updated libquantum 0.2.0 source files

CHANGES

@@ -1,3 +1,13 @@
+libquantum 0.2.0:
+	- Added Quantum Error Correction
+	- Included an Implementation of Grover's algorithm
+	- Added some inverse functions and conditional phase kick
+	- Improved speed of the decoherence simulation
+	- Fixed a memory leak in the quantum register deletion routine
+	- Fixed a segfault in the sigma functions
+	- Fixed a typo in the configure script that could result in a build 
+	  failure
+
 libquantum 0.1.1:
 	- Completed rotation gates (quantum_r_z)
 	- Fixed a build problem with the demo program

INSTALL

@@ -1,4 +1,4 @@
-libquantum 0.1.1 installation guide
+libquantum 0.2.0 installation guide
 -----------------------------------
 
 Contents:
@@ -37,16 +37,24 @@ Now you can build the beast:
 
 	make
 
-By now, you can create a sample program which implements Shor's
-factoring algorithm:
+By now, you can create two demo programs which show Shor's factoring
+algorithm and Grover's search algorithm:
 
-	make shor
+	make demos
 
-The number to be factored is given on the command line as the first
-parameter. To factor 15, simply type:
+For the Shor algorithm demo, the number to be factored is given on the
+command line as the first parameter. To factor 15, simply type:
 
 	./shor 15
 
+The demo for Grover's algorithm requires the number of the marked
+element (i.e. the desired result of the search) as the first argument
+on the command line. The number of qubits may be given as a second
+arguments. To mark element No. 42 in a database of 10 qubits (which
+means 2^10 = 1024 elements):
+
+	./grover 42 10
+
 
 2. Installation of the library
 ------------------------------
@@ -57,8 +65,9 @@ For this step you will need to have superuser privileges. Just type
 
 to get libquantum installed into the default directory, which is
 usually /usr/local/bin. Note that on some systems this directories is
-not in the standard search path. Take a look at the output of the last
-command to get some advice on how to deal with this.
+not in the standard search path for libraries. Take a look at the
+output of the last command to get some advice on how to deal with
+this.
 
 3. Writing your own programs
 ----------------------------

Makefile.in

@@ -36,29 +36,29 @@ top_builddir=.
 # Release information
 
 MAJOR=0
-MINOR=1
-RELEASE=1
+MINOR=2
+RELEASE=0
 
 # Tools needed to build libquantum
 
-CC=@CC@
+CC=@CC@ -O2 -g -pg
 INSTALL=@INSTALL@
 LIBTOOL=@LIBTOOL@
 
 # Flags passed to C compiler
 
 CFLAGS=@CFLAGS@
-LDFLAGS=-rpath $(LIBDIR) -version-info 1:1:1
+LDFLAGS=-rpath $(LIBDIR) -version-info 2:0:2
 
 # Dependencies
 
 all:	libquantum.la
 
 libquantum.la: complex.lo measure.lo matrix.lo gates.lo qft.lo classic.lo\
-	qureg.lo decoherence.lo oaddn.lo omuln.lo expn.lo Makefile
+	qureg.lo decoherence.lo oaddn.lo omuln.lo expn.lo qec.lo Makefile
 	$(LIBTOOL) $(CC) $(LDFLAGS) -o libquantum.la complex.lo measure.lo\
 	matrix.lo gates.lo oaddn.lo omuln.lo expn.lo qft.lo classic.lo\
-	qureg.lo decoherence.lo -lm
+	qureg.lo decoherence.lo qec.lo -lm
 
 complex.lo: complex.c complex.h Makefile
 	$(LIBTOOL) $(CC) $(CFLAGS) -c complex.c	
@@ -90,21 +90,30 @@ classic.lo: classic.c classic.h Makefile
 qureg.lo: qureg.c qureg.h matrix.h config.h complex.h Makefile
 	$(LIBTOOL) $(CC) $(CFLAGS) -c qureg.c
 
-decoherence.lo: decoherence.c decoherence.h measure.h gates.h qureg.h config.h\
-	Makefile
+decoherence.lo: decoherence.c decoherence.h measure.h gates.h qureg.h\
+	complex.h config.h Makefile
 	$(LIBTOOL) $(CC) $(CFLAGS) -c decoherence.c
 
+qec.lo: qec.c qec.h gates.h qureg.h config.h Makefile
+	$(LIBTOOL) $(CC) $(CFLAGS) -c qec.c
+
 # Bring this savage back home
 
 install: libquantum.la
 	$(LIBTOOL) $(INSTALL) -m 0644 libquantum.la $(LIBDIR)
 	$(INSTALL) -m 0644 quantum.h $(INCLUDEDIR)
 
-# Build a demo showing Shor's factoring algorithm
+# Build demos of Shor's and Grover's algorithms
+
+demos: shor grover
 
 shor: libquantum.la shor.c Makefile
 	$(LIBTOOL) $(CC) $(CFLAGS) -o shor shor.c -I./ -lquantum -static -lm
 
+grover: libquantum.la grover.c Makefile
+	$(LIBTOOL) $(CC) $(CFLAGS) -o grover grover.c -I./ -lquantum -static\
+	-lm
+
 # Make everything neat and tidy
 
 clean:
@@ -119,9 +128,9 @@ distclean:
 dist:
 	-rm quantum.h config.h
 	mkdir libquantum-$(MAJOR).$(MINOR).$(RELEASE)
-	cp *.c *.h quantum.h.in Makefile.in config.h.in configure COPYING\
-	install-sh ltmain.sh config.sub config.guess README INSTALL CHANGES\
-	libquantum-$(MAJOR).$(MINOR).$(RELEASE)
+	cp *.c *.h quantum.h.in Makefile.in config.h.in configure configure.in\
+	COPYING	install-sh ltmain.sh config.sub config.guess README INSTALL\
+	CHANGES	libquantum-$(MAJOR).$(MINOR).$(RELEASE)
 	tar czf libquantum-$(MAJOR).$(MINOR).$(RELEASE).tar.gz\
 	libquantum-$(MAJOR).$(MINOR).$(RELEASE)/
 	rm -rf libquantum-$(MAJOR).$(MINOR).$(RELEASE)

README

@@ -1,4 +1,4 @@
-libquantum 0.1.1 README file
+libquantum 0.2.0 README file
 ----------------------------
 
 libquantum is a C library for quantum computing. It provides quantum
@@ -6,16 +6,16 @@ registers, unitary operations and measurement functions. The main goal
 is a physically precise simulation of a quantum computer with high
 performance.
 
-An implementation of Shor's factoring algorithm is included with this
-release.
+Implementations of Shor's factoring algorithm and Grover's search
+algorithm are included with this release.
 
 See the file INSTALL for help on the installation.
 
-guardian is distributed under the terms of the GNU General Public
+libquantum is distributed under the terms of the GNU General Public
 License (GPL), which is located in the file COPYING.
 
 Send inquiries, comments, bug reports, suggestions, patches, etc. to:
 libquantum@enyo.de
 
-See also the guardian website:
+See also the libquantum website:
 http://www.enyo.de/libquantum

config.h.in

@@ -3,6 +3,9 @@
 /* Complex data type */
 #undef COMPLEX_FLOAT
 
+/* Define to 1 if you have the <dlfcn.h> header file. */
+#undef HAVE_DLFCN_H
+
 /* Define to 1 if you have the <fcntl.h> header file. */
 #undef HAVE_FCNTL_H
 

configure

@@ -1,6 +1,6 @@
 #! /bin/sh
 # Guess values for system-dependent variables and create Makefiles.
-# Generated by GNU Autoconf 2.57 for libquantum 0.1.1.
+# Generated by GNU Autoconf 2.57 for libquantum 0.2.0.
 #
 # Report bugs to <libquantum@enyo.de>.
 #
@@ -427,8 +427,8 @@ SHELL=${CONFIG_SHELL-/bin/sh}
 # Identity of this package.
 PACKAGE_NAME='libquantum'
 PACKAGE_TARNAME='libquantum'
-PACKAGE_VERSION='0.1.1'
-PACKAGE_STRING='libquantum 0.1.1'
+PACKAGE_VERSION='0.2.0'
+PACKAGE_STRING='libquantum 0.2.0'
 PACKAGE_BUGREPORT='libquantum@enyo.de'
 
 ac_unique_file="classic.c"
@@ -938,7 +938,7 @@ if test "$ac_init_help" = "long"; then
   # Omit some internal or obsolete options to make the list less imposing.
   # This message is too long to be a string in the A/UX 3.1 sh.
   cat <<_ACEOF
-\`configure' configures libquantum 0.1.1 to adapt to many kinds of systems.
+\`configure' configures libquantum 0.2.0 to adapt to many kinds of systems.
 
 Usage: $0 [OPTION]... [VAR=VALUE]...
 
@@ -999,7 +999,7 @@ fi
 
 if test -n "$ac_init_help"; then
   case $ac_init_help in
-     short | recursive ) echo "Configuration of libquantum 0.1.1:";;
+     short | recursive ) echo "Configuration of libquantum 0.2.0:";;
    esac
   cat <<\_ACEOF
 
@@ -1092,7 +1092,7 @@ fi
 test -n "$ac_init_help" && exit 0
 if $ac_init_version; then
   cat <<\_ACEOF
-libquantum configure 0.1.1
+libquantum configure 0.2.0
 generated by GNU Autoconf 2.57
 
 Copyright 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000, 2001, 2002
@@ -1107,7 +1107,7 @@ cat >&5 <<_ACEOF
 This file contains any messages produced by compilers while
 running configure, to aid debugging if configure makes a mistake.
 
-It was created by libquantum $as_me 0.1.1, which was
+It was created by libquantum $as_me 0.2.0, which was
 generated by GNU Autoconf 2.57.  Invocation command line was
 
   $ $0 $@
@@ -7877,7 +7877,7 @@ if test $ac_cv_type_uint_64t = yes; then
 #define MAX_UNSIGNED uint_64t
 _ACEOF
 
-	MU_TYPE="unint_64t"
+	MU_TYPE="uint_64t"
 fi
 
 if test "$MU_TYPE" = "none"
@@ -8620,7 +8620,7 @@ _ASBOX
 } >&5
 cat >&5 <<_CSEOF
 
-This file was extended by libquantum $as_me 0.1.1, which was
+This file was extended by libquantum $as_me 0.2.0, which was
 generated by GNU Autoconf 2.57.  Invocation command line was
 
   CONFIG_FILES    = $CONFIG_FILES
@@ -8680,7 +8680,7 @@ _ACEOF
 
 cat >>$CONFIG_STATUS <<_ACEOF
 ac_cs_version="\\
-libquantum config.status 0.1.1
+libquantum config.status 0.2.0
 configured by $0, generated by GNU Autoconf 2.57,
   with options \\"`echo "$ac_configure_args" | sed 's/[\\""\`\$]/\\\\&/g'`\\"
 
@@ -9358,4 +9358,3 @@ if test "$no_create" != yes; then
   # would make configure fail if this is the last instruction.
   $ac_cs_success || { (exit 1); exit 1; }
 fi
-

configure.in

@@ -0,0 +1,79 @@
+# Process this file with autoconf to produce a configure script.
+AC_INIT([libquantum], [0.2.0], [libquantum@enyo.de])
+AC_CONFIG_SRCDIR([classic.c])
+AC_CONFIG_HEADER([config.h])
+
+# The language of our choice
+AC_LANG([C])
+
+# Checks for programs.
+AC_PROG_CC
+AC_PROG_INSTALL
+AC_PROG_LIBTOOL
+
+# Checks for libraries.
+# FIXME: Replace `main' with a function in `-lm':
+AC_CHECK_LIB([m], [sqrt])
+
+# Checks for header files.
+AC_HEADER_STDC
+AC_CHECK_HEADERS([fcntl.h stdlib.h unistd.h])
+
+# Checks for typedefs, structures, and compiler characteristics.
+AC_C_INLINE
+
+# Check for 64-bit integer
+MU_TYPE="none"
+AC_CHECK_TYPE([uint_64t], [AC_DEFINE([MAX_UNSIGNED], [uint_64t]) 
+	MU_TYPE="uint_64t"])
+if test "$MU_TYPE" = "none"
+then
+	AC_CHECK_TYPE([u_int_64t], [AC_DEFINE([MAX_UNSIGNED], [u_int_64t])
+		MU_TYPE="u_int_64t"])
+fi
+if test "$MU_TYPE" = "none"
+then
+	AC_CHECK_TYPE([unsigned long long], [AC_DEFINE(MAX_UNSIGNED, 
+		[unsigned long long], [Integer type for quantum registers])
+		MU_TYPE="unsigned long long"])
+fi
+if test "$MU_TYPE" = "none"
+then
+	AC_MSG_ERROR([No 64-bit integer type!])
+fi
+
+# Check for complex number type
+CF_TYPE="none"
+AC_CHECK_TYPE([float _Complex], [AC_DEFINE([COMPLEX_FLOAT], [float _Complex])
+	CF_TYPE="float _Complex"])
+if test "$CF_TYPE" = "none"
+then
+	AC_CHECK_TYPE([__complex__ float], [AC_DEFINE([COMPLEX_FLOAT], 
+		[__complex__ float], [Complex data type]) 
+			CF_TYPE="__complex__ float"])
+fi
+if test "$CF_TYPE" = "none"
+then
+	AC_MSG_ERROR([No complex number type!])
+fi
+
+# Check for the imaginary unit
+AC_MSG_CHECKING([for the imaginary unit])
+I="none"
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([COMPLEX_FLOAT z;], [z=I;])], 
+	[AC_DEFINE([IMAGINARY], [I], [Imaginary unit]) I="I"])
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([COMPLEX_FLOAT z;], [z=_Complex_I;])], 
+	[AC_DEFINE([IMAGINARY], [_Complex_I]) I="_Complex_I"])
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([COMPLEX_FLOAT z;], [z=1i;])], 
+	[AC_DEFINE([IMAGINARY], [1i]) I="1i"])
+if test $I = "none"
+then
+	AC_MSG_ERROR([No imaginary unit!])
+fi
+AC_MSG_RESULT($I)
+
+AC_SUBST(MU_TYPE)
+AC_SUBST(CF_TYPE)
+
+AC_CONFIG_FILES([Makefile quantum.h])
+AC_OUTPUT

decoherence.c

@@ -40,6 +40,12 @@ int status = 0;
 
 float lambda = 0;
 
+float
+quantum_get_decoherence()
+{
+  return lambda;
+}
+
 /* Initialize the decoherence simulation and set the decoherence
    parameter. */
 
@@ -63,7 +69,8 @@ void
 quantum_decohere(quantum_reg *reg)
 {
   float u, v, s, x;
-  COMPLEX_FLOAT c0, c1;
+  float *nrands;
+  float angle;
   int i, j;
 
   /* Increase the gate counter */
@@ -72,9 +79,19 @@ quantum_decohere(quantum_reg *reg)
 
   if(status)
     {
-      for(j=0; j<reg->width; j++)
+      
+      nrands = calloc(reg->width, sizeof(float));
+      if(!nrands)
 	{
-	  /* Generate a normal distributed random number */
+	  printf("Not enough memory for %i-sized array of float!\n", 
+		 reg->width);
+	  exit(1);
+	}
+      quantum_memman(reg->width * sizeof(float));
+
+      for(i=0; i<reg->width; i++)
+	{
+	  /* Generate normal distributed random numbers */
 	  
      	  do {
 	    u = 2 * quantum_frand() - 1;
@@ -86,19 +103,29 @@ quantum_decohere(quantum_reg *reg)
 
 	  x *= sqrt(2 * lambda);
 
-	  /* Apply the phase shift gate for decoherence simulation */
+	  nrands[i] = x/2;
+	}
 
-	  c0 = quantum_cexp(-x / 2);
-	  c1 = quantum_cexp(x / 2);
+  
+      /* Apply the phase shifts for decoherence simulation */
 
       for(i=0; i<reg->size; i++)
 	{
-	      if(reg->node[i].state & ((MAX_UNSIGNED) 1 << j))
-		reg->node[i].amplitude *= c1;
+	  angle = 0;
 
+	  for(j=0; j<reg->width; j++)
+	    {
+	      if(reg->node[i].state & ((MAX_UNSIGNED) 1 << j))
+		angle += nrands[j];
 	      else
-		reg->node[i].amplitude *= c0;
-	    }
-	}
+		angle -= nrands[j];
+	    }
+
+	  reg->node[i].amplitude *= quantum_cexp(angle);
+	  
+	}
+      free(nrands);
+      quantum_memman(reg->width * sizeof(float));  
+  
     }
 }

decoherence.h

@@ -25,6 +25,8 @@
 
 #define __DECOHERENCE_H
 
+extern float quantum_get_decoherence();
+
 extern void quantum_set_decoherence(float lambda);
 
 extern void quantum_decohere(quantum_reg *reg);

gates.c

@@ -30,6 +30,7 @@
 #include "complex.h"
 #include "qureg.h"
 #include "decoherence.h"
+#include "qec.h"
 
 /* Apply a controlled-not gate */
 
@@ -37,7 +38,14 @@ void
 quantum_cnot(int control, int target, quantum_reg *reg)
 {
   int i;
+  int qec;
 
+  quantum_qec_get_status(&qec, NULL);
+
+  if(qec)
+    quantum_cnot_ft(control, target, reg);
+  else
+    {
       for(i=0; i<reg->size; i++)
 	{
 	  /* Flip the target bit of a base state if the control bit is set */
@@ -47,6 +55,7 @@ quantum_cnot(int control, int target, quantum_reg *reg)
 	}
       quantum_decohere(reg);
     }
+}
 
 /* Apply a toffoli (or controlled-controlled-not) gate */
 
@@ -54,7 +63,14 @@ void
 quantum_toffoli(int control1, int control2, int target, quantum_reg *reg)
 {
   int i;
+  int qec;
 
+  quantum_qec_get_status(&qec, NULL);
+
+  if(qec)
+    quantum_toffoli_ft(control1, control2, target, reg);
+  else
+    {
       for(i=0; i<reg->size; i++)
 	{
 	  /* Flip the target bit of a base state if both control bits are
@@ -70,6 +86,7 @@ quantum_toffoli(int control1, int control2, int target, quantum_reg *reg)
 	}
       quantum_decohere(reg);
     }
+}
 
 /* Apply a sigma_x (or not) gate */
 
@@ -77,7 +94,14 @@ void
 quantum_sigma_x(int target, quantum_reg *reg)
 {
   int i;
+  int qec;
 
+  quantum_qec_get_status(&qec, NULL);
+
+  if(qec)
+    quantum_sigma_x_ft(target, reg);
+  else
+    {
       for(i=0; i<reg->size; i++)
 	{
 	  /* Flip the target bit of each base state */
@@ -86,11 +110,12 @@ quantum_sigma_x(int target, quantum_reg *reg)
 	} 
       quantum_decohere(reg);
     }
+}
 
 /* Apply a sigma_y gate */
 
 void
-quantum_sigma_y(int target, int width, quantum_reg *reg)
+quantum_sigma_y(int target, quantum_reg *reg)
 {
   int i;
   
@@ -113,7 +138,7 @@ quantum_sigma_y(int target, int width, quantum_reg *reg)
 /* Apply a sigma_y gate */
 
 void
-quantum_sigma_z(int target, int width, quantum_reg *reg)
+quantum_sigma_z(int target, quantum_reg *reg)
 {
   int i;
 
@@ -128,15 +153,29 @@ quantum_sigma_z(int target, int width, quantum_reg *reg)
 }
 
 /* Swap the first WIDTH bits of the quantum register. This is done
-   classically by renaming the bits. */
+   classically by renaming the bits, unless QEC is enabled. */
 
 void
 quantum_swaptheleads(int width, quantum_reg *reg)
 {
   int i, j;
   int pat1, pat2;
+  int qec;
   MAX_UNSIGNED l;
 
+  quantum_qec_get_status(&qec, NULL);
+
+  if(qec)
+    {
+      for(i=0; i<width; i++)
+	{
+	  quantum_cnot(i, width+i, reg);
+	  quantum_cnot(width+i, i, reg);
+	  quantum_cnot(i, width+i, reg);
+	}
+    }
+  else
+    {
       for(i=0; i<reg->size; i++)
 	{
 	  /* calculate left bit pattern */
@@ -150,7 +189,7 @@ quantum_swaptheleads(int width, quantum_reg *reg)
 	  for(j=0; j<width; j++)
 	    pat2 += reg->node[i].state & ((MAX_UNSIGNED) 1 << (width + j));
 	  
-      /* construct the new base state */
+	  /* construct the new basis state */
 	  
 	  l = reg->node[i].state - (pat1 + pat2);
 	  l += (pat1 << width);
@@ -158,6 +197,7 @@ quantum_swaptheleads(int width, quantum_reg *reg)
 	  reg->node[i].state = l;
 	}
     }
+}
 
 /* Swap WIDTH bits starting at WIDTH and 2*WIDTH+2 controlled by
    CONTROL */
@@ -352,7 +392,7 @@ quantum_gate1(int target, quantum_matrix m, quantum_reg *reg)
 	    }
 	}
 
-      quantum_delete_qureg(reg);
+      quantum_delete_qureg_hashpreserve(reg);
       *reg = out;
     }
 
@@ -449,6 +489,22 @@ quantum_r_z(int target, float gamma, quantum_reg *reg)
   quantum_decohere(reg);
 }
 
+/* Scale the phase of qubit */
+
+void
+quantum_phase_scale(int target, float gamma, quantum_reg *reg)
+{
+  int i;
+  
+  for(i=0; i<reg->size; i++)
+    {
+      reg->node[i].amplitude *= quantum_cexp(gamma);
+    }
+
+  quantum_decohere(reg);
+}
+
+
 /* Apply a phase kick by the angle GAMMA */
 
 void
@@ -485,6 +541,45 @@ quantum_cond_phase(int control, int target, quantum_reg *reg)
   quantum_decohere(reg);
 }
 
+
+void
+quantum_cond_phase_inv(int control, int target, quantum_reg *reg)
+{
+  int i;
+
+  for(i=0; i<reg->size; i++)
+    {
+      if(reg->node[i].state & ((MAX_UNSIGNED) 1 << control))
+	{
+	  if(reg->node[i].state & ((MAX_UNSIGNED) 1 << target))
+	    reg->node[i].amplitude 
+	      *= quantum_cexp(-pi / ((MAX_UNSIGNED) 1 << (control - target)));
+	}
+    }
+
+  quantum_decohere(reg);
+}
+
+
+
+void
+quantum_cond_phase_kick(int control, int target, float gamma, quantum_reg *reg)
+{
+  int i;
+
+  for(i=0; i<reg->size; i++)
+    {
+      if(reg->node[i].state & ((MAX_UNSIGNED) 1 << control))
+	{
+	  if(reg->node[i].state & ((MAX_UNSIGNED) 1 << target))
+	    reg->node[i].amplitude *= quantum_cexp(gamma);
+	}
+     }
+  quantum_decohere(reg);
+}
+
+
+
 /* Increase the gate counter by INC steps or reset it if INC < 0. The
    current value of the counter is returned. */
 

gates.h

@@ -48,8 +48,14 @@ extern void quantum_r_z(int target, float gamma, quantum_reg *reg);
 extern void quantum_hadamard(int target, quantum_reg *reg);
 extern void quantum_walsh(int target, quantum_reg *reg);
 
+extern void quantum_phase_scale(int target, float gamma, quantum_reg *reg);
 extern void quantum_phase_kick(int target, float gamma, quantum_reg *reg);
+
 extern void quantum_cond_phase(int control, int target, quantum_reg *reg);
+extern void quantum_cond_phase_inv(int control, int target, quantum_reg *reg);
+
+extern void quantum_cond_phase_kick(int control, int target, float gamma, 
+				    quantum_reg *reg);
 
 extern int quantum_gate_counter(int inc);
 

grover.c

@@ -0,0 +1,183 @@
+ /* grover.c: Implementation of Grover's search algorithm
+
+   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 <quantum.h>
+#include <stdio.h>
+#include <math.h>
+#include <stdlib.h>
+
+#define pi 3.141592654
+
+void oracle(int state, quantum_reg *reg)
+{
+  int i;
+
+  for(i=0;i<reg->width;i++)
+    {
+      if(!(state & (1 << i)))
+	{
+	  quantum_sigma_x(i, reg);
+	}
+    }
+
+  quantum_toffoli(0, 1, reg->width+1, reg);
+
+  for(i=1;i<reg->width;i++)
+    {
+      quantum_toffoli(i, reg->width+i, reg->width+i+1, reg);
+    }
+
+  quantum_cnot(reg->width+i, reg->width, reg);
+  
+  for(i=reg->width-1;i>0;i--)
+    {
+      quantum_toffoli(i, reg->width+i, reg->width+i+1, reg);
+    }
+  
+  quantum_toffoli(0, 1, reg->width+1, reg);
+
+  for(i=0;i<reg->width;i++)
+    {
+      if(!(state & (1 << i)))
+	quantum_sigma_x(i, reg);
+    }
+
+}
+
+void inversion(quantum_reg *reg)
+{
+  int i;
+  
+  for(i=0;i<reg->width;i++)
+    quantum_sigma_x(i, reg);
+
+  quantum_phase_scale(0, pi/2, reg);
+  quantum_hadamard(reg->width-1, reg);
+
+  if(reg->width==3)
+    quantum_toffoli(0, 1, 2, reg);
+
+  else
+    {
+      quantum_toffoli(0, 1, reg->width+1, reg);
+
+      for(i=1;i<reg->width-1;i++)
+	{
+	  quantum_toffoli(i, reg->width+i, reg->width+i+1, reg);
+	}
+
+      quantum_cnot(reg->width+i, reg->width-1, reg);
+  
+      for(i=reg->width-2;i>0;i--)
+	{
+	  quantum_toffoli(i, reg->width+i, reg->width+i+1, reg);
+	}
+  
+      quantum_toffoli(0, 1, reg->width+1, reg);
+    }
+  
+  quantum_hadamard(reg->width-1, reg);
+  quantum_phase_scale(0, pi/2, reg);
+
+  for(i=0;i<reg->width;i++)
+    quantum_sigma_x(i, reg);
+}
+  
+
+void grover(int target, quantum_reg *reg)
+{
+  int i;
+
+  oracle(target, reg);
+
+  for(i=0;i<reg->width;i++)
+    quantum_hadamard(i, reg);
+
+  inversion(reg);
+
+  for(i=0;i<reg->width;i++)
+    quantum_hadamard(i, reg);
+
+}
+
+void print_grover(quantum_reg *reg)
+{
+  int i;
+
+  for(i=0;i<reg->size;i++)
+    printf("%llu %f\n", reg->node[i].state, __real__ reg->node[i].amplitude);
+}
+
+int main(int argc, char **argv)
+{
+  quantum_reg reg;
+  int i, N, width=0;
+
+  if(argc==1)
+    {
+      printf("Usage: grover [number] [[qubits]]\n\n");
+      return 3;
+    }
+
+  N=atoi(argv[1]);
+
+  if(argc > 2)
+    width = atoi(argv[2]);
+
+  if(width < quantum_getwidth(N+1))
+    width = quantum_getwidth(N+1);
+
+  reg = quantum_new_qureg(0, width);
+
+  quantum_sigma_x(reg.width, &reg);
+
+  for(i=0;i<reg.width;i++)
+    quantum_hadamard(i, &reg);
+
+  quantum_hadamard(reg.width, &reg);
+
+  printf("Iterating %i times\n", (int) (pi/4*sqrt(1<<reg.width)));
+
+  for(i=1; i<=pi/4*sqrt(1 << reg.width); i++)
+    {
+      printf("Iteration #%i\n", i);
+      grover(N, &reg);
+    }
+
+  quantum_hadamard(reg.width, &reg);
+
+  reg.width++;
+
+  quantum_bmeasure(reg.width-1, &reg);
+  
+  for(i=0; i<reg.size; i++)
+    {
+      if(reg.node[i].state == N)
+	printf("\nFound %i with a probability of %f\n\n", N, 
+	       quantum_prob(reg.node[i].amplitude));
+    }
+
+  quantum_delete_qureg(&reg);
+
+  return 0;
+}

matrix.c

@@ -39,7 +39,7 @@ unsigned long quantum_memman(long change)
   if(mem > max)
     max = mem;
 
-  return max;
+  return mem;
 }
 
 /* Create a new COLS x ROWS matrix */

measure.c

@@ -169,7 +169,7 @@ quantum_bmeasure(int pos, quantum_reg *reg)
 	}
     }
 
-  quantum_delete_qureg(reg);
+  quantum_delete_qureg_hashpreserve(reg);
   *reg = out;
   return result;
 }

qec.c

@@ -0,0 +1,280 @@
+/* qec.c: Quantum Error Correction
+
+   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 <stdlib.h>
+
+#include "qureg.h"
+#include "gates.h"
+#include "config.h"
+#include "decoherence.h"
+
+/* Type of the QEC. Currently implemented versions are:
+
+   0: no QEC (default)
+   1: Steane's 3-bit code */
+
+int type = 0;
+
+/* How many qubits are protected */
+
+int width = 0;
+
+
+/* Change the status of the QEC. */
+
+void
+quantum_qec_set_status(int stype, int swidth)
+{
+  type = stype;
+  width = swidth;
+}
+
+/* Get the current QEC status */
+ 
+void
+quantum_qec_get_status(int *ptype, int *pwidth)
+{
+  if(ptype)
+    *ptype = type;
+  if(pwidth)
+    *pwidth = width;
+} 
+
+/* Encode a quantum register. All qubits up to SWIDTH are protected,
+   the rest is expanded with a repition code. */
+
+void
+quantum_qec_encode(int type, int width, quantum_reg *reg)
+{
+  int i;
+  float lambda;
+
+  lambda = quantum_get_decoherence();
+
+  quantum_set_decoherence(0);
+
+  for(i=0;i<reg->width;i++)
+    {
+      if(i==reg->width-1)
+	quantum_set_decoherence(lambda);
+
+      if(i<width)
+	{
+	  quantum_hadamard(reg->width+i, reg);
+	  quantum_hadamard(2*reg->width+i, reg);
+
+	  quantum_cnot(reg->width+i, i, reg);
+	  quantum_cnot(2*reg->width+i, i, reg);
+	}
+      else
+	{
+	  quantum_cnot(i, reg->width+i, reg);
+	  quantum_cnot(i, 2*reg->width+i, reg);
+	}
+    }
+
+  quantum_qec_set_status(1, reg->width);
+
+  reg->width *= 3;
+}
+
+/* Decode a quantum register and perform Quantum Error Correction on
+   it */
+
+void
+quantum_qec_decode(int type, int width, quantum_reg *reg)
+{
+  int i, a, b;
+  int swidth;
+  float lambda;
+
+  lambda = quantum_get_decoherence();
+
+  quantum_set_decoherence(0);
+
+  swidth=reg->width/3;
+
+  quantum_qec_set_status(0, 0);
+
+  for(i=reg->width/3-1;i>=0;i--)
+    {
+      if(i==0)
+	quantum_set_decoherence(lambda);
+
+      if(i<width)
+	{
+	  quantum_cnot(2*swidth+i, i, reg);
+	  quantum_cnot(swidth+i, i, reg);
+	  
+	  quantum_hadamard(2*swidth+i, reg);
+	  quantum_hadamard(swidth+i, reg);
+	}
+      else
+	{
+	  quantum_cnot(i, 2*swidth+i, reg);
+	  quantum_cnot(i, swidth+i, reg);
+	}
+    }
+
+  for(i=1;i<=swidth;i++)
+    {
+      a = quantum_bmeasure(swidth, reg);
+      b = quantum_bmeasure(2*swidth-i, reg);
+      if(a == 1 && b == 1 && i-1 < width)
+	quantum_sigma_z(i-1, reg); /* Z = HXH */
+    }
+}
+
+/* Counter which can be used to apply QEC periodically */
+
+int
+quantum_qec_counter(int inc, int frequency, quantum_reg *reg)
+{
+  static int counter = 0;
+  static int freq = (1<<30);
+
+  if(inc > 0)
+    counter += inc;
+  else if(inc < 0)
+    counter = 0;
+
+  if(frequency > 0)
+    freq = frequency;
+
+  if(counter >= freq)
+    {
+      counter = 0;
+      quantum_qec_decode(type, width, reg);
+      quantum_qec_encode(type, width, reg);
+    }
+    
+  return counter;
+}
+
+/* Fault-tolerant version of the NOT gate */
+
+void
+quantum_sigma_x_ft(int target, quantum_reg *reg)
+{
+  int tmp;
+  float lambda;
+
+  tmp = type;
+  type = 0;
+
+  lambda = quantum_get_decoherence();
+  quantum_set_decoherence(0);
+
+  /* These operations can be performed simultaneously */
+  
+  quantum_sigma_x(target, reg);
+  quantum_sigma_x(target+width, reg);
+  quantum_set_decoherence(lambda);
+  quantum_sigma_x(target+2*width, reg);
+
+  quantum_qec_counter(1, 0, reg);
+
+  type = tmp;
+}
+
+/* Fault-tolerant version of the Controlled NOT gate */
+
+void
+quantum_cnot_ft(int control, int target, quantum_reg *reg)
+{
+  int tmp;
+  float lambda;
+
+  tmp = type;
+  type = 0;
+
+  /* These operations can be performed simultaneously */
+  
+  lambda = quantum_get_decoherence();
+  quantum_set_decoherence(0);
+
+  quantum_cnot(control, target, reg);
+  quantum_cnot(control+width, target+width, reg);
+  quantum_set_decoherence(lambda);
+  quantum_cnot(control+2*width, target+2*width, reg);
+
+  quantum_qec_counter(1, 0, reg);
+
+  type = tmp;
+
+}
+
+/* Fault-tolerant version of the Toffoli gate */
+
+void
+quantum_toffoli_ft(int control1, int control2, int target, quantum_reg *reg)
+{
+  int i;
+  int c1, c2;
+  MAX_UNSIGNED mask;
+
+  mask = ((MAX_UNSIGNED) 1 << target)
+    + ((MAX_UNSIGNED) 1 << (target+width))
+    + ((MAX_UNSIGNED) 1 << (target+2*width));
+
+  for(i=0;i<reg->size;i++)
+    {
+      c1 = 0;
+      c2 = 0;
+
+      if(reg->node[i].state & ((MAX_UNSIGNED) 1 << control1))
+	c1 = 1;
+      if(reg->node[i].state 
+	 & ((MAX_UNSIGNED) 1 << (control1+width)))
+	{
+	  c1 ^= 1;
+	}
+      if(reg->node[i].state 
+	 & ((MAX_UNSIGNED) 1 << (control1+2*width)))
+	{
+	  c1 ^= 1;
+	}
+
+      if(reg->node[i].state & ((MAX_UNSIGNED) 1 << control2))
+	c2 = 1;
+      if(reg->node[i].state 
+	 & ((MAX_UNSIGNED) 1 << (control2+width)))
+	{
+	  c2 ^= 1;
+	}
+      if(reg->node[i].state 
+	 & ((MAX_UNSIGNED) 1 << (control2+2*width)))
+	{
+	  c2 ^= 1;
+	}
+
+      if(c1 == 1 && c2 == 1)
+	reg->node[i].state = reg->node[i].state ^ mask;
+
+    }
+
+  quantum_decohere(reg);
+
+  quantum_qec_counter(1, 0, reg);
+
+}

qec.h

@@ -0,0 +1,41 @@
+/* gates.h: Declarations for qec.c
+
+   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
+
+*/
+
+#ifndef __QEC_H
+
+#define __QEC_H
+
+#include "qureg.h"
+
+extern void quantum_qec_set_status(int stype, int swidth);
+extern void quantum_qec_get_status(int *ptype, int *pwidth);
+
+extern void quantum_qec_encode(int type, int width, quantum_reg *reg);
+extern void quantum_qec_decode(int type, int width, quantum_reg *reg);
+
+extern void quantum_sigma_x_ft(int target, quantum_reg *reg);
+extern void quantum_cnot_ft(int control, int target, quantum_reg *reg);
+extern void quantum_toffoli_ft(int control1, int control2, int target, 
+			       quantum_reg *reg);
+
+#endif

quantum.h.in

@@ -84,10 +84,14 @@ extern void quantum_gate1(int target, quantum_matrix m, quantum_reg *reg);
 extern void quantum_r_x(int target, float gamma, quantum_reg *reg);
 extern void quantum_r_y(int target, float gamma, quantum_reg *reg);
 extern void quantum_r_z(int target, float gamma, quantum_reg *reg);
+extern void quantum_phase_scale(int target, float gamma, quantum_reg *reg);
 extern void quantum_phase_kick(int target, float gamma, quantum_reg *reg);
 extern void quantum_hadamard(int target, quantum_reg *reg);
 extern void quantum_walsh(int target, quantum_reg *reg);
 extern void quantum_cond_phase(int control, int target, quantum_reg *reg);
+extern void quantum_cond_phase_inv(int control, int target, quantum_reg *reg);
+extern void quantum_cond_phase_kick(int control, int target, float gamma, 
+				    quantum_reg *reg);
 extern int quantum_gate_counter(int inc);
 
 extern void quantum_qft(int width, quantum_reg *reg);
@@ -109,10 +113,14 @@ extern int quantum_getwidth(int n);
 
 extern float quantum_prob(COMPLEX_FLOAT a);
 
+extern float quantum_get_decoherence();
 extern void quantum_set_decoherence(float lambda);
 extern void quantum_decohere(quantum_reg *reg);
 
 extern quantum_reg quantum_matrix2qureg(quantum_matrix *m, int width);
 extern quantum_matrix quantum_qureg2matrix(quantum_reg reg);
 
+extern void quantum_qec_encode(int type, int width, quantum_reg *reg);
+extern void quantum_qec_decode(int type, int width, quantum_reg *reg);
+
 #endif

qureg.c

@@ -156,11 +156,44 @@ quantum_qureg2matrix(quantum_reg reg)
   return m;
 }
 
-/* Delete a quantum register. Note that the hash table is still
-   alive. */
+/* Destroys the entire hash table of a quantum register */
+
+void
+quantum_destroy_hash(quantum_reg *reg)
+{
+  int i;
+  quantum_reg_hash *p;
+
+  for(i=0; i<(1 << reg->hashw); i++)
+    {
+      while(reg->hash[i])
+	{
+	  p = reg->hash[i]->next;
+	  free(reg->hash[i]);
+	  quantum_memman(-sizeof(quantum_reg_hash));
+	  reg->hash[i] = p;
+	}
+    }
+
+  free(reg->hash);
+  quantum_memman(-(1 << reg->hashw) * sizeof(quantum_reg_hash *));
+}
+
+/* Delete a quantum register */
 
 void
 quantum_delete_qureg(quantum_reg *reg)
+{
+  quantum_destroy_hash(reg);
+  free(reg->node);
+  quantum_memman(-reg->size * sizeof(quantum_reg_node));
+  reg->node = 0;
+}
+
+/* Delete a quantum register but leave the hash table alive */
+
+void
+quantum_delete_qureg_hashpreserve(quantum_reg *reg)
 {
   free(reg->node);
   quantum_memman(-reg->size * sizeof(quantum_reg_node));

qureg.h

@@ -66,7 +66,9 @@ typedef struct quantum_reg_struct quantum_reg;
 extern quantum_reg quantum_matrix2qureg(quantum_matrix *m, int width);
 extern quantum_reg quantum_new_qureg(MAX_UNSIGNED initval, int width);
 extern quantum_matrix quantum_qureg2matrix(quantum_reg reg);
+extern void quantum_destroy_hash(quantum_reg *reg);
 extern void quantum_delete_qureg(quantum_reg *reg);
+extern void quantum_delete_qureg_hashpreserve(quantum_reg *reg);
 
 extern void quantum_print_qureg(quantum_reg reg);
 extern void quantum_print_expn(quantum_reg reg);

shor.c

@@ -1,3 +1,26 @@
+ /* shor.c: Implementation of Shor's factoring algorithm
+
+   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 <stdlib.h>
 #include <stdio.h>
 #include <math.h>
@@ -119,7 +142,7 @@ int main(int argc, char **argv) {
     
   quantum_delete_qureg(&qr);
 
-  //  printf("Memory usage: %i bytes\n", (int )memman(0));
+  //  printf("Memory leak: %i bytes\n", (int) quantum_memman(0));
 
   return 0;
 }