grover.html 14 KB

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  59. <ol class="chapter"><li><a href="qcgpu.html"><strong aria-hidden="true">1.</strong> QCGPU</a></li><li><ol class="section"><li><a href="getting-started.html"><strong aria-hidden="true">1.1.</strong> Getting Started</a></li></ol></li><li><a href="user-guide/user-guide.html"><strong aria-hidden="true">2.</strong> User Guide</a></li><li><ol class="section"><li><a href="user-guide/registers.html"><strong aria-hidden="true">2.1.</strong> Quantum Registers</a></li><li><a href="user-guide/gates.html"><strong aria-hidden="true">2.2.</strong> Quantum Gates</a></li><li><a href="user-guide/operations.html"><strong aria-hidden="true">2.3.</strong> Quantum Operations</a></li><li><a href="user-guide/examples.html"><strong aria-hidden="true">2.4.</strong> Examples</a></li><li><a href="user-guide/decoherence.html"><strong aria-hidden="true">2.5.</strong> Decoherence</a></li></ol></li><li><a href="algorithms/algorithms.html"><strong aria-hidden="true">3.</strong> Algorithms</a></li><li><ol class="section"><li><a href="algorithms/bernstein-vazirani.html"><strong aria-hidden="true">3.1.</strong> Bernstein-Vazirani</a></li><li><a href="algorithms/deutsch-jozsa.html"><strong aria-hidden="true">3.2.</strong> Deutsch-Jozsa</a></li><li><a href="algorithms/grover.html" class="active"><strong aria-hidden="true">3.3.</strong> Grovers</a></li><li><a href="algorithms/shor.html"><strong aria-hidden="true">3.4.</strong> Shors</a></li><li><a href="algorithms/super-dense.html"><strong aria-hidden="true">3.5.</strong> Super Dense Coding</a></li></ol></li></ol>
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  111. <a class="header" href="algorithms/grover.html#grovers-algorithm" id="grovers-algorithm"><h1>Grovers Algorithm</h1></a>
  112. <p>Given an unstructured set \(N = {a_1, a_2,\dots,a_n}\), find
  113. a given element \(a_i \in N\).</p>
  114. <p>This implementation looks for a given number \(target\) in the set \({0,1,\dots, \text{regwidth}}\).</p>
  115. <p>See <a href="https://cs.uwaterloo.ca/%7Ewatrous/LectureNotes.html">https://cs.uwaterloo.ca/~watrous/LectureNotes.html</a></p>
  116. <pre><pre class="playpen"><code class="language-rust">extern crate qcgpu;
  117. extern crate rand;
  118. use qcgpu::State;
  119. use std::f32::consts::PI;
  120. fn main() {
  121. let mut state = State::new(8, 1);
  122. let target = 5;
  123. let reg_width = 3;
  124. let num_inversions = ((PI / 4.0) * ((1 &lt;&lt; reg_width) as f32).sqrt()) as i32;
  125. state.x(reg_width);
  126. for i in 0..(reg_width + 1) {
  127. state.h(i);
  128. }
  129. for _ in 0..(num_inversions) {
  130. iteration(&amp;mut state, target, reg_width);
  131. }
  132. state.h(reg_width);
  133. println!(&quot;Measured: {:?}&quot;, state.measure_first(reg_width, 1000));
  134. }
  135. fn oracle(state: &amp;mut State, target: i32, reg_width: i32) {
  136. for i in 0..reg_width {
  137. if get_bit(target, i) == 0 {
  138. state.x(i);
  139. }
  140. }
  141. state.toffoli(0, 1, reg_width + 1);
  142. let mut i = 1;
  143. while i &lt; reg_width {
  144. state.toffoli(i, reg_width + i, reg_width + i + 1);
  145. i += 1;
  146. }
  147. state.cx(reg_width + i, reg_width);
  148. i = reg_width - 1;
  149. while i &gt; 0 {
  150. state.toffoli(i, reg_width + i, reg_width + i + 1);
  151. i -= 1;
  152. }
  153. state.toffoli(0, 1, reg_width + 1);
  154. for i in 0..reg_width {
  155. if get_bit(target, i) == 0 {
  156. state.x(i);
  157. }
  158. }
  159. }
  160. fn inversion(state: &amp;mut State, reg_width: i32) {
  161. for i in 0..reg_width {
  162. state.x(i);
  163. }
  164. state.h(reg_width - 1);
  165. if reg_width == 3 {
  166. state.toffoli(0, 1, 2);
  167. } else {
  168. state.toffoli(0, 1, reg_width + 1);
  169. let mut i = 1;
  170. while i &lt; reg_width {
  171. state.toffoli(i, reg_width + i, reg_width + i + 1);
  172. i += 1;
  173. }
  174. state.cx(reg_width + i, reg_width - 1);
  175. i = reg_width - 2;
  176. while i &gt; 0 {
  177. state.toffoli(i, reg_width + i, reg_width + i + 1);
  178. i -= 1;
  179. }
  180. state.toffoli(0, 1, reg_width + 1);
  181. }
  182. state.h(reg_width - 1);
  183. for i in 0..reg_width {
  184. state.x(i);
  185. }
  186. }
  187. fn iteration(state: &amp;mut State, target: i32, reg_width: i32) {
  188. oracle(state, target, reg_width);
  189. for i in 0..reg_width {
  190. state.h(i);
  191. }
  192. inversion(state, reg_width);
  193. for i in 0..reg_width {
  194. state.h(i);
  195. }
  196. }
  197. /// Get the value of a bit
  198. fn get_bit(number: i32, n: i32) -&gt; i32 {
  199. if number &amp; (1 &lt;&lt; n) != 0 {
  200. return 1;
  201. }
  202. 0
  203. }
  204. </code></pre></pre>
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