1 files changed, 76 insertions, 15 deletions

diff --git a/libpsi/src/core/component.rs b/libpsi/src/core/component.rs
index 51e0551..331021f 100644
--- a/libpsi/src/core/component.rs
+++ b/libpsi/src/core/component.rs
@@ -1,14 +1,9 @@
-use crate::{ColumnVector, Complex, Matrix, VectorMatrix};
+use crate::{complex, ColumnVector, Complex, Matrix, Vector, VectorMatrix};
 use std::ops;
 
 pub type QuantumBit = ColumnVector<Complex<f64>>;
 pub type QuantumGate = Matrix<Complex<f64>>;
 
-pub struct QuantumRegister {
-    state: ColumnVector<Complex<f64>>,
-    qubits: Vec<QuantumBit>,
-}
-
 #[macro_export]
 macro_rules! count {
     () => { 0 };
@@ -39,29 +34,81 @@ macro_rules! quantum_register {
     };
 }
 
+pub struct ClassicalRegister {
+    bits: Vec<i32>,
+}
+
+pub struct QuantumRegister {
+    state: ColumnVector<Complex<f64>>,
+    qubits: Vec<QuantumBit>,
+}
+
 impl QuantumBit {
-    pub fn get_state(&self) -> i32 {
-        (self[1] != Complex::new(0.0, 0.0)) as i32
+    pub fn measure(&self) -> i32 {
+        let alpha_abs = self[0].abs();
+        let beta_abs = self[1].abs();
+
+        let alpha_norm = alpha_abs * alpha_abs;
+        let beta_norm = beta_abs * beta_abs;
+
+        if alpha_norm > beta_norm {
+            0
+        } else {
+            1
+        }
+    }
+
+    pub fn state_0() -> QuantumBit {
+        QuantumBit::new(vec![complex!(1.0, 0.0), complex!(0.0, 0.0)])
+    }
+
+    pub fn state_1() -> QuantumBit {
+        QuantumBit::new(vec![complex!(0.0, 0.0), complex!(1.0, 0.0)])
+    }
+}
+
+impl ClassicalRegister {
+    pub fn new(count: usize) -> ClassicalRegister {
+        ClassicalRegister {
+            bits: Vec::with_capacity(count),
+        }
+    }
+
+    pub fn set_bits(&mut self, bits: Vec<i32>) {
+        self.bits = bits;
     }
 }
 
 impl QuantumRegister {
-    pub fn from(bits: &mut [QuantumBit]) -> QuantumRegister {
-        let matrices: Vec<Matrix<Complex<f64>>> = bits.iter().map(|bit| bit.to_matrix()).collect();
-        let mut result = matrices[0].clone();
+    fn update(&mut self) {
+        let matrices: Vec<Matrix<Complex<f64>>> =
+            self.qubits.iter().map(|qubit| qubit.to_matrix()).collect();
+        let mut new_result = matrices[0].clone();
         for matrix in &matrices[1..] {
-            result = result.kronecker(matrix);
+            new_result = new_result.kronecker(matrix);
         }
 
-        QuantumRegister {
+        self.state = ColumnVector::from_matrix(&new_result);
+    }
+
+    pub fn from(bits: &mut [QuantumBit]) -> QuantumRegister {
+        let mut register = QuantumRegister {
             qubits: bits.to_vec(),
-            state: ColumnVector::from_matrix(&result),
-        }
+            state: ColumnVector::new(vec![]),
+        };
+
+        register.update();
+        register
+    }
+
+    pub fn measure(&self, classical_register: &mut ClassicalRegister) {
+        classical_register.set_bits(self.qubits.iter().map(|qubit| qubit.measure()).collect());
     }
 
     pub fn apply(&mut self, gate: &QuantumGate, index: usize) {
         let result: ColumnVector<Complex<f64>> = self.state.mul_matrix(gate).unwrap();
         self.qubits[index] = result;
+        self.update();
     }
 }
 
@@ -78,3 +125,17 @@ impl ops::IndexMut<usize> for QuantumRegister {
         &mut self.qubits[index]
     }
 }
+
+impl ops::Index<usize> for ClassicalRegister {
+    type Output = i32;
+
+    fn index(&self, index: usize) -> &Self::Output {
+        &self.bits[index]
+    }
+}
+
+impl ops::IndexMut<usize> for ClassicalRegister {
+    fn index_mut(&mut self, index: usize) -> &mut Self::Output {
+        &mut self.bits[index]
+    }
+}