JKQ QCEC - A JKQ tool for Quantum Circuit Equivalence Checking

A JKQ tool for Quantum Circuit Equivalence Checking by the Institute for Integrated Circuits at the Johannes Kepler University Linz based on methods proposed in [1], [2], [3].

[1] L. Burgholzer and R. Wille. "Advanced Equivalence Checking for Quantum Circuits". IEEE Transactions on Computer Aided Design of Integrated Circuits and Systems (TCAD), 2021 (pre-print arXiv:2004.08420)

[2] L. Burgholzer, R. Raymond, and R. Wille. "Verifying Results of the IBM Qiskit Quantum Circuit Compilation Flow". In International Conference on Quantum Computing and Engineering (QCE), 2020 (pre-print arXiv:2009.02376)

[3] L. Burgholzer, R. Kueng, and R. Wille. "Random Stimuli Generation for the Verification of Quantum Circuits". In Asia and South Pacific Design Automation Conference (ASP-DAC), 2021 (pre-print arxiv:2011.07288)

This tool can be used for checking the equivalence of two quantum circuits provided in any of the following formats:

• Real (e.g. from RevLib),
• OpenQASM (e.g. used by IBM's Qiskit),
• TFC (e.g. from Reversible Logic Synthesis Benchmarks Page)
• QC (e.g. from Feynman)

with the following available methods:

• Reference - Construct and compare the DD for both circuits [1, Section III.B],
• - Starting from the identity I, either apply gates from G or (inverted) gates from G' according to one of the following strategies [1, Section IV.A]:
  • Naive - Alternate between applications of G and G' [1, Section V.A],
  • Proportional - Proportionally apply gates according to the gate count ratio of G and G' [1, Section V.B],
  • Lookahead - Always apply the gate yielding the smaller DD [1, Section V.C],
• Simulation - Conduct simulation runs to prove non-equivalence or give a strong indication of equivalence [1, Section IV.B] using:
  • Classical Stimuli - computational basis states [1, Section IV.B], [3, Section 3.1]
  • Local Quantum Stimuli - each qubit value is independently chosen from any of the six basis states (|0>, |1>, |+>, |->, |L>, |R>) [3, Section 3.2]
  • Global Quantum Stimuli - random stabilizer states [3, Section 3.3]
• Verification of compilation results - A dedicated scheme for verifying results of the IBM Qiskit Compilation Flow explicitly exploiting certain knowledge about the compilation process. [2]

The tool builds upon our decision diagram (DD) package as well as our quantum functionality representation (QFR). For more information, please visit iic.jku.at/eda/research/quantum_verification. If you want to visually explore decision diagrams for quantum computing, check out our installation-free web-tool JKQ DDVis.

If you have any questions, feel free to contact us via iic-quantum@jku.at or by creating an issue on GitHub.

Usage

JKQ QCEC is mainly developed as a C++ library with a commandline interface. However, using it in Python is as easy as

pip install jkq.qcec

and then in Python

from jkq import qcec
qcec.verify(...)

where the verify function is defined as follows:

"""
Interface to the JKQ QCEC tool for verifying quantum circuits

Params:
    file1 – Path to first file (required)
    file2 – Path to second file (required)
    method – Equivalence checking method to use (reference | naive | *proportional* | lookahead | simulation | compilation flow)
    tolerance – Numerical tolerance used during computation
    nsims – Number of simulations to conduct (for simulation method)
    fidelity – Fidelity limit for comparison (for simulation method)
    stimuliType - Type of stimuli to use (for simulation method: *classical* | localquantum | globalquantum)
    csv – Create CSV string for result
    statistics – Print statistics
    storeCEXinput: Store counterexample input state vector (for simulation method)
    storeCEXoutput: Store resulting counterexample state vectors (for simulation method)
    swapGateFusion – Optimization pass reconstructing SWAP operations
    singleQubitGateFusion – Optimization pass fusing consecutive single qubit gates
    removeDiagonalGatesBeforeMeasure – Optimization pass removing diagonal gates before measurements
Returns:
    JSON object containing results
"""
def verify(file1: Union[str, bytes, PathLike],
            file2: Union[str, bytes, PathLike],
            method: Method = Method.proportional,
            tolerance: float = 1e-13,
            nsims: int = 16,
            fidelity: float = 0.999,
            stimuliType: StimuliType = StimuliType.classical,
            csv: bool = False,
            statistics: bool = False,
            storeCEXinput: bool = False,
            storeCEXoutput: bool = False,
            swapGateFusion: bool = False,
            singleQubitGateFusion: bool = False,
            removeDiagonalGatesBeforeMeasure: bool = False) -> object

Command-line Executable

JKQ QCEC also provides a standalone executable with command-line interface called qcec_app. It provides the same options as the Python module as flags (e.g., --ps for printing statistics, or --method <method>for setting the method). Per default, this produces JSON formatted output. If the --csv flag is present, a CSV entry according to the following header is printed

filename1;nqubits1;ngates1;filename2;nqubits2;ngates2;expectedEquivalent;equivalent;method;time;maxActive;nsims

For a full list of options, call qcec_app --help.

Library Organisation

Internally the JKQ QCEC library works in the following way

• Import both input files into a qc::QuantumComputation object

  std::string file1 = "<PATH_TO_FILE_1>";
  qc::QuantumComputation qc1(file1);
  
  std::string file2 = "<PATH_TO_FILE_2>";
  qc::QuantumComputation qc2(file2);
  

• Instantiate an ec::EquivalenceChecker object with both circuits

  ec::Method method = ec::{ Reference | Naive | Proportional | Lookahead };
  auto eq = ec::ImprovedDDEquivalenceChecker(qc1, qc2, method);
  

  or

  auto eq = ec::PowerOfSimulationEquivalenceChecker(qc1, qc2);
  

  or

  auto eq = ec::CompilationFlowEquivalenceChecker(qc1, qc2);
  

• Set configuration options, e.g.,

  ec::Configuration config{};
  config.printStatistics = true;
  

• Perform the actual equivalence check

  eq.check(config);
  

• Print the results

  ec.printJSONResult(config.printStatistics);
  

  or access them through the eq.results member.

System requirements

Building (and running) is continuously tested under Linux, MacOS, and Windows using the latest available system versions for GitHub Actions. However, the implementation should be compatible with any current C++ compiler supporting C++14 and a minimum CMake version of 3.10.

Configure, Build, and Install

In order to build the library execute the following in the project's main directory

1. Configure CMake

   cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
   

   Windows users using Visual Studio and the MSVC compiler may try

   cmake -S . -B build -G "Visual Studio 15 2017" -A x64 -DCMAKE_BUILD_TYPE=Release
   

   Older CMake versions not supporting the above syntax (< 3.13) may be used with

   mkdir build && cd build
   cmake .. -DCMAKE_BUILD_TYPE=Release
   

2. Build the respective target.

   cmake --build ./build --config Release --target <target>
   

   The following CMake targets are available

   • qcec_app: The commandline executable
   • qcec_sim_app: Commandline tool dedicated for simulative verification
   • qcec: The standalone library
   • qcec_example: A small commandline demo example
   • qcec_test: Unit tests using GoogleTest

3. Optional: The QCEC library and tool may be installed on the system by executing

   cmake --build ./build --config Release --target install
   

   It can then also be included in other projects using the following CMake snippet

   find_package(qcec)
   target_link_libraries(${TARGET_NAME} PRIVATE JKQ::qcec)
   

Reference

If you use our tool for your research, we will be thankful if you refer to it by citing the appropriate publication:

@article{burgholzer2020advanced,
    author = {Burgholzer, Lukas and Wille, Robert},
    title = {Advanced Equivalence Checking for Quantum Circuits},
    year = 2021,
    journaltitle = {{IEEE} Trans. on {CAD} of Integrated Circuits and Systems}
}

@inproceedings{burgholzer2020verifyingResultsIBM,
  title = {Verifying results of the {{IBM Qiskit}} quantum circuit compilation flow},
  booktitle = {International Conference on Quantum Computing and Engineering},
  author = {Burgholzer, Lukas and Raymond, Rudy and Wille, Robert},
  year = {2020}
}

@inproceedings{burgholzer2021randomStimuliGenerationQuantum,
  title = {Random stimuli generation for the verification of quantum circuits},
  booktitle = {Asia and South Pacific Design Automation Conf.},
  author = {Burgholzer, Lukas and Richard, Kueng and Wille, Robert},
  year = {2021}
}