EquivalenceLibrary.set_entry does not clear old entries in graph

[jakelishman]

Environment

• Qiskit version: 1.0.1
• Python version: 3.10
• Operating system: macOS

What is happening?

When using EquivalenceLibrary.set_entry to replace a set of entries with another, the get_entry method will update with the new entries, but the graph attribute will not have suitably changed the edges, meaning that the BasisTranslator will use the old rules.

How can we reproduce the issue?

import math
from qiskit.transpiler.passes import BasisTranslator
from qiskit.circuit.equivalence import EquivalenceLibrary
from qiskit.circuit import library, QuantumCircuit

equiv = EquivalenceLibrary()

cx_to_cz = QuantumCircuit(2)
cx_to_cz.ry(-math.pi / 4, 1)
cx_to_cz.cz(0, 1)
cx_to_cz.ry(math.pi / 2, 1)
equiv.add_equivalence(library.CXGate(), cx_to_cz)

cx_to_cz_worse = QuantumCircuit(2, global_phase=math.pi)
cx_to_cz_worse.ry(math.pi / 2, 1)
cx_to_cz_worse.rx(math.pi, 1)
cx_to_cz_worse.cz(0, 1)
cx_to_cz_worse.ry(math.pi / 2, 1)
cx_to_cz_worse.rx(math.pi, 1)
equiv.set_entry(library.CXGate(), [cx_to_cz_worse])

qc = QuantumCircuit(2)
qc.cx(0, 1)
BasisTranslator(equiv, ["cz", "rx", "ry", "rz"])(qc).draw()

q_0: ─────────────■────────────
     ┌──────────┐ │ ┌─────────┐
q_1: ┤ Ry(-π/4) ├─■─┤ Ry(π/2) ├
     └──────────┘   └─────────┘

What should happen?

Since we replaced the "good" rule with a "bad" rule, the basis translator should only be able to find the bad rule and the output should be:

global phase: π

q_0: ─────────────────────■─────────────────────
     ┌─────────┐┌───────┐ │ ┌─────────┐┌───────┐
q_1: ┤ Ry(π/2) ├┤ Rx(π) ├─■─┤ Ry(π/2) ├┤ Rx(π) ├
     └─────────┘└───────┘   └─────────┘└───────┘

Any suggestions?

No response