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R. G. Herb Condensed Matter Seminar
Strained Si/SiGe quantum wells with oscillating Ge concentration: valley and spin-orbit physics
Date: Thursday, September 14th
Time: 10:00 am - 6:00 pm
Place: 5310 Chamberlin
Speaker: Benjamin Woods, UW-Madison
Abstract: Electron spin qubits in Si/SiGe quantum dots hold promise for quantum computation due to their scalability and long coherence times. However, challenges persist, notably small and variable valley splitting introduces low-energy states near the qubit subspace, causing decoherence and read-out difficulties. In addition, reliance on magnetic field gradients from micromagnets in leading Si/SiGe qubit designs poses scalability issues. I will outline our solution to both problems, which utilizes Si/SiGe heterostructures featuring long-wavelength λ ≈ 1.7 nm Ge concentration oscillations and shear strain. For such a structure, we show that the spin-orbit coupling is dramatically enhanced compared to conventional Si/SiGe quantum wells without Ge concentration oscillations. This enhancement permits rapid spin manipulation via electric dipole spin resonance without the need for micromagnets. Furthermore, we show that the necessary level of shear strain for valley splitting enhancement aligns with existing fabrication techniques. Finally, I will touch on promising future directions. This includes the exploration of electric dipole spin resonance under the influence of valley disorder and the potential for significant g-factor renormalization in multi-electron quantum dots.
Host: Robert McDermott
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