Prof. Dr. Pasquale Scarlino


Hybrid Circuit Quantum Electrodynamics with Semiconductor QDs and Superconducting Resonators


Semiconductor qubits rely on the control of charge and spin degrees of freedom of electrons or holes confined in quantum dots (QDs). Typically, semiconductor qubit-qubit coupling is short-range, effectively limiting qubit distance to the spatial extent of the wavefunction of the confined particle (a few hundred nanometers). Inspired by techniques initially developed for circuit QED, we demonstrated the strong coupling limit of individual electron charges [1,2] confined in GaAs quantum dots by using the enhancement of the electric component of the vacuum fluctuations of a resonator with impedance beyond the typical 50 Ohm of standard coplanar waveguide technology.
By making use of this hybrid technology, we realized a proof-of-concept experiment, where the coupling between a transmon and a double QD (DQD) is mediated by virtual microwave photon excitations in a high impedance SQUID array resonator, which acts as a quantum bus enabling long-range coupling between dissimilar qubits [3]. Similarly, we achieved coherent coupling between two DQD charge qubits separated by approximately ~50 um [4].
We have further investigated how to in-situ tune the strength of the electric dipole interaction between the DQD qubit and the resonator [5]. We find that the qubit-resonator coupling strength, qubit decoherence, and detuning noise can be tuned systematically over more than one order of magnitude. The methods and techniques developed in this work are transferable to QD devices based on other material systems and can be beneficial for spin-based hybrid systems [6].
[1] A. Stockklauser*, P. Scarlino*, et al., Phys. Rev. X 7, 011030 (2017).
[2] P. Scarlino*, D. J. van Woerkom*, et al., Phys. Rev. Lett. 122, 206802 (2019).
[3] P. Scarlino*, D. J. van Woerkom*, et al., Nat. Comm. 10, 3011 (2019).
[4] D. J. van Woerkom*, P. Scarlino*, et al., Phys. Rev. X 8, 041018 (2018).
[5] P. Scarlino, et al., arXiv:2104.03045.
[6] A. Landig*, J. Koski*, et al., Nature 560, 179-184 (2018).


Pasquale Scarlino obtained his master's degree in Physics at the University of Salento, Lecce (Italy), in February 2011. He obtained his Ph.D. degree in February 2016 at the Quantum Transport Group at TU Delft, under the supervision of Prof. L.M.K. Vandersypen, leading the Si/SiGe spin qubits project, in collaboration with the M. Eriksson Group at Wisconsin University.
Further, he underwent post-doctoral training in Prof. A. Wallraff (Quantum Device Lab) group at ETH Zurich, where he, in collaboration with the group of Prof. K. Ensslin and Prof. T. Ihn, worked on integrating semiconductor and superconductor technologies. From June 2019 till September 2020, he worked as Senior Researcher at Microsoft Station Q Copenhagen and at the Center for Quantum Devices in Copenhagen, focusing on developing semiconductor-superconducting hybrid hardware for topologically protected quantum computation. Since November 2020, he is a tenure track Assistant Professor of Physics in the School of Basic Sciences at the EPFL, where he founded the Hybrid Quantum Circuit (HQC) laboratory.