PauliWithQbit

PauliWithQbit represents a single Pauli matrix ($I$, $X$, $Y$, or $Z$) associated with a specific qubit index. It is the most granular building block in the Hamiltonian module -- each PauliTerm is composed of a collection of PauliWithQbit instances, one per qubit.

Methods

qbit

PauliWithQbit.qbit() -> int

Returns the qubit index that this Pauli matrix acts on.

Returns: An integer qubit index.

is_I

PauliWithQbit.is_I() -> bool

Returns True if this Pauli is the identity matrix $I$.

Returns: A boolean.

is_X

PauliWithQbit.is_X() -> bool

Returns True if this Pauli is the $X$ (bit-flip) matrix.

Returns: A boolean.

is_Y

PauliWithQbit.is_Y() -> bool

Returns True if this Pauli is the $Y$ matrix.

Returns: A boolean.

is_Z

PauliWithQbit.is_Z() -> bool

Returns True if this Pauli is the $Z$ (phase-flip) matrix.

Returns: A boolean.

to_qgate

PauliWithQbit.to_qgate() -> QGate

Converts this Pauli into the corresponding quantum gate object. The mapping is:

Pauli	Gate
$I$	Identity (no-op)
$X$	X gate
$Y$	Y gate
$Z$	Z gate

Returns: A QGate applied to the qubit at index qbit().

pauli_char

PauliWithQbit.pauli_char() -> str

Returns a single-character string identifying the Pauli type: "I", "X", "Y", or "Z".

Returns: A one-character string.

Examples

Inspect Paulis in a term

from pyqpanda3.hamiltonian import PauliOperator

h = PauliOperator({"X0 Y1 Z2": 1.0})
term = h.terms()[0]

for pwq in term.paulis():
    print(f"Qubit {pwq.qbit()}: {pwq.pauli_char()}")
    print(f"  is_X: {pwq.is_X()}, is_Y: {pwq.is_Y()}, is_Z: {pwq.is_Z()}, is_I: {pwq.is_I()}")

Convert a Pauli to a quantum gate

from pyqpanda3.hamiltonian import PauliOperator

h = PauliOperator({"X0 Z1": 1.0})
term = h.terms()[0]

for pwq in term.paulis():
    if not pwq.is_I():
        gate = pwq.to_qgate()
        print(f"Gate on qubit {pwq.qbit()}: {gate}")

See Also

• PauliTerm -- A collection of PauliWithQbit instances forming a single term
• PauliOperator -- Multi-term Pauli operator containing PauliTerms
• Hamiltonian -- Higher-level Hamiltonian wrapper