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302 lines (245 loc) · 9.76 KB
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# %%
# ============================================================
# BASELINE: ALL WALKS (uniform superposition) +
# VALIDITY ORACLE (parity-based) +
# FULL COST PHASE ORACLE
# Then: statevector analysis + classical comparison table
#
# No amplitude amplification, no QSVT.
# ============================================================
import numpy as np
import pandas as pd
import pennylane as qml
import src.classical_funcs as cf
# -------------------------
# Problem + cost matrix
# -------------------------
np.random.seed(42)
n = 7
start_node = n - 1
cost_matrix_raw = cf.generate_cost_matrix(n)
all_walks = cf.generate_all_walks(n, start_node=start_node)
all_costs_raw = cf.find_all_cost(cost_matrix_raw, all_walks)
C_max = float(np.max(all_costs_raw))
cost_matrix = cost_matrix_raw / C_max # entries are phases in radians in [0, ~1]
# -------------------------
# Encoding (time-register)
# -------------------------
T_steps = n - 1
n_qubits_step = int(np.ceil(np.log2(n - 1)))
def twire(t, q):
return f"t{t}_q{q}"
def pos_wires_at_t(t):
return [twire(t, q) for q in range(n_qubits_step)]
time_wires = [twire(t, q) for t in range(T_steps) for q in range(n_qubits_step)]
state_wires = [f"s{i}" for i in range(n - 1)] # parity flags
good_wire = "good"
phase_anc = "phase"
# Keep only the active registers (no optional work wires).
wires = time_wires + state_wires + [good_wire, phase_anc]
dev = qml.device("lightning.qubit", wires=wires)
# -------------------------
# Init: uniform over ALL time-register bitstrings
# -------------------------
def init_pos():
for w in time_wires:
qml.Hadamard(wires=w)
# -------------------------
# Validity compute (your parity-based oracle)
# Writes parity flags into state_wires and ANDs into good_wire
# -------------------------
def check_pos_compute():
for t in range(T_steps):
pos = pos_wires_at_t(t)
for i in range(n - 1):
bits = format(i, f"0{n_qubits_step}b")
for w, b in zip(pos, bits):
if b == "0":
qml.PauliX(wires=w)
qml.MultiControlledX(wires=pos + [state_wires[i]])
for w, b in zip(pos, bits):
if b == "0":
qml.PauliX(wires=w)
qml.MultiControlledX(wires=state_wires + [good_wire])
# -------------------------
# FULL cost oracle (Start + transitions + return)
# Uses phase kickback via toggling phase_anc
# -------------------------
def apply_transition_phase(t):
pos_t = pos_wires_at_t(t)
pos_tp1 = pos_wires_at_t(t + 1)
for i in range(n - 1):
for j in range(n - 1):
bits_i = format(i, f"0{n_qubits_step}b")
bits_j = format(j, f"0{n_qubits_step}b")
for w, b in zip(pos_t, bits_i):
if b == "0":
qml.PauliX(wires=w)
for w, b in zip(pos_tp1, bits_j):
if b == "0":
qml.PauliX(wires=w)
controls = pos_t + pos_tp1
qml.MultiControlledX(wires=controls + [phase_anc])
qml.PhaseShift(float(cost_matrix[i, j]), wires=phase_anc)
qml.MultiControlledX(wires=controls + [phase_anc])
for w, b in zip(pos_tp1, bits_j):
if b == "0":
qml.PauliX(wires=w)
for w, b in zip(pos_t, bits_i):
if b == "0":
qml.PauliX(wires=w)
def cost_oracle_full():
# Start -> first
pos0 = pos_wires_at_t(0)
for j in range(n - 1):
bits = format(j, f"0{n_qubits_step}b")
for w, b in zip(pos0, bits):
if b == "0":
qml.PauliX(wires=w)
qml.MultiControlledX(wires=pos0 + [phase_anc])
qml.PhaseShift(float(cost_matrix[start_node, j]), wires=phase_anc)
qml.MultiControlledX(wires=pos0 + [phase_anc])
for w, b in zip(pos0, bits):
if b == "0":
qml.PauliX(wires=w)
# Inner transitions
for t in range(T_steps - 1):
apply_transition_phase(t)
# Last -> start
pos_last = pos_wires_at_t(T_steps - 1)
for i in range(n - 1):
bits = format(i, f"0{n_qubits_step}b")
for w, b in zip(pos_last, bits):
if b == "0":
qml.PauliX(wires=w)
qml.MultiControlledX(wires=pos_last + [phase_anc])
qml.PhaseShift(float(cost_matrix[i, start_node]), wires=phase_anc)
qml.MultiControlledX(wires=pos_last + [phase_anc])
for w, b in zip(pos_last, bits):
if b == "0":
qml.PauliX(wires=w)
# -------------------------
# QNode: Uniform -> validity compute -> cost phase
# (No Grover, no QSVT)
# -------------------------
@qml.qnode(dev)
def circuit_baseline():
init_pos()
check_pos_compute() # marks allowed walks into good_wire (and sets state_wires)
cost_oracle_full() # encodes loss as phase
return qml.state()
state = circuit_baseline()
# -------------------------
# Decode helpers (robust to wire order)
# -------------------------
def bits_by_wire_from_index(idx):
bitstr = format(idx, f"0{len(wires)}b")
# PennyLane uses wires list ordering; map bitstring to wires robustly:
# The least-significant bit corresponds to the last wire in 'wires'.
return bitstr, {w: int(b) for w, b in zip(reversed(wires), reversed(bitstr))}
def decode_path_from_bits(bits_by_wire):
time_bits = "".join(str(bits_by_wire[w]) for w in time_wires)
path = []
for t in range(T_steps):
chunk = time_bits[t * n_qubits_step : (t + 1) * n_qubits_step]
path.append(int(chunk, 2))
return path
def is_valid_classical(path):
# valid iff it's a permutation of 0..n-2
return sorted(path) == list(range(n - 1))
def classical_cost_norm(path):
# cost in normalized matrix
cost = float(cost_matrix[start_node, path[0]])
for t in range(T_steps - 1):
cost += float(cost_matrix[path[t], path[t+1]])
cost += float(cost_matrix[path[-1], start_node])
return float(cost)
def wrap_to_pi(x):
return (x + np.pi) % (2*np.pi) - np.pi
# -------------------------
# Build table + phase check
# We use one valid state as reference to compare relative phases:
# dphi(pi) should match dcost(pi) (mod 2pi) for valid paths.
# -------------------------
def build_table_with_phase_check(statevec, amp_eps=1e-12):
ref_phase = None
ref_cost = None
# find a reference VALID state with good=1 (and phase_anc=0 ideally)
for idx, amp in enumerate(statevec):
if abs(amp) < amp_eps:
continue
_, bw = bits_by_wire_from_index(idx)
path = decode_path_from_bits(bw)
good_q = int(bw[good_wire])
valid_c = is_valid_classical(path)
phase_bit = int(bw[phase_anc])
if good_q == 1 and valid_c and phase_bit == 0:
ref_phase = float(np.angle(amp))
ref_cost = float(classical_cost_norm(path))
break
if ref_phase is None:
raise RuntimeError("No valid+good reference state found (try lowering amp_eps).")
rows = []
for idx, amp in enumerate(statevec):
if abs(amp) < amp_eps:
continue
bitstr, bw = bits_by_wire_from_index(idx)
path = decode_path_from_bits(bw)
good_q = int(bw[good_wire])
valid_c = is_valid_classical(path)
phase_bit = int(bw[phase_anc])
phase = float(np.angle(amp))
dphi = float(wrap_to_pi(phase - ref_phase))
if valid_c:
cost = float(classical_cost_norm(path))
dcost = float(cost - ref_cost)
diff_wrapped = float(abs(wrap_to_pi(dphi - dcost)))
else:
cost = np.nan
dcost = np.nan
diff_wrapped = np.nan
rows.append({
"idx": idx,
# "bitstr": bitstr,
"path": path,
"good_quantum": good_q,
"is_valid_classical": int(valid_c),
"phase_anc_bit": phase_bit,
"amp_abs": round(float(abs(amp)), 4),
"prob": round(float(abs(amp)**2), 4),
"phase": round(float(phase), 4),
"dphi": round(float(dphi), 4),
"cost_norm": round(float(cost), 4) if not np.isnan(cost) else np.nan,
"dcost": round(float(dcost), 4) if not np.isnan(dcost) else np.nan,
"diff_wrapped": round(float(diff_wrapped), 4) if not np.isnan(diff_wrapped) else np.nan,
})
return pd.DataFrame(rows)
df = build_table_with_phase_check(state)
# -------------------------
# Report + save
# -------------------------
# Compare quantum good flag vs classical validity
mismatch = df[df["good_quantum"] != df["is_valid_classical"]]
print("mismatches (good_quantum != is_valid_classical):", len(mismatch))
# Probability mass by classical validity (should be near 1 on all states because uniform;
# but note: we're summing only populated basis states; should sum to 1)
p_valid = float(df.loc[df["is_valid_classical"] == 1, "prob"].sum())
p_invalid = float(df.loc[df["is_valid_classical"] == 0, "prob"].sum())
print("Prob mass valid:", p_valid)
print("Prob mass invalid:", p_invalid)
print("Total prob mass (rows summed):", p_valid + p_invalid)
# Phase consistency on valid states
max_diff = float(np.nanmax(df.loc[df["is_valid_classical"] == 1, "diff_wrapped"].values))
print("max |wrap(dphi - dcost)| over valid states:", max_diff)
# Sort for convenience: valid & good on top, then by cost
df_sorted = df.sort_values(
["is_valid_classical", "good_quantum", "cost_norm"],
ascending=[False, False, True],
).reset_index(drop=True)
out_path = "tsp_baseline_validity_cost_phase.csv"
df_sorted.to_csv(out_path, index=False)
print("Saved:", out_path)
# optional preview
print("\nTop-20 valid states (by increasing cost_norm):")
print(df_sorted[df_sorted["is_valid_classical"] == 1][["path","good_quantum","cost_norm","phase","diff_wrapped"]].to_string(index=False))
# %%