Constant‐time solution to database searching by NMR ensemble computing
Chih-Cheng Hsueh, C.‐Y. Chen · Fortschritte der Physik · 2006
Abstract Brüschweiler's Ensemble algorithm requires n = log N queries to discover the wanted object from the database of the size N. In this paper, we use a new oracle query function g(.) to improve Brüschweiler's algorithm such that only one query is needed for searching the single object. Our algorithm extends from one ancillary qubit to n ancillary qubits. We then construct the oracle query function g(.) satisfying g(x) = 0 for all input x, except for one, say x = z, where g(z) = z. We first prepare 2n qubits, including n qubits for representing the elements and n ancillary qubits for storing the result of the oracle query function. After one query, we obtain z by measuring these ancillary qubits. Our algorithm can efficiently discover the wanted object if N ≤ 230 according to current NMR spectrometer technology.