Qulacs

Bug fixes

* State sum and constant multiplication on QuantumStateGpu (163, thanks to puyokw)
* Bugfix on state norm (164, thanks to puyokw)

New features & Updates
* Two qubit depolarizing noise gate (148, thanks to corryvrequan)
* Show error message, return NULL ptr, and raise exception for invalid gate instantiation (158 and 159, thanks to kenjikun and corryvrequan)
* Add get_qubit_count function for python (153, thanks to yamamoto-takahiro and corryvrequan)

Bug fixes
* Bugfix in two qubit dense gate in C simulator (145, thanks to k-ishizaka and corryvrequan)
* Fix cmake script for GPU on ubuntu (149 and 150, thanks to shukob)
* Fix parametric quantum gates to be compatible with recently added `DensityMatrix` class (152, thanks to corryvrequan)
* Bugfix on gpu state load (154, thanks to corryvrequan and yoooopeeee)
* Fix a problem in CMake script which didn't work when path contains "./src/" (155, thanks to miyo and corryvrequan)
* Bugfix of freeing unreleased memory in sampling gpu (157, thanks to puyokw)
* Add gpu version of inner_product to python (160, thanks to puyokw)

This is a hot-fix release that fixes an issue on parametric gate (https://github.com/qulacs/qulacs/pull/140).

For those who have installed Qulacs 0.1.4, please update qulacs from PyPI (`$ pip install --upgrade qulacs`).

New features & Updates
- Add `DensityMatrix` class (131, thanks to corryvrequan)
- Add Dockerfile (129, thanks to yurisan)
- Add functions of cudaStream version in order to launch several kernels simultaneously (130, thanks to puyokw )
- Add 'get_name' method for `QuantumGateBase` class (135, thanks to yamamoto-takahiro)

Bug fixes
- Debug gpu version of transition_amplitude_multi_qubit_pauli_operator_Z_mask (130, thanks to puyokw )
- Bugfix for independent XZ noise (131, thanks to corryvrequan)
- Bugfix for parametric gate bugs in gpu state (138, thanks to corryvrequan)

New features
* Add gpu version of `state_add` and `multiply_coef` (118, thanks to puyokw )

Updates
* Add tests for `state_add` and `multiply_coef` (118, thanks to puyokw )
* Update LICENSE (123, thanks to TenninYan )

Bug fixes
* Fix gpu version of load function: add `copy_quantum_state_from_cppstate_host` in `gpusim` (118, thanks to puyokw )
* Bugfix for GPU codes (120, thanks to corryvrequan )
* Enabled some functions (on parametric quantum gate and quantum gate base) which used to be available only in cpp ver. of qulacs, also in python ver. (124, thanks to corryvrequan )

New features
* New quantum gate `ReversibleBooleanGate`, which supplies easy way to implement classical reversible function as an quantum gate(104, thanks to corryvrequan )
* Implementation of new gates, `StateReflection`, which is frequently used in algorithms such as Grover's search or HHL, and `SparseMatrix` (108, thanks to corryvrequan )
* New methods `QuantumStateCpu::add_state` and `QuantumStateCpu::multiply_coef` for use of analysis (111, thanks to corryvrequan )
* New methods in `multi_qubit_dense_matrix_gate_host` to be called when the number of target qubits is small (112, thanks to puyokw )

Updates
* Changes in return value policy of copy function and gate factory from `automatic_reference` to `take_ownership` (101, thanks to corryvrequan )
* New test class for pointer handling, checking if there is no segfault in typical codes (101, thanks to corryvrequan )
* New constructor for `PauliOperator` in python and new methods `GeneralQuantumOperator.is_hermitian()`, to check if an operator is hermitian (103, thanks to hal0taso )
* New initialization to `expectation_value_single_qubit_Pauli_operator_hos` (105, thanks to puyokw )

Bug fixes
* Bugfix of path (95, thanks to kwkbtr )
* GCC version updates, changes in instruction and typo fixed in `README`(96, 97, and 98, thanks to yoooopeeee , corryvrequan )
* Bugfix of CI travis test (100, thanks to y-yu )
* Bugfix in `QuantumState::get_zero_probability` (107, thanks to corryvrequan )
* Bugfix in `QuantumState::get_marginal_probability` (109 , thanks to corryvrequan )
* Bugfix of the GPU codes not been called when calculating expectation values (114, thanks to puyokw )