Targeted Spin-electric Control of Molecules for Quantum Technologies

KIT

Targeted control of individual quantum states is considered a key requirement for future quantum computers and other quantum technologies. Researchers of the Karlsruhe Institute of Technology (KIT) have now found a new way to precisely control the quantum-mechanical state, called spin, of single magnetic molecules on a surface by means of electric voltage. The results open up new possibilities for the development of efficient quantum computers and electrically controlled quantum operations. The results have been published in Nature Physics. (DOI: 10.1038/s41567-026-03353-w)

Quantum technologies are considered an important prospect for the development of more powerful computers, secure communication devices, and high-precision sensors. Single magnetic molecules are highly promising building blocks for qubits – the basic information units of quantum computers. Due to their small size, they have distinct quantum properties and can be adapted precisely to different applications using advanced chemical synthesis processes.

Targeted Spin-electric Control

“For the future use of magnetic molecules, we must be able to control their quantum-mechanical state, i.e. their spin, precisely and locally,” said Professor Philip Willke from KIT’s Physikalisches Institut (PHI). So far, this has been mainly achieved by means of magnetic fields. These, however, are difficult to confine to single molecules and can only be switched at a limited speed. Electric voltage, on the other hand, enables fast and local control of the spins using spin-electric coupling.

The team led by Willke combined electron spin resonance with scanning tunneling microscopy to specifically investigate iron phthalocyanine (FePc) molecules and Fe–FePc complexes adsorbed on a surface. These molecules are particularly well-suited because they are firmly attached to the surface. The researchers were able to locally address the individual molecules and electrically tune them using an applied bias voltage.  

New Prospects for Quantum Components

“Our findings show that molecular spins can be controlled efficiently and locally using electrical signals. This opens up new prospects for the development of fast and compact quantum components,” said Willke. “Unlike magnetic fields, electric fields can be set up more precisely in space, and switching of electrical signals is much faster.”

The investigations involved researchers from the Ewha Womans University in South Korea. They worked out the theoretical principles providing an explanation of the physics underlying the spin-electric coupling they observed.

Electrical control methods might become an attractive alternative to the complex magnetic methods in the future. In the long run, this approach could provide new impetus for the development of powerful quantum computers and applications in quantum-sensing technology and spintronics.