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libquantum/gates.c
libquantum 8f37efac24 updated libquantum 0.2.2 source files
2016-10-27 04:16:13 +09:00

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/* gates.c: Basic gates for quantum register manipulation
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>
#include <stdarg.h>
#include "matrix.h"
#include "defs.h"
#include "complex.h"
#include "qureg.h"
#include "decoherence.h"
#include "qec.h"
#include "objcode.h"
/* Apply a controlled-not gate */
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
{
if(quantum_objcode_put(CNOT, control, target))
return;
for(i=0; i<reg->size; i++)
{
/* Flip the target bit of a basis state if the control bit is set */
if((reg->node[i].state & ((MAX_UNSIGNED) 1 << control)))
reg->node[i].state ^= ((MAX_UNSIGNED) 1 << target);
}
quantum_decohere(reg);
}
}
/* Apply a toffoli (or controlled-controlled-not) gate */
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
{
if(quantum_objcode_put(TOFFOLI, control1, control2, target))
return;
for(i=0; i<reg->size; i++)
{
/* Flip the target bit of a basis state if both control bits are
set */
if(reg->node[i].state & ((MAX_UNSIGNED) 1 << control1))
{
if(reg->node[i].state & ((MAX_UNSIGNED) 1 << control2))
{
reg->node[i].state ^= ((MAX_UNSIGNED) 1 << target);
}
}
}
quantum_decohere(reg);
}
}
/* Apply an unbounded toffoli gate. This gate is not considered
elementary and is not available on all physical realizations of a
quantum computer. Be sure to pass the function the correct number of
controlling qubits. The target is given in the last argument. */
void
quantum_unbounded_toffoli(int controlling, quantum_reg *reg, ...)
{
va_list bits;
int target;
int *controls;
int i, j;
controls = malloc(controlling * sizeof(int));
if(!controls)
{
printf("Error allocating %i-element int array!\n", controlling);
exit(1);
}
quantum_memman(controlling * sizeof(int));
va_start(bits, reg);
for(i=0; i<controlling; i++)
controls[i] = va_arg(bits, int);
target = va_arg(bits, int);
va_end(bits);
for(i=0; i<reg->size; i++)
{
for(j=0; (j < controlling) &&
(reg->node[i].state & (MAX_UNSIGNED) 1 << controls[j]); j++);
if(j == controlling) /* all control bits are set */
reg->node[i].state ^= ((MAX_UNSIGNED) 1 << target);
}
free(controls);
quantum_memman(-controlling * sizeof(int));
quantum_decohere(reg);
}
/* Apply a sigma_x (or not) gate */
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
{
if(quantum_objcode_put(SIGMA_X, target))
return;
for(i=0; i<reg->size; i++)
{
/* Flip the target bit of each basis state */
reg->node[i].state ^= ((MAX_UNSIGNED) 1 << target);
}
quantum_decohere(reg);
}
}
/* Apply a sigma_y gate */
void
quantum_sigma_y(int target, quantum_reg *reg)
{
int i;
if(quantum_objcode_put(SIGMA_Y, target))
return;
for(i=0; i<reg->size;i++)
{
/* Flip the target bit of each basis state and multiply with
+/- i */
reg->node[i].state ^= ((MAX_UNSIGNED) 1 << target);
if(reg->node[i].state & ((MAX_UNSIGNED) 1 << target))
reg->node[i].amplitude *= IMAGINARY;
else
reg->node[i].amplitude *= -IMAGINARY;
}
quantum_decohere(reg);
}
/* Apply a sigma_y gate */
void
quantum_sigma_z(int target, quantum_reg *reg)
{
int i;
if(quantum_objcode_put(SIGMA_Z, target))
return;
for(i=0; i<reg->size; i++)
{
/* Multiply with -1 if the target bit is set */
if(reg->node[i].state & ((MAX_UNSIGNED) 1 << target))
reg->node[i].amplitude *= -1;
}
quantum_decohere(reg);
}
/* Swap the first WIDTH bits of the quantum register. This is done
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++)
{
if(quantum_objcode_put(SWAPLEADS, width))
return;
/* calculate left bit pattern */
pat1 = reg->node[i].state % ((MAX_UNSIGNED) 1 << width);
/*calculate right but pattern */
pat2 = 0;
for(j=0; j<width; j++)
pat2 += reg->node[i].state & ((MAX_UNSIGNED) 1 << (width + j));
/* construct the new basis state */
l = reg->node[i].state - (pat1 + pat2);
l += (pat1 << width);
l += (pat2 >> width);
reg->node[i].state = l;
}
}
}
/* Swap WIDTH bits starting at WIDTH and 2*WIDTH+2 controlled by
CONTROL */
void
quantum_swaptheleads_omuln_controlled(int control, int width, quantum_reg *reg)
{
int i;
for(i=0; i<width; i++)
{
quantum_toffoli(control, width+i, 2*width+i+2, reg);
quantum_toffoli(control, 2*width+i+2, width+i, reg);
quantum_toffoli(control, width+i, 2*width+i+2, reg);
}
}
/* Apply the 2x2 matrix M to the target bit. M should be unitary and
having a determinant of 1. */
void
quantum_gate1(int target, quantum_matrix m, quantum_reg *reg)
{
int i, j, k, iset;
int addsize=0, decsize=0;
COMPLEX_FLOAT t, tnot=0;
float limit;
char *done;
if((m.cols != 2) || (m.rows != 2))
{
printf("Matrix is not a 2x2 matrix!\n");
exit(1);
}
/* Build hash table */
for(i=0; i<(1 << reg->hashw); i++)
reg->hash[i] = 0;
for(i=0; i<reg->size; i++)
quantum_add_hash(reg->node[i].state, i, reg);
/* calculate the number of basis states to be added */
for(i=0; i<reg->size; i++)
{
j = quantum_get_state(reg->node[i].state ^ ((MAX_UNSIGNED) 1 << target),
*reg);
if(j == -1)
{
if((m.t[1] != 0) && (reg->node[i].state
& ((MAX_UNSIGNED) 1 << target)))
addsize++;
if((m.t[2] != 0) && !(reg->node[i].state
& ((MAX_UNSIGNED) 1 << target)))
addsize++;
}
}
/* allocate memory for the new basis states */
reg->node = realloc(reg->node,
(reg->size + addsize) * sizeof(quantum_reg_node));
if(!reg->node)
{
printf("Not enough memory for %i-sized qubit!\n", reg->size + addsize);
exit(1);
}
quantum_memman(addsize*sizeof(quantum_reg_node));
for(i=0; i<addsize; i++)
{
reg->node[i+reg->size].state = 0;
reg->node[i+reg->size].amplitude = 0;
}
done = calloc(reg->size + addsize, sizeof(char));
if(!done)
{
printf("Not enough memory for %i bytes array!\n",
(reg->size + addsize) * sizeof(char));
exit(1);
}
quantum_memman(reg->size + addsize * sizeof(char));
k = reg->size;
limit = (1.0 / ((MAX_UNSIGNED) 1 << reg->width)) / 1000000;
/* perform the actual matrix multiplication */
for(i=0; i<reg->size; i++)
{
if(!done[i])
{
/* determine if the target of the basis state is set */
iset = reg->node[i].state & ((MAX_UNSIGNED) 1 << target);
tnot = 0;
j = quantum_get_state(reg->node[i].state
^ ((MAX_UNSIGNED) 1<<target), *reg);
t = reg->node[i].amplitude;
if(j >= 0)
tnot = reg->node[j].amplitude;
if(iset)
reg->node[i].amplitude = m.t[2] * tnot + m.t[3] * t;
else
reg->node[i].amplitude = m.t[0] * t + m.t[1] * tnot;
if(j >= 0)
{
if(iset)
reg->node[j].amplitude = m.t[0] * tnot + m.t[1] * t;
else
reg->node[j].amplitude = m.t[2] * t + m.t[3] * tnot;
}
else /* new basis state will be created */
{
if((m.t[1] == 0) && (iset))
break;
if((m.t[2] == 0) && !(iset))
break;
reg->node[k].state = reg->node[i].state
^ ((MAX_UNSIGNED) 1 << target);
if(iset)
reg->node[k].amplitude = m.t[1] * t;
else
reg->node[k].amplitude = m.t[2] * t;
k++;
}
if(j >= 0)
done[j] = 1;
}
}
reg->size += addsize;
free(done);
quantum_memman(-reg->size * sizeof(char));
/* remove basis states with extremely small amplitude */
for(i=0, j=0; i<reg->size; i++)
{
if(quantum_prob_inline(reg->node[i].amplitude) < limit)
{
j++;
decsize++;
}
else if(j)
{
reg->node[i-j].state = reg->node[i].state;
reg->node[i-j].amplitude = reg->node[i].amplitude;
}
}
if(decsize)
{
reg->size -= decsize;
reg->node = realloc(reg->node, reg->size * sizeof(quantum_reg_node));
if(!reg->node)
{
printf("Not enough memory for %i-sized qubit!\n",
reg->size + addsize);
exit(1);
}
quantum_memman(-decsize * sizeof(quantum_reg_node));
}
quantum_decohere(reg);
}
/* Apply a hadamard gate */
void
quantum_hadamard(int target, quantum_reg *reg)
{
quantum_matrix m;
if(quantum_objcode_put(HADAMARD, target))
return;
m = quantum_new_matrix(2, 2);
m.t[0] = sqrt(1.0/2); m.t[1] = sqrt(1.0/2);
m.t[2] = sqrt(1.0/2); m.t[3] = -sqrt(1.0/2);
quantum_gate1(target, m, reg);
quantum_delete_matrix(&m);
}
/* Apply a walsh-hadamard transform */
void
quantum_walsh(int width, quantum_reg *reg)
{
int i;
for(i=0; i<width; i++)
quantum_hadamard(i, reg);
}
/* Apply a rotation about the x-axis by the angle GAMMA */
void
quantum_r_x(int target, float gamma, quantum_reg *reg)
{
quantum_matrix m;
if(quantum_objcode_put(ROT_X, target, (double) gamma))
return;
m = quantum_new_matrix(2, 2);
m.t[0] = cos(gamma / 2); m.t[1] = -IMAGINARY * sin(gamma / 2);
m.t[2] = -IMAGINARY * sin(gamma / 2); m.t[3] = cos(gamma / 2);
quantum_gate1(target, m, reg);
quantum_delete_matrix(&m);
}
/* Apply a rotation about the y-axis by the angle GAMMA */
void
quantum_r_y(int target, float gamma, quantum_reg *reg)
{
quantum_matrix m;
if(quantum_objcode_put(ROT_Y, target, (double) gamma))
return;
m = quantum_new_matrix(2, 2);
m.t[0] = cos(gamma / 2); m.t[1] = -sin(gamma / 2);
m.t[2] = sin(gamma / 2); m.t[3] = cos(gamma / 2);
quantum_gate1(target, m, reg);
quantum_delete_matrix(&m);
}
/* Apply a rotation about the z-axis by the angle GAMMA */
void
quantum_r_z(int target, float gamma, quantum_reg *reg)
{
int i;
COMPLEX_FLOAT z;
if(quantum_objcode_put(ROT_Z, target, (double) gamma))
return;
z = quantum_cexp(gamma/2);
for(i=0; i<reg->size; i++)
{
if(reg->node[i].state & ((MAX_UNSIGNED) 1 << target))
reg->node[i].amplitude *= z;
else
reg->node[i].amplitude /= z;
}
quantum_decohere(reg);
}
/* Scale the phase of qubit */
void
quantum_phase_scale(int target, float gamma, quantum_reg *reg)
{
int i;
COMPLEX_FLOAT z;
if(quantum_objcode_put(PHASE_SCALE, target, (double) gamma))
return;
z = quantum_cexp(gamma);
for(i=0; i<reg->size; i++)
{
reg->node[i].amplitude *= z;
}
quantum_decohere(reg);
}
/* Apply a phase kick by the angle GAMMA */
void
quantum_phase_kick(int target, float gamma, quantum_reg *reg)
{
int i;
COMPLEX_FLOAT z;
if(quantum_objcode_put(PHASE_KICK, target, (double) gamma))
return;
z = quantum_cexp(gamma);
for(i=0; i<reg->size; i++)
{
if(reg->node[i].state & ((MAX_UNSIGNED) 1 << target))
reg->node[i].amplitude *= z;
}
quantum_decohere(reg);
}
/* Apply a conditional phase shift by PI / 2^(CONTROL - TARGET) */
void
quantum_cond_phase(int control, int target, quantum_reg *reg)
{
int i;
COMPLEX_FLOAT z;
if(quantum_objcode_put(COND_PHASE, control, target))
return;
z = quantum_cexp(pi / ((MAX_UNSIGNED) 1 << (control - target)));
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 *= z;
}
}
quantum_decohere(reg);
}
void
quantum_cond_phase_inv(int control, int target, quantum_reg *reg)
{
int i;
COMPLEX_FLOAT z;
z = quantum_cexp(-pi / ((MAX_UNSIGNED) 1 << (control - target)));
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 *= z;
}
}
quantum_decohere(reg);
}
void
quantum_cond_phase_kick(int control, int target, float gamma, quantum_reg *reg)
{
int i;
COMPLEX_FLOAT z;
if(quantum_objcode_put(COND_PHASE, control, target, (double) gamma))
return;
z = quantum_cexp(gamma);
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 *= z;
}
}
quantum_decohere(reg);
}
/* Increase the gate counter by INC steps or reset it if INC < 0. The
current value of the counter is returned. */
int
quantum_gate_counter(int inc)
{
static int counter = 0;
if(inc > 0)
counter += inc;
else if(inc < 0)
counter = 0;
return counter;
}
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