quantify-scheduler exporter

The quantify-scheduler exporter (ExportFormat.QUANTIFY_SCHEDULER) exports the circuit to Schedule object and a bitstring mapping.

The latter can be used to relate the measurement outcomes to the (virtual) bit variables they have been assigned to in the cQASM circuit: this connection is lost in the Schedule.

Under active development

The bitstring mapping, currently, consists of a list of ordered pairs; the first element denotes the acquisition index \(i\) and the second element denotes the qubit index \(j\). The acquisition index represents the \(i\)-th measurement on qubit at index \(j\). The index \(k\) of the ordered pair in the bitstring mapping corresponds to the index of the (virtual) bit register, referring to the (virtual) bit variable the outcome of measurement \((i,j)\) has been assigned to in the cQASM circuit.

[
    (<acquisition-index-i: int>, <qubit-index-j: int>),
    (<acquisition-index-i: int>, <qubit-index-j: int>),
    ...
    <(i,j)-at-index-k: tuple[int, int]>,
    ...
]

A redesign of the bitstring mapping is under active development.

Here are some important differences to take note of:

All qubit register declarations are combined into a single (virtual) qubit register (q) statement.
Bit registers declarations and assignments of measurement outcomes to bit register variables are discarded; quantify-scheduler does not support bit registers or variables. Note that the measurement statement is not discarded; the measure instruction is translated to Measure. Furthermore, measurement outcomes are related to the (virtual) bit registers they were assigned to in the cQASM circuit through the bitstring mapping, as described above.
The non-unitary init instruction is ignored and reset instruction is translated to Reset. The reset instruction can be used to set the state of the qubit to the \(|0\rangle\) state, similar to the effect of the init instruction.
Single gate multi qubit (SGMQ) notation is unpacked; the gate is applied to each qubit on a separate line.
Control instructions (barrier and wait) are currently not supported. Note: processing of the control instructions is currently under active development, but not yet part of the latest version of OpenSquirrel.
Angles are translated from radians to degrees.

Unsupported gates

The quantify-scheduler exporter does not support the Rn gate in general. Unless both the \(n_x\) and \(n_y\) components are zero, or just the \(n_z\) component is zero, it will raise an error (UnSupportedGateError) if this gate is part of the circuit that is to be exported.

The same error is raised if the circuit to be exported contains a Hadamard, SWAP, or any arbitrary two-qubit gate that is not either a CNOT or CZ gate. Decomposition passes can be used to decompose the circuit to gates that the quantify-scheduler exporter supports.

The four examples below show how circuits written in cQASM are exported to a quantify-scheduler Schedule.

Simple circuitRegistersinit and reset

from opensquirrel import Circuit
from opensquirrel.passes.exporter import ExportFormat

circuit = Circuit.from_string(
    """
    version 3.0

    qubit[2] q
    bit[2] b

    H q[0]
    CNOT q[0], q[1]
    b = measure q
    """
)

exported_schedule, bitstring_mapping = circuit.export(fmt=ExportFormat.QUANTIFY_SCHEDULER)

for schedulable in exported_schedule.schedulables.values():
    print(exported_schedule.operations[schedulable["operation_id"]].name)
print('\n', "bitstring mapping: ", bitstring_mapping)

Rxy(90, 90, 'q[0]')
Rxy(180, 0, 'q[0]')
CNOT (q[0], q[1])
Measure q[0]
Measure q[1]

bitstring mapping:  [(0, 0), (0, 1)]

Note that the bit register declaration and assignment to bit variables have been discarded (2.), the SGMQ notation has been unpacked (4.), and the angles have been translated from radians to degrees (6.). The numbers refer to the differences listed above.

According to the description of the bitstring mapping above, note that the outcome of the first measurement on qubit at index \(0\), \((i,j) = (0,0)\), is mapped to the (virtual) bit variable (\(k=0\); the first ordered pair), and the outcome of the first measurement on qubit at index \(1\), \((i,j) = (0,1)\), is mapped to the (virtual) bit variable (\(k=1\); the second ordered pair).

from opensquirrel import Circuit
from opensquirrel.passes.exporter import ExportFormat

circuit = Circuit.from_string(
    """
    version 3.0

    qubit[2] qA
    bit[3] bA

    H qA[0]
    CNOT qA[0], qA[1]

    bA[1,2] = measure qA

    qubit[3] qB
    bit[2] bB

    H qB[1]
    CNOT qB[1], qA[1]

    bB[0] = measure qB[1]
    bB[1] = measure qA[1]
    """
)

exported_circuit = circuit.export(fmt=ExportFormat.QUANTIFY_SCHEDULER)
for schedulable in exported_schedule.schedulables.values():
    print(exported_schedule.operations[schedulable["operation_id"]].name)
print('\n', "bitstring mapping: ", bitstring_mapping)

Rxy(90, 90, 'q[0]')
Rxy(180, 0, 'q[0]')
CNOT (q[0], q[1])
Measure q[0]
Measure q[1]
Rxy(90, 90, 'q[3]')
Rxy(180, 0, 'q[3]')
CNOT (q[3], q[1])
Measure q[3]
Measure q[1]

bitstring mapping:  [(None, None), (0, 0), (0, 1), (0, 3), (1, 1)]

Note that all qubit register declarations are combined into a single (virtual) qubit register (1.), the bit register declaration and assignment to bit variables have been discarded (2.), the SGMQ notation has been unpacked (4.), and the angles have been translated from radians to degrees (6.). The numbers refer to the differences listed above.

In particular, this example illustrates that all qubit registers have been combined into a single (virtual) qubit register q, i.e., the registers qA and qB have been concatenated into q, such that qA[0], qA[1] = q[0], q[1] and qB[0], qB[1], qB[2] = q[2], q[3], q[4]. The qubit registers are concatenated in the order they are declared.

Moreover, even though the bit registers have been discarded in the circuit, the mapping from meausurement to (virtual) bit variable has been stored in the bitstring mapping. Note that, just like with the translation of the qubit register declarations to the single virtual register q, the bit register declarations are also concatenated in the order they are declared into a single bit register b. In this example, the virtual bit register translation is as follows: bA[0], bA[1], bA[2] = b[0], b[1], b[2] and bB[0], bB[1] = b[3], b[4]. Accodingly, the \(k\)-th element in the bitstring mapping corresponds to the \(k\)-th element of the bit register.

For instance, the statement bB[1] = measure qA[1] in the original circuit becomes, in terms of virtual registers, b[4] = measure q[1]. Since this is the second measurement on q[1], the acquisition index is \(i = 1\) (counting starts at \(0\)) and the qubit index is \(j = 1\), such that the measurement is given by the ordered pair \((1, 1)\). Because the outcome of this measurement is stored in b[4], the ordered pair is at index \(4\) in the bitregister mapping.

from opensquirrel import Circuit
from opensquirrel.passes.exporter import ExportFormat

circuit = Circuit.from_string(
    """
    version 3.0

    qubit[2] q
    bit[2] b

    init q

    H q[0]
    CNOT q[0], q[1]
    b = measure q

    reset q

    H q[0]
    Z q[0]
    CNOT q[0], q[1]
    b = measure q
    """
)

exported_circuit = circuit.export(fmt=ExportFormat.QUANTIFY_SCHEDULER)
for schedulable in exported_schedule.schedulables.values():
    print(exported_schedule.operations[schedulable["operation_id"]].name)
print('\n', "bitstring mapping: ", bitstring_mapping)

Rxy(90, 90, 'q[0]')
Rxy(180, 0, 'q[0]')
CNOT (q[0], q[1])
Measure q[0]
Measure q[1]
Reset q[0]
Reset q[1]
Rxy(90, 90, 'q[0]')
Rxy(180, 0, 'q[0]')
Rz(180, 'q[0]')
CNOT (q[0], q[1])
Measure q[0]
Measure q[1]

bitstring mapping:  [(1, 0), (1, 1)]

Note that the bit register declaration and assignment to bit variables have been discarded (2.), the init instructions have been ignored and the reset instructions have been translated to Reset, the SGMQ notation has been unpacked (4.), and the angles have been translated from radians to degrees (6.). The numbers refer to the differences listed above.

The quantify-scheduler operation library does not distinguish between an init and a reset instruction. For now, the init instruction is ignored and the reset instruction is translated to Reset. Note that one can us the reset instruction to set the state of the qubit to the \(|0\rangle\) state, which is similar to the effect of the init instruction.

macOS ARM not supported

The quantify-scheduler exporter cannot run on macOS ARM, due to the fact that the required dependency pyqt5-qt5==5.15.2 does provide binaries for that architecture.