refactor: added function for converting qibo circuit to quimb circuit directly. modified expectation making use of it. added new test script.
This commit is contained in:
Mattia Robbiano
50
examples/quimb_intro/test.py
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50
examples/quimb_intro/test.py
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@@ -0,0 +1,50 @@
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import numpy as np
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import jax
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from qibo.backends import construct_backend
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from qibo import Circuit, gates, hamiltonians
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from qibo.symbols import Z, X, Y
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# construct qibotn backend
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quimb_backend = construct_backend(backend="qibotn", platform="quimb")
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quimb_backend.setup_backend_specifics(
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qimb_backend="jax",
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optimizer='auto-hq'
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)
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quimb_backend.configure_tn_simulation(
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max_bond_dimension=10
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)
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# define Hamiltonian
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form = 0.5 * Z(0) * Z(1) +- 1.5 * X(0) * Z(2) + Z(3)
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hamiltonian = hamiltonians.SymbolicHamiltonian(form)
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# define circuit
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def build_circuit(nqubits, nlayers):
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"""Construct a Qibo parametric quantum circuit."""
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circ = Circuit(nqubits)
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for _ in range(nlayers):
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for q in range(nqubits):
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circ.add(gates.RY(q=q, theta=0.))
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circ.add(gates.RZ(q=q, theta=0.))
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[circ.add(gates.CNOT(q%nqubits, (q+1)%nqubits) for q in range(nqubits))]
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circ.add(gates.M(*range(nqubits)))
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return circ
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nqubits = 4
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circuit = build_circuit(nqubits=nqubits, nlayers=3)
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def f(params):
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circuit.set_parameters(params)
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return quimb_backend.expectation(
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circuit=circuit,
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observable=hamiltonian,
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)
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parameters = np.random.uniform(-np.pi, np.pi, size=len(circuit.get_parameters()))
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print(f(parameters))
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print(jax.value_and_grad(f)(parameters))
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@@ -3,6 +3,8 @@ import warnings
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from collections import Counter, defaultdict
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import numpy as np
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import jax
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import jax.numpy as jnp
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import quimb as qu
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import quimb.tensor as qtn
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from qibo.backends import NumpyBackend
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@@ -12,6 +14,43 @@ from qibo.result import QuantumState
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from qibotn.backends.abstract import QibotnBackend
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from qibotn.result import TensorNetworkResult
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GATE_MAP = {
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"h": "H",
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"x": "X",
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"y": "Y",
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"z": "Z",
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"s": "S",
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"sdg": "SDG",
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"t": "T",
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"tdg": "TDG",
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"sx": "SX",
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"sxdg": "SXDG",
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"rx": "RX",
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"ry": "RY",
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"rz": "RZ",
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"u1": "U1",
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"u2": "U2",
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"u3": "U3",
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"cx": "CNOT",
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"cnot": "CNOT",
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"cy": "CY",
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"cz": "CZ",
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"iswap": "ISWAP",
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"swap": "SWAP",
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"ccx": "CCX",
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"toffoli": "CCX",
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"ccz": "CCZ",
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"cswap": "CSWAP",
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"fredkin": "CSWAP",
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"crx": "CRX",
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"cry": "CRY",
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"crz": "CRZ",
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"fsim": "FSIM",
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"rxx": "RXX",
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"ryy": "RYY",
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"rzz": "RZZ",
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"m": None, # measurement, skip
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}
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class QuimbBackend(QibotnBackend, NumpyBackend):
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@@ -147,6 +186,50 @@ class QuimbBackend(QibotnBackend, NumpyBackend):
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)
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def expectation(self, circuit, observable):
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"""
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Compute the expectation value of a Qibo-friendly ``observable`` on the Tensor Network constructed from a Qibo ``circuit``.
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This method takes a Qibo-style symbolic Hamiltonian (e.g., `X(0)*Z(1) + 2.0*Y(2)*Z(0)`)
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as the observable, converts it into a Quimb observable and computes its expectation
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value using the provided circuit.
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Args:
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circuit: A Qibo quantum circuit object on which the expectation value
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is computed.
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observable: The observable whose expectation value we want to compute.
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This must be provided in the symbolic Hamiltonian form supported by Qibo
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(e.g., `X(0)*Y(1)` or `Z(0)*Z(1) + 1.5*Y(2)`).
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Returns:
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float: The expectation value (real part).
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"""
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'''Convert Qibo observables to Quimb'''
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operators_list, sites_list, coeffs_list = self._qiboobs_to_quimbobs(observable)
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'''Convert Qibo circuit to Quimb circuit'''
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parameters = circuit.get_parameters()
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quimb_circuit = self._qibo_circuit_to_quimb(
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circuit, quimb_circuit_type=qtn.Circuit, to_backend=jnp.array, convert_eager=True
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)
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quimb_parameters = {
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key: jnp.asarray(parameters[i]) for i, key in enumerate(quimb_circuit.get_params().keys())
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}
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quimb_circuit.set_params(quimb_parameters)
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'''Compute expectation value'''
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expectation_value = 0.0
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for ops, sites, coeffs in zip(operators_list, sites_list, coeffs_list):
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exp_values = quimb_circuit.local_expectation(
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ops,
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where=sites,
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backend=self.backend,
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optimize=self.optimizer
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)
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expectation_value = expectation_value + coeffs * exp_values
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return jnp.real(expectation_value)
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def expectation_old(self, circuit, observable):
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"""Compute the expectation value of a Qibo-friendly ``observable`` on the Tensor Network constructed from a Qibo ``circuit``.
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This method takes a Qibo-style symbolic Hamiltonian (e.g., `X(0)*Z(1) + 2.0*Y(2)*Z(0)`)
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@@ -191,6 +274,7 @@ class QuimbBackend(QibotnBackend, NumpyBackend):
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else:
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circ_ansatz = qtn.circuit.Circuit
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circ = circ_ansatz.from_openqasm2_str(circuit.to_qasm())
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expectation_value = 0.0
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for ops, sites, coeffs in zip(
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operators_list_grouped, sites_list_grouped, coeffs_list_grouped
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@@ -283,3 +367,42 @@ class QuimbBackend(QibotnBackend, NumpyBackend):
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C_new = list(grouped_C.values())
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return A_new, B_new, C_new
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def _qibo_circuit_to_quimb(self, qibo_circ, quimb_circuit_type=qtn.Circuit, **circuit_kwargs):
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"""
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Convert a Qibo Circuit to a Quimb Circuit.
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Parameters
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----------
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qibo_circ : qibo.models.circuit.Circuit
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The circuit to convert.
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quimb_circuit_type : type
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The Quimb circuit class to use (Circuit, CircuitMPS, etc).
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circuit_kwargs : dict
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Extra arguments to pass to the Quimb circuit constructor.
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Returns
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-------
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circ : quimb.tensor.circuit.Circuit
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The converted circuit.
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"""
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nqubits = qibo_circ.nqubits
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quimb_gates = []
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for gate in qibo_circ.queue:
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gname = getattr(gate, "name", None)
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qname = GATE_MAP.get(gname, None)
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if qname is None:
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continue # skip measurements and unknown gates
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# Handle parametrized gates (Qibo: .parameters, Quimb: expects flat tuple)
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params = getattr(gate, "parameters", ())
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qubits = getattr(gate, "qubits", ())
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# Quimb expects (*params, *qubits)
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gate_spec = (qname,) + tuple(params) + tuple(qubits)
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quimb_gates.append(gate_spec)
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circ = quimb_circuit_type(nqubits, **circuit_kwargs)
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circ.apply_gates(quimb_gates)
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return circ
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