Title: [Joint CQSE & NCTS Seminar] Quantum information processing using semiconductor quantum dot arrays: control, readout, and quantum simulation
Speaker: Prof. Tzu-Kan Hsiao (National Tsing Hua University)
Time: Mar. 03, 2023, 14:30-15:30
Place: NCTS Physics Lecture Hall, 4F, Chee-Chun Leung Cosmology Hall, NTU
Online: https://nationaltaiwanuniversity-zbh.my.webex.com/nationaltaiwanuniversity-zbh.my/j.php?MTID=m210715f40b11b5794be46cfbb95824d1

Abstract:
Electrostatically-defined semiconductor quantum dot arrays offer a promising
platform for quantum computation and quantum simulation. In this talk I will briefly
introduce the basics of quantum-dot spin qubits, and then I will discuss our
experimental works on control, readout, and near-term application of quantum dot
arrays.

First, we demonstrate efficient calibration of tunnel coupling crosstalk in a
quadruple quantum dot array and define a set of virtual barrier gates, with which we
show orthogonal control of all inter-dot tunnel couplings [1]. Next, we report on
cascade-based fast, high-fidelity and scalable spin readout. The cascade consists of an
initial charge transition, far from the sensor, and subsequent charge transitions induced
by Coulomb repulsion, with the final transition nearby the sensor. Combined with spin-
to-charge conversion a cascade enables the readout of charge and spin occupation of
quantum dots remote from the charge sensor [2]. Finally, we used the quadruple
quantum dot array as a quantum simulator for Heisenberg model [3]. For this purpose
we develop several experimental techniques including many-body spin-state
preparation, singlet-triplet correlation measurements, and characterization of the
quantum system with energy spectroscopy and global coherent oscillations. We use
these techniques to tune and probe a homogeneously coupled Heisenberg spin chain
formed in the dot array, and find good agreement between experiment and numerical
simulation. Our works pave the ways for scaling up spin qubit systems and studying
quantum magnetism with quantum dot arrays.

Reference to publications:
[1] T.-K. Hsiao, C. J. van Diepen, U. Mukhopadhyay, C. Reichl, W. Wegscheider, and L. M. K.
Vandersypen, Efficient Orthogonal Control of Tunnel Couplings in a Quantum Dot Array, Physical
Review Applied 13, 054018 (2020)
[2] C. J. van Diepen, T.-K. Hsiao, U. Mukhopadhyay, C. Reichl, W. Wegscheider, and L. M. K.
Vandersypen, Electron Cascade for Distant Spin Readout, Nature Communications 12, 77 (2021)
[5] C. J. van Diepen*, T.-K. Hsiao*, U. Mukhopadhyay, C. Reichl, W. Wegscheider, and L. M. K.
Vandersypen, Quantum Simulation of Antiferromagnetic Heisenberg Chain with Gate-Defined Quantum
Dots, Physical Review X 11, 041025 (2021)

Biography:
2004-2008學士-清華大學物理系
2010-2012碩士-台灣大學應用物理系
2013-2018博士-英國劍橋大學物理系
2019-2022擔任荷蘭台夫特大學QuTech博士後研究員
2023開始擔任清華大學物理系助理教授