FermionicMeasure¶

class FermionicMeasure(*args, _force_mutable=False, **kwargs)¶

Bases: FermionicInstruction, Measure

A measurement of a single fermionic mode, writing its outcome into one classical bit.

This is the fermionic counterpart of Measure, and the one instruction on a FermionicCircuit that is not a FermionicGate: a measurement is not unitary, and Gate admits no classical bits. Place it with FermionicCircuit.measure() or FermionicCircuit.measure_all() rather than constructing it directly.

It subclasses Measure so that the circuit drawers, which dispatch on isinstance(op, Measure), render it with the usual measurement symbol rather than as a generic boxed instruction.

Important

What the measured bit means is decided by the fermion-to-qubit encoding, not by this instruction. Under an occupation-basis encoding such as Jordan-Wigner, mode \(i\) is carried by a single qubit and the bit is that mode’s occupation, which is the reading TrivialOccupationFermionicMeasureSynthesis implements. A F2QLayout relates whole registers whose two sides may differ in size, so in general a mode has no single qubit to measure; an encoding for which that is the case needs its own synthesis plugin, and this instruction carries no encoding assumption of its own.