RQC Seminar

7th RQC Seminar

• 講演者

  Pasquale Scarlino（スイス連邦工科大学ローザンヌ校 (EPFL)

• 日程

  2022年2月9日（水）17:00-18:00（JST）

• 開催場所

  オンライン

• 講演タイトル

  Hybrid Circuit Quantum Electrodynamics with Semiconductor QDs and Superconducting Resonators

• お問合せ

  RQC 超伝導量子エレクトロニクス連携研究ユニット

講演概要
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). This is a significant constraint towards scaling of the QD-based architectures to reach dense 1D or 2D arrays of QDs. Inspired by techniques originally 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 Ω of standard coplanar waveguide technology.
By making use of this hybrid technology, we recently 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 µm [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. By employing a Josephson junction array resonator with an impedance of ∼4 kΩ and a resonance frequency of ωr/2π∼5.6 GHz, we observe a coupling strength of g/2π∼630 MHz,
demonstrating the possibility to achieve the ultra-strong coupling regime for electrons hosted in a semiconductor DQD. 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]. References
[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 (2018)

Flyer: 7th RQC Seminar Flyer