workbench_algorithms.subroutines.compression_gadget

Implementation of the Compression Gadget (arxiv:2208.06941).

CompressionGadgetStrategy

Bases: Protocol

Interface for applying block-encodings in compression gadget.

apply_compression_gadget_block_encoding

apply_compression_gadget_block_encoding(
    system_reg: Qubits,
    be_anc: Qubits,
    idx: int,
    ctrl: Qubits | int = 0,
)

Method describing how to apply the block encodings.

Parameters:

Name	Type	Description	Default
system_reg	Qubits	System qubits.	required
be_anc	Qubits	Block-encoding's ancillary qubits.	required
idx	int	Iteration of the compression gadget.	required
ctrl	Qubits | int	Control register.	0

CompressionGadget

CompressionGadget(
    strategy: CompressionGadgetStrategy,
    adder: Qubrick = None,
    **kwargs,
)

Bases: Qubrick

Compression gadget for block-encoding powers.

Given BE[H_i], applies a BE[Prod H_i] according to https://arxiv.org/pdf/2208.06941 Fig. 3.

Note

The block-encoding is successful in the subspace where counter == 0. The controlled version is such that the controlled unitary is applied accordingly when the block-encoding's ancillae qubits are in the zero state. However, the controlled-qubrick might still have an action in other subspace. This allows to reduce the cost of the implementation.

Parameters:

Name	Type	Description	Default
strategy	CompressionGadgetStrategy	block-encoding of the hamiltonian H	required
adder	Qubrick	Adder qubrick	None
**kwargs	dict[str, Any]	Other arguments to pass to the init.	{}

strategy property

strategy

Set the strategy property so it can't be modified.

Returns:

Type	Description
CompressionGadgetStrategy	The Compression gadget strategy

compute

compute(
    system_reg,
    be_anc,
    idx_stop,
    idx_start: int = 0,
    counter=None,
    ctrl: int = 0,
) -> None

Compute CompressionGadget.

Parameters:

Name	Type	Description	Default
system_reg	Qubits	System qubits to apply to block-encodings.	required
be_anc	int	Block-encoding ancilla register.	required
idx_stop	int	Final index of the multiplication.	required
idx_start	int	Starting index of the multiplication.	0
counter	Qubits	Counter register to perform the compression, if None will be allocated at compute.	None
ctrl	(Qubits, int)	Control register.	0