Quantum computing with molecules for a quicker search of unsorted databases

November 14, 2017
Upon execution of Grover’s quantum algorithm, the terbium single-molecule transistor reads out unsorted databases. Credit: KIT/Institut Néel

Scrapbooks or social networks are collections of mostly unsorted data. The search for single elements in very large data volumes, i.e. for the needle in the data haystack, is extremely complex for classical computers. Scientists of Karlsruhe Institute of Technology (KIT) have now quantum mechanically implemented and successfully executed Glover's algorithm, a process for the quick finding of a search element in unsorted databases. Their results are reported in the Physical Review Letters.

A universal computer still is a vision. Special quantum systems that promise to solve certain tasks more quickly than a classical computer, however, are already playing an important role in science. To reliably find a certain in unsorted data, a conventional computer has to run through all search elements successively in the most unfavorable case. A quantum system with an implemented Grover's search algorithm quadratically accelerates search.

Research teams headed by Professors Wolfgang Wernsdorfer and Mario Ruben of KIT, together with scientists of the Institut Néel (Grenoble), have succeeded in doing this: The scientists applied Grover's algorithm to a molecular magnet and, thus, created a quantum system, whose task is the rapid finding of search elements in unsorted data.

In their latest research project, they demonstrated feasibility of a quick search for a small database of four elements. "But this method can be implemented in any quantum system with many, non-equidistant energy levels, which opens up the way towards a universal quantum search algorithm," Professor Ruben says.

The scientists implemented Grover's in a molecular magnet that was subjected to superposition with specially designed microwaves. Superposition is a quantum effect, in which a particle assumes different states at the same time. Upon execution of the quantum operations, a single-molecule transistor read out the search results. An animation illustrates this process.

Wolfgang Wernsdorfer, Professor of KIT's Physikalisches Institut and Institute of Nanotechnology (INT), emphasizes that the quantum states were manipulated at very low temperatures using electric fields exclusively. "That is why we hope that this technology can be integrated into current electronic devices," Wernsdorfer adds.

The customized molecule transistor was synthesized by Mario Ruben's team at INT and KIT's Institute for Inorganic Chemistry. In its center, a terbium atom with a pronounced magnetic moment, a spin, is located. The terbium is surrounded by organic molecules that shield it against external impacts.

Explore further: A new kind of quantum computer

More information: C. Godfrin et al. Operating Quantum States in Single Magnetic Molecules: Implementation of Grover's Quantum Algorithm, Physical Review Letters (2017). DOI: 10.1103/PhysRevLett.119.187702

Related Stories

A new kind of quantum computer

November 6, 2017

Quantum mechanics incorporates some very non-intuitive properties of matter. Quantum superposition, for example, allows an atom to be simultaneously in two different states with its spin axis pointed both up and down, or ...

Electrical control of nuclear spin qubits

June 6, 2014

Researchers of Karlsruhe Institute of Technology (KIT) and their French partners succeeded in making an important step towards quantum computers. Using a spin cascade in single-molecule magnet, the scientists demonstrated ...

Researchers develop data bus for quantum computer

November 6, 2017

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass ...

Nature: Electronic read-out of quantum bits

August 16, 2012

Quantum computers promise to reach computation speeds far beyond that of today's computers. As they would use quantum effects, however, they would also be susceptible to external interferences. Information flow into and out ...

Recommended for you

How the Earth stops high-energy neutrinos in their tracks

November 22, 2017

Neutrinos are abundant subatomic particles that are famous for passing through anything and everything, only very rarely interacting with matter. About 100 trillion neutrinos pass through your body every second. Now, scientists ...

Quantum internet goes hybrid

November 22, 2017

In a recent study published in Nature, ICFO researchers led by ICREA Prof. Hugues de Riedmatten report an elementary "hybrid" quantum network link and demonstrate photonic quantum communication between two distinct quantum ...

Enhancing the quantum sensing capabilities of diamond

November 22, 2017

Researchers have discovered that dense ensembles of quantum spins can be created in diamond with high resolution using an electron microscopes, paving the way for enhanced sensors and resources for quantum technologies.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.