updated libquantum 0.1.0 source files

2025-10-03 08:42:01 +00:00 · 2016-10-27 04:09:05 +09:00
parent 617e4b91f3
commit fb55e54b6e
34 changed files with 20389 additions and 0 deletions
--- a/decoherence.c
+++ b/decoherence.c
@@ -0,0 +1,104 @@
+/* decoherence.c: Simulation of decoherence effects
+
+   Copyright 2003 Bjoern Butscher, Hendrik Weimer
+
+   This file is part of libquantum
+
+   libquantum is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published
+   by the Free Software Foundation; either version 2 of the License,
+   or (at your option) any later version.
+
+   libquantum is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with libquantum; if not, write to the Free Software
+   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+   USA
+
+*/
+
+#include <math.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "measure.h"
+#include "qureg.h"
+#include "gates.h"
+#include "complex.h"
+
+/* Status of the decoherence simulation. Non-zero means enabled and
+   decoherence effects will be simulated. */
+
+int status = 0;
+
+/* Decoherence parameter. The higher the value, the greater the
+   decoherence impact. */
+
+float lambda = 0;
+
+/* Initialize the decoherence simulation and set the decoherence
+   parameter. */
+
+void 
+quantum_set_decoherence(float l)
+{
+  if(l)
+    {
+      status = 1;
+      lambda = l;
+    }
+  else
+    status = 0;
+}
+
+/* Perform the actual decoherence of a quantum register for a single
+   step of time. This is done by applying a phase shift by a normal
+   distributed angle with the variance LAMBDA. */
+
+void
+quantum_decohere(quantum_reg *reg)
+{
+  float u, v, s, x;
+  COMPLEX_FLOAT c0, c1;
+  int i, j;
+
+  /* Increase the gate counter */
+
+  quantum_gate_counter(1);
+
+  if(status)
+    {
+      for(j=0; j<reg->width; j++)
+	{
+	  /* Generate a normal distributed random number */
+	  
+     	  do {
+	    u = 2 * quantum_frand() - 1;
+	    v = 2 * quantum_frand() - 1;
+	    s = u * u + v * v;
+	  } while (s >= 1);
+
+	  x = u * sqrt(-2 * log(s) / s);
+
+	  x *= sqrt(2 * lambda);
+	  
+	  /* Apply the phase shift gate for decoherence simulation */
+
+	  c0 = quantum_cexp(-x / 2);
+	  c1 = quantum_cexp(x / 2);
+
+	  for(i=0; i<reg->size; i++)
+	    {
+	      if(reg->node[i].state & ((MAX_UNSIGNED) 1 << j))
+		reg->node[i].amplitude *= c1;
+
+	      else
+		reg->node[i].amplitude *= c0;
+	    }
+	}
+    }
+}