mirror of
https://github.com/libquantum/libquantum.git
synced 2025-10-03 08:42:01 +00:00
158 lines
3.1 KiB
C
158 lines
3.1 KiB
C
/* 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 3 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., 51 Franklin Street, Fifth Floor, Boston,
|
|
MA 02110-1301, USA
|
|
|
|
*/
|
|
|
|
#include <stdlib.h>
|
|
#include <stdio.h>
|
|
#include <math.h>
|
|
#include <time.h>
|
|
|
|
#include <quantum.h>
|
|
|
|
int main(int argc, char **argv) {
|
|
|
|
quantum_reg qr;
|
|
int i;
|
|
int width, swidth;
|
|
int x = 0;
|
|
int N;
|
|
int c,q,a,b, factor;
|
|
|
|
srand(time(0));
|
|
|
|
if(argc == 1)
|
|
{
|
|
printf("Usage: shor [number]\n\n");
|
|
return 3;
|
|
}
|
|
|
|
N=atoi(argv[1]);
|
|
|
|
if(N<15)
|
|
{
|
|
printf("Invalid number\n\n");
|
|
return 3;
|
|
}
|
|
|
|
width=quantum_getwidth(N*N);
|
|
swidth=quantum_getwidth(N);
|
|
|
|
printf("N = %i, %i qubits required\n", N, width+3*swidth+2);
|
|
|
|
if(argc >= 3)
|
|
{
|
|
x = atoi(argv[2]);
|
|
}
|
|
while((quantum_gcd(N, x) > 1) || (x < 2))
|
|
{
|
|
x = rand() % N;
|
|
}
|
|
|
|
printf("Random seed: %i\n", x);
|
|
|
|
qr=quantum_new_qureg(0, width);
|
|
|
|
for(i=0;i<width;i++)
|
|
quantum_hadamard(i, &qr);
|
|
|
|
quantum_addscratch(3*swidth+2, &qr);
|
|
|
|
quantum_exp_mod_n(N, x, width, swidth, &qr);
|
|
|
|
for(i=0;i<3*swidth+2;i++)
|
|
{
|
|
quantum_bmeasure(0, &qr);
|
|
}
|
|
|
|
quantum_qft(width, &qr);
|
|
|
|
for(i=0; i<width/2; i++)
|
|
{
|
|
quantum_cnot(i, width-i-1, &qr);
|
|
quantum_cnot(width-i-1, i, &qr);
|
|
quantum_cnot(i, width-i-1, &qr);
|
|
}
|
|
|
|
c=quantum_measure(qr);
|
|
|
|
if(c==-1)
|
|
{
|
|
printf("Impossible Measurement!\n");
|
|
return 1;
|
|
}
|
|
|
|
if(c==0)
|
|
{
|
|
printf("Measured zero, try again.\n");
|
|
return 2;
|
|
}
|
|
|
|
q = 1<<(width);
|
|
|
|
printf("Measured %i (%f), ", c, (float)c/q);
|
|
|
|
quantum_frac_approx(&c, &q, width);
|
|
|
|
printf("fractional approximation is %i/%i.\n", c, q);
|
|
|
|
if((q % 2 == 1) && (2*q<(1<<width)))
|
|
{
|
|
printf("Odd denominator, trying to expand by 2.\n");
|
|
q *= 2;
|
|
}
|
|
|
|
if(q % 2 == 1)
|
|
{
|
|
printf("Odd period, try again.\n");
|
|
return 2;
|
|
}
|
|
|
|
printf("Possible period is %i.\n", q);
|
|
|
|
a = quantum_ipow(x, q/2) + 1 % N;
|
|
b = quantum_ipow(x, q/2) - 1 % N;
|
|
|
|
a = quantum_gcd(N, a);
|
|
b = quantum_gcd(N, b);
|
|
|
|
if(a>b)
|
|
factor=a;
|
|
else
|
|
factor=b;
|
|
|
|
if((factor < N) && (factor > 1))
|
|
{
|
|
printf("%i = %i * %i\n", N, factor, N/factor);
|
|
}
|
|
else
|
|
{
|
|
printf("Unable to determine factors, try again.\n");
|
|
return 2;
|
|
}
|
|
|
|
quantum_delete_qureg(&qr);
|
|
|
|
/* printf("Memory leak: %i bytes\n", (int) quantum_memman(0)); */
|
|
|
|
return 0;
|
|
}
|