quairkit.operator.channel.base¶

The source file of the basic class for the quantum channels.

class quairkit.operator.channel.base.Channel(type_repr, representation=None, system_idx=None, acted_system_dim=None, check_legality=True)¶

Basic class for quantum channels.

Parameters:¶

type_repr : str¶: type of a representation. should be 'choi', 'kraus', 'stinespring'.
representation : Tensor | None¶: the representation of this channel. Defaults to None i.e. not specified.
system_idx : Iterable[Iterable[int]] | Iterable[int] | int | None¶: indices of the system on which this channel acts on. Defaults to None. i.e. list(range(number of acted systems)).
acted_system_dim : List[int] | int | None¶: dimension of systems that this channel acts on. Can be a list of system dimensions or an int representing the dimension of all systems. Defaults to None.
check_legality : bool | None¶: whether check the completeness of the representation if provided. Defaults to True.

Raises:¶

ValueError – Unsupported channel representation for type_repr.
NotImplementedError – The noisy channel can only run in density matrix mode.
TypeError – Unexpected data type for Channel representation.

Note

Assume the input dimension is the same as the output.

property choi_repr : Tensor¶

Choi representation of a channel

Returns:¶: a tensor with shape \([d_\text{out}^2, d_\text{in}^2]\), where \(d_\text{in/out}\) is the input/output dimension of this channel
Raises:¶: ValueError – Need to specify the Choi representation in this Channel instance.

property kraus_repr : list[Tensor]¶

Kraus representation of a channel

Returns:¶: a list of tensors with shape \([d_\text{out}, d_\text{in}]\), where \(d_\text{in/out}\) is the input/output dimension of this channel
Raises:¶: ValueError – Need to specify the Kraus representation in this Channel instance.

property stinespring_repr : Tensor¶

Stinespring representation of a channel

Returns:¶: a tensor with shape \([r * d_\text{out}, d_\text{in}]\), where \(r\) is the rank of this channel and \(d_\text{in/out}\) is the input/output dimension of this channel
Raises:¶: ValueError – Need to specify the Stinespring representation in this Channel instance.