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50 lines
1.4 KiB
C
50 lines
1.4 KiB
C
/* qft.c: Quantum Fourier Transform
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Copyright 2003 Bjoern Butscher, Hendrik Weimer
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This file is part of libquantum
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libquantum is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published
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by the Free Software Foundation; either version 2 of the License,
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or (at your option) any later version.
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libquantum is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with libquantum; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
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USA
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*/
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#include "gates.h"
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#include "qureg.h"
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/* Perform a QFT on a quantum register. This is done by application of
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conditional phase shifts and hadamard gates. At the end, the
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position of the bits is reversed. */
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void quantum_qft(int width, quantum_reg *reg)
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{
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int i, j;
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for(i=width-1; i>=0; i--)
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{
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for(j=width-1; j>i; j--)
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quantum_cond_phase(j, i, reg);
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quantum_hadamard(i, reg);
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}
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for(i=0; i<width/2; i++)
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{
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quantum_cnot(i, width-i-1, reg);
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quantum_cnot(width-i-1, i, reg);
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quantum_cnot(i, width-i-1, reg);
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}
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}
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