def test_non_gaussian_operation(self):
        """Test that a non-Gaussian operation succeeding
        a differentiable Gaussian operation results in
        numeric differentiation."""

        with qml.tape.JacobianTape() as tape:
            qml.Rotation(1.0, wires=[0])
            qml.Rotation(1.0, wires=[1])
            # Non-Gaussian
            qml.Kerr(1.0, wires=[1])
            qml.expval(qml.P(0))
            qml.expval(qml.X(1))

        # First rotation gate has no succeeding non-Gaussian operation
        assert _grad_method(tape, 0) == "A"
        # Second rotation gate does no succeeding non-Gaussian operation
        assert _grad_method(tape, 1) == "F"
        # Kerr gate does not support the parameter-shift rule
        assert _grad_method(tape, 2) == "F"

        with qml.tape.JacobianTape() as tape:
            qml.Rotation(1.0, wires=[0])
            qml.Rotation(1.0, wires=[1])
            # entangle the modes
            qml.Beamsplitter(1.0, 0.0, wires=[0, 1])
            # Non-Gaussian
            qml.Kerr(1.0, wires=[1])
            qml.expval(qml.P(0))
            qml.expval(qml.X(1))

        # After entangling the modes, the Kerr gate now succeeds
        # both initial rotations
        assert _grad_method(tape, 0) == "F"
        assert _grad_method(tape, 1) == "F"
        assert _grad_method(tape, 2) == "F"
    def test_higher_order_observable(self, monkeypatch):
        """An exception should be raised if the observable is higher than 2nd order."""
        monkeypatch.setattr(qml.P, "ev_order", 3)

        with pytest.raises(NotImplementedError,
                           match="order > 2 not implemented"):
            _transform_observable(qml.P(0), np.identity(3), device_wires=[0])
    def test_incorrect_heisenberg_size(self, monkeypatch):
        """The number of dimensions of a CV observable Heisenberg representation does
        not match the ev_order attribute."""
        monkeypatch.setattr(qml.P, "ev_order", 2)

        with pytest.raises(ValueError, match="Mismatch between the polynomial order"):
            CVParamShiftTape._transform_observable(qml.P(0), np.identity(3), device_wires=[0])
    def test_variance(self):
        """If the variance of the observable is first order, then
        parameter-shift is supported. If the observable is second order,
        however, only finite-differences is supported."""

        with qml.tape.JacobianTape() as tape:
            qml.Rotation(1.0, wires=[0])
            qml.var(qml.P(0))  # first order

        assert _grad_method(tape, 0) == "A"

        with qml.tape.JacobianTape() as tape:
            qml.Rotation(1.0, wires=[0])
            qml.var(qml.NumberOperator(0))  # second order

        assert _grad_method(tape, 0) == "F"

        with qml.tape.JacobianTape() as tape:
            qml.Rotation(1.0, wires=[0])
            qml.Rotation(1.0, wires=[1])
            qml.Beamsplitter(0.5, 0.0, wires=[0, 1])
            qml.var(qml.NumberOperator(0))  # fourth order
            qml.expval(qml.NumberOperator(1))

        assert _grad_method(tape, 0) == "F"
        assert _grad_method(tape, 1) == "F"
        assert _grad_method(tape, 2) == "F"
        assert _grad_method(tape, 3) == "F"
    def test_no_graph_exception(self):
        """Test that an exception is raised for analytically differentiable
        operations if use_graph=False"""
        with CVParamShiftTape() as tape:
            qml.Rotation(0.543, wires=[0])
            expval(qml.P(0))

        with pytest.raises(ValueError, match="must always use the graph"):
            tape._grad_method(0, use_graph=False)
def test_get_spectrum_complains_no_generator():
    """Test that an error is raised if the operator has no generator defined."""

    # Observables have no generator attribute
    with pytest.raises(ValueError, match="Generator of operation"):
        get_spectrum(qml.P(wires=0), decimals=10)

    # CNOT is an operation where generator is an abstract property
    with pytest.raises(ValueError, match="Generator of operation"):
        get_spectrum(qml.CNOT(wires=[0, 1]), decimals=10)
    def test_finite_diff(self, monkeypatch):
        """If an op has grad_method=F, this should be respected
        by the qml.tape.JacobianTape"""
        monkeypatch.setattr(qml.Rotation, "grad_method", "F")

        with qml.tape.JacobianTape() as tape:
            qml.Rotation(0.543, wires=[0])
            qml.Squeezing(0.543, 0, wires=[0])
            qml.expval(qml.P(0))

        assert _grad_method(tape, 0) == "F"
        assert _grad_method(tape, 1) == "A"
        assert _grad_method(tape, 2) == "A"
    def test_finite_diff(self, monkeypatch):
        """If an op has grad_method=F, this should be respected
        by the CVParamShiftTape"""
        monkeypatch.setattr(qml.Rotation, "grad_method", "F")

        with CVParamShiftTape() as tape:
            qml.Rotation(0.543, wires=[0])
            qml.Squeezing(0.543, 0, wires=[0])
            expval(qml.P(0))

        assert tape._grad_method(0) == "F"
        assert tape._grad_method(1) == "A"
        assert tape._grad_method(2) == "A"
    def test_independent(self):
        """Test that an independent variable is properly marked
        as having a zero gradient"""

        with qml.tape.JacobianTape() as tape:
            qml.Rotation(0.543, wires=[0])
            qml.Rotation(-0.654, wires=[1])
            qml.expval(qml.P(0))

        assert _grad_method(tape, 0) == "A"
        assert _grad_method(tape, 1) == "0"

        _gradient_analysis(tape)

        assert tape._par_info[0]["grad_method"] == "A"
        assert tape._par_info[1]["grad_method"] == "0"
    def test_independent(self):
        """Test that an independent variable is properly marked
        as having a zero gradient"""

        with CVParamShiftTape() as tape:
            qml.Rotation(0.543, wires=[0])
            qml.Rotation(-0.654, wires=[1])
            expval(qml.P(0))

        assert tape._grad_method(0) == "A"
        assert tape._grad_method(1) == "0"

        tape._update_gradient_info()

        assert tape._par_info[0]["grad_method"] == "A"
        assert tape._par_info[1]["grad_method"] == "0"
    def test_multiple_output_values(self, tol):
        """Tests correct output shape and evaluation for a tape
        with multiple measurement types"""
        dev = qml.device("default.gaussian", wires=2)
        x = 0.543
        y = -0.654

        with QuantumTape() as tape:
            qml.Displacement(x, 0, wires=[0])
            qml.Squeezing(y, 0, wires=[1])
            qml.Beamsplitter(np.pi / 4, 0, wires=[0, 1])
            qml.expval(qml.PolyXP(np.diag([0, 1, 0]), wires=0))  # X^2
            qml.var(qml.P(1))

        assert tape.output_dim == 2

        res = tape.execute(dev)
        assert res.shape == (2, )
class TestRepresentationResolver:
    """Test the RepresentationResolver class."""
    @pytest.mark.parametrize(
        "list,element,index,list_after",
        [
            ([1, 2, 3], 2, 1, [1, 2, 3]),
            ([1, 2, 2, 3], 2, 1, [1, 2, 2, 3]),
            ([1, 2, 3], 4, 3, [1, 2, 3, 4]),
        ],
    )
    def test_index_of_array_or_append(self, list, element, index, list_after):
        """Test the method index_of_array_or_append."""

        assert RepresentationResolver.index_of_array_or_append(element,
                                                               list) == index
        assert list == list_after

    @pytest.mark.parametrize(
        "par,expected",
        [
            (3, "3"),
            (5.236422, "5.24"),
        ],
    )
    def test_single_parameter_representation(self,
                                             unicode_representation_resolver,
                                             par, expected):
        """Test that single parameters are properly resolved."""
        assert unicode_representation_resolver.single_parameter_representation(
            par) == expected

    @pytest.mark.parametrize(
        "op,wire,target",
        [
            (qml.PauliX(wires=[1]), 1, "X"),
            (qml.CNOT(wires=[0, 1]), 1, "X"),
            (qml.CNOT(wires=[0, 1]), 0, "C"),
            (qml.Toffoli(wires=[0, 2, 1]), 1, "X"),
            (qml.Toffoli(wires=[0, 2, 1]), 0, "C"),
            (qml.Toffoli(wires=[0, 2, 1]), 2, "C"),
            (qml.CSWAP(wires=[0, 2, 1]), 1, "SWAP"),
            (qml.CSWAP(wires=[0, 2, 1]), 2, "SWAP"),
            (qml.CSWAP(wires=[0, 2, 1]), 0, "C"),
            (qml.PauliY(wires=[1]), 1, "Y"),
            (qml.PauliZ(wires=[1]), 1, "Z"),
            (qml.CZ(wires=[0, 1]), 1, "Z"),
            (qml.CZ(wires=[0, 1]), 0, "C"),
            (qml.Identity(wires=[1]), 1, "I"),
            (qml.Hadamard(wires=[1]), 1, "H"),
            (qml.PauliRot(3.14, "XX", wires=[0, 1]), 1, "RX(3.14)"),
            (qml.PauliRot(3.14, "YZ", wires=[0, 1]), 1, "RZ(3.14)"),
            (qml.PauliRot(3.14, "IXYZI", wires=[0, 1, 2, 3, 4
                                                ]), 0, "RI(3.14)"),
            (qml.PauliRot(3.14, "IXYZI", wires=[0, 1, 2, 3, 4
                                                ]), 1, "RX(3.14)"),
            (qml.PauliRot(3.14, "IXYZI", wires=[0, 1, 2, 3, 4
                                                ]), 2, "RY(3.14)"),
            (qml.PauliRot(3.14, "IXYZI", wires=[0, 1, 2, 3, 4
                                                ]), 3, "RZ(3.14)"),
            (qml.PauliRot(3.14, "IXYZI", wires=[0, 1, 2, 3, 4
                                                ]), 4, "RI(3.14)"),
            (qml.MultiRZ(3.14, wires=[0, 1]), 0, "RZ(3.14)"),
            (qml.MultiRZ(3.14, wires=[0, 1]), 1, "RZ(3.14)"),
            (qml.CRX(3.14, wires=[0, 1]), 1, "RX(3.14)"),
            (qml.CRX(3.14, wires=[0, 1]), 0, "C"),
            (qml.CRY(3.14, wires=[0, 1]), 1, "RY(3.14)"),
            (qml.CRY(3.14, wires=[0, 1]), 0, "C"),
            (qml.CRZ(3.14, wires=[0, 1]), 1, "RZ(3.14)"),
            (qml.CRZ(3.14, wires=[0, 1]), 0, "C"),
            (qml.CRot(3.14, 2.14, 1.14, wires=[0, 1
                                               ]), 1, "Rot(3.14, 2.14, 1.14)"),
            (qml.CRot(3.14, 2.14, 1.14, wires=[0, 1]), 0, "C"),
            (qml.PhaseShift(3.14, wires=[0]), 0, "Rϕ(3.14)"),
            (qml.Beamsplitter(1, 2, wires=[0, 1]), 1, "BS(1, 2)"),
            (qml.Beamsplitter(1, 2, wires=[0, 1]), 0, "BS(1, 2)"),
            (qml.Squeezing(1, 2, wires=[1]), 1, "S(1, 2)"),
            (qml.TwoModeSqueezing(1, 2, wires=[0, 1]), 1, "S(1, 2)"),
            (qml.TwoModeSqueezing(1, 2, wires=[0, 1]), 0, "S(1, 2)"),
            (qml.Displacement(1, 2, wires=[1]), 1, "D(1, 2)"),
            (qml.NumberOperator(wires=[1]), 1, "n"),
            (qml.Rotation(3.14, wires=[1]), 1, "R(3.14)"),
            (qml.ControlledAddition(3.14, wires=[0, 1]), 1, "X(3.14)"),
            (qml.ControlledAddition(3.14, wires=[0, 1]), 0, "C"),
            (qml.ControlledPhase(3.14, wires=[0, 1]), 1, "Z(3.14)"),
            (qml.ControlledPhase(3.14, wires=[0, 1]), 0, "C"),
            (qml.ThermalState(3, wires=[1]), 1, "Thermal(3)"),
            (
                qml.GaussianState(np.array([[2, 0], [0, 2]]),
                                  np.array([1, 2]),
                                  wires=[1]),
                1,
                "Gaussian(M0,M1)",
            ),
            (qml.QuadraticPhase(3.14, wires=[1]), 1, "P(3.14)"),
            (qml.RX(3.14, wires=[1]), 1, "RX(3.14)"),
            (qml.S(wires=[2]), 2, "S"),
            (qml.T(wires=[2]), 2, "T"),
            (qml.RX(3.14, wires=[1]), 1, "RX(3.14)"),
            (qml.RY(3.14, wires=[1]), 1, "RY(3.14)"),
            (qml.RZ(3.14, wires=[1]), 1, "RZ(3.14)"),
            (qml.Rot(3.14, 2.14, 1.14, wires=[1]), 1, "Rot(3.14, 2.14, 1.14)"),
            (qml.U1(3.14, wires=[1]), 1, "U1(3.14)"),
            (qml.U2(3.14, 2.14, wires=[1]), 1, "U2(3.14, 2.14)"),
            (qml.U3(3.14, 2.14, 1.14, wires=[1]), 1, "U3(3.14, 2.14, 1.14)"),
            (qml.BasisState(np.array([0, 1, 0]), wires=[1, 2, 3]), 1, "|0⟩"),
            (qml.BasisState(np.array([0, 1, 0]), wires=[1, 2, 3]), 2, "|1⟩"),
            (qml.BasisState(np.array([0, 1, 0]), wires=[1, 2, 3]), 3, "|0⟩"),
            (qml.QubitStateVector(np.array([0, 1, 0, 0]),
                                  wires=[1, 2]), 1, "QubitStateVector(M0)"),
            (qml.QubitStateVector(np.array([0, 1, 0, 0]),
                                  wires=[1, 2]), 2, "QubitStateVector(M0)"),
            (qml.QubitUnitary(np.eye(2), wires=[1]), 1, "U0"),
            (qml.QubitUnitary(np.eye(4), wires=[1, 2]), 2, "U0"),
            (qml.Kerr(3.14, wires=[1]), 1, "Kerr(3.14)"),
            (qml.CrossKerr(3.14, wires=[1, 2]), 1, "CrossKerr(3.14)"),
            (qml.CrossKerr(3.14, wires=[1, 2]), 2, "CrossKerr(3.14)"),
            (qml.CubicPhase(3.14, wires=[1]), 1, "V(3.14)"),
            (qml.InterferometerUnitary(
                np.eye(4), wires=[1, 3]), 1, "InterferometerUnitary(M0)"),
            (qml.InterferometerUnitary(
                np.eye(4), wires=[1, 3]), 3, "InterferometerUnitary(M0)"),
            (qml.CatState(3.14, 2.14, 1,
                          wires=[1]), 1, "CatState(3.14, 2.14, 1)"),
            (qml.CoherentState(3.14, 2.14,
                               wires=[1]), 1, "CoherentState(3.14, 2.14)"),
            (
                qml.FockDensityMatrix(np.kron(np.eye(4), np.eye(4)),
                                      wires=[1, 2]),
                1,
                "FockDensityMatrix(M0)",
            ),
            (
                qml.FockDensityMatrix(np.kron(np.eye(4), np.eye(4)),
                                      wires=[1, 2]),
                2,
                "FockDensityMatrix(M0)",
            ),
            (
                qml.DisplacedSqueezedState(3.14, 2.14, 1.14, 0.14, wires=[1]),
                1,
                "DisplacedSqueezedState(3.14, 2.14, 1.14, 0.14)",
            ),
            (qml.FockState(7, wires=[1]), 1, "|7⟩"),
            (qml.FockStateVector(np.array([4, 5, 7]), wires=[1, 2, 3
                                                             ]), 1, "|4⟩"),
            (qml.FockStateVector(np.array([4, 5, 7]), wires=[1, 2, 3
                                                             ]), 2, "|5⟩"),
            (qml.FockStateVector(np.array([4, 5, 7]), wires=[1, 2, 3
                                                             ]), 3, "|7⟩"),
            (qml.SqueezedState(3.14, 2.14,
                               wires=[1]), 1, "SqueezedState(3.14, 2.14)"),
            (qml.Hermitian(np.eye(4), wires=[1, 2]), 1, "H0"),
            (qml.Hermitian(np.eye(4), wires=[1, 2]), 2, "H0"),
            (qml.X(wires=[1]), 1, "x"),
            (qml.P(wires=[1]), 1, "p"),
            (qml.FockStateProjector(np.array([4, 5, 7]),
                                    wires=[1, 2, 3]), 1, "|4,5,7╳4,5,7|"),
            (
                qml.PolyXP(np.array([1, 2, 0, -1.3, 6]), wires=[1]),
                2,
                "1+2x₀-1.3x₁+6p₁",
            ),
            (
                qml.PolyXP(np.array([[1.2, 2.3, 4.5], [-1.2, 1.2, -1.5],
                                     [-1.3, 4.5, 2.3]]),
                           wires=[1]),
                1,
                "1.2+1.1x₀+3.2p₀+1.2x₀²+2.3p₀²+3x₀p₀",
            ),
            (
                qml.PolyXP(
                    np.array([
                        [1.2, 2.3, 4.5, 0, 0],
                        [-1.2, 1.2, -1.5, 0, 0],
                        [-1.3, 4.5, 2.3, 0, 0],
                        [0, 2.6, 0, 0, 0],
                        [0, 0, 0, -4.7, -1.0],
                    ]),
                    wires=[1],
                ),
                1,
                "1.2+1.1x₀+3.2p₀+1.2x₀²+2.3p₀²+3x₀p₀+2.6x₀x₁-p₁²-4.7x₁p₁",
            ),
            (qml.QuadOperator(3.14, wires=[1]), 1, "cos(3.14)x+sin(3.14)p"),
            (qml.PauliX(wires=[1]).inv(), 1, "X⁻¹"),
            (qml.CNOT(wires=[0, 1]).inv(), 1, "X⁻¹"),
            (qml.CNOT(wires=[0, 1]).inv(), 0, "C"),
            (qml.Toffoli(wires=[0, 2, 1]).inv(), 1, "X⁻¹"),
            (qml.Toffoli(wires=[0, 2, 1]).inv(), 0, "C"),
            (qml.Toffoli(wires=[0, 2, 1]).inv(), 2, "C"),
            (qml.measure.sample(wires=[0, 1]), 0,
             "basis"),  # not providing an observable in
            (qml.measure.sample(wires=[0, 1]), 1,
             "basis"),  # sample gets displayed as raw
            (two_wire_quantum_tape(), 0, "QuantumTape:T0"),
            (two_wire_quantum_tape(), 1, "QuantumTape:T0"),
        ],
    )
    def test_operator_representation_unicode(self,
                                             unicode_representation_resolver,
                                             op, wire, target):
        """Test that an Operator instance is properly resolved."""
        assert unicode_representation_resolver.operator_representation(
            op, wire) == target

    @pytest.mark.parametrize(
        "op,wire,target",
        [
            (qml.PauliX(wires=[1]), 1, "X"),
            (qml.CNOT(wires=[0, 1]), 1, "X"),
            (qml.CNOT(wires=[0, 1]), 0, "C"),
            (qml.Toffoli(wires=[0, 2, 1]), 1, "X"),
            (qml.Toffoli(wires=[0, 2, 1]), 0, "C"),
            (qml.Toffoli(wires=[0, 2, 1]), 2, "C"),
            (qml.CSWAP(wires=[0, 2, 1]), 1, "SWAP"),
            (qml.CSWAP(wires=[0, 2, 1]), 2, "SWAP"),
            (qml.CSWAP(wires=[0, 2, 1]), 0, "C"),
            (qml.PauliY(wires=[1]), 1, "Y"),
            (qml.PauliZ(wires=[1]), 1, "Z"),
            (qml.CZ(wires=[0, 1]), 1, "Z"),
            (qml.CZ(wires=[0, 1]), 0, "C"),
            (qml.Identity(wires=[1]), 1, "I"),
            (qml.Hadamard(wires=[1]), 1, "H"),
            (qml.CRX(3.14, wires=[0, 1]), 1, "RX(3.14)"),
            (qml.CRX(3.14, wires=[0, 1]), 0, "C"),
            (qml.CRY(3.14, wires=[0, 1]), 1, "RY(3.14)"),
            (qml.CRY(3.14, wires=[0, 1]), 0, "C"),
            (qml.CRZ(3.14, wires=[0, 1]), 1, "RZ(3.14)"),
            (qml.CRZ(3.14, wires=[0, 1]), 0, "C"),
            (qml.CRot(3.14, 2.14, 1.14, wires=[0, 1
                                               ]), 1, "Rot(3.14, 2.14, 1.14)"),
            (qml.CRot(3.14, 2.14, 1.14, wires=[0, 1]), 0, "C"),
            (qml.PhaseShift(3.14, wires=[0]), 0, "Rϕ(3.14)"),
            (qml.Beamsplitter(1, 2, wires=[0, 1]), 1, "BS(1, 2)"),
            (qml.Beamsplitter(1, 2, wires=[0, 1]), 0, "BS(1, 2)"),
            (qml.Squeezing(1, 2, wires=[1]), 1, "S(1, 2)"),
            (qml.TwoModeSqueezing(1, 2, wires=[0, 1]), 1, "S(1, 2)"),
            (qml.TwoModeSqueezing(1, 2, wires=[0, 1]), 0, "S(1, 2)"),
            (qml.Displacement(1, 2, wires=[1]), 1, "D(1, 2)"),
            (qml.NumberOperator(wires=[1]), 1, "n"),
            (qml.Rotation(3.14, wires=[1]), 1, "R(3.14)"),
            (qml.ControlledAddition(3.14, wires=[0, 1]), 1, "X(3.14)"),
            (qml.ControlledAddition(3.14, wires=[0, 1]), 0, "C"),
            (qml.ControlledPhase(3.14, wires=[0, 1]), 1, "Z(3.14)"),
            (qml.ControlledPhase(3.14, wires=[0, 1]), 0, "C"),
            (qml.ThermalState(3, wires=[1]), 1, "Thermal(3)"),
            (
                qml.GaussianState(np.array([[2, 0], [0, 2]]),
                                  np.array([1, 2]),
                                  wires=[1]),
                1,
                "Gaussian(M0,M1)",
            ),
            (qml.QuadraticPhase(3.14, wires=[1]), 1, "P(3.14)"),
            (qml.RX(3.14, wires=[1]), 1, "RX(3.14)"),
            (qml.S(wires=[2]), 2, "S"),
            (qml.T(wires=[2]), 2, "T"),
            (qml.RX(3.14, wires=[1]), 1, "RX(3.14)"),
            (qml.RY(3.14, wires=[1]), 1, "RY(3.14)"),
            (qml.RZ(3.14, wires=[1]), 1, "RZ(3.14)"),
            (qml.Rot(3.14, 2.14, 1.14, wires=[1]), 1, "Rot(3.14, 2.14, 1.14)"),
            (qml.U1(3.14, wires=[1]), 1, "U1(3.14)"),
            (qml.U2(3.14, 2.14, wires=[1]), 1, "U2(3.14, 2.14)"),
            (qml.U3(3.14, 2.14, 1.14, wires=[1]), 1, "U3(3.14, 2.14, 1.14)"),
            (qml.BasisState(np.array([0, 1, 0]), wires=[1, 2, 3]), 1, "|0>"),
            (qml.BasisState(np.array([0, 1, 0]), wires=[1, 2, 3]), 2, "|1>"),
            (qml.BasisState(np.array([0, 1, 0]), wires=[1, 2, 3]), 3, "|0>"),
            (qml.QubitStateVector(np.array([0, 1, 0, 0]),
                                  wires=[1, 2]), 1, "QubitStateVector(M0)"),
            (qml.QubitStateVector(np.array([0, 1, 0, 0]),
                                  wires=[1, 2]), 2, "QubitStateVector(M0)"),
            (qml.QubitUnitary(np.eye(2), wires=[1]), 1, "U0"),
            (qml.QubitUnitary(np.eye(4), wires=[1, 2]), 2, "U0"),
            (qml.Kerr(3.14, wires=[1]), 1, "Kerr(3.14)"),
            (qml.CrossKerr(3.14, wires=[1, 2]), 1, "CrossKerr(3.14)"),
            (qml.CrossKerr(3.14, wires=[1, 2]), 2, "CrossKerr(3.14)"),
            (qml.CubicPhase(3.14, wires=[1]), 1, "V(3.14)"),
            (qml.InterferometerUnitary(
                np.eye(4), wires=[1, 3]), 1, "InterferometerUnitary(M0)"),
            (qml.InterferometerUnitary(
                np.eye(4), wires=[1, 3]), 3, "InterferometerUnitary(M0)"),
            (qml.CatState(3.14, 2.14, 1,
                          wires=[1]), 1, "CatState(3.14, 2.14, 1)"),
            (qml.CoherentState(3.14, 2.14,
                               wires=[1]), 1, "CoherentState(3.14, 2.14)"),
            (
                qml.FockDensityMatrix(np.kron(np.eye(4), np.eye(4)),
                                      wires=[1, 2]),
                1,
                "FockDensityMatrix(M0)",
            ),
            (
                qml.FockDensityMatrix(np.kron(np.eye(4), np.eye(4)),
                                      wires=[1, 2]),
                2,
                "FockDensityMatrix(M0)",
            ),
            (
                qml.DisplacedSqueezedState(3.14, 2.14, 1.14, 0.14, wires=[1]),
                1,
                "DisplacedSqueezedState(3.14, 2.14, 1.14, 0.14)",
            ),
            (qml.FockState(7, wires=[1]), 1, "|7>"),
            (qml.FockStateVector(np.array([4, 5, 7]), wires=[1, 2, 3
                                                             ]), 1, "|4>"),
            (qml.FockStateVector(np.array([4, 5, 7]), wires=[1, 2, 3
                                                             ]), 2, "|5>"),
            (qml.FockStateVector(np.array([4, 5, 7]), wires=[1, 2, 3
                                                             ]), 3, "|7>"),
            (qml.SqueezedState(3.14, 2.14,
                               wires=[1]), 1, "SqueezedState(3.14, 2.14)"),
            (qml.Hermitian(np.eye(4), wires=[1, 2]), 1, "H0"),
            (qml.Hermitian(np.eye(4), wires=[1, 2]), 2, "H0"),
            (qml.X(wires=[1]), 1, "x"),
            (qml.P(wires=[1]), 1, "p"),
            (qml.FockStateProjector(np.array([4, 5, 7]),
                                    wires=[1, 2, 3]), 1, "|4,5,7X4,5,7|"),
            (
                qml.PolyXP(np.array([1, 2, 0, -1.3, 6]), wires=[1]),
                2,
                "1+2x_0-1.3x_1+6p_1",
            ),
            (
                qml.PolyXP(np.array([[1.2, 2.3, 4.5], [-1.2, 1.2, -1.5],
                                     [-1.3, 4.5, 2.3]]),
                           wires=[1]),
                1,
                "1.2+1.1x_0+3.2p_0+1.2x_0^2+2.3p_0^2+3x_0p_0",
            ),
            (
                qml.PolyXP(
                    np.array([
                        [1.2, 2.3, 4.5, 0, 0],
                        [-1.2, 1.2, -1.5, 0, 0],
                        [-1.3, 4.5, 2.3, 0, 0],
                        [0, 2.6, 0, 0, 0],
                        [0, 0, 0, -4.7, 0],
                    ]),
                    wires=[1],
                ),
                1,
                "1.2+1.1x_0+3.2p_0+1.2x_0^2+2.3p_0^2+3x_0p_0+2.6x_0x_1-4.7x_1p_1",
            ),
            (qml.QuadOperator(3.14, wires=[1]), 1, "cos(3.14)x+sin(3.14)p"),
            (qml.QuadOperator(3.14, wires=[1]), 1, "cos(3.14)x+sin(3.14)p"),
            (qml.PauliX(wires=[1]).inv(), 1, "X^-1"),
            (qml.CNOT(wires=[0, 1]).inv(), 1, "X^-1"),
            (qml.CNOT(wires=[0, 1]).inv(), 0, "C"),
            (qml.Toffoli(wires=[0, 2, 1]).inv(), 1, "X^-1"),
            (qml.Toffoli(wires=[0, 2, 1]).inv(), 0, "C"),
            (qml.Toffoli(wires=[0, 2, 1]).inv(), 2, "C"),
            (qml.measure.sample(wires=[0, 1]), 0,
             "basis"),  # not providing an observable in
            (qml.measure.sample(wires=[0, 1]), 1,
             "basis"),  # sample gets displayed as raw
            (two_wire_quantum_tape(), 0, "QuantumTape:T0"),
            (two_wire_quantum_tape(), 1, "QuantumTape:T0"),
        ],
    )
    def test_operator_representation_ascii(self, ascii_representation_resolver,
                                           op, wire, target):
        """Test that an Operator instance is properly resolved."""
        assert ascii_representation_resolver.operator_representation(
            op, wire) == target

    @pytest.mark.parametrize(
        "obs,wire,target",
        [
            (qml.expval(qml.PauliX(wires=[1])), 1, "⟨X⟩"),
            (qml.expval(qml.PauliY(wires=[1])), 1, "⟨Y⟩"),
            (qml.expval(qml.PauliZ(wires=[1])), 1, "⟨Z⟩"),
            (qml.expval(qml.Hadamard(wires=[1])), 1, "⟨H⟩"),
            (qml.expval(qml.Hermitian(np.eye(4), wires=[1, 2])), 1, "⟨H0⟩"),
            (qml.expval(qml.Hermitian(np.eye(4), wires=[1, 2])), 2, "⟨H0⟩"),
            (qml.expval(qml.NumberOperator(wires=[1])), 1, "⟨n⟩"),
            (qml.expval(qml.X(wires=[1])), 1, "⟨x⟩"),
            (qml.expval(qml.P(wires=[1])), 1, "⟨p⟩"),
            (
                qml.expval(
                    qml.FockStateProjector(np.array([4, 5, 7]),
                                           wires=[1, 2, 3])),
                1,
                "⟨|4,5,7╳4,5,7|⟩",
            ),
            (
                qml.expval(qml.PolyXP(np.array([1, 2, 0, -1.3, 6]), wires=[1
                                                                           ])),
                2,
                "⟨1+2x₀-1.3x₁+6p₁⟩",
            ),
            (
                qml.expval(
                    qml.PolyXP(np.array([[1.2, 2.3, 4.5], [-1.2, 1.2, -1.5],
                                         [-1.3, 4.5, 2.3]]),
                               wires=[1])),
                1,
                "⟨1.2+1.1x₀+3.2p₀+1.2x₀²+2.3p₀²+3x₀p₀⟩",
            ),
            (qml.expval(qml.QuadOperator(
                3.14, wires=[1])), 1, "⟨cos(3.14)x+sin(3.14)p⟩"),
            (qml.var(qml.PauliX(wires=[1])), 1, "Var[X]"),
            (qml.var(qml.PauliY(wires=[1])), 1, "Var[Y]"),
            (qml.var(qml.PauliZ(wires=[1])), 1, "Var[Z]"),
            (qml.var(qml.Hadamard(wires=[1])), 1, "Var[H]"),
            (qml.var(qml.Hermitian(np.eye(4), wires=[1, 2])), 1, "Var[H0]"),
            (qml.var(qml.Hermitian(np.eye(4), wires=[1, 2])), 2, "Var[H0]"),
            (qml.var(qml.NumberOperator(wires=[1])), 1, "Var[n]"),
            (qml.var(qml.X(wires=[1])), 1, "Var[x]"),
            (qml.var(qml.P(wires=[1])), 1, "Var[p]"),
            (
                qml.var(
                    qml.FockStateProjector(np.array([4, 5, 7]),
                                           wires=[1, 2, 3])),
                1,
                "Var[|4,5,7╳4,5,7|]",
            ),
            (
                qml.var(qml.PolyXP(np.array([1, 2, 0, -1.3, 6]), wires=[1])),
                2,
                "Var[1+2x₀-1.3x₁+6p₁]",
            ),
            (
                qml.var(
                    qml.PolyXP(np.array([[1.2, 2.3, 4.5], [-1.2, 1.2, -1.5],
                                         [-1.3, 4.5, 2.3]]),
                               wires=[1])),
                1,
                "Var[1.2+1.1x₀+3.2p₀+1.2x₀²+2.3p₀²+3x₀p₀]",
            ),
            (qml.var(qml.QuadOperator(
                3.14, wires=[1])), 1, "Var[cos(3.14)x+sin(3.14)p]"),
            (qml.sample(qml.PauliX(wires=[1])), 1, "Sample[X]"),
            (qml.sample(qml.PauliY(wires=[1])), 1, "Sample[Y]"),
            (qml.sample(qml.PauliZ(wires=[1])), 1, "Sample[Z]"),
            (qml.sample(qml.Hadamard(wires=[1])), 1, "Sample[H]"),
            (qml.sample(qml.Hermitian(np.eye(4), wires=[1, 2
                                                        ])), 1, "Sample[H0]"),
            (qml.sample(qml.Hermitian(np.eye(4), wires=[1, 2
                                                        ])), 2, "Sample[H0]"),
            (qml.sample(qml.NumberOperator(wires=[1])), 1, "Sample[n]"),
            (qml.sample(qml.X(wires=[1])), 1, "Sample[x]"),
            (qml.sample(qml.P(wires=[1])), 1, "Sample[p]"),
            (
                qml.sample(
                    qml.FockStateProjector(np.array([4, 5, 7]),
                                           wires=[1, 2, 3])),
                1,
                "Sample[|4,5,7╳4,5,7|]",
            ),
            (
                qml.sample(qml.PolyXP(np.array([1, 2, 0, -1.3, 6]), wires=[1
                                                                           ])),
                2,
                "Sample[1+2x₀-1.3x₁+6p₁]",
            ),
            (
                qml.sample(
                    qml.PolyXP(np.array([[1.2, 2.3, 4.5], [-1.2, 1.2, -1.5],
                                         [-1.3, 4.5, 2.3]]),
                               wires=[1])),
                1,
                "Sample[1.2+1.1x₀+3.2p₀+1.2x₀²+2.3p₀²+3x₀p₀]",
            ),
            (qml.sample(qml.QuadOperator(
                3.14, wires=[1])), 1, "Sample[cos(3.14)x+sin(3.14)p]"),
            (
                qml.expval(
                    qml.PauliX(wires=[1]) @ qml.PauliY(wires=[2])
                    @ qml.PauliZ(wires=[3])),
                1,
                "⟨X ⊗ Y ⊗ Z⟩",
            ),
            (
                qml.expval(
                    qml.FockStateProjector(np.array([4, 5, 7]),
                                           wires=[1, 2, 3])
                    @ qml.X(wires=[4])),
                1,
                "⟨|4,5,7╳4,5,7| ⊗ x⟩",
            ),
            (
                qml.expval(
                    qml.FockStateProjector(np.array([4, 5, 7]),
                                           wires=[1, 2, 3])
                    @ qml.X(wires=[4])),
                2,
                "⟨|4,5,7╳4,5,7| ⊗ x⟩",
            ),
            (
                qml.expval(
                    qml.FockStateProjector(np.array([4, 5, 7]),
                                           wires=[1, 2, 3])
                    @ qml.X(wires=[4])),
                3,
                "⟨|4,5,7╳4,5,7| ⊗ x⟩",
            ),
            (
                qml.expval(
                    qml.FockStateProjector(np.array([4, 5, 7]),
                                           wires=[1, 2, 3])
                    @ qml.X(wires=[4])),
                4,
                "⟨|4,5,7╳4,5,7| ⊗ x⟩",
            ),
            (
                qml.sample(
                    qml.Hermitian(np.eye(4), wires=[1, 2]) @ qml.Hermitian(
                        np.eye(4), wires=[0, 3])),
                0,
                "Sample[H0 ⊗ H0]",
            ),
            (
                qml.sample(
                    qml.Hermitian(np.eye(4), wires=[1, 2]) @ qml.Hermitian(
                        2 * np.eye(4), wires=[0, 3])),
                0,
                "Sample[H0 ⊗ H1]",
            ),
            (qml.probs([0]), 0, "Probs"),
            (state(), 0, "State"),
        ],
    )
    def test_output_representation_unicode(self,
                                           unicode_representation_resolver,
                                           obs, wire, target):
        """Test that an Observable instance with return type is properly resolved."""
        assert unicode_representation_resolver.output_representation(
            obs, wire) == target

    def test_fallback_output_representation_unicode(
            self, unicode_representation_resolver):
        """Test that an Observable instance with return type is properly resolved."""
        obs = qml.PauliZ(0)
        obs.return_type = "TestReturnType"

        assert unicode_representation_resolver.output_representation(
            obs, 0) == "TestReturnType[Z]"

    @pytest.mark.parametrize(
        "obs,wire,target",
        [
            (qml.expval(qml.PauliX(wires=[1])), 1, "<X>"),
            (qml.expval(qml.PauliY(wires=[1])), 1, "<Y>"),
            (qml.expval(qml.PauliZ(wires=[1])), 1, "<Z>"),
            (qml.expval(qml.Hadamard(wires=[1])), 1, "<H>"),
            (qml.expval(qml.Hermitian(np.eye(4), wires=[1, 2])), 1, "<H0>"),
            (qml.expval(qml.Hermitian(np.eye(4), wires=[1, 2])), 2, "<H0>"),
            (qml.expval(qml.NumberOperator(wires=[1])), 1, "<n>"),
            (qml.expval(qml.X(wires=[1])), 1, "<x>"),
            (qml.expval(qml.P(wires=[1])), 1, "<p>"),
            (
                qml.expval(
                    qml.FockStateProjector(np.array([4, 5, 7]),
                                           wires=[1, 2, 3])),
                1,
                "<|4,5,7X4,5,7|>",
            ),
            (
                qml.expval(qml.PolyXP(np.array([1, 2, 0, -1.3, 6]), wires=[1
                                                                           ])),
                2,
                "<1+2x_0-1.3x_1+6p_1>",
            ),
            (
                qml.expval(
                    qml.PolyXP(np.array([[1.2, 2.3, 4.5], [-1.2, 1.2, -1.5],
                                         [-1.3, 4.5, 2.3]]),
                               wires=[1])),
                1,
                "<1.2+1.1x_0+3.2p_0+1.2x_0^2+2.3p_0^2+3x_0p_0>",
            ),
            (qml.expval(qml.QuadOperator(
                3.14, wires=[1])), 1, "<cos(3.14)x+sin(3.14)p>"),
            (qml.var(qml.PauliX(wires=[1])), 1, "Var[X]"),
            (qml.var(qml.PauliY(wires=[1])), 1, "Var[Y]"),
            (qml.var(qml.PauliZ(wires=[1])), 1, "Var[Z]"),
            (qml.var(qml.Hadamard(wires=[1])), 1, "Var[H]"),
            (qml.var(qml.Hermitian(np.eye(4), wires=[1, 2])), 1, "Var[H0]"),
            (qml.var(qml.Hermitian(np.eye(4), wires=[1, 2])), 2, "Var[H0]"),
            (qml.var(qml.NumberOperator(wires=[1])), 1, "Var[n]"),
            (qml.var(qml.X(wires=[1])), 1, "Var[x]"),
            (qml.var(qml.P(wires=[1])), 1, "Var[p]"),
            (
                qml.var(
                    qml.FockStateProjector(np.array([4, 5, 7]),
                                           wires=[1, 2, 3])),
                1,
                "Var[|4,5,7X4,5,7|]",
            ),
            (
                qml.var(qml.PolyXP(np.array([1, 2, 0, -1.3, 6]), wires=[1])),
                2,
                "Var[1+2x_0-1.3x_1+6p_1]",
            ),
            (
                qml.var(
                    qml.PolyXP(np.array([[1.2, 2.3, 4.5], [-1.2, 1.2, -1.5],
                                         [-1.3, 4.5, 2.3]]),
                               wires=[1])),
                1,
                "Var[1.2+1.1x_0+3.2p_0+1.2x_0^2+2.3p_0^2+3x_0p_0]",
            ),
            (qml.var(qml.QuadOperator(
                3.14, wires=[1])), 1, "Var[cos(3.14)x+sin(3.14)p]"),
            (qml.sample(qml.PauliX(wires=[1])), 1, "Sample[X]"),
            (qml.sample(qml.PauliY(wires=[1])), 1, "Sample[Y]"),
            (qml.sample(qml.PauliZ(wires=[1])), 1, "Sample[Z]"),
            (qml.sample(qml.Hadamard(wires=[1])), 1, "Sample[H]"),
            (qml.sample(qml.Hermitian(np.eye(4), wires=[1, 2
                                                        ])), 1, "Sample[H0]"),
            (qml.sample(qml.Hermitian(np.eye(4), wires=[1, 2
                                                        ])), 2, "Sample[H0]"),
            (qml.sample(qml.NumberOperator(wires=[1])), 1, "Sample[n]"),
            (qml.sample(qml.X(wires=[1])), 1, "Sample[x]"),
            (qml.sample(qml.P(wires=[1])), 1, "Sample[p]"),
            (
                qml.sample(
                    qml.FockStateProjector(np.array([4, 5, 7]),
                                           wires=[1, 2, 3])),
                1,
                "Sample[|4,5,7X4,5,7|]",
            ),
            (
                qml.sample(qml.PolyXP(np.array([1, 2, 0, -1.3, 6]), wires=[1
                                                                           ])),
                2,
                "Sample[1+2x_0-1.3x_1+6p_1]",
            ),
            (
                qml.sample(
                    qml.PolyXP(np.array([[1.2, 2.3, 4.5], [-1.2, 1.2, -1.5],
                                         [-1.3, 4.5, 2.3]]),
                               wires=[1])),
                1,
                "Sample[1.2+1.1x_0+3.2p_0+1.2x_0^2+2.3p_0^2+3x_0p_0]",
            ),
            (qml.sample(qml.QuadOperator(
                3.14, wires=[1])), 1, "Sample[cos(3.14)x+sin(3.14)p]"),
            (
                qml.expval(
                    qml.PauliX(wires=[1]) @ qml.PauliY(wires=[2])
                    @ qml.PauliZ(wires=[3])),
                1,
                "<X @ Y @ Z>",
            ),
            (
                qml.expval(
                    qml.FockStateProjector(np.array([4, 5, 7]),
                                           wires=[1, 2, 3])
                    @ qml.X(wires=[4])),
                1,
                "<|4,5,7X4,5,7| @ x>",
            ),
            (
                qml.expval(
                    qml.FockStateProjector(np.array([4, 5, 7]),
                                           wires=[1, 2, 3])
                    @ qml.X(wires=[4])),
                2,
                "<|4,5,7X4,5,7| @ x>",
            ),
            (
                qml.expval(
                    qml.FockStateProjector(np.array([4, 5, 7]),
                                           wires=[1, 2, 3])
                    @ qml.X(wires=[4])),
                3,
                "<|4,5,7X4,5,7| @ x>",
            ),
            (
                qml.expval(
                    qml.FockStateProjector(np.array([4, 5, 7]),
                                           wires=[1, 2, 3])
                    @ qml.X(wires=[4])),
                4,
                "<|4,5,7X4,5,7| @ x>",
            ),
            (
                qml.sample(
                    qml.Hermitian(np.eye(4), wires=[1, 2]) @ qml.Hermitian(
                        np.eye(4), wires=[0, 3])),
                0,
                "Sample[H0 @ H0]",
            ),
            (
                qml.sample(
                    qml.Hermitian(np.eye(4), wires=[1, 2]) @ qml.Hermitian(
                        2 * np.eye(4), wires=[0, 3])),
                0,
                "Sample[H0 @ H1]",
            ),
            (qml.probs([0]), 0, "Probs"),
            (state(), 0, "State"),
        ],
    )
    def test_output_representation_ascii(self, ascii_representation_resolver,
                                         obs, wire, target):
        """Test that an Observable instance with return type is properly resolved."""
        assert ascii_representation_resolver.output_representation(
            obs, wire) == target

    def test_element_representation_none(self,
                                         unicode_representation_resolver):
        """Test that element_representation properly handles None."""
        assert unicode_representation_resolver.element_representation(None,
                                                                      0) == ""

    def test_element_representation_str(self, unicode_representation_resolver):
        """Test that element_representation properly handles strings."""
        assert unicode_representation_resolver.element_representation(
            "Test", 0) == "Test"

    def test_element_representation_calls_output(
            self, unicode_representation_resolver):
        """Test that element_representation calls output_representation for returned observables."""

        unicode_representation_resolver.output_representation = Mock()

        obs = qml.sample(qml.PauliX(3))
        wire = 3

        unicode_representation_resolver.element_representation(obs, wire)

        assert unicode_representation_resolver.output_representation.call_args[
            0] == (obs, wire)

    def test_element_representation_calls_operator(
            self, unicode_representation_resolver):
        """Test that element_representation calls operator_representation for all operators that are not returned."""

        unicode_representation_resolver.operator_representation = Mock()

        op = qml.PauliX(3)
        wire = 3

        unicode_representation_resolver.element_representation(op, wire)

        assert unicode_representation_resolver.operator_representation.call_args[
            0] == (op, wire)