qrisp.QuantumCircuit.parity#

QuantumCircuit.parity(clbits, expectation=0, observable=False)[source]#

Instructs a parity operation on a set of classical bits.

This method creates a parity check (XOR) on measurement results, useful for quantum error correction and when interfacing with Stim. When the circuit is converted to Stim (via to_stim()), this creates either a DETECTOR instruction (if observable=False) or an OBSERVABLE_INCLUDE instruction (if observable=True).

Parameters:

clbitslist[Clbit] or Clbit: The classical bits to compute parity over. Can be a single Clbit or a list of Clbits representing measurement results.
expectationint, optional: The expected parity value (0 or 1). Default is 0.
observablebool, optional: If True, this parity is treated as a Stim observable rather than a detector. Default is False.

Returns:

ParityHandle: A ParityHandle object representing the parity result. This handle can be used as a key to look up detector/observable indices in the maps returned by to_stim().

See also

qrisp.parity(): The gate function version for use in QuantumSessions
to_stim(): Convert to Stim circuit with detector/observable maps
qrisp.jasp.ParityHandle: Documentation of the ParityHandle class

Examples

Create a simple detector checking that two qubits have even parity:

>>> from qrisp import QuantumCircuit
>>> qc = QuantumCircuit(2, 2)
>>> qc.h(0)
>>> qc.cx(0, 1)
>>> qc.measure([0, 1], [0, 1])
>>> handle = qc.parity([qc.clbits[0], qc.clbits[1]], expectation=0)
>>> print(handle)
ParityHandle(Clbit(cb_2), Clbit(cb_3))

Convert to Stim and check the detector:

>>> stim_circuit, meas_map, det_map = qc.to_stim(
...     return_measurement_map=True,
...     return_detector_map=True
... )
>>> det_map[handle]  # Get the Stim detector index
0