workbench_algorithms.subroutines.qpe_window_functions

Module containing Qubricks for window functions.

RectWindow

RectWindow(**kwargs)

Bases: Qubrick

Rectangular/Dirichlet window. This is the default window function for the textbook QPE.

compute

compute(
    phase_reg: Qubits, ctrl: Qubits | int = 0, **kwargs
)

Executes circuit for implementing rectangular window.

Parameters:

Name	Type	Description	Default
phase_reg	Qubits	Phase qubit register	required
ctrl	(Optional, int, Qubits)	Control register	0
**kwargs	dict[str, Any]	Optional positional arguments. Included to stay consistent with the arguments of window emulators.	{}

CosineWindow

CosineWindow(adder: Adder | None = None, **kwargs)

Bases: Qubrick

Cosine window from arxiv:2110.09590 .

compute

compute(
    phase_reg: Qubits, ctrl: Qubits | int = 0, **kwargs
)

Executes circuit for implementing cosine window.

Parameters:

Name	Type	Description	Default
phase_reg	Qubits	Phase qubit register	required
ctrl	(Optional, int, Qubits)	Control register	0
**kwargs	dict[str, Any]	Optional keyword arguments. Included to stay consistent with the arguments of window emulators.	{}

SineWindow

SineWindow(**kwargs)

Bases: Qubrick

Qubrick for window state with the sine function over the amplitudes.

This window state can be used to achieve an optimal Holevo variance as outlined in Section II B. of arxiv:1805.03662 . See \(\Xi_m\) state.

Note

The state prepared here has a global phase of pi. Additionally, if the user does not care about having purely real or purely imaginary values in the prepared state, the rz gates can be replaced by phase gates in which case the magnitudes will be the same as the expected state, but each amplitude will be rotated by some (global) phase.

compute

compute(
    target_reg,
    flag_reg,
    ctrl: int = 0,
    use_real_amps: bool = False,
    **kwargs,
) -> None

Computes sine window function.

Parameters:

Name	Type	Description	Default
target_reg	Qubits	register on which the sine window state is prepared	required
flag_reg	Qubits	flag qubit when 0, the sine window state is prepared	required
ctrl	Qubits	control qubit	0
use_real_amps	bool	If True, prepares real amplitudes	False
**kwargs	dict[str, Any]	Optional keyword arguments	{}

Note

• Needs a round of amplitude amplification.

SineWindowPhaseCatalysis

SineWindowPhaseCatalysis(**kwargs)

Bases: Qubrick

Qubrick for window state with the sine function over the amplitudes.

Prepared via phase catalyst register.

This window state can be used to achieve an optimal Holevo variance as outlined in Section II B. of arxiv:1805.03662 . See \(\Xi_m\) state.

The phase catalyst implementation is outlined in Appendix B of arxiv:1805.03662

Note

The state prepared here will be the same as SineWindow up to a global phase.

compute

compute(
    target_reg: Qubits,
    flag_reg: Qubits,
    ctrl: Qubits | int = 0,
    **kwargs,
)

Computes sine window function via phase catalyst state.

Note

• Needs a round of amplitude amplification.

SineWindowQubitEfficient

SineWindowQubitEfficient(**kwargs)

Bases: Qubrick

Qubrick for window state with the sine function over the amplitudes using only two active qubits at a time.

This window state can be used to achieve an optimal Holevo variance with the construction of the circuit outlined in Section IV of arxiv:2303.12505.

compute

compute(
    phase_reg: Qubits, ctrl: Qubits | int = 0, **kwargs
)

Computes sine window function.

Parameters:

Name	Type	Description	Default
phase_reg	Qubits	phase qubit register	required
ctrl	(Optional, int, Qubits)	control register	0
**kwargs	dict[str, Any]	optional keyword arguments	{}

WindowStatePrep

WindowStatePrep(amps, state_prep=None, **kwargs)

Bases: Qubrick

General class for simulating window state via state prep.

Parameters:

Name	Type	Description	Default
amps	ndarray	Amplitudes for window state.	required
state_prep	Qubrick	Qubrick to implement the state preparation for the window function.	None
**kwargs	dict[str, Any]	Other arguments to pass to the init.	{}

compute

compute(
    phase_reg: Qubits, ctrl: Qubits | int = 0, **kwargs
)

Executes circuit for preparing window state.

Parameters:

Name	Type	Description	Default
phase_reg	Qubits	Phase qubit register.	required
ctrl	(Optional, int, Qubits)	Control register.	0
**kwargs	dict[str, Any]	Optional keyword arguments. Included to stay consistent with the arguments of window emulators.	{}

WindowEmulator

WindowEmulator(
    emulator_func: Callable[Concatenate[int, P], NDArray],
    emulator_function_options: dict[str, Any] | None = None,
    **kwargs,
)

Bases: Qubrick

Constructor for window emulator.

Note

• Check the window utils module for emulator_func options.
• Note that this Qubrick does not execute quantum operations; it directly touches the state vector and is not meant to run on a real QPU program.

Parameters:

Name	Type	Description	Default
emulator_func	callable	method for computing amplitudes of a window state	required
emulator_function_options	dict[str, Any]	Extra keyword arguments for the emulator_func	None
**kwargs	dict[str, Any]	Other arguments to pass to the init.	{}

compute

compute(phase_reg, psi, ctrl: int = 0, **kwargs) -> None

Compute amplitudes of taper state.

Note

Assumes Qubits in QC are ordered as: (1) Psi (2) Phase Register (3) All other qubits

Parameters:

Name	Type	Description	Default
phase_reg	Qubits	Phase qubit register	required
psi	Qubits	System register	required
ctrl	(Optional, int, Qubits)	Control register	0
**kwargs	dict[str, Any]	Optional keyword arguments. Included to stay consistent with the arguments of window emulators.	{}

Note

• Use emulators for a reasonably small number of phase qubits!
• The control version is not currently implemented

uncompute

uncompute() -> None

Override the default uncomputation.