QubitBaseClass#

class scqubits.core.qubit_base.QubitBaseClass(id_str, evals_method=None, evals_method_options=None, esys_method=None, esys_method_options=None)[source]#

Base class for superconducting qubit objects. Provide general mechanisms and routines for plotting spectra, matrix elements, and writing data to files

Methods

QubitBaseClass.E01()

Returns the qubit's fundamental energy splitting, E_1 - E_0.

QubitBaseClass.__init__(id_str[, ...])

QubitBaseClass.anharmonicity()

Returns the qubit's anharmonicity, (E_2 - E_1) - (E_1 - E_0).

QubitBaseClass.broadcast(event, **kwargs)

Request a broadcast from CENTRAL_DISPATCH reporting event.

QubitBaseClass.create()

Use ipywidgets to create a new class instance

QubitBaseClass.default_params()

Return dictionary with default parameter values for initialization of class instance

QubitBaseClass.eigensys([evals_count, ...])

Calculates eigenvalues and corresponding eigenvectors using scipy.linalg.eigh.

QubitBaseClass.eigenvals([evals_count, ...])

Calculates eigenvalues using scipy.linalg.eigh, returns numpy array of eigenvalues.

QubitBaseClass.get_dispersion_vs_paramvals(...)

Calculates eigenvalues/eigenstates for a varying system parameter, given an array of parameter values.

QubitBaseClass.get_initdata()

Returns dict appropriate for creating/initializing a new Serializable object.

QubitBaseClass.get_matelements_vs_paramvals(...)

Calculates matrix elements for a varying system parameter, given an array of parameter values.

QubitBaseClass.get_operator_names()

Returns a list of all operator names for the quantum system.

QubitBaseClass.get_spectrum_vs_paramvals(...)

Calculates eigenvalues/eigenstates for a varying system parameter, given an array of parameter values.

QubitBaseClass.hamiltonian()

Returns the Hamiltonian

QubitBaseClass.hilbertdim()

Returns dimension of Hilbert space

QubitBaseClass.matrixelement_table(operator)

Returns table of matrix elements for operator with respect to the eigenstates of the qubit.

QubitBaseClass.plot_dispersion_vs_paramvals(...)

Generates a simple plot of a set of curves representing the charge or flux dispersion of transition energies.

QubitBaseClass.plot_evals_vs_paramvals(...)

Generates a simple plot of a set of eigenvalues as a function of one parameter.

QubitBaseClass.plot_matelem_vs_paramvals(...)

Generates a simple plot of a set of eigenvalues as a function of one parameter.

QubitBaseClass.plot_matrixelements(operator)

Plots matrix elements for operator, given as a string referring to a class method that returns an operator matrix.

QubitBaseClass.process_hamiltonian(...[, ...])

Return qubit Hamiltonian in chosen basis: either return unchanged (i.e., in native basis) or transform into eigenenergy basis

QubitBaseClass.process_op(native_op[, ...])

Processes the operator native_op: either hand back native_op unchanged, or transform it into the energy eigenbasis.

QubitBaseClass.receive(event, sender, **kwargs)

Receive a message from CENTRAL_DISPATCH and initiate action on it.

QubitBaseClass.set_and_return(attr_name, value)

Allows to set an attribute after which self is returned. This is useful for doing something like example::.

QubitBaseClass.set_params(**kwargs)

Set new parameters through the provided dictionary.

QubitBaseClass.set_params_from_gui(change)

Set new parameters through the provided dictionary.

QubitBaseClass.supported_noise_channels()

Returns a list of noise channels this QuantumSystem supports.

QubitBaseClass.widget([params])

Use ipywidgets to modify parameters of class instance

Attributes

id_str

truncated_dim

Descriptor class for properties that are to be monitored for changes.
Return type:

QuantumSystemType

E01()[source]#

Returns the qubit’s fundamental energy splitting, E_1 - E_0.

Return type:

float

anharmonicity()[source]#

Returns the qubit’s anharmonicity, (E_2 - E_1) - (E_1 - E_0).

Return type:

float

broadcast(event, **kwargs)#

Request a broadcast from CENTRAL_DISPATCH reporting event.

Parameters:

  • event (str) – event name from EVENTS

  • **kwargs –

Return type:

None

classmethod create()#

Use ipywidgets to create a new class instance

Return type:

QuantumSystem

abstract static default_params()#

Return dictionary with default parameter values for initialization of class instance

Return type:

Dict[str, Any]

eigensys(evals_count=6, filename=None, return_spectrumdata=False)[source]#

Calculates eigenvalues and corresponding eigenvectors using scipy.linalg.eigh. Returns two numpy arrays containing the eigenvalues and eigenvectors, respectively.

Parameters:

  • evals_count (int) – number of desired eigenvalues/eigenstates (default value = 6)

  • filename (Optional[str]) – path and filename without suffix, if file output desired (default value = None)

  • return_spectrumdata (if set to true, the returned data is provided as a SpectrumData object) – (default value = False)

Return type:

Union[Tuple[ndarray, ndarray], SpectrumData]

Returns:

eigenvalues, eigenvectors as numpy arrays or in form of a SpectrumData object

eigenvals(evals_count=6, filename=None, return_spectrumdata=False)[source]#

Calculates eigenvalues using scipy.linalg.eigh, returns numpy array of eigenvalues.

Parameters:

  • evals_count (int) – number of desired eigenvalues/eigenstates (default value = 6)

  • filename (Optional[str]) – path and filename without suffix, if file output desired (default value = None)

  • return_spectrumdata (bool) – if set to true, the returned data is provided as a SpectrumData object (default value = False)

Return type:

Union[SpectrumData, ndarray]

Returns:

eigenvalues as ndarray or in form of a SpectrumData object

get_dispersion_vs_paramvals(dispersion_name, param_name, param_vals, ref_param=None, transitions=(0, 1), levels=None, point_count=50, num_cpus=None)[source]#

Calculates eigenvalues/eigenstates for a varying system parameter, given an array of parameter values. Returns a SpectrumData object with energy_data[n] containing eigenvalues calculated for parameter value param_vals[n].

Parameters:

  • dispersion_name (str) – parameter inducing the dispersion, typically ‘ng’ or ‘flux’ (will be scanned over range from 0 to 1)

  • param_name (str) – name of parameter to be varied

  • param_vals (ndarray) – parameter values to be plugged in

  • ref_param (Optional[str]) – optional, name of parameter to use as reference for the parameter value; e.g., to compute charge dispersion vs. EJ/EC, use EJ as param_name and EC as ref_param

  • transitions (Union[Tuple[int, int], Tuple[Tuple[int, int], ...]]) – integer tuple or tuples specifying for which transitions dispersion is to be calculated (default: = (0,1))

  • levels (Union[int, Tuple[int, ...], None]) – tuple specifying levels (rather than transitions) for which dispersion should be plotted; overrides transitions parameter when given

  • point_count (int) – number of points scanned for the dispersion parameter for determining min and max values of transition energies (default: 50)

  • num_cpus (Optional[int]) – number of cores to be used for computation (default value: settings.NUM_CPUS)

Return type:

SpectrumData

get_initdata()#

Returns dict appropriate for creating/initializing a new Serializable object.

Return type:

Dict[str, Any]

get_matelements_vs_paramvals(operator, param_name, param_vals, evals_count=6, num_cpus=None)[source]#

Calculates matrix elements for a varying system parameter, given an array of parameter values. Returns a SpectrumData object containing matrix element data, eigenvalue data, and eigenstate data..

Parameters:

  • operator (str) – name of class method in string form, returning operator matrix

  • param_name (str) – name of parameter to be varied

  • param_vals (ndarray) – parameter values to be plugged in

  • evals_count (int) – number of desired eigenvalues (sorted from smallest to largest) (default value = 6)

  • num_cpus (Optional[int]) – number of cores to be used for computation (default value: settings.NUM_CPUS)

Return type:

SpectrumData

classmethod get_operator_names()#

Returns a list of all operator names for the quantum system. Note that this list omits any operators that start with “_”.

Parameters:

subsys – Class instance of quantum system

Return type:

List[str]

Returns:

list of operator names

get_spectrum_vs_paramvals(param_name, param_vals, evals_count=6, subtract_ground=False, get_eigenstates=False, filename=None, num_cpus=None)[source]#

Calculates eigenvalues/eigenstates for a varying system parameter, given an array of parameter values. Returns a SpectrumData object with energy_data[n] containing eigenvalues calculated for parameter value param_vals[n].

Parameters:

  • param_name (str) – name of parameter to be varied

  • param_vals (ndarray) – parameter values to be plugged in

  • evals_count (int) – number of desired eigenvalues (sorted from smallest to largest) (default value = 6)

  • subtract_ground (bool) – if True, eigenvalues are returned relative to the ground state eigenvalue (default value = False)

  • get_eigenstates (bool) – return eigenstates along with eigenvalues (default value = False)

  • filename (Optional[str]) – file name if direct output to disk is wanted

  • num_cpus (Optional[int]) – number of cores to be used for computation (default value: settings.NUM_CPUS)

Return type:

SpectrumData

abstract hamiltonian()[source]#

Returns the Hamiltonian

abstract hilbertdim()#

Returns dimension of Hilbert space

Return type:

int

matrixelement_table(operator, evecs=None, evals_count=6, filename=None, return_datastore=False)[source]#

Returns table of matrix elements for operator with respect to the eigenstates of the qubit. The operator is given as a string matching a class method returning an operator matrix. E.g., for an instance trm of Transmon, the matrix element table for the charge operator is given by trm.op_matrixelement_table(‘n_operator’). When esys is set to None, the eigensystem is calculated on-the-fly.

Parameters:

  • operator (str) – name of class method in string form, returning operator matrix in qubit-internal basis.

  • evecs (Optional[ndarray]) – if not provided, then the necessary eigenstates are calculated on the fly

  • evals_count (int) – number of desired matrix elements, starting with ground state (default value = 6)

  • filename (Optional[str]) – output file name

  • return_datastore (bool) – if set to true, the returned data is provided as a DataStore object (default value = False)

Return type:

Union[DataStore, ndarray]

plot_dispersion_vs_paramvals(dispersion_name, param_name, param_vals, ref_param=None, transitions=(0, 1), levels=None, point_count=50, num_cpus=None, **kwargs)[source]#

Generates a simple plot of a set of curves representing the charge or flux dispersion of transition energies.

Parameters:

  • dispersion_name (str) – parameter inducing the dispersion, typically ‘ng’ or ‘flux’ (will be scanned over range from 0 to 1)

  • param_name (str) – name of parameter to be varied

  • param_vals (ndarray) – parameter values to be plugged in

  • ref_param (Optional[str]) – optional, name of parameter to use as reference for the parameter value; e.g., to compute charge dispersion vs. EJ/EC, use EJ as param_name and EC as ref_param

  • transitions (Union[Tuple[int, int], Tuple[Tuple[int, int], ...]]) – integer tuple or tuples specifying for which transitions dispersion is to be calculated (default: = (0,1))

  • levels (Union[int, Tuple[int, ...], None]) – int or tuple specifying level(s) (rather than transitions) for which dispersion should be plotted; overrides transitions parameter when given

  • point_count (int) – number of points scanned for the dispersion parameter for determining min and max values of transition energies (default: 50)

  • num_cpus (Optional[int]) – number of cores to be used for computation (default value: settings.NUM_CPUS)

  • **kwargs – standard plotting option (see separate documentation)

Return type:

Tuple[Figure, Axes]

plot_evals_vs_paramvals(param_name, param_vals, evals_count=6, subtract_ground=False, num_cpus=None, **kwargs)[source]#

Generates a simple plot of a set of eigenvalues as a function of one parameter. The individual points correspond to the a provided array of parameter values.

Parameters:

  • param_name (str) – name of parameter to be varied

  • param_vals (ndarray) – parameter values to be plugged in

  • evals_count (int) – number of desired eigenvalues (sorted from smallest to largest) (default value = 6)

  • subtract_ground (bool) – whether to subtract ground state energy from all eigenvalues (default value = False)

  • num_cpus (Optional[int]) – number of cores to be used for computation (default value: settings.NUM_CPUS)

  • **kwargs – standard plotting option (see separate documentation)

Return type:

Tuple[Figure, Axes]

plot_matelem_vs_paramvals(operator, param_name, param_vals, select_elems=4, mode='abs', num_cpus=None, **kwargs)[source]#

Generates a simple plot of a set of eigenvalues as a function of one parameter. The individual points correspond to the a provided array of parameter values.

Parameters:

  • operator (str) – name of class method in string form, returning operator matrix

  • param_name (str) – name of parameter to be varied

  • param_vals (ndarray) – parameter values to be plugged in

  • select_elems (Union[int, List[Tuple[int, int]]]) – either maximum index of desired matrix elements, or list [(i1, i2), (i3, i4), …] of index tuples for specific desired matrix elements (default value = 4)

  • mode (str) – idx_entry from MODE_FUNC_DICTIONARY, e.g., ‘abs’ for absolute value (default value = ‘abs’)

  • num_cpus (Optional[int]) – number of cores to be used for computation (default value: settings.NUM_CPUS)

  • **kwargs – standard plotting option (see separate documentation)

Return type:

Tuple[Figure, Axes]

plot_matrixelements(operator, evecs=None, evals_count=6, mode='abs', show_numbers=False, show3d=True, **kwargs)[source]#

Plots matrix elements for operator, given as a string referring to a class method that returns an operator matrix. E.g., for instance trm of Transmon, the matrix element plot for the charge operator n is obtained by trm.plot_matrixelements(‘n’). When esys is set to None, the eigensystem with which eigenvectors is calculated.

Parameters:

  • operator (str) – name of class method in string form, returning operator matrix

  • evecs (Optional[ndarray]) – eigensystem data of evals, evecs; eigensystem will be calculated if set to None (default value = None)

  • evals_count (int) – number of desired matrix elements, starting with ground state (default value = 6)

  • mode (str) – idx_entry from MODE_FUNC_DICTIONARY, e.g., ‘abs’ for absolute value (default)

  • show_numbers (bool) – determines whether matrix element values are printed on top of the plot (default: False)

  • show3d (bool) – whether to show a 3d skyscraper plot of the matrix alongside the 2d plot (default: True)

  • **kwargs – standard plotting option (see separate documentation)

Return type:

Union[Tuple[Figure, Tuple[Axes, Axes]], Tuple[Figure, Axes]]

process_hamiltonian(native_hamiltonian, energy_esys=False)[source]#

Return qubit Hamiltonian in chosen basis: either return unchanged (i.e., in native basis) or transform into eigenenergy basis

Parameters:

  • native_hamiltonian (Union[ndarray, csc_matrix]) – Hamiltonian in native basis

  • energy_esys (Union[bool, Tuple[ndarray, ndarray]]) – If False (default), returns Hamiltonian in the native basis If True, the energy eigenspectrum is computed, returns Hamiltonian in the energy eigenbasis if energy_esys is the energy eigenspectrum, in the form of a tuple containing two ndarrays (eigenvalues and energy eigenvectors), returns Hamiltonian in the energy eigenbasis, and does not have to recalculate eigenspectrum.

Return type:

Union[ndarray, csc_matrix]

Returns:

Hamiltonian, either unchanged in native basis, or transformed into eigenenergy basis

process_op(native_op, energy_esys=False)[source]#

Processes the operator native_op: either hand back native_op unchanged, or transform it into the energy eigenbasis. (Native basis refers to the basis used internally by each qubit, e.g., charge basis in the case of Transmon.

Parameters:

  • native_op (Union[ndarray, csc_matrix]) – operator in native basis

  • energy_esys (Union[bool, Tuple[ndarray, ndarray]]) – If False (default), returns operator in the native basis If True, the energy eigenspectrum is computed, returns operator in the energy eigenbasis if energy_esys is the energy eigenspectrum, in the form of a tuple containing two ndarrays (eigenvalues and energy eigenvectors), returns operator in the energy eigenbasis, and does not have to recalculate eigenspectrum.

Return type:

Union[ndarray, csc_matrix]

Returns:

native_op either unchanged or transformed into eigenenergy basis

receive(event, sender, **kwargs)#

Receive a message from CENTRAL_DISPATCH and initiate action on it.

Parameters:

  • event (str) – event name from EVENTS

  • sender (DispatchClient) – original sender reporting the event

  • **kwargs –

Return type:

None

set_and_return(attr_name, value)[source]#

Allows to set an attribute after which self is returned. This is useful for doing something like example:

qubit.set_and_return('flux', 0.23).some_method()

instead of example:

qubit.flux=0.23
qubit.some_method()
Parameters:

  • attr_name (str) – name of class attribute in string form

  • value (Any) – value that the attribute is to be set to

Return type:

QubitBaseClass

Returns:

self

set_params(**kwargs)#

Set new parameters through the provided dictionary.

set_params_from_gui(change)#

Set new parameters through the provided dictionary.

supported_noise_channels()#

Returns a list of noise channels this QuantumSystem supports. If none, return an empty list.

Return type:

List

widget(params=None)#

Use ipywidgets to modify parameters of class instance

Parameters:

params (Dict[str, Any] | None) –