DQCsim cQASM frontend

See also: DQCsim and libqasm.

This repository contains some glue code to allow DQCsim to run cQASM files (file extension *.cq).

Status

The implementation is currently incomplete. The following things are missing:

• The error model specified in the cQASM file is ignored. You'll have to configure stuff related to error modeling yourself through the respective simulation backend and/or operators.

• measure_parity is not implemented.

Install

You can install using pip using pip install dqcsim-cqasm or equivalent. If you're installing with --user, make sure that the path Python installs the executables into is in your system path, otherwise DQCsim will not be able to find the plugin. A simple way to see where the files are installed is to run pip uninstall dqcsim-cqasm; it shows which files it's about to delete before querying for confirmation.

Building/installing from source

• Make sure all git submodules are checked out: git submodule update --init --recursive

• Build the wheel file locally: python3 setup.py build bdist_wheel

• Install the wheel file you just built: pip install target/python/dist/* (or equivalent)

Don't push a build like this to PyPI or attempt to distribute this wheel; it will likely only work locally due to hardcoded paths and the likes. Refer to release.md for more info.

Usage

Once the plugin is installed, DQCsim will parse any file with a .cq file extension as a cQASM file through this plugin, so something like dqcsim test.cq qx should work (assuming dqcsim-qx is installed and test.cq exists).

The frontend ignores any arguments passed to its run callback and doesn't have anything useful to return (it just echoes back what you passed it).

As with QX, the display_binary "gate" is used to print simulation results to the terminal by means of printing the most recent measurement state. The frontend also outputs the measurement register contents at the end of the program as the ArbData returned by the run() call, in the following format:

{
    "qubits": [
        {  /* data for qubit 0 */
            "value": <value in qubit measurement register as 0 or 1>,
            "average": <measurement averaging register value>,
            "raw": <raw value returned by backend; 0 or 1, or null for undefined>,
            "json": <JSON part of the optional ArbData associated with the measurement>,
            "binary": [
                [<bytes of binary string 0 of ArbData associated with measurement>],
                [<bytes of binary string 1>],
                <etc., empty list if no ArbData>
            ]
        },
        {<data for qubit 1>},
        {<data for qubit 2>},
        <etc. for all qubits>
    ]
}

The raw, json, and binary keys are not present when the qubit was never measured at all. value defaults to 0 in that case. average is only present when the qubit has been measured since the latest reset_averaging operation.

The display "gate" doesn't provide any additional information over display_binary, as DQCsim frontends don't know what the actual quantum state is; this information is private to the backend. Refer to the documentation of the backend for ways to get additional information, if any. Be aware that DQCsim's qubit numbering starts at one, so the cQASM frontend adds 1 to the zero-referenced cQASM qubit indices to convert.

There is currently no way to attach arbs to gates or to the qubits themselves. If you need to do this, you can write an operator and insert it immediately behind the cQASM frontend.