They develop superconducting spin quantum bits

Quantum computers have the potential to overcome all current computing paradigms. Now, groundbreaking research presents a promising implementation for the storage and manipulation of quantum information. The results of the study are an important advance in the field of quantum computing.

Said implementation corresponds to the fusion of two already known platforms: on the one hand, the one based on electromagnetic modes in superconducting circuits and, on the other, the one based on the spin of electrons trapped in semiconductor quantum dots. This new implementation has the potential to inherit the beneficial aspects of both platforms.

The research has been carried out by an international team that includes Javier Cerrillo and Alfredo Yeyati, both from the Autonomous University of Madrid (UAM) in Spain.

“The qubit (quantum bit) consists of the spin of a single superconducting quasiparticle, which corresponds to a coherent superposition of electrons and holes, trapped in a Josephson junction formed in a semiconductor nanowire,” the authors explain.

“Due to the spin-orbit interaction, the supercurrent flowing through the nanowire depends on the spin state of the quasiparticle. Our work demonstrates how it is possible to take advantage of the spin-dependent supercurrent to perform both detection and coherent spin manipulation, ”they add.

This work also represents a significant advance in the theoretical understanding and possible control of the so-called Andreev levels. These levels are fermionic modes that exist in all superconducting junctions and that allow us to explain the microscopic origin of the famous Josephson effect.

Principle of the superconducting spin qubit. A quasiparticle trapped in a Josephson junction formed by a semiconductor nanowire (white) coated by a superconductor (light blue). Due to the spin-orbit interaction, the supercurrent is sensitive to the spin of the quasiparticle, allowing its detection and coherent manipulation by techniques commonly used in conventional superconducting qubits. (Image: UAM)

In superconductor-semiconductor heterostructures, such as the junctions formed by nanowires studied in this work, Andreev levels are precursors of so-called Majorana states, which have unique properties for storing quantum information in a decoherence-resistant form. This experiment, therefore, is also important in relation to the development of devices based on these types of states.

The study is titled “Coherent manipulation of an Andreev spin qubit.” And it has been published in the academic journal Science.

The research team has been led from Yale University in the United States. Scientists from the University of Copenhagen in Denmark, the Polytechnic of Cartagena in Spain and the Chalmers of Technology in Sweden have also participated. (Source: UAM)

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