v2.7.1

Bugfixes

• The changes to operator estimation (gh-870, gh-896) were not made in a backwards-compatible fashion, and therefore this patch release aims to remedy that. Going forward, there will be much more stringent requirements around backwards compatibility and deprecation (@karalekas, gh-899).

v2.7.0

Improvements and Changes

• Standard deviation -> standard error in operator estimation (@msohaibalam, gh-870).

• Update what pyQuil expects from quilc in terms of rewiring pragmas -- they are now comments rather than distinct instructions (@ecpeterson, gh-878).

• Allow users to deprioritize QPU jobs -- mostly a Rigetti-internal feature (@jvalery2, gh-877).

• Remove the qubits field from the TomographyExperiment dataclass (@msohaibalam, gh-896).

Bugfixes

• Ensure that shots aren't lost when passing a Program through address_qubits (@notmgsk, gh-895).

• Fixed the conda install command in the README (@seandiscovery, gh-890).

v2.6.0

Improvements and Changes

• Added a CODEOWNERS file for default reviewers (@karalekas, gh-855).

• Bifurcated the QPUCompiler endpoint parameter into two -- quilc_endpoint and qpu_compiler_endpoint -- to reflect changes in Quantum Cloud Services (@karalekas, gh-856).

• Clarified documentation around the DELAY pragma (@willzeng, gh-862).

• Added information about the local_qvm context manager to the getting started documentation (@willzeng, gh-851).

• Added strict version lower bounds on the rpcq and networkx dependencies (@notmgsk, gh-828).

• A slice of a Program object now returns a Program object (@notmgsk, gh-848).

Bugfixes

• Added a non-None default timeout to the QVMCompiler object and the get_benchmarker function (@karalekas, gh-850, gh-854).

• Fixed the docstring for the apply_clifford_to_pauli function (@kylegulshen, gh-836).

• Allowed the apply_clifford_to_pauli function to now work with the Identity as input (@msohaibalam, gh-849).

• Updated a stale link to the Rigetti Forest Slack workspace (@karalekas, gh-860).

• Fixed a notation typo in the documentation for noise (@willzeng, gh-861).

• An IndexError is now raised when trying to access an out-of-bounds entry in a MemoryReference (@notmgsk, gh-819).

• Added a check to ensure that measure_observables takes as many shots as requested (@marcusps, gh-846).

Special thanks to @willzeng for all the contributions this release!

v2.5.2

This is a bugfix release, repairing a bug in the serialization of ExperimentResults objects.

v2.5.1

This is a bugfix release that corrects some errors found in the operator expectation code.

v2.5.0

Improvements and Changes

• PyQuil's Gate objects now expose .controlled(q) and .dagger() modifiers, which turn a gate respectively into its controlled variant, conditional on the qubit q, or into its inverse.
• The operator estimation suite's measure_observables method now exposes a readout_symmetrize argument, which helps mitigate a machine's fidelity asymmetry between recognizing a qubit in the ground state versus the excited state.
• The MEASURE instruction in pyQuil now has a mandatory second argument. Previously, the second argument could be omitted to induce "measurement for effect", without storing the readout result to a classical register, but users found this to be a common source of accidental error and a generally rude surprise. To ensure the user really intends to measure only for effect, we now require that they supply an explicit None as the second argument.

Bugfixes

• Some stale tests have been brought into the modern era.

v2.4.0

Announcements

• The Quil Compiler (quilc) and the Quantum Virtual Machine (qvm), which are part of the Forest SDK, have been open sourced! In addition to downloading the binaries, you can now build these applications locally from source, or run them via the Docker images rigetti/quilc and rigetti/qvm. These Docker images are now used as the services in the GitLab CI build plan YAML (gh-792, gh-794, gh-795).

Improvements and Changes

• The WavefunctionSimulator now supports the use of parametric Quil programs, via the memory_map parameter for its various methods (gh-787).

• Operator estimation data structures introduced in v2.2 have changed. Previously, ExperimentSettings had two members: in_operator and out_operator. The out_operator is unchanged, but in_operator has been renamed to in_state and its data type is now TensorProductState instead of PauliTerm. It was always an abuse of notation to interpret pauli operators as defining initial states. Analogous to the Pauli helper functions sI, sX, sY, and sZ, TensorProductState objects are constructed by multiplying together terms generated by the helper functions plusX, minusX, plusY, minusY, plusZ, and minusZ. This functionality enables process tomography and process DFE (gh-770).

• Operator estimation now offers a "greedy" method for grouping tomography-like experiments that share a natural tensor product basis (ntpb), as an alternative to the clique cover version (gh-754).

• The quilc endpoint for rewriting Quil parameter arithmetic has been changed from resolve_gate_parameter_arithmetic to rewrite_arithmetic (gh-802).

• The difference between ProtoQuil and QPU-supported Quil is now better defined (gh-798).

Bugfixes

• Resolved an issue with post-gate noise in the pyQVM (gh-801).

• A TypeError with a useful error message is now raised when a Program object is run on a QPU-backed QuantumComputer, rather than a confusing AttributeError (gh-799).

pyQuil 2.3

PyQuil 2.3 is the latest release of pyQuil, Rigetti's toolkit for constructing and running
quantum programs. A major new feature is the release of a new suite of simulators:

• We're proud to introduce the first iteration of a Python-based quantum virtual machine (QVM) called PyQVM. This QVM is completely contained within pyQuil and does not need any external dependencies. Try using it with get_qc("9q-square-pyqvm") or explore the pyquil.pyqvm.PyQVM object directly. Under-the-hood, there are three quantum simulator backends:

  • ReferenceWavefunctionSimulator uses standard matrix-vector multiplication to evolve a statevector. This includes a suite of tools in pyquil.unitary_tools for dealing with unitary matrices.
  • NumpyWavefunctionSimulator uses numpy's tensordot functionality to efficiently evolve a statevector. For most simulations, performance is quite good.
  • ReferenceDensitySimulator uses matrix-matrix multiplication to evolve a density matrix.

• Matrix representations of Quil standard gates are included in pyquil.gate_matrices (gh-552).

• The density simulator has extremely limited support for Kraus-operator based noise models. Let us know if you're interested in contributing more robust noise-model support.

• This functionality should be considered experimental and may undergo minor API changes.

Important changes to note:

• Quil math functions (like COS, SIN, ...) used to be ambiguous with respect to case sensitivity. They are now case-sensitive and should be uppercase (gh-774).
• In the next release of pyQuil, communication with quilc will happen exclusively via the rpcq protocol. LocalQVMCompiler and LocalBenchmarkConnection will be removed in favor of a unified QVMCompiler and BenchmarkConnection. This change should be transparent if you use get_qc and get_benchmarker, respectively. In anticipation of this change we recommend that you upgrade your version of quilc to 1.3, released Jan 30, 2019 (gh-730).
• When using a paramaterized gate, the QPU control electronics only allowed multiplying parameters by powers of two. If you only ever multiply a parameter by the same constant, this isn't too much of a problem because you can fold the multiplicative constant into the definition of the parameter. However, if you are multiplying the same variable (e.g. gamma in QAOA) by different constants (e.g. weighted maxcut edge weights) it doesn't work. PyQuil will now transparently handle the latter case by expanding to a vector of parameters with the constants folded in, allowing you to multiply variables by whatever you want (gh-707).

As always, this release contains bug fixes and improvements:

• The CZ gate fidelity metric available in the Specs object now has its associated standard error, which is accessible from the method Specs.fCZ_std_errs (gh-751).
• Operator estimation code now correctly handles identity terms with coefficients. Previously, it would always estimate these terms as 1.0 (gh-758).
• Operator estimation results include the total number of counts (shots) taken.
• Operator estimation JSON serialization uses utf-8. Please let us know if this causes problems (gh-769).
• The example quantum die program now can roll dice that are not powers of two (gh-749).
• The teleportation and Meyer penny game examples had a syntax error (gh-778, gh-772).
• When running on the QPU, you could get into trouble if the QPU name passed to get_qc did not match the lattice you booked. This is now validated (gh-771).

We extend thanks to community member estamm12 for their contribution to this release.

pyQuil 2.2

PyQuil 2.2 is the latest release of pyQuil, Rigetti's toolkit for constructing and running quantum programs. Bug fixes and improvements include:

• pauli.is_zero and paulis.is_identity would sometimes return erroneous answers (gh-710).
• Parameter expressions involving addition and subtraction are now converted to Quil with spaces around the operators, e.g. theta + 2 instead of theta+2. This disambiguates subtracting two parameters, e.g. alpha - beta is not one variable named alpha-beta (gh-743).
• T1 is accounted for in T2 noise models (gh-745).
• Documentation improvements (gh-723, gh-719, gh-720, gh-728, gh-732, gh-742).
• Support for PNG generation of circuit diagrams via LaTeX (gh-745).
• We've started transitioning to using Gitlab as our continuous integration provider for pyQuil (gh-741, gh-752).

This release includes a new module for facilitating the estimation of quantum observables/operators (gh-682). First-class support for estimating observables should make it easier to express near-term algorithms. This release includes:

• data structures for expressing tomography-like experiments and their results
• grouping of experiment settings that can be simultaneously estimated
• functionality to executing a tomography-like experiment on a quantum computer

Please look forward to more features and polish in future releases. Don't hesitate to submit feedback or suggestions as GitHub issues.

We extend thanks to community member petterwittek for their contribution to this release.

pyQuil 2.1

PyQuil 2.1 is an incremental release of pyQuil, Rigetti's toolkit for constructing and running quantum programs. Changes include:

• Major documentation improvements.
• QuantumComputer.run() accepts an optional memory_map parameter to facilitate running parametric executables (gh-657).
• QuantumComputer.reset() will reset the state of a QAM to recover from an error condition (gh-703).
• Bug fixes (gh-674, gh-696).
• Quil parser improvements (gh-689, gh-685).
• Optional interleaver argument when generating RB sequences (gh-673).
• Our GitHub organization name has changed from rigetticomputing to rigetti (gh-713).