From 1a9ef4a7f0cbd4ed848ccf0903ebbbd4fdab6adf Mon Sep 17 00:00:00 2001
From: hachem <im@hachem.wtf>
Date: Sun, 22 Sep 2024 13:07:30 +0200
Subject: First quantum calculation

---
 libpsi-tester/src/main.rs    | 10 ++++++----
 libpsi/src/core/component.rs | 39 ++++++++++++++++++++++++++++++++++-----
 libpsi/src/core/gates.rs     |  0
 libpsi/src/maths/vector.rs   |  1 +
 4 files changed, 41 insertions(+), 9 deletions(-)
 create mode 100644 libpsi/src/core/gates.rs

diff --git a/libpsi-tester/src/main.rs b/libpsi-tester/src/main.rs
index 4aaa92d..5ecc2f0 100644
--- a/libpsi-tester/src/main.rs
+++ b/libpsi-tester/src/main.rs
@@ -1,8 +1,10 @@
 use libpsi::*;
 
 fn main() {
-    let bit_1 = qubit![(1.0, 2.0), (1.0, 2.0)];
-    let bit_2 = qubit![(1.0, 2.0), (1.0, 2.0)];
-    let register: QuantumRegister = quantum_register![bit_1, bit_2];
-    println!("{}", register);
+    let mut register = quantum_register![qubit![(1.0, 0.0), (0.0, 0.0)]];
+    let hadamard = matrix!([Complex::one(), Complex::one()]; [Complex::one(), -Complex::one()])
+        .scale(complex!(1.0 / f64::sqrt(2.0), 0.0));
+    println!("Before:\n{}", register[0]);
+    register.apply(&hadamard, 0);
+    println!("\nAfter H Gate:\n{}", register[0]);
 }
diff --git a/libpsi/src/core/component.rs b/libpsi/src/core/component.rs
index bd18b52..51e0551 100644
--- a/libpsi/src/core/component.rs
+++ b/libpsi/src/core/component.rs
@@ -1,7 +1,13 @@
 use crate::{ColumnVector, Complex, Matrix, VectorMatrix};
+use std::ops;
 
-pub type QuantumRegister = ColumnVector<Complex<f64>>;
 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 {
@@ -27,8 +33,8 @@ macro_rules! quantum_register {
     ($($bit:expr),*) => {
         {
             const N: usize = count!($($bit),*);
-            let bits: [QuantumBit; N] = [$($bit),*];
-            QuantumRegister::from(&bits)
+            let mut bits: [QuantumBit; N] = [$($bit),*];
+            QuantumRegister::from(&mut bits)
         }
     };
 }
@@ -40,12 +46,35 @@ impl QuantumBit {
 }
 
 impl QuantumRegister {
-    pub fn from(bits: &[QuantumBit]) -> 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();
         for matrix in &matrices[1..] {
             result = result.kronecker(matrix);
         }
-        ColumnVector::from_matrix(&result)
+
+        QuantumRegister {
+            qubits: bits.to_vec(),
+            state: ColumnVector::from_matrix(&result),
+        }
+    }
+
+    pub fn apply(&mut self, gate: &QuantumGate, index: usize) {
+        let result: ColumnVector<Complex<f64>> = self.state.mul_matrix(gate).unwrap();
+        self.qubits[index] = result;
+    }
+}
+
+impl ops::Index<usize> for QuantumRegister {
+    type Output = QuantumBit;
+
+    fn index(&self, index: usize) -> &Self::Output {
+        &self.qubits[index]
+    }
+}
+
+impl ops::IndexMut<usize> for QuantumRegister {
+    fn index_mut(&mut self, index: usize) -> &mut Self::Output {
+        &mut self.qubits[index]
     }
 }
diff --git a/libpsi/src/core/gates.rs b/libpsi/src/core/gates.rs
new file mode 100644
index 0000000..e69de29
diff --git a/libpsi/src/maths/vector.rs b/libpsi/src/maths/vector.rs
index 0c13e4c..243061d 100644
--- a/libpsi/src/maths/vector.rs
+++ b/libpsi/src/maths/vector.rs
@@ -43,6 +43,7 @@ pub trait VectorMatrix<T: Float> {
     fn to_matrix(&self) -> Matrix<T>;
 }
 
+#[derive(Clone)]
 pub struct VectorImpl<T: Float, const ROWS: usize, const COLS: usize>(Vec<T>);
 pub type RowVector<T> = VectorImpl<T, 1, 0>;
 pub type ColumnVector<T> = VectorImpl<T, 0, 1>;
-- 
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