jaunatisblue
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110 lines
3.7 KiB
Python
110 lines
3.7 KiB
Python
"""Compute and cache a qibojit state-vector reference for the ring-XZ observable."""
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import argparse
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import json
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import math
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import time
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from pathlib import Path
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import numpy as np
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import qibo
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from qibo import Circuit, gates
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def build_circuit(nqubits, nlayers, seed):
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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 ring_xz_expectation(state, nqubits, chunk_size):
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value = 0.0
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for qubit in range(nqubits):
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next_qubit = (qubit + 1) % nqubits
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x_flip = 1 << (nqubits - 1 - qubit)
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z_shift = nqubits - 1 - next_qubit
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term = 0.0
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for start in range(0, state.size, chunk_size):
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stop = min(start + chunk_size, state.size)
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indices = np.arange(start, stop, dtype=np.int64)
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z_bit = (indices >> z_shift) & 1
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z_phase = 1 - 2 * z_bit
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term += np.vdot(state[indices ^ x_flip], z_phase * state[start:stop]).real
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value += 0.5 * term
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return float(value)
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def default_output_path(nqubits, nlayers, seed):
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return Path("references") / (
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f"qibojit_ring_xz_n{nqubits}_l{nlayers}_seed{seed}.json"
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)
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def main():
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parser = argparse.ArgumentParser()
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parser.add_argument("--nqubits", type=int, default=32)
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parser.add_argument("--nlayers", type=int, default=3)
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parser.add_argument("--seed", type=int, default=42)
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parser.add_argument("--output")
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parser.add_argument("--force", action="store_true")
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parser.add_argument("--allow-large", action="store_true")
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parser.add_argument("--max-state-gb", type=float, default=32.0)
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parser.add_argument("--chunk-size", type=int, default=1 << 20)
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args = parser.parse_args()
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output = Path(args.output) if args.output else default_output_path(
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args.nqubits, args.nlayers, args.seed
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)
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if output.exists() and not args.force:
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with open(output, "r", encoding="utf-8") as f:
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data = json.load(f)
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print(f"loaded {output}")
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print(f"expectation={float(data['expectation']):.16e}")
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return
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state_gb = (2**args.nqubits) * np.dtype(np.complex128).itemsize / (1024**3)
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if state_gb > args.max_state_gb and not args.allow_large:
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raise MemoryError(
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f"Estimated state vector alone is {state_gb:.1f} GiB. "
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"Pass --allow-large after confirming the node has enough memory."
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)
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qibo.set_backend("qibojit")
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circuit = build_circuit(args.nqubits, args.nlayers, args.seed)
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start = time.perf_counter()
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state = circuit().state(numpy=True).reshape(-1)
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expectation = ring_xz_expectation(state, args.nqubits, args.chunk_size)
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elapsed = time.perf_counter() - start
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data = {
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"backend": "qibojit",
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"observable": "0.5 * sum_i X_i Z_((i+1) mod n)",
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"nqubits": args.nqubits,
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"nlayers": args.nlayers,
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"seed": args.seed,
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"expectation": expectation,
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"seconds": elapsed,
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"state_vector_gib_estimate": state_gb,
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}
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output.parent.mkdir(parents=True, exist_ok=True)
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with open(output, "w", encoding="utf-8") as f:
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json.dump(data, f, indent=2, sort_keys=True)
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f.write("\n")
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print(f"saved {output}")
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print(f"expectation={expectation:.16e}")
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print(f"seconds={elapsed:.3f}")
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if __name__ == "__main__":
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main()
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