c: quantum gate and state foundations

4 files changed, 97 insertions, 0 deletions

diff --git a/include/core/quantum_components.h b/include/core/quantum_components.h
new file mode 100644
index 0000000..b0acabc
--- /dev/null
+++ b/include/core/quantum_components.h
@@ -0,0 +1,20 @@
+#pragma once
+
+#include <stddef.h>
+
+#include "maths/matrix.h"
+#include "maths/vector.h"
+
+struct PsiVector psi_new_state_0(void);
+struct PsiVector psi_new_state_1(void);
+
+struct PsiQuantumGate
+{
+	const char *name;
+	struct PsiMatrix matrix;
+	size_t num_qubits;
+};
+
+struct PsiQuantumGate psi_new_quantum_gate(const char *name, struct PsiMatrix matrix, size_t num_qubits);
+struct PsiQuantumGate psi_new_quantum_gate_from_matrix(const char *name, struct PsiMatrix matrix);
+void psi_free_quantum_gate(struct PsiQuantumGate *gate);
diff --git a/src/core/quantum_components.c b/src/core/quantum_components.c
new file mode 100644
index 0000000..3b9eef5
--- /dev/null
+++ b/src/core/quantum_components.c
@@ -0,0 +1,51 @@
+#include "core/quantum_components.h"
+
+#include <assert.h>
+
+struct PsiVector psi_new_state_0(void)
+{
+	return psi_column_vector(psi_new_complex(1.0, 0.0), psi_new_complex(0.0, 0.0));
+}
+
+struct PsiVector psi_new_state_1(void)
+{
+	return psi_column_vector(psi_new_complex(0.0, 0.0), psi_new_complex(1.0, 0.0));
+}
+
+struct PsiQuantumGate psi_new_quantum_gate(const char *name, struct PsiMatrix matrix, size_t num_qubits)
+{
+	size_t expected_dim = (size_t)1 << num_qubits;
+	assert(matrix.rows == expected_dim);
+	assert(matrix.cols == expected_dim);
+
+	return (struct PsiQuantumGate)
+	{
+		name,
+		matrix,
+		num_qubits,
+	};
+}
+
+struct PsiQuantumGate psi_new_quantum_gate_from_matrix(const char *name, struct PsiMatrix matrix)
+{
+	assert(matrix.rows == matrix.cols);
+
+	size_t dim = matrix.rows;
+	assert(dim > 0 && (dim & (dim - 1)) == 0);
+
+	size_t num_qubits = 0;
+	while (((size_t)1 << num_qubits) < dim)
+		num_qubits++;
+
+	return (struct PsiQuantumGate)
+	{
+		name,
+		matrix,
+		num_qubits,
+	};
+}
+
+void psi_free_quantum_gate(struct PsiQuantumGate *gate)
+{
+	psi_free_matrix(&gate->matrix);
+}
diff --git a/src/maths/matrix.c b/src/maths/matrix.c
index 400c2a7..44b953c 100644
--- a/src/maths/matrix.c
+++ b/src/maths/matrix.c
@@ -30,6 +30,15 @@ struct PsiMatrix psi_clone_matrix(struct PsiMatrix m)
 	return psi_new_matrix_from(m.data, m.rows, m.cols);
 }
 
+struct PsiMatrix psi_identity_matrix(size_t size)
+{
+	struct PsiMatrix m = psi_new_matrix(size, size);
+	for (size_t i = 0; i < size; i++)
+		m.data[i * size + i] = psi_new_complex(1.0, 0.0);
+
+	return m;
+}
+
 void psi_free_matrix(struct PsiMatrix *m)
 {
 	free(m->data);
diff --git a/tester/main.c b/tester/main.c
index 334291f..cba5d28 100644
--- a/tester/main.c
+++ b/tester/main.c
@@ -1,5 +1,6 @@
 #include <stdio.h>
 
+#include "core/quantum_components.h"
 #include "maths/complex.h"
 #include "maths/matrix.h"
 #include "maths/vector.h"
@@ -60,5 +61,21 @@ int main(void)
 	psi_free_matrix(&m);
 	psi_free_matrix(&mm);
 
+	double inv_sqrt2 = 0.7071067811865475;
+	struct PsiMatrix h = psi_matrix(2, 2,
+		psi_new_complex(inv_sqrt2, 0.0), psi_new_complex(inv_sqrt2, 0.0),
+		psi_new_complex(inv_sqrt2, 0.0), psi_new_complex(-inv_sqrt2, 0.0));
+	struct PsiQuantumGate gate = psi_new_quantum_gate_from_matrix("H", h);
+
+	struct PsiVector s0 = psi_new_state_0();
+	struct PsiVector hs0 = psi_mul_vector_matrix(s0, gate.matrix);
+
+	printf("gate    = %s (%zu qubit)\n", gate.name, gate.num_qubits);
+	printf("H|0>    = [%g, %g]\n", hs0.data[0].real, hs0.data[1].real);
+
+	psi_free_vector(&s0);
+	psi_free_vector(&hs0);
+	psi_free_quantum_gate(&gate);
+
 	return 0;
 }