WIP: Add QFT example

Author: long-long-float

examples/qft.rs

@@ -0,0 +1,32 @@
+use std::f64::consts::PI;
+
+use anyhow::Result;
+use simple_qsim::{circuit::GateKind, Circuit, QState};
+
+fn main() -> Result<()> {
+    let num_of_qubits = 3;
+
+    let mut circuit = Circuit::new(num_of_qubits);
+
+    // Initialize input with H
+    for i in 0..num_of_qubits {
+        circuit.add_gate(GateKind::H, i);
+    }
+
+    for i in (0..num_of_qubits).rev() {
+        circuit.add_gate(GateKind::H, i);
+        for j in (0..i).rev() {
+            let angle = 2.0 * PI / 2.0f64.powi((num_of_qubits - j) as i32);
+            circuit.add_control(i, j, GateKind::Phase(angle))?;
+        }
+    }
+
+    println!("Circuit:\n{}", circuit);
+
+    let qs = QState::from_str("000")?;
+
+    let result = circuit.apply(&qs)?;
+    println!("Resulting state:\n{}", result);
+
+    Ok(())
+}

src/circuit.rs

@@ -4,7 +4,7 @@ use nalgebra_sparse::{coo::CooMatrix, csr::CsrMatrix};
 use num_complex::Complex;
 
 use crate::gates::{
-    h_matrix, inv_t_matrix, rx_dence_matrix, rx_matrix, ry_dence_matrix, ry_matrix,
+    h_matrix, inv_t_matrix, phase_matrix, rx_dence_matrix, rx_matrix, ry_dence_matrix, ry_matrix,
     rz_dence_matrix, rz_matrix, s_dence_matrix, s_matrix, t_matrix, x_dence_matrix, x_matrix,
     y_dence_matrix, y_matrix, z_dence_matrix, z_matrix,
 };
@@ -40,6 +40,7 @@ pub enum GateKind {
     RX(f64),
     RY(f64),
     RZ(f64),
+    Phase(f64),
 }
 
 pub enum ParameterizedGate {
@@ -190,14 +191,19 @@ impl Circuit {
         self.gate_at(index, GateKind::H)
     }
 
-    pub fn control(mut self, control: usize, target: usize, kind: GateKind) -> Result<Self> {
+    pub fn add_control(&mut self, control: usize, target: usize, kind: GateKind) -> Result<()> {
         self.gates.push(Gate {
             kind,
             index: GateIndex::Control {
                 controls: vec![control],
                 target,
             },
         });
+        Ok(())
+    }
+
+    pub fn control(mut self, control: usize, target: usize, kind: GateKind) -> Result<Self> {
+        self.add_control(control, target, kind)?;
         Ok(self)
     }
 
@@ -372,6 +378,7 @@ impl Circuit {
             GateKind::RX(angle) => rx_matrix(*angle),
             GateKind::RY(angle) => ry_matrix(*angle),
             GateKind::RZ(angle) => rz_matrix(*angle),
+            GateKind::Phase(angle) => phase_matrix(*angle),
         };
         Ok(matrix)
     }

src/gates.rs

@@ -56,10 +56,8 @@ pub fn ry_dence_matrix(angle: f64) -> Matrix2<Qbit> {
 
 pub fn rz_matrix(angle: f64) -> CsrMatrix<Qbit> {
     let mut rz_coo = CooMatrix::new(2, 2);
-    rz_coo.push(0, 0, Complex::from_polar(1.0, -angle / 2.0).exp());
-    // rz_coo.push(0, 1, Complex::ZERO);
-    // rz_coo.push(1, 0, Complex::ZERO);
-    rz_coo.push(1, 1, Complex::from_polar(1.0, angle / 2.0).exp());
+    rz_coo.push(0, 0, Complex::from_polar(1.0, -angle / 2.0));
+    rz_coo.push(1, 1, Complex::from_polar(1.0, angle / 2.0));
     CsrMatrix::from(&rz_coo)
 }
 
@@ -72,6 +70,13 @@ pub fn rz_dence_matrix(angle: f64) -> Matrix2<Qbit> {
     ])
 }
 
+pub fn phase_matrix(angle: f64) -> CsrMatrix<Qbit> {
+    let mut phase_coo = CooMatrix::new(2, 2);
+    phase_coo.push(0, 0, Complex::ONE);
+    phase_coo.push(1, 1, Complex::from_polar(1.0, angle));
+    CsrMatrix::from(&phase_coo)
+}
+
 pub fn x_matrix() -> CsrMatrix<Qbit> {
     let mut x_coo = CooMatrix::new(2, 2);
     x_coo.push(0, 1, Complex::new(1.0, 0.0));