The material is a common blue pigment, called copper phthalocyanine (CuPc), which is used in the £5 British note. Researchers from the London Centre for Nanotechnology at UCL and the
CuPc is a low-cost organic semiconductor found in many household products, and can be processed into a thin film that can be easily used for device fabrication. This gives the material a considerable advantage over similar materials researched. The team of researchers showed that the electrons in CuPc can remain in 'superposition', a quantum effect where the electron exists in two states at once, for inordinately long periods of time. This shows the dye molecule could potentially be used as a medium for quantum technologies.
Quantum computing requires precise control of ‘qubits’. Qubits are units of quantum information that are the quantum analogues of the binary bits ‘0’ and ‘1’. Bits are the basic units of information and are used to represent information by computers. A bit is always understood to be a 0 or a 1. A qubit can also have two possible values – normally a 0 or a 1. Quantum mechanics allows the qubit to be in a superposition of both states at the same time. The difference between a bit and a qubit is that a bit must be either 0 or 1 whereas a qubit can be 0, 1 or a superposition of both.
It is the decay time of these superpositions that indicates how useful a candidate qubit could be in quantum technologies. The longer the time, the more likely it is that quantum data storage, manipulation and transmission are possible. A quantum computer could in theory solve problems that a classical computer cannot in the lifetime of the universe. The times were found to be surprisingly long for CuPc, with the lifetime of a quantum bit encoded in the phase of the quantum state found to be 2.6 μs at 5 Kelvin and 1 μs at 80 K.
CuPc, despite being a common blue dye, seems to have more potential for quantum computing than other exotic materials considered. The material has many attributes that could exploit the spin of electrons, rather than their charge, to store and process information. The pigment strongly absorbs visible light and is easy to modify chemically and physically. This means that its magnetic and electrical properties can be controlled.