PiecewisePolynomialPauliRotations

class PiecewisePolynomialPauliRotations(num_state_qubits=None, breakpoints=None, coeffs=None, basis='Y', name='pw_poly')

GitHub

Bases: qiskit.circuit.library.arithmetic.functional_pauli_rotations.FunctionalPauliRotations

Piecewise-polynomially-controlled Pauli rotations.

This class implements a piecewise polynomial (not necessarily continuous) function, $f(x)$ , on qubit amplitudes, which is defined through breakpoints and coefficients as follows. Suppose the breakpoints $(x_0, ..., x_J)$ are a subset of $[0, 2^n-1]$ , where $n$ is the number of state qubits. Further on, denote the corresponding coefficients by $[a_{j,1},...,a_{j,d}]$ , where $d$ is the highest degree among all polynomials.

Then $f(x)$ is defined as:

\begin{split}f(x) = \begin{cases} 0, x < x_0 \\ \sum_{i=0}^{i=d}a_{j,i}/2 x^i, x_j \leq x < x_{j+1} \end{cases}\end{split}

where if given the same number of breakpoints as polynomials, we implicitly assume $x_{J+1} = 2^n$ .

Note

Note the $1/2$ factor in the coefficients of $f(x)$ , this is consistent with Qiskit’s Pauli rotations.

Examples

>>> from qiskit import QuantumCircuit
>>> from qiskit.circuit.library.arithmetic.piecewise_polynomial_pauli_rotations import\
... PiecewisePolynomialPauliRotations
>>> qubits, breakpoints, coeffs = (2, [0, 2], [[0, -1.2],[-1, 1, 3]])
>>> poly_r = PiecewisePolynomialPauliRotations(num_state_qubits=qubits,
...breakpoints=breakpoints, coeffs=coeffs)
>>>
>>> qc = QuantumCircuit(poly_r.num_qubits)
>>> qc.h(list(range(qubits)));
>>> qc.append(poly_r.to_instruction(), list(range(qc.num_qubits)));
>>> qc.draw()
     ┌───┐┌──────────┐
q_0: ┤ H ├┤0         ├
     ├───┤│          │
q_1: ┤ H ├┤1         ├
     └───┘│          │
q_2: ─────┤2         ├
          │  pw_poly │
q_3: ─────┤3         ├
          │          │
q_4: ─────┤4         ├
          │          │
q_5: ─────┤5         ├
          └──────────┘

References

[1]: Haener, T., Roetteler, M., & Svore, K. M. (2018).

Optimizing Quantum Circuits for Arithmetic. arXiv:1805.12445

[2]: Carrera Vazquez, A., Hiptmair, R., & Woerner, S. (2020).

Enhancing the Quantum Linear Systems Algorithm using Richardson Extrapolation. arXiv:2009.04484

Parameters

num_state_qubits (Optional[int]) – The number of qubits representing the state.
breakpoints (Optional[List[int]]) – The breakpoints to define the piecewise-linear function. Defaults to [0].
coeffs (Optional[List[List[float]]]) – The coefficients of the polynomials for different segments of the
function. coeffs**[j]****[i] **is the coefficient of the i-th power of x (piecewise-linear) –
the j-th polynomial. (for) – Defaults to linear: [[1]].
basis (str) – The type of Pauli rotation ('X', 'Y', 'Z').
name (str) – The name of the circuit.

Methods Defined Here

evaluate

PiecewisePolynomialPauliRotations.evaluate(x)

Classically evaluate the piecewise polynomial rotation.

Parameters

x (float) – Value to be evaluated at.

Return type

float

Returns

Value of piecewise polynomial function at x.

Attributes

ancillas

Returns a list of ancilla bits in the order that the registers were added.

Return type

List[AncillaQubit]

basis

The kind of Pauli rotation to be used.

Set the basis to ‘X’, ‘Y’ or ‘Z’ for controlled-X, -Y, or -Z rotations respectively.

Return type

str

Returns

The kind of Pauli rotation used in controlled rotation.

breakpoints

The breakpoints of the piecewise polynomial function.

The function is polynomial in the intervals [point_i, point_{i+1}] where the last point implicitly is 2**(num_state_qubits + 1).

Return type

List[int]

Returns

The list of breakpoints.

calibrations

Return calibration dictionary.

The custom pulse definition of a given gate is of the form

{‘gate_name’: {(qubits, params): schedule}}

Return type

dict

clbits

Returns a list of classical bits in the order that the registers were added.

Return type

List[Clbit]

coeffs

The coefficients of the polynomials.

Return type

List[List[float]]

Returns

The polynomial coefficients per interval as nested lists.

contains_zero_breakpoint

Whether 0 is the first breakpoint.

Return type

bool

Returns

True, if 0 is the first breakpoint, otherwise False.

data

extension_lib

Default value: 'include "qelib1.inc";'

global_phase

Return the global phase of the circuit in radians.

Return type

Union[ParameterExpression, float]

header

Default value: 'OPENQASM 2.0;'

instances

Default value: 9

mapped_coeffs

The coefficients mapped to the internal representation, since we only compare x>=breakpoint.

Return type

List[List[float]]

Returns

The mapped coefficients.

metadata

The user provided metadata associated with the circuit

The metadata for the circuit is a user provided dict of metadata for the circuit. It will not be used to influence the execution or operation of the circuit, but it is expected to be passed between all transforms of the circuit (ie transpilation) and that providers will associate any circuit metadata with the results it returns from execution of that circuit.

Return type

dict

num_ancilla_qubits

The minimum number of ancilla qubits in the circuit.

Return type

int

Returns

The minimal number of ancillas required.

num_ancillas

Return the number of ancilla qubits.

Return type

int

num_clbits

Return number of classical bits.

Return type

int

num_parameters

Return type

int

num_qubits

Return number of qubits.

Return type

int

num_state_qubits

The number of state qubits representing the state $|x\rangle$ .

Return type

int

Returns

The number of state qubits.

parameters

Return type

ParameterView

prefix

Default value: 'circuit'

qregs

A list of the quantum registers associated with the circuit.

qubits

Returns a list of quantum bits in the order that the registers were added.

Return type

List[Qubit]

Was this page helpful?

Report a bug or request content on GitHub.