Change Log¶

Bug Fixes¶

• Fix bug in create(), which returned a Qobj with CSC data instead of CSR.
• Fix several bugs in mcsolve: Incorrect storing of collapse times and collapse operator records. Incorrect averaging of expectation values for different trajectories when using only 1 CPU.
• Fix bug in parsing of time-dependent Hamiltonian/collapse operator arguments that occured when the args argument is not a dictionary.
• Fix bug in internal _version2int function that cause a failure when parsing the version number of the Cython package.

New Features¶

• New module qutip.stochastic with stochastic master equation and stochastic Schrödinger equation solvers.
• Expanded steady state solvers. The function steady has been deprecated in favor of steadystate. The steadystate solver no longer use umfpack by default. New pre-processing methods for reordering and balancing the linear equation system used in direct solution of the steady state.
• New module qutip.qip with utilities for quantum information processing, including pre-defined quantum gates along with functions for expanding arbitrary 1, 2, and 3 qubit gates to N qubit registers, circuit representations, library of quantum algorithms, and basic physical models for some common QIP architectures.
• New module qutip.distributions with unified API for working with distribution functions.
• New format for defining time-dependent Hamiltonians and collapse operators, using a precalculated numpy array that specifies the values of the Qobj-coefficients for each time step.
• New functions for working with different superoperator representations, including Kraus and Chi representation.
• New functions for visualizing quantum states using Qubism and Schimdt plots: plot_qubism and plot_schmidt.
• Dynamics solver now support taking argument e_ops (expectation value operators) in dictionary form.
• Public plotting functions from the qutip.visualization module are now prefixed with plot_ (e.g., plot_fock_distribution). The plot_wigner and plot_wigner_fock_distribution now supports 3D views in addition to contour views.
• New API and new functions for working with spin operators and states, including for example spin_Jx, spin_Jy, spin_Jz and spin_state, spin_coherent.
• The expect function now supports a list of operators, in addition to the previously supported list of states.
• Simplified creation of qubit states using ket function.
• The module qutip.cyQ has been renamed to qutip.cy and the sparse matrix-vector functions spmv and spmv1d has been combined into one function spmv. New functions for operating directly on the underlaying sparse CSR data have been added (e.g., spmv_csr). Performance improvements. New and improved Cython functions for calculating expectation values for state vectors, density matrices in matrix and vector form.
• The concurrence function now supports both pure and mixed states. Added function for calculating the entangling power of a two-qubit gate.
• Added function for generating (generalized) Lindblad dissipator superoperators.
• New functions for generating Bell states, and singlet and triplet states.
• QuTiP no longer contains the demos GUI. The examples are now available on the QuTiP web site. The qutip.gui module has been renamed to qutip.ui and does no longer contain graphical UI elements. New text-based and HTML-based progressbar classes.
• Support for harmonic oscillator operators/states in a Fock state basis that does not start from zero (e.g., in the range [M,N+1]). Support for eliminating and extracting states from Qobj instances (e.g., removing one state from a two-qubit system to obtain a three-level system).
• Support for time-dependent Hamiltonian and Liouvillian callback functions that depend on the instantaneous state, which for example can be used for solving master eqautions with mean field terms.

Improvements¶

• Restructured and optimized implementation of Qobj, which now has significantly lower memory footprint due to avoiding excessive copying of internal matrix data.
• The classes OdeData, Odeoptions, Odeconfig are now called Result, Options, and Config, respectively, and are available in the module qutip.solver.
• The squeez function has been renamed to squeeze.
• Better support for sparse matrices when calculating propagators using the propagator function.
• Improved Bloch sphere.
• Restructured and improved the module qutip.sparse, which now only operates directly on sparse matrices (not on Qobj instances).
• Improved and simplified implement of the tensor function.
• Improved performance, major code cleanup (including namespace changes), and numerous bug fixes.
• Benchmark scripts improved and restructued.
• QuTiP is now using continous integration tests (TravisCI).

New Features¶

• Added Support for Windows
• New Bloch3d class for plotting 3D Bloch spheres using Mayavi.
• Bloch sphere vectors now look like arrows.
• Partial transpose function.
• Continuos variable functions for calculating correlation and covariance matrices, the Wigner covariance matrix and the logarithmic negativity for for multimode fields in Fock basis.
• The master-equation solver (mesolve) now accepts pre-constructed Liouvillian terms, which makes it possible to solve master equations that are not on the standard Lindblad form.
• Optional Fortran Monte Carlo solver (mcsolve_f90) by Arne Grimsmo.
• A module of tools for using QuTiP in IPython notebooks.
• Increased performance of the steady state solver.
• New Wigner colormap for highlighting negative values.
• More graph styles to the visualization module.

Bug Fixes:¶

• Function based time-dependent Hamiltonians now keep the correct phase.
• mcsolve no longer prints to the command line if ntraj=1.

New Features¶

• New method for generating Wigner functions based on Laguerre polynomials.
• coherent(), coherent_dm(), and thermal_dm() can now be expressed using analytic values.
• Unittests now use nose and can be run after installation.
• Added iswap and sqrt-iswap gates.
• Functions for quantum process tomography.
• Window icons are now set for Ubuntu application launcher.
• The propagator function can now take a list of times as argument, and returns a list of corresponding propagators.

Bug Fixes:¶

• mesolver now correctly uses the user defined rhs_filename in Odeoptions().
• rhs_generate() now handles user defined filenames properly.
• Density matrix returned by propagator_steadystate is now Hermitian.
• eseries_value returns real list if all imag parts are zero.
• mcsolver now gives correct results for strong damping rates.
• Odeoptions now prints mc_avg correctly.
• Do not check for PyObj in mcsolve when gui=False.
• Eseries now correctly handles purely complex rates.
• thermal_dm() function now uses truncated operator method.
• Cython based time-dependence now Python 3 compatible.
• Removed call to NSAutoPool on mac systems.
• Progress bar now displays the correct number of CPU’s used.
• Qobj.diag() returns reals if operator is Hermitian.
• Text for progress bar on Linux systems is no longer cutoff.

New Features¶

• QuTiP now includes solvers for both Floquet and Bloch-Redfield master equations.
• The Lindblad master equation and Monte Carlo solvers allow for time-dependent collapse operators.
• It is possible to automatically compile time-dependent problems into c-code using Cython (if installed).
• Python functions can be used to create arbitrary time-dependent Hamiltonians and collapse operators.
• Solvers now return Odedata objects containing all simulation results and parameters, simplifying the saving of simulation results.

• mesolve and mcsolve can reuse Hamiltonian data when only the initial state, or time-dependent arguments, need to be changed.
• QuTiP includes functions for creating random quantum states and operators.
• The generation and manipulation of quantum objects is now more efficient.
• Quantum objects have basis transformation and matrix element calculations as built-in methods.
• The quantum object eigensolver can use sparse solvers.
• The partial-trace (ptrace) function is up to 20x faster.
• The Bloch sphere can now be used with the Matplotlib animation function, and embedded as a subplot in a figure.
• QuTiP has built-in functions for saving quantum objects and data arrays.
• The steady-state solver has been further optimized for sparse matrices, and can handle much larger system Hamiltonians.
• The steady-state solver can use the iterative bi-conjugate gradient method instead of a direct solver.
• There are three new entropy functions for concurrence, mutual information, and conditional entropy.
• Correlation functions have been combined under a single function.
• The operator norm can now be set to trace, Frobius, one, or max norm.
• Global QuTiP settings can now be modified.
• QuTiP includes a collection of unit tests for verifying the installation.
• Demos window now lets you copy and paste code from each example.

Bug Fixes:¶

• Fixed bug pointed out by Brendan Abolins.
• Qobj.tr() returns zero-dim ndarray instead of float or complex.
• Updated factorial import for scipy version 0.10+

New Functions:¶

• Allow custom naming of Bloch sphere.

Bug Fixes:¶

• Fixed text alignment issues in AboutBox.
• Added fix for SciPy V>0.10 where factorial was moved to scipy.misc module.
• Added tidyup function to tensor function output.
• Removed openmp flags from setup.py as new Mac Xcode compiler does not recognize them.
• Qobj diag method now returns real array if all imaginary parts are zero.
• Examples GUI now links to new documentation.
• Fixed zero-dimensional array output from metrics module.

Bug Fixes¶

• Fixed issue where Monte Carlo states were not output properly.

New Functions¶

• Added linear entropy function.
• Number of CPU’s can now be changed.

Bug Fixes¶

• Metrics no longer use dense matrices.
• Fixed Bloch sphere grid issue with matplotlib 1.1.
• Qobj trace operation uses only sparse matrices.
• Fixed issue where GUI windows do not raise to front.

New Functions¶

• tidyup function to remove small elements from a Qobj.
• Added concurrence function.
• Added simdiag for simultaneous diagonalization of operators.
• Added eigenstates method returning eigenstates and eigenvalues to Qobj class.
• Added fileio for saving and loading data sets and/or Qobj’s.
• Added hinton function for visualizing density matrices.

Bug Fixes¶

• Switched Examples to new Signals method used in PySide 1.0.6+.
• Switched ProgressBar to new Signals method.
• Fixed memory issue in expm functions.
• Fixed memory bug in isherm.
• Made all Qobj data complex by default.
• Reduced ODE tolerance levels in Odeoptions.
• Fixed bug in ptrace where dense matrix was used instead of sparse.
• Fixed issue where PyQt4 version would not be displayed in about box.
• Fixed issue in Wigner where xvec was used twice (in place of yvec).