ def __init__(
             phase: The rotation angle in radians.
             channel: The channel this instruction operates on.
             name: Display name for this instruction.
+        Raises:
+            PulseError: If channel is not a PulseChannel.
         """
+        if not isinstance(channel, PulseChannel):
+            raise PulseError(
+                "The `channel` argument to `SetPhase` must be of type `channels.PulseChannel`."
+            )
         super().__init__(operands=(phase, channel), name=name)
 
     @property

qiskit/pulse/instructions/play.py

@@ -41,7 +41,7 @@ def __init__(self, pulse: Pulse, channel: PulseChannel, name: Optional[str] = No
             name: Name of the instruction for display purposes. Defaults to ``pulse.name``.
 
         Raises:
-            PulseError: If pulse is not a Pulse type.
+            PulseError: If pulse is not a Pulse type, or channel is not a PulseChannel.
         """
         if not isinstance(pulse, Pulse):
             raise PulseError("The `pulse` argument to `Play` must be of type `library.Pulse`.")

qiskit/pulse/transforms/canonicalization.py

@@ -18,6 +18,7 @@
 import numpy as np
 
 from qiskit.pulse import channels as chans, exceptions, instructions
+from qiskit.pulse.channels import ClassicalIOChannel
 from qiskit.pulse.exceptions import PulseError
 from qiskit.pulse.exceptions import UnassignedDurationError
 from qiskit.pulse.instruction_schedule_map import InstructionScheduleMap
@@ -475,6 +476,8 @@ def pad(
     channels = channels or schedule.channels
 
     for channel in channels:
+        if isinstance(channel, ClassicalIOChannel):
+            continue
         if channel not in schedule.channels:
             schedule |= instructions.Delay(until, channel)
             continue

releasenotes/notes/introduce-classical-io-channel-0a616e6ca75b7687.yaml

@@ -0,0 +1,13 @@
+---
+features:
+  - |
+    In the qiskit.pulse.channels package, ClassicalIOChannel class has been added
+    as an abstract base class of MemorySlot, RegisterSlot, and SnapshotChannel.
+
+    The qiskit.pulse.transforms.canonicalization.pad method does not introduce
+    delays to any channels which are instances of ClassicalIOChannel.
+
+    In qiskit.pulse.instructions, the constructors to SetPhase, ShiftPhase,
+    SetFrequency and ShiftFrequency now throw a PulseError if the channel parameter
+    is not of type PulseChannel.
+

test/python/pulse/test_channels.py

@@ -17,8 +17,9 @@
 from qiskit.pulse.channels import (
     AcquireChannel,
     Channel,
-    DriveChannel,
+    ClassicalIOChannel,
     ControlChannel,
+    DriveChannel,
     MeasureChannel,
     MemorySlot,
     PulseChannel,
@@ -67,15 +68,25 @@ def test_channel_hash(self):
         self.assertEqual(hash_1, hash_2)
 
 
+class TestClassicalIOChannel(QiskitTestCase):
+    """Test base classical IO channel."""
+
+    def test_cannot_be_instantiated(self):
+        """Test base classical IO channel cannot be instantiated."""
+        with self.assertRaises(NotImplementedError):
+            ClassicalIOChannel(0)
+
+
 class TestMemorySlot(QiskitTestCase):
-    """AcquireChannel tests."""
+    """MemorySlot tests."""
 
     def test_default(self):
         """Test default memory slot."""
         memory_slot = MemorySlot(123)
 
         self.assertEqual(memory_slot.index, 123)
         self.assertEqual(memory_slot.name, "m123")
+        self.assertTrue(isinstance(memory_slot, ClassicalIOChannel))
 
 
 class TestRegisterSlot(QiskitTestCase):
@@ -87,6 +98,7 @@ def test_default(self):
 
         self.assertEqual(register_slot.index, 123)
         self.assertEqual(register_slot.name, "c123")
+        self.assertTrue(isinstance(register_slot, ClassicalIOChannel))
 
 
 class TestSnapshotChannel(QiskitTestCase):
@@ -98,6 +110,7 @@ def test_default(self):
 
         self.assertEqual(snapshot_channel.index, 0)
         self.assertEqual(snapshot_channel.name, "s0")
+        self.assertTrue(isinstance(snapshot_channel, ClassicalIOChannel))
 
 
 class TestDriveChannel(QiskitTestCase):

test/python/pulse/test_instructions.py

@@ -156,6 +156,64 @@ def test_freq(self):
         )
         self.assertEqual(repr(set_freq), "SetFrequency(4500000000.0, DriveChannel(1), name='test')")
 
+    def test_freq_non_pulse_channel(self):
+        """Test set frequency constructor with illegal channel"""
+        with self.assertRaises(exceptions.PulseError):
+            instructions.SetFrequency(4.5e9, channels.RegisterSlot(1), name="test")
+
+
+class TestShiftFrequency(QiskitTestCase):
+    """Shift frequency tests."""
+
+    def test_shift_freq(self):
+        """Test shift frequency basic functionality."""
+        shift_freq = instructions.ShiftFrequency(4.5e9, channels.DriveChannel(1), name="test")
+
+        self.assertIsInstance(shift_freq.id, int)
+        self.assertEqual(shift_freq.duration, 0)
+        self.assertEqual(shift_freq.frequency, 4.5e9)
+        self.assertEqual(shift_freq.operands, (4.5e9, channels.DriveChannel(1)))
+        self.assertEqual(
+            shift_freq, instructions.ShiftFrequency(4.5e9, channels.DriveChannel(1), name="test")
+        )
+        self.assertNotEqual(
+            shift_freq, instructions.ShiftFrequency(4.5e8, channels.DriveChannel(1), name="test")
+        )
+        self.assertEqual(
+            repr(shift_freq), "ShiftFrequency(4500000000.0, DriveChannel(1), name='test')"
+        )
+
+    def test_freq_non_pulse_channel(self):
+        """Test shift frequency constructor with illegal channel"""
+        with self.assertRaises(exceptions.PulseError):
+            instructions.ShiftFrequency(4.5e9, channels.RegisterSlot(1), name="test")
+
+
+class TestSetPhase(QiskitTestCase):
+    """Test the instruction construction."""
+
+    def test_default(self):
+        """Test basic SetPhase."""
+        set_phase = instructions.SetPhase(1.57, channels.DriveChannel(0))
+
+        self.assertIsInstance(set_phase.id, int)
+        self.assertEqual(set_phase.name, None)
+        self.assertEqual(set_phase.duration, 0)
+        self.assertEqual(set_phase.phase, 1.57)
+        self.assertEqual(set_phase.operands, (1.57, channels.DriveChannel(0)))
+        self.assertEqual(
+            set_phase, instructions.SetPhase(1.57, channels.DriveChannel(0), name="test")
+        )
+        self.assertNotEqual(
+            set_phase, instructions.SetPhase(1.57j, channels.DriveChannel(0), name="test")
+        )
+        self.assertEqual(repr(set_phase), "SetPhase(1.57, DriveChannel(0))")
+
+    def test_set_phase_non_pulse_channel(self):
+        """Test shift phase constructor with illegal channel"""
+        with self.assertRaises(exceptions.PulseError):
+            instructions.SetPhase(1.57, channels.RegisterSlot(1), name="test")
+
 
 class TestShiftPhase(QiskitTestCase):
     """Test the instruction construction."""
@@ -177,6 +235,11 @@ def test_default(self):
         )
         self.assertEqual(repr(shift_phase), "ShiftPhase(1.57, DriveChannel(0))")
 
+    def test_shift_phase_non_pulse_channel(self):
+        """Test shift phase constructor with illegal channel"""
+        with self.assertRaises(exceptions.PulseError):
+            instructions.ShiftPhase(1.57, channels.RegisterSlot(1), name="test")
+
 
 class TestSnapshot(QiskitTestCase):
     """Snapshot tests."""

test/python/pulse/test_transforms.py

@@ -29,7 +29,13 @@
     Constant,
 )
 from qiskit.pulse import transforms, instructions
-from qiskit.pulse.channels import MemorySlot, DriveChannel, AcquireChannel
+from qiskit.pulse.channels import (
+    MemorySlot,
+    DriveChannel,
+    AcquireChannel,
+    RegisterSlot,
+    SnapshotChannel,
+)
 from qiskit.pulse.instructions import directives
 from qiskit.test import QiskitTestCase
 from qiskit.providers.fake_provider import FakeOpenPulse2Q
@@ -349,6 +355,23 @@ def test_padding_prepended_delay(self):
 
         self.assertEqual(transforms.pad(sched, until=30, inplace=True), ref_sched)
 
+    def test_pad_no_delay_on_classical_io_channels(self):
+        """Test padding does not apply to classical IO channels."""
+        delay = 10
+        sched = (
+            Delay(delay, MemorySlot(0)).shift(20)
+            + Delay(delay, RegisterSlot(0)).shift(10)
+            + Delay(delay, SnapshotChannel())
+        )
+
+        ref_sched = (
+            Delay(delay, MemorySlot(0)).shift(20)
+            + Delay(delay, RegisterSlot(0)).shift(10)
+            + Delay(delay, SnapshotChannel())
+        )
+
+        self.assertEqual(transforms.pad(sched, until=15), ref_sched)
+
 
 def get_pulse_ids(schedules: List[Schedule]) -> Set[int]:
     """Returns ids of pulses used in Schedules."""