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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

Hole spin qubits

In this video we describe the concept of Pauli spin-blockade, go through the energy diagram of a double quantum dot, and explain the operation of a (Germanium) hole singlet-triplet qubit. 

Prerequisite knowledge

  • Semiconductor physics/Solid State Physics 
  • Quantum Mechanics

Main takeaways

  • Singlet-triplet spin qubits can be realized if the magnetic field seen by the two quantum dots is different or if they have different g-factors. 
  • The g-factor difference controls the X-rotations. 
  • The exchange interaction controls the Z-rotations. 

Further thinking

The energy of the singlet state in a double quantum dot:

a. is lower that the T- state in the (1,1) configuration
b. does not change with detuning
c. exceeds the T+ state in the (1,1) configuration
d. is lower than the other states in the (2,0) configuration

Solution

Further reading

G. Scappucci et al., The Germanium Quantum Information route, Nature Reviews Materials 6, 926 (2021)

D. Jirovec et al., A singlet-triplet hole spin qubit in planar Ge, Nature Materials 20, 1106 (2021)