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minor improvements to examples, documentation, internally used variable names

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mattia-robbiano
2025-11-13 10:45:32 +02:00
parent 7ea8dc861b
commit d4ab3eba52
2 changed files with 59 additions and 33 deletions
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37
src/qibotn/backends/quimb.py
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@@ -20,7 +20,7 @@ GATE_MAP = {
"rx": "RX",
"ry": "RY",
"rz": "RZ",
"u3": "U3", # TODO: check
"u3": "U3",
"cx": "CX",
"cnot": "CNOT",
"cy": "CY",
@@ -210,7 +210,10 @@ def expectation_observable_symbolic(
This method takes a Qibo circuit, converts it to a Quimb tensor network circuit, and evaluates the expectation value
of a Hamiltonian specified by three lists of strings: operators, sites, and coefficients.
The expectation value is computed by summing the contributions from each term in the Hamiltonian, where each term's
expectation is calculated using Quimb's `local_expectation` function.
expectation is calculated using Quimb's `local_expectation` function.
Each operator string must act on all different qubits, i.e., for each term, the corresponding sites tuple must contain unique qubit indices.
Example: operators_list = ['xyz', 'xyz'], sites_list = [(1,2,3), (1,2,3)], coeffs_list = [1, 2]
Parameters
----------
@@ -218,15 +221,23 @@ def expectation_observable_symbolic(
The quantum circuit to evaluate, provided as a Qibo circuit object.
operators_list : list of str
List of operator strings representing the symbolic Hamiltonian terms.
sites_list : list of str
List of strings, each specifying the qubits (sites) the corresponding operator acts on.
coeffs_list : list of str
List of strings representing the coefficients for each Hamiltonian term.
sites_list : list of tuple of int
Tuples each specifying the qubits (sites) the corresponding operator acts on.
coeffs_list : list of real/complex
The coefficients for each Hamiltonian term.
Returns
-------
float
The real part of the expectation value of the Hamiltonian on the given circuit state.
"""
# Validate that no term acts multiple times on the same qubit (no repeated indices in a sites tuple)
for sites in sites_list:
if len(sites) != len(set(sites)):
raise_error(
ValueError,
f"Invalid Hamiltonian term sites {sites}: repeated qubit indices are not allowed "
"within a single term (e.g. (0,0,0) is invalid).",
)
quimb_circuit = self._qibo_circuit_to_quimb(
circuit,
quimb_circuit_type=self.circuit_ansatz,
@@ -276,12 +287,12 @@ def _qibo_circuit_to_quimb(
circ = quimb_circuit_type(nqubits, **circuit_kwargs)
for gate in qibo_circ.queue:
gname = getattr(gate, "name", None)
qname = GATE_MAP.get(gname, None)
if qname == "measure":
gate_name = getattr(gate, "name", None)
quimb_gate_name = GATE_MAP.get(gate_name, None)
if quimb_gate_name == "measure":
continue
if qname is None:
raise_error(ValueError, f"Gate {gname} not supported in Quimb backend.")
if quimb_gate_name is None:
raise_error(ValueError, f"Gate {gate_name} not supported in Quimb backend.")
params = getattr(gate, "parameters", ())
qubits = getattr(gate, "qubits", ())
@@ -290,10 +301,10 @@ def _qibo_circuit_to_quimb(
gate, "trainable", True
)
if is_parametrized:
circ.apply_gate(qname, *params, *qubits, parametrized=is_parametrized)
circ.apply_gate(quimb_gate_name, *params, *qubits, parametrized=is_parametrized)
else:
circ.apply_gate(
qname,
quimb_gate_name,
*params,
*qubits,
)