|
| 1 | +import jax |
| 2 | +import jax.numpy as jnp |
| 3 | +from jax import tree_util |
| 4 | +import flax.linen as nn |
| 5 | +import pennylane as qml |
| 6 | +import logging |
| 7 | +from typing import Callable, List, Tuple, Optional, Any, Dict |
| 8 | +from functools import partial |
| 9 | +from flax import struct |
| 10 | + |
| 11 | +class QuantumNeuralNetwork(nn.Module): |
| 12 | + """ |
| 13 | + A quantum neural network module that combines classical and quantum computations. |
| 14 | +
|
| 15 | + This class implements a variational quantum circuit that can be used as a layer |
| 16 | + in a hybrid quantum-classical neural network. |
| 17 | +
|
| 18 | + Attributes: |
| 19 | + num_qubits (int): The number of qubits in the quantum circuit. |
| 20 | + num_layers (int): The number of layers in the variational quantum circuit. |
| 21 | + input_shape (Tuple[int, ...]): The shape of the input tensor. |
| 22 | + output_shape (Tuple[int, ...]): The shape of the output tensor (excluding batch dimension). |
| 23 | + max_retries (int): The maximum number of retries for quantum circuit execution. |
| 24 | + """ |
| 25 | + |
| 26 | + num_qubits: int |
| 27 | + num_layers: int |
| 28 | + input_shape: Tuple[int, ...] |
| 29 | + output_shape: Tuple[int, ...] |
| 30 | + max_retries: int = 3 |
| 31 | + device: Optional[qml.Device] = None |
| 32 | + qlayer: Optional[Callable] = None |
| 33 | + vmap_qlayer: Optional[Callable] = None |
| 34 | + |
| 35 | + def setup(self): |
| 36 | + logging.info(f"Setting up QuantumNeuralNetwork with {self.num_qubits} qubits, {self.num_layers} layers, input shape {self.input_shape}, and output shape {self.output_shape}") |
| 37 | + self._validate_init_params() |
| 38 | + |
| 39 | + self.param('weights', nn.initializers.uniform(scale=0.1), (self.num_layers, self.num_qubits, 3)) |
| 40 | + try: |
| 41 | + quantum_components = self._initialize_quantum_components() |
| 42 | + self.device = quantum_components['device'] |
| 43 | + self.qlayer = quantum_components['qlayer'] |
| 44 | + self.vmap_qlayer = quantum_components['vmap_qlayer'] |
| 45 | + self.variable('quantum_components', 'components', lambda: quantum_components) |
| 46 | + except Exception as e: |
| 47 | + logging.error(f"Error initializing quantum components: {str(e)}") |
| 48 | + fallback_components = self._fallback_initialization() |
| 49 | + self.device = fallback_components['device'] |
| 50 | + self.qlayer = fallback_components['qlayer'] |
| 51 | + self.vmap_qlayer = fallback_components['vmap_qlayer'] |
| 52 | + self.variable('quantum_components', 'components', lambda: fallback_components) |
| 53 | + |
| 54 | + def _validate_init_params(self): |
| 55 | + if not isinstance(self.num_qubits, int) or self.num_qubits <= 0: |
| 56 | + raise ValueError(f"Number of qubits must be a positive integer, got {self.num_qubits}") |
| 57 | + if not isinstance(self.num_layers, int) or self.num_layers <= 0: |
| 58 | + raise ValueError(f"Number of layers must be a positive integer, got {self.num_layers}") |
| 59 | + if not isinstance(self.input_shape, tuple) or len(self.input_shape) != 2 or self.input_shape[1] != self.num_qubits: |
| 60 | + raise ValueError(f"Invalid input_shape: {self.input_shape}. Expected shape (batch_size, {self.num_qubits})") |
| 61 | + if not isinstance(self.output_shape, tuple) or len(self.output_shape) != 1 or self.output_shape[0] != self.num_qubits: |
| 62 | + raise ValueError(f"Invalid output_shape: {self.output_shape}. Expected shape ({self.num_qubits},)") |
| 63 | + |
| 64 | + def _initialize_quantum_components(self): |
| 65 | + try: |
| 66 | + self.device = qml.device("default.qubit", wires=self.num_qubits) |
| 67 | + self.qlayer = qml.QNode(self.quantum_circuit, self.device, interface="jax") |
| 68 | + self.vmap_qlayer = jax.vmap(self.qlayer, in_axes=(0, None)) |
| 69 | + logging.info("Quantum components created successfully") |
| 70 | + return { |
| 71 | + 'device': self.device, |
| 72 | + 'qlayer': self.qlayer, |
| 73 | + 'vmap_qlayer': self.vmap_qlayer |
| 74 | + } |
| 75 | + except Exception as e: |
| 76 | + logging.error(f"Error creating quantum components: {str(e)}") |
| 77 | + return self._fallback_initialization() |
| 78 | + |
| 79 | + def quantum_circuit(self, inputs: jnp.ndarray, weights: jnp.ndarray) -> List[qml.measurements.ExpectationMP]: |
| 80 | + qml.AngleEmbedding(inputs, wires=range(self.num_qubits)) |
| 81 | + for l in range(self.num_layers): |
| 82 | + qml.StronglyEntanglingLayers(weights[l], wires=range(self.num_qubits)) |
| 83 | + return [qml.expval(qml.PauliZ(i)) for i in range(self.num_qubits)] |
| 84 | + |
| 85 | + def validate_input_shape(self, x: jnp.ndarray) -> None: |
| 86 | + if len(x.shape) != 2 or x.shape[1] != self.num_qubits: |
| 87 | + raise ValueError(f"Input shape {x.shape} does not match expected shape (batch_size, {self.num_qubits})") |
| 88 | + |
| 89 | + def __call__(self, x: jnp.ndarray, deterministic: bool = False) -> jnp.ndarray: |
| 90 | + try: |
| 91 | + self.validate_input_shape(x) |
| 92 | + if jnp.any(jnp.isnan(x)) or jnp.any(jnp.isinf(x)): |
| 93 | + raise ValueError(f"Input contains NaN or Inf values: {x}") |
| 94 | + |
| 95 | + logging.debug(f"Executing quantum circuit with input shape: {x.shape}") |
| 96 | + if self.vmap_qlayer is None: |
| 97 | + logging.warning("Quantum components not initialized. Attempting initialization.") |
| 98 | + self._initialize_quantum_components() |
| 99 | + if self.vmap_qlayer is None: |
| 100 | + logging.error("Quantum components initialization failed. Using fallback.") |
| 101 | + return self._fallback_output(x) |
| 102 | + |
| 103 | + result_array = self._execute_quantum_circuit(x) |
| 104 | + |
| 105 | + expected_shape = (x.shape[0],) + self.output_shape |
| 106 | + if result_array.shape != expected_shape: |
| 107 | + logging.warning(f"Output shape mismatch. Expected {expected_shape}, got {result_array.shape}. Reshaping.") |
| 108 | + result_array = jnp.reshape(result_array, expected_shape) |
| 109 | + |
| 110 | + result_array = jnp.clip(result_array, -1, 1) |
| 111 | + logging.info(f"Quantum circuit executed successfully. Input shape: {x.shape}, Output shape: {result_array.shape}") |
| 112 | + return result_array |
| 113 | + except ValueError as ve: |
| 114 | + logging.error(f"ValueError during quantum circuit execution: {str(ve)}") |
| 115 | + return self._fallback_output(x) |
| 116 | + except Exception as e: |
| 117 | + logging.error(f"Unexpected error during quantum circuit execution: {str(e)}") |
| 118 | + return self._fallback_output(x) |
| 119 | + |
| 120 | + def _execute_quantum_circuit(self, x: jnp.ndarray) -> jnp.ndarray: |
| 121 | + weights = self.variable('params', 'weights').value |
| 122 | + for attempt in range(self.max_retries): |
| 123 | + try: |
| 124 | + logging.debug(f"Attempt {attempt + 1}/{self.max_retries} to execute quantum circuit") |
| 125 | + if self.vmap_qlayer is None: |
| 126 | + raise ValueError("Quantum components not properly initialized") |
| 127 | + result = self.vmap_qlayer(x, weights) |
| 128 | + result_array = jnp.array(result) |
| 129 | + if jnp.all(jnp.isfinite(result_array)): |
| 130 | + logging.info(f"Quantum circuit execution successful on attempt {attempt + 1}") |
| 131 | + return result_array |
| 132 | + else: |
| 133 | + raise ValueError("Quantum circuit produced non-finite values") |
| 134 | + except Exception as e: |
| 135 | + logging.warning(f"Quantum circuit execution failed on attempt {attempt + 1}: {str(e)}") |
| 136 | + if attempt == self.max_retries - 1: |
| 137 | + logging.error("Max retries reached. Quantum circuit execution failed.") |
| 138 | + return self._fallback_output(x) |
| 139 | + return self._fallback_output(x) # Ensure a return value if loop completes |
| 140 | + |
| 141 | + def _fallback_output(self, x: jnp.ndarray) -> jnp.ndarray: |
| 142 | + fallback = jnp.zeros((x.shape[0],) + self.output_shape) |
| 143 | + noise = jax.random.normal(jax.random.PRNGKey(0), fallback.shape) * 0.1 |
| 144 | + return jnp.clip(fallback + noise, -1, 1) |
| 145 | + |
| 146 | + def _fallback_initialization(self): |
| 147 | + logging.warning("Falling back to classical initialization") |
| 148 | + fallback_components = { |
| 149 | + 'device': None, |
| 150 | + 'qlayer': lambda x, w: jnp.zeros(self.output_shape), |
| 151 | + 'vmap_qlayer': jax.vmap(lambda x, w: jnp.zeros(self.output_shape), in_axes=(0, None)) |
| 152 | + } |
| 153 | + logging.info("Classical fallback initialization completed") |
| 154 | + self.sow('quantum_components', 'components', fallback_components) |
| 155 | + return fallback_components |
| 156 | + |
| 157 | + def reinitialize_device(self): |
| 158 | + try: |
| 159 | + new_device = qml.device("default.qubit", wires=self.num_qubits) |
| 160 | + new_qlayer = qml.QNode(self.quantum_circuit, new_device, interface="jax") |
| 161 | + new_vmap_qlayer = jax.vmap(new_qlayer, in_axes=(0, None)) |
| 162 | + new_components = { |
| 163 | + 'device': new_device, |
| 164 | + 'qlayer': new_qlayer, |
| 165 | + 'vmap_qlayer': new_vmap_qlayer |
| 166 | + } |
| 167 | + self.variable('quantum_components', 'components', lambda: new_components) |
| 168 | + logging.info("Quantum device reinitialized successfully") |
| 169 | + except Exception as e: |
| 170 | + logging.error(f"Error reinitializing quantum device: {str(e)}") |
| 171 | + fallback_components = self._fallback_initialization() |
| 172 | + self.variable('quantum_components', 'components', lambda: fallback_components) |
| 173 | + return self.variable('quantum_components', 'components').value |
| 174 | + |
| 175 | +@partial(jax.jit, static_argnums=(0, 1, 2, 3)) |
| 176 | +def create_quantum_nn(num_qubits: int, num_layers: int, input_shape: Tuple[int, ...], output_shape: Tuple[int, ...]) -> QuantumNeuralNetwork: |
| 177 | + return QuantumNeuralNetwork(num_qubits=num_qubits, num_layers=num_layers, input_shape=input_shape, output_shape=output_shape) |
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