v2.5.0

Improvements and Changes

• PyQuil's Gate objects now expose .controlled(q) and .dagger() modifiers, which turn a gate respectively into its controlled variant, conditional on the qubit q, or into its inverse.
• The operator estimation suite's measure_observables method now exposes a readout_symmetrize argument, which helps mitigate a machine's fidelity asymmetry between recognizing a qubit in the ground state versus the excited state.
• The MEASURE instruction in pyQuil now has a mandatory second argument. Previously, the second argument could be omitted to induce "measurement for effect", without storing the readout result to a classical register, but users found this to be a common source of accidental error and a generally rude surprise. To ensure the user really intends to measure only for effect, we now require that they supply an explicit None as the second argument.

Bugfixes

• Some stale tests have been brought into the modern era.