qml.qchem.qubit_observable

qubit_observable(o_ferm, cutoff=1e-12)

Convert a fermionic observable to a PennyLane qubit observable.

The fermionic operator is a tuple containing the fermionic coefficients and operators. For instance, the one-body fermionic operator \(a_2^\dagger a_0\) is specified as [2, 0] and the two-body operator \(a_4^\dagger a_3^\dagger a_2 a_1\) is specified as [4, 3, 2, 1].

Parameters

• tuple (o_ferm) – fermionic operator

• cutoff (float) – cutoff value for discarding the negligible terms

Returns

Simplified PennyLane Hamiltonian

Return type

Hamiltonian

Example

>>> coeffs = np.array([1.0, 1.0])
>>> ops = [[0, 0], [0, 0]]
>>> f = (coeffs, ops)
>>> print(qubit_observable(f))
((-1+0j)) [Z0]
+ ((1+0j)) [I0]

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