Quantum Computing and Pattern Recognition

Recently, we realized a novel quantum pattern recognition scheme, which combines the idea of a classic Hopfield neural network with quantum adiabatic computation. In contrast to classic neural networks, the algorithm can simultaneously return multiple recognized patterns. The approach also promises extension of classic memory capacity. A proof of principle for the algorithm for two qubits is provided using a liquid state NMR quantum computer.

Together with researchers from Siemens Corporate Technology (CT), we have achieved the first experimental implementation of an artificial neural network on a simple quantum computer. The simulation of pattern recognition conducted by the CT researchers was evaluated with a nuclear magnetic resonance spectrometer (NMR) at the TU München.

The patterns used are composed of pixels, and each pixel can assume two colors, which are depicted by means of qubits. Using special algorithm, simulations can predict how a real quantum processor would behave if confronted with a new color pattern. The algorithm compares the patterns with patterns stored in the memory and indicates the degree of similarity.

For the experiments at the TU München, a solution of sodium formiate at room temperature was used. Each sodium formiate molecule contains one carbon and one hydrogen atom. In a strong magnetic field, each of the two particles forms one quantum bit (qubit). The measured signals of the actual quantum computer corresponded exactly to the signals that had previously been predicted by numerical simulations.


The simple stored patterns consisted of the values 1 (green) and -1 (red). The left colum shows incomplete input patterns. The experimentally recognized complete patterns (and their spectral signatures) are shown in the middle column for the case, where the stored patterns are (1,-1) and (-1,1). The right colums show the results for the case, where the stored patterns are (1,1) und (-1,-1).



Photo: Siemens

Rodion Neigovzen and Prof. Steffen Glaser in the NMR laboratory, TUMünchen.


Original manuscript:

Further information:

Further publications in the field of quantum information processing by the Glaser group:



Photo by Volker Steger/Science Photo Library

Nuclear magnetic resonance (NMR) spectrometer at the TU München


Molecular "hard ware" of the first five-qubit NMR quantum computer Preprint: quant-ph/9905087 press reports

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