“Digital Superconducting Quantum Machines” among the winners of “Start Cup Toscana”

Claudio Puglia collects the award for the project DSQM Claudio Puglia collects the award for the project DSQM

Digital superconducting quantum machines” (DSQM), an innovative project by SQEL researchers, is among the four winning projects of the “Start Cup Toscana 2020” an initiative that rewards the best innovative ideas born in the world of university research.

DSQM is the development of ultra-fast, low-power consumption superconducting circuits. This new frontier of information technology will contribute to the development of supercomputers 100 times faster than current ones. The project was developed by a team composed of Francesco Giazotto, Giorgio De Simoni, Elia Strambini, Federico Paolucci and Claudio Puglia from SQEL, Simone Gasparinetti (University of Chalmers) and Angelo Di Bernardo (University of Konstanz).

The technology of the DSQM project is based on the possibility of modifying the electrical current flowing in a superconductor through the application of an electric field. The team, ranked third in the competition, received a cash prize and the opportunity to participate to the “National Award for Innovation“, along with the other three awarded projects.

“Gate-Controlled Suspended Titanium Nanobridge Supercurrent Transistor” published on ACS Nano

"Gate-Controlled Suspended Titanium Nanobridge Supercurrent Transistor" published on ACS Nano “Gate-Controlled Suspended Titanium Nanobridge Supercurrent Transistor” published on ACS Nano

Under standard conditions, the electrostatic field-effect is negligible in conventional metals and was expected to be completely ineffective also in superconducting metals. This common belief was recently put under question by a family of experiments that displayed full gate-voltage-induced suppression of critical current in superconducting all-metallic gated nanotransistors.

A new research carried out at the SQEL add an another piece to this intriguing puzzle showing the control of the supercurrent in fully suspended superconducting nanobridges.

The research, published on ACS Nano by M. Rocci and co-authors, allows to take a different perspective compared to previous studies and promise a better understanding of the field effect in superconducting metals, ruling out some of the hypothesis as possible mechanisms driving for the observed phenomenology.

Rocci, M., De Simoni, G., Puglia, C., Esposti, D. D., Strambini, E., … Giazotto, F. (2020). Gate-Controlled Suspended Titanium Nanobridge Supercurrent Transistor. ACS Nano. doi:10.1021/acsnano.0c05355. arXiv: https://doi.org/10.1021/acsnano.0c05355

Press review of “A Josephson phase battery”

"A Josephson phase battery" has been featured on PhysicsWorld, LaRepubblica and others “A Josephson phase battery” has been featured on PhysicsWorld, LaRepubblica and others

We are very glad that our research work about the Josephson quantum phase battery (recently published on Nature Nanotechnology), raised a considerable interest in the past weeks and has been featured on the main national and international press.

You can find below some of the most relevant articles: check them out ad read what they are saying about us!

“A Josephson phase battery” has been published on “Nature Nanotechnology”

The first quantum phase battery, consisting of an indium arsenide (InAs) nanowire in contact with aluminum superconducting leads. Device concept by Andrea Iorio (SQEL). The first quantum phase battery, consisting of an indium arsenide (InAs) nanowire in contact with aluminum superconducting leads. Device concept by Andrea Iorio (SQEL).

A classical battery converts chemical energy into a persistent voltage bias that can power electronic circuits. Similarly, a phase battery is a quantum device that provides a persistent phase bias to the wave function of a quantum circuit. In a recent experiment carried out at SQEL, E. Strambini and co-workers have demonstrated and realized the first quantum phase battery in a hybrid superconducting circuit. The research, published on Nature Nanotechnology, is the result of an international collaboration which sees involved CNR-Nano, Scuola Normale Superiore, Salerno University in Italy and Material Physics Center (CFM), Donostia International Physics Center (DIPC) in Spain.

The quantum device that we realized is able to provide a persistent phase bias in a superconducting circuit effectively behaving like a quantum phase battery.

says Francesco Giazotto, group leader of SQEL.

The idea was first conceived in 2015, by Sebastian Bergeret and Ilya Tokatly, which proposed a theoretical system with the properties needed to build the phase battery. A few years later Francesco Giazotto and Elia Strambini from SQEL identified a suitable material combination, consisting of an n-doped InAs nanowire forming the core of the battery (the pile) and Al superconducting leads as poles and carried out the experiment at NEST Laboratory.

We found that the ferromagnetic polarization of the unpaired-spin states on the nanowire surface is efficiently converted into a persistent phase bias φ0 across the wire, leading to the anomalous Josephson effect. By applying an external in-plane magnetic field we achieved a continuous tuning of φ0 that persisted also in the absence of the field, thus realizing a phase battery.

comments Elia Strambini, first author of the research.

The next steps will consist in improving the control and performance of the battery by employing new material choices and design. This work contributes to the enormous advances being made in quantum technology that are expected to revolutionize both computing and sensing techniques, as well as medicine, and telecommunications in the near future.

More information:
Strambini, E., Iorio, A., Durante, O. et al. A Josephson phase battery. Nature Nanotechnology (2020). DOI: 10.1038/s41565-020-0712-7, www.nature.com/articles/s41565-020-0712-7

“Nonlocal thermoelectricity in a topological Josephson junction” just published on “Physical Review Letters”

Sketch of the setup used to probe the nonlocal Thermoelectricity in a topological Josephson junction Sketch of the setup used to probe the nonlocal Thermoelectricity in a topological Josephson junction

In a paper just published on Physical Review Letters, a NEST-CNR-NANO team lead by SQEL member Alessandro Braggio identified a unique non-local thermoelectrical effect in a Quantum spin Hall system in 2-dimensional topological insulators, proximized with superconductors, also called topological Josephson junctions.

The quantum spin Hall state is characterised by Kramer paired helical edge states which propagate in opposite directions with opposite spin orientations (spin-momentum locking). Unambiguous identification of those edge state is fundamental to certify their topological nature and has prominent implications in condensed matter research and its applications in topological quantum computation and sensing.

The team, composed by Gianmichele Blasi, Fabio Taddei, Matteo Carrega and coordinated by Alessandro Braggio from SQEL and NEST laboratory (Scuola Normale Superiore and CnrNano) collaborating with Liliana Arrachea from ECyT-UNSAM (Argentina), investigated a three-terminal setup with helical edge states proximized by two superconductors and contacted with a normal-metal probe, in the presence of an external magnetic field. Since the whole system is particle-hole symmetric, nonlocality is the only way to generate linear thermoelectricity. Nonlocal thermoelectrical transport is generated in the probe by applying a thermal gradient between the superconductors.

Blasi, G., Taddei, F., Arrachea, L., Carrega, M., & Braggio, A. (2020). Nonlocal Thermoelectricity in a S-TI-S Junction in Contact with a N-Metal Probe: Evidence for Helical Edge States. Physical Review Letters, 124(22), 227701. DOI: https://doi.org/10.1103/PhysRevLett.124.227701. arXiv: http://arxiv.org/abs/1911.04367