£5 note could hold key to advancement of quantum computing

  • 28 Oct 2013
Rendered simulation of a quantum processor
Rendered simulation of a quantum processor

The blue pigment found on £5 notes could hold the key to furthering the development of quantum computers. According to research carried out by Marc Warner from University College London and his colleagues at the University of British Columbia, the pigment copper phthalocyanine (CuPc) is a low-cost organic semiconductor that can be turned into a thin film and used as an integrated circuit. The electrons in this film can then remain in quantum superposition -- an effect where an electron exists in all its theoretically possible states at once, unless observed -- for an unprecedented length of time.

Quantum computing differs from regular computing in that it relies on quantum bits (qubits) rather than binary bits.

Unlike binary, the 0s and 1s that form all of our computational communications, qubits have the unique ability to exist in superposition. A useful qubit candidate needs to be able to sustain superposition for a long period of time so that data storage, manipulation and transmission become possible. This inability to effectively sustain superposition has long been one of the more challenging areas of quantum computing, making the discovery of this readily available organic superconductor remarkable.

Warner, who works at the London Centre for Nanotechnology, said: "In theory, a quantum computer can easily solve problems that a normal, classical, computer would not be able to answer in the lifetime of the universe. We just don't know how to build one yet.

"Our research shows that a common blue dye has more potential for quantum computing than many of the more exotic molecules that have been considered previously. The properties of copper phthalocyanine make it of interest for the emerging field of quantum engineering, which seeks to exploit the quantum properties of matter to perform tasks like information processing or sensing more effectively than has ever been possible."

CuPc possesses many other attributes that could exploit the spin of electrons, rather than their charge, to store and process information, which are highly desirable in a more conventional quantum technology. For example, the pigment strongly absorbs visible light and is easy to modify chemically and physically, so its magnetic and electrical properties can be controlled.