cirq.measure_pauli_string rejects negated pauli strings

[Strilanc]

import cirq
cirq.measure_single_paulistring(-cirq.Y(cirq.LineQubit(0))*cirq.Y(cirq.LineQubit(1)), key='1')

[tanujkhattar]

This should be fairly straightforward to fix. We raise an error if the pauli string is does not have a coefficient of 1 here -

Cirq/cirq-core/cirq/ops/measure_util.py

Line 55 in 9a1609c

if pauli_observable.coefficient != 1:

However, the underlying PauliMeasurementGate does support DensePauliStrings with coefficient +1 and -1. So, instead of passing pauli_observable.values() to construct the PauliMeasurementGate, we can just pass pauli_observable.dense(pauli_observable.keys()) and then remove the check for coefficient being exactly +1.

Cirq/cirq-core/cirq/ops/measure_util.py

Line 60 in 9a1609c

return PauliMeasurementGate(pauli_observable.values(), key).on(*pauli_observable.keys())

[skushnir123]

I can take this issue.