Qiskit#2262 | Acquire commands on a single qubit (Qiskit#3574)

* Acquire: AcquireInstruction change to sigle qbit, mem_slot, reg_slot

* Acquire: change usage of AcquireInstruction

* Tests: partial test fixing

* Assembler: tweak scheduler assembler to laverage new acquire + tests fixes

* Scheduler: fix scheduler to use acquire on single qubit + tests fix

* Style: fix lint errors

* Acquire: remove unecessary properties

* Style: fix lint errors

* Acuqire: back compatibility on acquire multiple qubits

* Acuqire: fix linter

* Acquire: refactor

* Acquire: fix implicit acquires; todo: revisit _validate_meas_map method

* Acquire: pylint fix

* Acquire: minor fixes

* Acquire: fix add implicits acquires function

* Acquire: instruction properties fix

* Acquire: remove test for validating meas map

* Linter: fix errors

* Acquire: style fix

* Acquire: remove deprecation in acquires property + fix positional arguments

* Acquire: back and forward compatibility

* Acquire: remove deprecation warning (hm, I thought I removed it before... weird ;) )

* Acquire: grammar fixes + split schedule acquire test

* Acquire: add release note

* Acquire: release notes remove issues

Co-authored-by: Lauren Capelluto <laurencapelluto@gmail.com>

qiskit/assembler/assemble_schedules.py

@@ -81,6 +81,7 @@ def assemble_schedules(schedules, qobj_id, qobj_header, run_config):
         # instructions
         max_memory_slot = 0
         qobj_instructions = []
+        acquire_instructions = []
 
         # Instructions are returned as tuple of shifted time and instruction
         for shift, instruction in schedule.instructions:
@@ -111,13 +112,16 @@ def assemble_schedules(schedules, qobj_id, qobj_header, run_config):
             elif isinstance(instruction, AcquireInstruction):
                 max_memory_slot = max(max_memory_slot,
                                       *[slot.index for slot in instruction.mem_slots])
-                if meas_map:
-                    # verify all acquires satisfy meas_map
-                    _validate_meas_map(instruction, meas_map)
+
+                acquire_instructions.append(instruction)
 
             converted_instruction = instruction_converter(shift, instruction)
             qobj_instructions.append(converted_instruction)
 
+        if meas_map:
+            # verify all acquires satisfy meas_map
+            _validate_meas_map(acquire_instructions, meas_map)
+
         # memory slot size is memory slot index + 1 because index starts from zero
         exp_memory_slot_size = max_memory_slot + 1
         memory_slot_size = max(memory_slot_size, exp_memory_slot_size)
@@ -199,11 +203,16 @@ def assemble_schedules(schedules, qobj_id, qobj_header, run_config):
                      header=qobj_header)
 
 
-def _validate_meas_map(acquire, meas_map):
+def _validate_meas_map(instructions, meas_map):
     """Validate all qubits tied in meas_map are to be acquired."""
     meas_map_set = [set(m) for m in meas_map]
     # Verify that each qubit is listed once in measurement map
-    measured_qubits = {acq_ch.index for acq_ch in acquire.acquires}
+
+    acquires = []
+    for inst in instructions:
+        acquires += inst.acquires
+    measured_qubits = {acq_ch.index for acq_ch in acquires}
+
     tied_qubits = set()
     for meas_qubit in measured_qubits:
         for map_inst in meas_map_set:

qiskit/pulse/commands/acquire.py

@@ -15,7 +15,8 @@
 """
 Acquire.
 """
-from typing import Union, List, Optional
+import warnings
+from typing import Optional, Union, List
 
 from qiskit.pulse.channels import Qubit, MemorySlot, RegisterSlot, AcquireChannel
 from qiskit.pulse.exceptions import PulseError
@@ -93,11 +94,15 @@ def __repr__(self):
 
     # pylint: disable=arguments-differ
     def to_instruction(self,
-                       qubits: Union[Qubit, List[Qubit]],
-                       mem_slots: Optional[Union[MemorySlot, List[MemorySlot]]] = None,
+                       qubit: Union[AcquireChannel, List[AcquireChannel]],
+                       mem_slot: Optional[Union[MemorySlot, List[MemorySlot]]] = None,
                        reg_slots: Optional[Union[RegisterSlot, List[RegisterSlot]]] = None,
+                       mem_slots: Optional[Union[List[MemorySlot]]] = None,
+                       reg_slot: Optional[RegisterSlot] = None,
                        name: Optional[str] = None) -> 'AcquireInstruction':
-        return AcquireInstruction(self, qubits, mem_slots, reg_slots, name=name)
+
+        return AcquireInstruction(self, qubit, mem_slot=mem_slot, reg_slot=reg_slot,
+                                  mem_slots=mem_slots, reg_slots=reg_slots, name=name)
     # pylint: enable=arguments-differ
 
 
@@ -106,40 +111,72 @@ class AcquireInstruction(Instruction):
 
     def __init__(self,
                  command: Acquire,
-                 acquires: Union[AcquireChannel, List[AcquireChannel]],
-                 mem_slots: Union[MemorySlot, List[MemorySlot]],
+                 acquire: Union[AcquireChannel, List[AcquireChannel]],
+                 mem_slot: Optional[Union[MemorySlot, List[MemorySlot]]] = None,
                  reg_slots: Optional[Union[RegisterSlot, List[RegisterSlot]]] = None,
+                 mem_slots: Optional[Union[List[MemorySlot]]] = None,
+                 reg_slot: Optional[RegisterSlot] = None,
                  name: Optional[str] = None):
 
-        if not isinstance(acquires, list):
-            acquires = [acquires]
+        if isinstance(acquire, list) or isinstance(mem_slot, list) or reg_slots:
+            warnings.warn('The AcquireInstruction no longer supports multiple qubits, '
+                          'multiple memory slots and multiple reg slots. '
+                          'This behavior has been deprecated. The parameter '
+                          '"mem_slots" has been replaced by "mem_slot" and '
+                          '"reg_slots" has been replaced by "reg_slot"', DeprecationWarning, 3)
+
+        if not isinstance(acquire, list):
+            acquire = [acquire]
 
-        if isinstance(acquires[0], Qubit):
+        if isinstance(acquire[0], Qubit):
             raise PulseError("AcquireInstruction can not be instantiated with Qubits, "
                              "which are deprecated.")
 
-        if not (mem_slots or reg_slots):
+        if mem_slot and not isinstance(mem_slot, list):
+            mem_slot = [mem_slot]
+        elif mem_slots:
+            mem_slot = mem_slots
+
+        if reg_slot:
+            reg_slot = [reg_slot]
+        elif reg_slots and not isinstance(reg_slots, list):
+            reg_slot = [reg_slots]
+        else:
+            reg_slot = reg_slots
+
+        if not (mem_slot or reg_slot):
             raise PulseError('Neither memoryslots or registers were supplied')
 
-        if mem_slots:
-            if isinstance(mem_slots, MemorySlot):
-                mem_slots = [mem_slots]
-            elif len(acquires) != len(mem_slots):
-                raise PulseError("#mem_slots must be equals to #acquires")
-
-        if reg_slots:
-            if isinstance(reg_slots, RegisterSlot):
-                reg_slots = [reg_slots]
-            if len(acquires) != len(reg_slots):
-                raise PulseError("#reg_slots must be equals to #acquires")
+        if mem_slot and len(acquire) != len(mem_slot):
+            raise PulseError("The number of mem_slots must be equals to the number of acquires")
+
+        if reg_slot:
+            if len(acquire) != len(reg_slot):
+                raise PulseError("The number of reg_slots must be equals "
+                                 "to the number of acquires")
         else:
-            reg_slots = []
+            reg_slot = []
 
-        super().__init__(command, *acquires, *mem_slots, *reg_slots, name=name)
+        super().__init__(command, *acquire, *mem_slot, *reg_slot, name=name)
 
-        self._acquires = acquires
-        self._mem_slots = mem_slots
-        self._reg_slots = reg_slots
+        self._acquires = acquire
+        self._mem_slots = mem_slot
+        self._reg_slots = reg_slot
+
+    @property
+    def acquire(self):
+        """Acquire channel to be acquired on."""
+        return self._acquires[0] if self._acquires else None
+
+    @property
+    def mem_slot(self):
+        """MemorySlot."""
+        return self._mem_slots[0] if self._mem_slots else None
+
+    @property
+    def reg_slot(self):
+        """RegisterSlot."""
+        return self._reg_slots[0] if self._reg_slots else None
 
     @property
     def acquires(self):
@@ -149,9 +186,13 @@ def acquires(self):
     @property
     def mem_slots(self):
         """MemorySlots."""
+        warnings.warn('"mem_slots" is deprecated and being replaced by "mem_slot"',
+                      DeprecationWarning, 3)
         return self._mem_slots
 
     @property
     def reg_slots(self):
         """RegisterSlots."""
+        warnings.warn('"reg_slots" is deprecated and being replaced by "reg_slot"',
+                      DeprecationWarning, 3)
         return self._reg_slots

qiskit/pulse/commands/instruction.py

@@ -45,7 +45,7 @@ def __init__(self, command, *channels: List[Channel],
         duration = command.duration
 
         self._timeslots = TimeslotCollection(*(Timeslot(Interval(0, duration), channel)
-                                               for channel in channels))
+                                               for channel in channels if channel is not None))
 
         channels = self.channels
 

qiskit/pulse/reschedule.py

@@ -140,12 +140,14 @@ def add_implicit_acquires(schedule: ScheduleComponent, meas_map: List[List[int]]
         Schedule
     """
     new_schedule = Schedule(name=schedule.name)
+    acquire_map = dict()
 
     for time, inst in schedule.instructions:
         if isinstance(inst, AcquireInstruction):
             if any([acq.index != mem.index for acq, mem in zip(inst.acquires, inst.mem_slots)]):
                 warnings.warn("One of your acquires was mapped to a memory slot which didn't match"
                               " the qubit index. I'm relabeling them to match.")
+
             cmd = Acquire(inst.duration, inst.command.discriminator, inst.command.kernel)
             # Get the label of all qubits that are measured with the qubit(s) in this instruction
             existing_qubits = {chan.index for chan in inst.acquires}
@@ -155,10 +157,14 @@ def add_implicit_acquires(schedule: ScheduleComponent, meas_map: List[List[int]]
                     all_qubits.extend(sublist)
             # Replace the old acquire instruction by a new one explicitly acquiring all qubits in
             # the measurement group.
-            new_schedule |= AcquireInstruction(
-                cmd,
-                [AcquireChannel(i) for i in all_qubits],
-                [MemorySlot(i) for i in all_qubits]) << time
+            for i in all_qubits:
+                explicit_inst = AcquireInstruction(cmd, AcquireChannel(i), MemorySlot(i)) << time
+                if time not in acquire_map:
+                    new_schedule |= explicit_inst
+                    acquire_map = {time: {i}}
+                elif i not in acquire_map[time]:
+                    new_schedule |= explicit_inst
+                    acquire_map[time].add(i)
         else:
             new_schedule |= inst << time
 

qiskit/qobj/converters/pulse_instruction.py

@@ -321,15 +321,15 @@ def convert_acquire(self, instruction):
         t0 = instruction.t0
         duration = instruction.duration
         qubits = instruction.qubits
-        qubit_channels = [channels.AcquireChannel(qubit) for qubit in qubits]
+        acquire_channels = [channels.AcquireChannel(qubit) for qubit in qubits]
 
         mem_slots = [channels.MemorySlot(instruction.memory_slot[i]) for i in range(len(qubits))]
 
         if hasattr(instruction, 'register_slot'):
             register_slots = [channels.RegisterSlot(instruction.register_slot[i])
                               for i in range(len(qubits))]
         else:
-            register_slots = None
+            register_slots = [None] * len(qubits)
 
         discriminators = (instruction.discriminators
                           if hasattr(instruction, 'discriminators') else None)
@@ -356,8 +356,9 @@ def convert_acquire(self, instruction):
 
         cmd = commands.Acquire(duration, discriminator=discriminator, kernel=kernel)
         schedule = Schedule()
-        schedule |= commands.AcquireInstruction(cmd, qubit_channels, mem_slots,
-                                                register_slots) << t0
+
+        for acquire_channel, mem_slot, reg_slot in zip(acquire_channels, mem_slots, register_slots):
+            schedule |= commands.AcquireInstruction(cmd, acquire_channel, mem_slot, reg_slot) << t0
 
         return schedule
 

qiskit/scheduler/methods/basic.py

@@ -157,16 +157,15 @@ def get_measure_schedule() -> CircuitPulseDef:
             default_sched = inst_map.get('measure', qubits)
             for time, inst in default_sched.instructions:
                 if isinstance(inst, AcquireInstruction):
-                    mem_slots = []
                     for channel in inst.acquires:
                         if channel.index in qubit_mem_slots.keys():
-                            mem_slots.append(MemorySlot(qubit_mem_slots[channel.index]))
+                            mem_slot = MemorySlot(qubit_mem_slots[channel.index])
                         else:
-                            mem_slots.append(MemorySlot(unused_mem_slots.pop()))
-                    new_acquire = AcquireInstruction(command=inst.command,
-                                                     acquires=inst.acquires,
-                                                     mem_slots=mem_slots)
-                    sched._union((time, new_acquire))
+                            mem_slot = MemorySlot(unused_mem_slots.pop())
+                        sched._union((time, AcquireInstruction(command=inst.command,
+                                                               acquire=channel,
+                                                               mem_slot=mem_slot)))
+
                 # Measurement pulses should only be added if its qubit was measured by the user
                 elif inst.channels[0].index in qubit_mem_slots.keys():
                     sched._union((time, inst))

releasenotes/notes/acquire-single-channel-ea83cef8d991f945.yaml

@@ -0,0 +1,20 @@
+---
+prelude: >
+    Acquire and AcquireInstruction now can be applied to a single channel
+features:
+  - |
+    Within the terra API allow acquires be applied to a single qubit.
+    This makes pulse programming more consistent and easier to reason
+    about as all operations in pulse would then be for single channels.
+    For example:
+
+      acquire = Acquire(duration=10)
+      schedule = Schedule()
+      schedule.insert(60, acquire(AcquireChannel(0), MemorySlot(0), RegisterSlot(0)))
+      schedule.insert(60, acquire(AcquireChannel(1), MemorySlot(1), RegisterSlot(1)))
+
+deprecations:
+  - |
+    Acquire on multiple qubits has been deprecated.
+    ``AcquireInstruction`` parameters ``mem_slots``, ``reg_slots`` has been deprecated,
+    use ``reg_slot``, ``mem_slot`` instead.