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Searching with Quantum Computers

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Apr01: Searching with Quantum Computers

int qrandom(); 
				   /* qrandom(N,r) returns a random number between 0 and (N-1) */ 
int f(); 
				   /* f(r) is an arbitrary binary function that returns 1 only  
              		      for a single value of r, for all other values of r it returns 0 */ 
   int i, r; 
   r = qrandom(N,0); 
   for(i = 0; i < eta; i++)  /* eta is a number of order <img src="">N */ 
      if (f(r) == 1)  invert_phase();
                           /* f(r) is evaluated within the program itself  
                           this does not need an external observation  
                           (any observation would perturb the system) */ 
      r = qrandom(N,r); 
      if (r==0)       invert_phase(); 
      r = qrandom(N,r); 

Figure 3: Quantum program.

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