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QiskitBackend translates a b01t IRProgram into a Qiskit QuantumCircuit. Use it as the final step after building and (optionally) lowering your b01t program. The backend requires qiskit to be installed separately — b01t does not depend on it by default. 
pip install qiskit

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QiskitBackend

from b01t import QiskitBackend

backend = QiskitBackend()
QiskitBackend has no constructor arguments. Create one instance and reuse it across multiple programs.

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QiskitBackend.emit

backend.emit(ir: IRProgram) -> QuantumCircuit
Compiles an IRProgram into a Qiskit QuantumCircuit. Each QReg in the program becomes a QuantumRegister with the same name and size. Measurement ops add a corresponding ClassicalRegister automatically.
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ir
IRProgram
required
The compiled IR program to emit. Obtain this from .build() on a @parametric or @adaptive function, or from lower_exact_program() on an ExactProgram.
Returns: a qiskit.QuantumCircuit with the same register layout and gate sequence as the input IR. Raises:
  • DSLValidationError — if qiskit is not installed, or if the IR contains an IfOp (classical feed-forward is not supported in the current release).
  • DSLValidationError — if the IR contains a gate name not supported by the backend.

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Supported gates

The backend supports all gates in the b01t exact and parametric gate sets: x, h, z, s, sdg, t, tdg, rx, ry, rz, cx, cz, swap, cry, crz, ccx, ccz, mcx, mcz, measure, measure_all. IfOp (from if_then) is not lowered and raises DSLValidationError.

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Full example: @coherent to QuantumCircuit

from b01t import coherent, QReg, h, cx
from b01t import QiskitBackend
from b01t.core.exact_lowering import lower_exact_program

@coherent
def bell(a: QReg, b: QReg) -> None:
    h(a[0])
    cx(a[0], b[0])

# Step 1: build the exact program
exact = bell.build_exact(("a", 1), ("b", 1))

# Step 2: lower to broad IR
ir = lower_exact_program(exact)

# Step 3: emit to Qiskit
backend = QiskitBackend()
circuit = backend.emit(ir)

print(circuit)
#      ┌───┐
# a_0: ┤ H ├──■──
#      └───┘┌─┴─┐
# b_0: ─────┤ X ├
#            └───┘

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Example: @parametric to QuantumCircuit

from b01t import parametric, QReg, h, rz, cx
from b01t import QiskitBackend
import math

@parametric
def ansatz(q: QReg) -> None:
    h(q[0])
    rz(math.pi / 4, q[0])
    cx(q[0], q[1])

ir = ansatz.build(("q", 2))
backend = QiskitBackend()
circuit = backend.emit(ir)

print(circuit)

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Example: @adaptive with measurement

from b01t import adaptive, QReg, h, measure, x
from b01t import QiskitBackend

@adaptive
def measure_and_reset(q: QReg) -> None:
    h(q[0])
    measure(q[0])

ir = measure_and_reset.build(("q", 1))
backend = QiskitBackend()
circuit = backend.emit(ir)
# A ClassicalRegister "c_q_0" is automatically added

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Unsupported gate error

If you pass an IR that contains an unrecognised gate name, the backend raises DSLValidationError: 
from b01t.core.types import IRProgram, GateOp, Wire, Effect

bad_ir = IRProgram(
    name="bad",
    effect=Effect.COHERENT,
    regs=[],
    ops=[GateOp(name="unknown_gate", wires=(Wire("q", 0),))],
    is_safe=False,
)

backend = QiskitBackend()
backend.emit(bad_ir)
# DSLValidationError: backend does not support gate 'unknown_gate'