qnet.algebra.library.circuit_components module¶

Collection of essential circuit components

Summary¶

Classes:

`Beamsplitter`	Infinite bandwidth beamsplitter component.
`CoherentDriveCC`	Coherent displacement of the input field
`PhaseCC`	Coherent phase shift cicuit component

__all__: Beamsplitter, CoherentDriveCC, PhaseCC

Reference¶

class qnet.algebra.library.circuit_components.CoherentDriveCC(*, label=None, **kwargs)[source]¶

Bases: qnet.algebra.core.circuit_algebra.Component

Coherent displacement of the input field

Typically, the input field is the, displaced by a complex amplitude \(\alpha\). This component serves as the model of an ideal laser source without internal non-classical internal dynamics.

The coherent drive is represented as an inhomogeneous Lindblad operator \(L = \alpha\), with a trivial Hamiltonian and scattering matrix. For a complete circuit with coherent drives, the inhomogeneous Lindblad operators can be transformed to driving terms in the total network Hamiltonian through move_drive_to_H().

Parameters:	label – label for the component. displacement – the coherent displacement amplitude. Defaults to a complex symbol ‘alpha’

CDIM = 1¶: circuit dimension

PORTSIN = ('in',)¶

PORTSOUT = ('out',)¶

ARGNAMES = ('displacement',)¶

DEFAULTS = {'displacement': alpha}¶

IDENTIFIER = 'W'¶

displacement¶: The displacement argument.

class qnet.algebra.library.circuit_components.PhaseCC(*, label=None, **kwargs)[source]¶

Bases: qnet.algebra.core.circuit_algebra.Component

Coherent phase shift cicuit component

The field passing through obtains a phase factor \(e^{i \phi}\) for a real-valued phase \(\phi\). The component has no dynamics, i.e. a trivial Hamiltonian and Lindblad operators

Parameters:	label – label for the component. phase – the phase. Defaults to a real symbol ‘phi’

CDIM = 1¶

PORTSIN = ('in',)¶

PORTSOUT = ('out',)¶

ARGNAMES = ('phase',)¶

DEFAULTS = {'phase': phi}¶

IDENTIFIER = 'Phase'¶

phase¶: The phase argument.

class qnet.algebra.library.circuit_components.Beamsplitter(*, label=None, **kwargs)[source]¶

Bases: qnet.algebra.core.circuit_algebra.Component

Infinite bandwidth beamsplitter component.

It is a pure scattering component, i.e. it’s internal dynamics are not modeled explicitly (trivial Hamiltonian and Lindblad operators). The single real parameter is the mixing_angle for the two signals.

\[\begin{split}S = \begin{pmatrix} \cos{\theta} & -\sin{\theta} \\ \sin{\theta} & \cos{\theta} \end{pmatrix}\end{split}\]

The beamsplitter uses the following labeled input/output channels:

     │1:vac
     │
0:in v 0:tr
────>/────>
     │
     │1:rf
     v

That is, output channel 0 is the transmission of input channel 0 (“in”), and output channel 1 is the reflection of input channel 0; vice versa for the secondary input channel 1 (“vac”: often connected to a vacuum mode). For \(\theta=0\), the beam splitter results in full transmission, and full reflection for \(\theta=\pi/2\).

Parameters:	label – label for the beamsplitter. mixing_angle – the angle that determines the ratio of transmission and reflection defaults to \(\pi/4\), corresponding to a 50-50-beamsplitter. It is recommended to use a sympy expression for the mixing angle.

Note

We use a real-valued, but asymmetric scattering matrix. A common alternative convention for the beamsplitter is the symmetric scattering matrix

\[\begin{split}S = \begin{pmatrix} \cos{\theta} & i\sin{\theta} \\ i \sin{\theta} & \cos{\theta} \end{pmatrix}\end{split}\]

To achieve the symmetric beamsplitter (or any general beamsplitter), the Beamsplitter component can be combined with one or more appropriate PhaseCC components.

CDIM = 2¶: circuit dimension

PORTSIN = ('in', 'vac')¶

PORTSOUT = ('tr', 'rf')¶

ARGNAMES = ('mixing_angle',)¶

DEFAULTS = {'mixing_angle': pi/4}¶

IDENTIFIER = 'BS'¶

mixing_angle¶: The mixing_angle argument.