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Germanium Quantum Technology

01 /What can CMOS technology do for quantum computing? 02 /Semiconductor devices and scaling with industrial approach 03 /Semiconductor foundry facilities: the good and the bad for qubits 04 /IMEC's latest qubit developments 05 /Summary and outlook 06 /Semiconductors for spin qubits 07 /Germanium quantum wells on silicon 08 /Germanium quantum wells on silicon-germanium 09 /Growth methods 10 /Characterization techniques 11 /Electrical characterization of germanium quantum wells 12 /Fabrication of H-FET 13 /Semiconductor qubits: vision and challenges 14 /Quantum materials 15 /Quantum dot qubits and their operation 16 /Types of quantum dot qubits 17 /Qubit Readout 18 /Qubit Control 19 /Qubit Coherence and Fidelity 20 /Multi-qubit control and quantum algorithms 21 /Quantum links and scaling 22 /Physics of holes 23 /Hole spin qubits 24 /Introduction to electronics for quantum computing 25 /Room temperature electronics 26 /Cryogenic qubit chip carriers 27 /Contribution to IGNITE 28 /Quantum Control Stack for Spin Qubits 29 /Auto-tuning a quantum computer 30 /Tuning and operation of arrays 31 /Finding operation points example 32 /What is auto-tuning? 33 /Neural network tuning 34 /Navigating charge stability diagrams 35 /Experimental implementation 36 /Towards universal quantum algorithms 37 /Classical error correction 38 /Quantum error correction 39 /Progress and challenges 40 /Introduction to quantum algorithms 41 /The first algorithms 42 /Quantum annealing 43 /Quantum Machine Learning

Quantum materials

In this video, Menno Veldhorst presents the development of quantum materials from the first spin qubits demonstration in GaAs to the strained Germanium heterostructures. 

Prerequisite knowledge

  • Semiconductor spin qubits

Main takeaways

  • First quantum dot spin qubits demonstrated in GaAs, but the nuclear spins are limiting the coherence of the qubit 
  • Si MOS devices are foundry compatible, it has a zero nuclear spin isotope, but are very sensitive to charge noise due to the oxide interface  
  • Strained Si/SiGe demonstrated linear array of quantum dot qubits in combination with micromagnets 
  • Germanium has a small effective mass thus bigger quantum dots are possible, hole in germanium can be all electrically controlled due to the spin-orbit interaction  

Further thinking

What mechanism(s) allows electrical control of planar germanium qubits?

a. Strains in the heterostructure
b. Small effective mass
c. Intrinsic spin-orbit coupling
d. Absence of degenerate valley states

Solution

Further reading

The germanium quantum information route: https://arxiv.org/abs/2004.08133 
First spin qubits in GaAs: https://www.science.org/doi/abs/10.1126/science.1116955
Scaling silicon-based quantum computing using CMOS technology: https://arxiv.org/pdf/2011.11753.pdf
6-qubit processor in Si/SiGe: https://arxiv.org/abs/2202.09252
4-qubit processor in Ge/SiGe: https://arxiv.org/abs/2009.04268