Release notes: https://docs.quantum.ibm.com/api/qiskit/release-notes/1.2

Changelog

Deprecated

• Deprecate BackendV1 and qiskit.providers.models (backport #12629) (#12864)
• Deprecate fake backends based on BackendV1 (backport #12660) (#12837)
• fixes #9355 deprecate visualize_transition (#12287) (#12822)
• Deprecate V1 Primitives and their utils (#12575)
• Deprecate Qobj and assemble (#12649)
• Deprecate accidentally public internal helper methods on QuantumCircuit (#12785)
• Improve the performance of the ProductFormula synthesizers (#12724)
• Add warning for bad justify input, in circuit_drawer (#12458)
• Deprecate tuple-like access to CircuitInstruction (#12640)

Added

• 'Peephole' optimization - or: collecting and optimizing two-qubit blocks - before routing (#12727) (#12881)
• Avoid operator creation in transpiler (#12826) (#12875)
• Port star_preroute to rust (backport #12761) (#12846)
• Add config option to leverage all cores for sabre (#12780) (#12841)
• Bitarray postselect (#12693) (#12836)
• Add AnnotatedOperation.params and fix some control issues (#12752) (#12828)
• Move generate_preset_pass_manager to a standalone file (#12762)
• Update version of OpenQASM 3.0 standard library (#12387)
• Port synth_permutation_depth_lnn_kms to Rust (#12746)
• Rewrite OpenQASM 3 exporter symbol table (#12776)
• Port synth_clifford_bm to Rust. (#12714)
• Update MCX recursive synthesis method to reduce number of CX gates (#12772)
• Barebone generic backend options (#12747)
• Adding QFT gate to natively reason about Quantum Fourier Transforms (#11463)
• Improve the performance of the ProductFormula synthesizers (#12724)
• Improved MCXVChain with dirty auxiliary qubits (#9687)
• Oxidize synth_cnot_count_full_pmh (#12588)
• Add Uniform State Preparation (#12112)
• Port synth_clifford_greedy to Rust (#12601)
• Oxidize synth_permutation_acg (#12543)
• improving quantum_causal_cone method in python (#12668)
• binary matrices utils in rust (#12456)
• Add infrastructure for gates, instruction, and operations in Rust (#12459)
• Add option to user config to control idle_wires in circuit drawer (#12462)
• [unitaryHACK] Controlling the Insertion of Multi-Qubit Gates in the Generation of Random Circuits #12059 (#12483)
• Add pos for Parameter (#12496)
• Update transpile() and generate_preset_pass_manager to convert loose input of constraints to a Target with Target.from_configuration() (#12185)
• Add DenseLayout trial to SabreLayout (#12453)
• add insert_barrier argument to UnitaryOverlap (#12321)
• Add new method for single bitstring target when measuring stabilizerstate probabilities_dict (#12147)
• Replace initialization method by Isometry in StatePreparation (#12178)

Changed

• Update metadata of Primitives V2 (#12784) (#12857)
• Change the default routing_method to sabre (#12806) (#12847)
• Use rustworkx 0.15.0 features in DAGCircuit.remove_op_node (#12756)
• Add infrastructure for gates, instruction, and operations in Rust (#12459)

Fixed

• Fix error message upon misalignment in PadDynamicalDecoupling (#12952) (#12954)
• Improve error message on bad OpenQASM 3 basis_gates argument (#12945) (#12946)
• Fix dag visualization with Var wires (#12848) (#12924)
• Remove init peephole optimization discrete basis check (#12898) (#12920)
• Fix parsing of huge OpenQASM 2 conditionals (#12774) (#12854)
• Fix StatevectorSampler to raise an error if a circuit with c_if is passed (#12842) (#12851)
• Make BitArray.{slice_bits,slice_shots,__getitem__} raise IndexError when indices are not valid (#12755) (#12845)
• Add AnnotatedOperation.params and fix some control issues (#12752) (#12828)
• Fix BitArray.from_counts/from_samples to not fail for input with only 0 outcome and num_bits=None (#12800) (#12820)
• fix issue/12311 with fractional gate in basis (#12511)
• Validate order kwarg in BitArray.from_bool_array() (#12686)
• Rewrite OpenQASM 3 exporter symbol table (#12776)
• Fixing and documenting how the Estimator calculates stds (#12670)
• Add clifford gates to collect_cliffords (#12750)
• Fix C3SXGate to_matrix method (#12742)
• Oxidize synth_cnot_count_full_pmh (#12588)
• Fix replace_block_with_op on operations with wrong number of qubits (#12637)
• Enable the new efficient MCX decompose (#12628)
• GenericBackendV2 should fail when the backend cannot allocate the basis gate because its size (#12653)
• Fix some bugs in loading Solovay Kitaev decompositions (#12579)
• Invalidate parameters cache on circuit copy (#12619)
• Fix v2 pulse drawer (#12608)
• Use hash of numeric value for bound parameter expressions (#12488)
• Fix bugs with VF2Layout pass and Qiskit Aer 0.13 (#11585)
• Fix QuantumCircuit.depth with zero-operands and Expr nodes (#12429)
• Avoid exception in Target.has_calibration for instruction without properties (#12526)
• Implement __array__ for qasm2._DefinedGate (#12119)
• Fix a bug in isometry.rs (#12469)
• Avoid lossing precision when scaling frequencies (#12392) (#12416)
• Avoid lossing precision when scaling frequencies (#12392)
• Fix unnecessary serialisation of PassManager in serial contexts (#12410) (#12413)
• Fix unnecessary serialisation of PassManager in serial contexts (#12410)
• Handle huge integers in OpenQASM 2 expression evaluator (#12140) (#12400)
• Fix a corner case of SparsePauliOp.apply_layout (#12375) (#12402)
• Fix a corner case of SparsePauliOp.apply_layout (#12375)
• Handle huge integers in OpenQASM 2 expression evaluator (#12140)
• Fix {Pauli,SparsePauliOp}.apply_layout to raise an error with negative or duplicate indices (#12385) (#12386)
• Fix {Pauli,SparsePauliOp}.apply_layout to raise an error with negative or duplicate indices (#12385)
• fix edge coloring bug in plot_coupling_map (#12369) (#12379)
• Fix missing layout in Commuting2qGateRouter (#12137) (#12383)
• Fix missing layout in Commuting2qGateRouter (#12137)
• fix edge coloring bug in plot_coupling_map (#12369)