jaunatisblue
57d5fbcbb0
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84 lines
2.9 KiB
Python
84 lines
2.9 KiB
Python
"""Baseline MPS expectation scan with the qmatchatea backend."""
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import argparse
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import logging
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import math
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import time
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from qibo import Circuit, gates, hamiltonians
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from qibo.symbols import X, Z
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from qibotn.backends.qmatchatea import QMatchaTeaBackend
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def parse_bonds(value):
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return [int(item) for item in value.split(",") if item.strip()]
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def build_circuit(nqubits, nlayers, seed):
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import numpy as np
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rng = np.random.default_rng(seed)
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circuit = Circuit(nqubits)
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for _ in range(nlayers):
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for qubit in range(nqubits):
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circuit.add(gates.RY(qubit, theta=rng.uniform(-math.pi, math.pi)))
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circuit.add(gates.RZ(qubit, theta=rng.uniform(-math.pi, math.pi)))
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for qubit in range(0, nqubits - 1, 2):
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circuit.add(gates.CNOT(qubit, qubit + 1))
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for qubit in range(1, nqubits - 1, 2):
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circuit.add(gates.CNOT(qubit, qubit + 1))
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return circuit
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def build_observable(nqubits):
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form = 0
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for qubit in range(nqubits - 1):
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form += 0.5 * Z(qubit) * Z(qubit + 1)
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form += 0.25 * X(0)
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return hamiltonians.SymbolicHamiltonian(form=form)
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def main():
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parser = argparse.ArgumentParser()
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parser.add_argument("--nqubits", type=int, default=20)
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parser.add_argument("--nlayers", type=int, default=8)
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parser.add_argument("--bonds", type=parse_bonds, default=parse_bonds("2,4,8,16,32"))
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parser.add_argument("--seed", type=int, default=42)
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parser.add_argument("--cut-ratio", type=float, default=1e-12)
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parser.add_argument("--svd-control", default="V")
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parser.add_argument("--no-exact", action="store_true")
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args = parser.parse_args()
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logging.getLogger("qibo.config").setLevel(logging.ERROR)
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logging.getLogger("qtealeaves").setLevel(logging.ERROR)
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circuit = build_circuit(args.nqubits, args.nlayers, args.seed)
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observable = build_observable(args.nqubits)
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exact = None
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if not args.no_exact:
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exact = float(observable.expectation_from_state(circuit().state()).real)
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print(f"nqubits={args.nqubits} nlayers={args.nlayers} seed={args.seed}")
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if exact is not None:
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print(f"exact={exact:.16e}")
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print("bond_dim expval abs_error rel_error seconds")
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backend = QMatchaTeaBackend()
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for bond in args.bonds:
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backend.configure_tn_simulation(
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ansatz="MPS",
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max_bond_dimension=bond,
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cut_ratio=args.cut_ratio,
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svd_control=args.svd_control,
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)
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start = time.perf_counter()
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value = float(backend.expectation(circuit, observable, preprocess=False).real)
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elapsed = time.perf_counter() - start
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abs_error = float("nan") if exact is None else abs(value - exact)
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rel_error = float("nan") if exact is None else abs_error / max(abs(exact), 1e-15)
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print(f"{bond:d} {value:.16e} {abs_error:.6e} {rel_error:.6e} {elapsed:.3f}")
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if __name__ == "__main__":
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main()
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