Permutation Bloq

qualtran/bloqs/arithmetic/addition.py

@@ -14,6 +14,7 @@
 import math
 from functools import cached_property
 from typing import (
+    cast,
     Dict,
     Iterable,
     Iterator,
@@ -44,6 +45,7 @@
     DecomposeTypeError,
     GateWithRegisters,
     QBit,
+    QDType,
     QInt,
     QMontgomeryUInt,
     QUInt,
@@ -59,12 +61,12 @@
 from qualtran.bloqs.mcmt.multi_control_multi_target_pauli import MultiControlX
 from qualtran.cirq_interop import decompose_from_cirq_style_method
 from qualtran.drawing import directional_text_box, Text
+from qualtran.symbolics import is_symbolic, SymbolicInt
 
 if TYPE_CHECKING:
     from qualtran.drawing import WireSymbol
     from qualtran.resource_counting import BloqCountT, SympySymbolAllocator
     from qualtran.simulation.classical_sim import ClassicalValT
-    from qualtran.symbolics import SymbolicInt
 
 
 @frozen
@@ -359,6 +361,63 @@ def _cvs_converter(vv):
     return tuple(int(v) for v in vv)
 
 
+@frozen
+class XorK(Bloq):
+    r"""Maps |x> to |x \oplus k> for a constant k.
+
+    Args:
+        dtype: Data type of the input register `x`.
+        k: The classical integer value to be XOR-ed to x.
+        cvs: A tuple of control values. Each entry specifies whether that control line is a
+            "positive" control (`cv[i]=1`) or a "negative" control (`cv[i]=0`).
+
+    Registers:
+        x: A quantum register of type `self.dtype` (see above).
+        ctrls: A sequence of control qubits (only when `cvs` is non-empty).
+    """
+    dtype: QDType
+    k: SymbolicInt
+    cvs: Tuple[int, ...] = field(converter=_cvs_converter, default=())
+
+    @cached_property
+    def signature(self) -> 'Signature':
+        return Signature(
+            ((Register('ctrls', QBit(), shape=(len(self.cvs),)),) if len(self.cvs) > 0 else ())
+            + (Register('x', self.dtype),)
+        )
+
+    @cached_property
+    def bitsize(self) -> SymbolicInt:
+        return self.dtype.num_qubits
+
+    def is_symbolic(self):
+        return is_symbolic(self.k, self.dtype)
+
+    def build_composite_bloq(self, bb: 'BloqBuilder', **soqs: 'SoquetT') -> Dict[str, 'SoquetT']:
+        if self.is_symbolic():
+            raise DecomposeTypeError(f"cannot decompose symbolic {self}")
+
+        xs = bb.split(cast(Soquet, soqs.pop('x')))
+        ctrls = soqs.pop('ctrls', None)
+
+        for i, bit in enumerate(self.dtype.to_bits(self.k)):
+            if bit == 1:
+                if len(self.cvs) > 0 and ctrls is not None:
+                    ctrls, xs[i] = bb.add(MultiControlX(cvs=self.cvs), ctrls=ctrls, x=xs[i])
+                else:
+                    xs[i] = bb.add(XGate(), q=xs[i])
+
+        soqs['x'] = bb.join(xs)
+        if ctrls is not None:
+            soqs['ctrls'] = ctrls
+        return soqs
+
+    def build_call_graph(self, ssa: 'SympySymbolAllocator') -> Set['BloqCountT']:
+        bit_flip_bloq = MultiControlX(cvs=self.cvs) if len(self.cvs) > 0 else XGate()
+        num_flips = self.bitsize if self.is_symbolic() else sum(self.dtype.to_bits(self.k))
+        return {(bit_flip_bloq, num_flips)}
+
+
 @frozen
 class AddK(Bloq):
     r"""Takes |x> to |x + k> for a classical integer `k`.
@@ -431,46 +490,23 @@ def build_composite_bloq(
             ctrls = None
         k = bb.allocate(dtype=x.reg.dtype)
 
-        # Get binary representation of k and split k into separate wires.
-        k_split = bb.split(k)
-        if self.signed:
-            binary_rep = QInt(self.bitsize).to_bits(self.k)
+        xor_k_bloq = XorK(x.reg.dtype, self.k, self.cvs)
+        if ctrls is not None:
+            ctrls, k = bb.add(xor_k_bloq, ctrls=ctrls, x=k)
         else:
-            binary_rep = QUInt(self.bitsize).to_bits(self.k)
-
-        # Apply XGates to qubits in k where the bitstring has value 1. Apply CNOTs when the gate is
-        # controlled.
-        for i in range(self.bitsize):
-            if binary_rep[i] == 1:
-                if len(self.cvs) > 0 and ctrls is not None:
-                    ctrls, k_split[i] = bb.add(
-                        MultiControlX(cvs=self.cvs), ctrls=ctrls, x=k_split[i]
-                    )
-                else:
-                    k_split[i] = bb.add(XGate(), q=k_split[i])
+            k = bb.add(xor_k_bloq, x=k)
 
-        # Rejoin the qubits representing k for in-place addition.
-        k = bb.join(k_split, dtype=x.reg.dtype)
         if not isinstance(x.reg.dtype, (QInt, QUInt, QMontgomeryUInt)):
             raise ValueError(
                 "Only QInt, QUInt and QMontgomerUInt types are supported for composite addition."
             )
         k, x = bb.add(Add(x.reg.dtype, x.reg.dtype), a=k, b=x)
 
-        # Resplit the k qubits in order to undo the original bit flips to go from the binary
-        # representation back to the zero state.
-        k_split = bb.split(k)
-        for i in range(self.bitsize):
-            if binary_rep[i] == 1:
-                if len(self.cvs) > 0 and ctrls is not None:
-                    ctrls, k_split[i] = bb.add(
-                        MultiControlX(cvs=self.cvs), ctrls=ctrls, x=k_split[i]
-                    )
-                else:
-                    k_split[i] = bb.add(XGate(), q=k_split[i])
-
+        if ctrls is not None:
+            ctrls, k = bb.add(xor_k_bloq, ctrls=ctrls, x=k)
+        else:
+            k = bb.add(xor_k_bloq, x=k)
         # Free the ancilla qubits.
-        k = bb.join(k_split, dtype=x.reg.dtype)
         bb.free(k)
 
         # Return the output registers.

qualtran/bloqs/arithmetic/comparison.py

@@ -38,6 +38,7 @@
     Bloq,
     bloq_example,
     BloqDocSpec,
+    DecomposeTypeError,
     GateWithRegisters,
     QAny,
     QBit,
@@ -48,12 +49,12 @@
     Soquet,
     SoquetT,
 )
-from qualtran.bloqs.basic_gates import CNOT, TGate, XGate
+from qualtran.bloqs.basic_gates import CNOT, XGate
 from qualtran.bloqs.mcmt.and_bloq import And, MultiAnd
 from qualtran.bloqs.mcmt.multi_control_multi_target_pauli import MultiControlX
 from qualtran.drawing import WireSymbol
 from qualtran.drawing.musical_score import Text, TextBox
-from qualtran.symbolics import is_symbolic, SymbolicInt
+from qualtran.symbolics import HasLength, is_symbolic, SymbolicInt
 
 if TYPE_CHECKING:
     from qualtran import BloqBuilder
@@ -926,7 +927,7 @@ def _gt_k() -> GreaterThanConstant:
 
 @frozen
 class EqualsAConstant(Bloq):
-    r"""Implements $U_a|x\rangle = U_a|x\rangle|z\rangle = |x\rangle |z \land (x = a)\rangle$
+    r"""Implements $U_a|x\rangle|z\rangle = |x\rangle |z \oplus (x = a)\rangle$
 
     The bloq_counts and t_complexity are derived from:
     https://qualtran.readthedocs.io/en/latest/bloqs/comparison_gates.html#equality-as-a-special-case
@@ -940,8 +941,8 @@ class EqualsAConstant(Bloq):
         target: Register to hold result of comparison.
     """
 
-    bitsize: int
-    val: int
+    bitsize: SymbolicInt
+    val: SymbolicInt
 
     @cached_property
     def signature(self) -> Signature:
@@ -956,10 +957,62 @@ def wire_symbol(self, reg: Optional[Register], idx: Tuple[int, ...] = tuple()) -
             return TextBox(f"⨁(x = {self.val})")
         raise ValueError(f'Unknown register symbol {reg.name}')
 
+    def is_symbolic(self):
+        return is_symbolic(self.bitsize, self.val)
+
+    def build_composite_bloq(
+        self, bb: 'BloqBuilder', x: 'Soquet', target: 'Soquet'
+    ) -> Dict[str, 'SoquetT']:
+        if self.is_symbolic():
+            raise DecomposeTypeError(f"cannot decompose symbolic {self}")
+
+        bits_k = x.reg.dtype.to_bits(self.val)
+
+        if self.bitsize == 1:
+            # Note: when self.val = 0, this is just a negative-control CNOT.
+            if self.val == 0:
+                x = bb.add(XGate(), q=x)
+            x, target = bb.add(CNOT(), ctrl=x, target=target)
+            if self.val == 0:
+                x = bb.add(XGate(), q=x)
+        elif self.bitsize == 2:
+            and_bloq = And(bits_k[0], bits_k[1])
+
+            xs = bb.split(x)
+            xs, and_xs = bb.add(and_bloq, ctrl=xs)
+            and_xs, target = bb.add(CNOT(), ctrl=and_xs, target=target)
+            xs = bb.add(and_bloq.adjoint(), ctrl=xs, target=and_xs)
+            x = bb.join(xs)
+        else:
+            multi_and_bloq = MultiAnd(tuple(bits_k))
+
+            xs = bb.split(x)
+            xs, junk, and_xs = bb.add(multi_and_bloq, ctrl=xs)
+            and_xs, target = bb.add(CNOT(), ctrl=and_xs, target=target)
+            xs = bb.add(multi_and_bloq.adjoint(), ctrl=xs, junk=junk, target=and_xs)
+            x = bb.join(xs)
+
+        return {'x': x, 'target': target}
+
     def build_call_graph(self, ssa: 'SympySymbolAllocator') -> Set['BloqCountT']:
-        # See: https://github.com/quantumlib/Qualtran/issues/219
-        # See: https://github.com/quantumlib/Qualtran/issues/217
-        return {(TGate(), 4 * (self.bitsize - 1))}
+        if not self.is_symbolic():
+            return super().build_call_graph(ssa)
+
+        op: Bloq
+        if not is_symbolic(self.bitsize) and self.bitsize <= 2:
+            if self.bitsize == 1:
+                op = XGate()
+            else:
+                cv = ssa.new_symbol('cv')
+                op = And(cv, cv)
+        else:
+            op = MultiAnd(HasLength(self.bitsize))
+
+        bloq_counts: dict[Bloq, int] = defaultdict(lambda: 0)
+        bloq_counts[op] += 1
+        bloq_counts[op.adjoint()] += 1
+        bloq_counts[CNOT()] += 1
+        return set(bloq_counts.items())
 
 
 def _make_equals_a_constant():

qualtran/bloqs/arithmetic/comparison_test.py

@@ -298,7 +298,9 @@ def test_equals_a_constant():
     qlt_testing.assert_wire_symbols_match_expected(
         EqualsAConstant(bitsize, 17), ['In(x)', '⨁(x = 17)']
     )
-    assert t_complexity(EqualsAConstant(bitsize, 17)) == TComplexity(t=4 * (bitsize - 1))
+    assert t_complexity(EqualsAConstant(bitsize, 17)) == TComplexity(
+        t=4 * (bitsize - 1), clifford=65
+    )
 
 
 @pytest.mark.notebook