pygsti.modelmembers.states.tpstate
The TPState class and supporting functionality.
Module Contents
Classes
A fixed-unit-trace state vector. |
- class pygsti.modelmembers.states.tpstate.TPState(vec, basis=None, evotype='default', state_space=None)
Bases:
pygsti.modelmembers.states.densestate.DenseState
A fixed-unit-trace state vector.
This state vector is fully parameterized except for the first element, which is frozen to be 1/(d**0.25). This is so that, when the state vector is interpreted in the Pauli or Gell-Mann basis, the represented density matrix has trace == 1. This restriction is frequently used in conjuction with trace-preserving (TP) gates, hence its name.
Parameters
- vecarray_like or State
a 1D numpy array representing the state. The shape of this array sets the dimension of the state.
- basisBasis or str
The basis that vec is in.
- evotypeEvotype or str, optional
The evolution type. The special value “default” is equivalent to specifying the value of pygsti.evotypes.Evotype.default_evotype.
- state_spaceStateSpace, optional
The state space for this operation. If None a default state space with the appropriate number of qubits is used.
Initialize a new state Vector
- property columnvec
Direct access the the underlying data as column vector, i.e, a (dim,1)-shaped array.
- property num_params
Get the number of independent parameters which specify this state vector.
Returns
- int
the number of independent parameters.
- set_dense(vec)
Set the dense-vector value of this state vector.
Attempts to modify this state vector’s parameters so that the raw state vector becomes vec. Will raise ValueError if this operation is not possible.
Parameters
- vecarray_like or State
A numpy array representing a state vector, or a State object.
Returns
None
- to_vector()
Get the state vector parameters as an array of values.
Returns
- numpy array
The parameters as a 1D array with length num_params().
- from_vector(v, close=False, dirty_value=True)
Initialize the state vector using a 1D array of parameters.
Parameters
- vnumpy array
The 1D vector of state vector parameters. Length must == num_params()
- closebool, optional
Whether v is close to this state vector’s current set of parameters. Under some circumstances, when this is true this call can be completed more quickly.
- dirty_valuebool, optional
The value to set this object’s “dirty flag” to before exiting this call. This is passed as an argument so it can be updated recursively. Leave this set to True unless you know what you’re doing.
Returns
None
- deriv_wrt_params(wrt_filter=None)
The element-wise derivative this state vector.
Construct a matrix whose columns are the derivatives of the state vector with respect to a single param. Thus, each column is of length dimension and there is one column per state vector parameter.
Parameters
- wrt_filterlist or numpy.ndarray
List of parameter indices to take derivative with respect to. (None means to use all the this operation’s parameters.)
Returns
- numpy array
Array of derivatives, shape == (dimension, num_params)