Manipulating hole spins

Delft researchers have demonstrated that not just electron spins but also hole spins in semiconductors are good candidates for qubits, the information carriers in quantum computers.

In the future, quantum computers could perform calculations far faster than current computers. However, this requires a robust qubit that can rapidly be manipulated. Electrons and so-called ‘holes’ (the absence of an electron) have a magnetic moment. This magnetic moment, the ‘spin’, of electrons or holes can serve as a qubit. The two possible states of the spin (up or down) are then used to code information.

Most research to date has focused on electron spins as qubits. However, these rapidly lose the information stored. The spins of holes are potentially more stable but up until now it had not been possible to manipulate these.

Together with colleagues from FOM Foundation and TU Eindhoven, researchers from the faculty of Applied Sciences however have managed to electrically manipulate hole spins. The research was published online in Nature Nanotechnology on the 17th of February. The lead author is Dr. Vlad Pribiag (AS faculty).

The researchers managed to make nanowires containing both electron spins and hole spins. Using microwave radiation they could electrically fully reverse both types of spin, thereby changing the state of the qubits. This made a comparison between electron qubits and hole qubits possible.

Hole spins have various advantages compared to electron spins. Therefore with the manipulation of hole spins the researchers have developed a highly promising new qubit system. “Hole spins have the potential to retain quantum information for longer and can be more quickly manipulated,” says Pribiag in a press release. “Furthermore, the manipulation of both hole spins and electron spins might make it possible to exchange quantum information over large distances.”

The research was partly financed by the FOM Foundation, NWO and the European Research Council (ERC). Pribiag received a Veni grant from NWO for this research.

V. S. Pribiag et al. ‘Electrical control of single hole spins in nanowire quantum dots’, Nature Nanotechnology (2013), DOI: 10.1038/NNANO.2013.5


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