Quantum Computing Architectures 2022/5

Which phonons are relevant for electron spin relaxation in a quantum dot

• acoustic low-frequency phonons

• acoustic high-frequency phonons

• optical low-frequency phonons

• optical high-frequency phonons

Which condition is the basis for the dipole approximation?

• dot size is much smaller than phonon wavelength

• phonon wavelength is much smaller than dot size

• dot size is much smaller than phonon wave number

• phonon wave number is much smaller than dot size

Assume that in a GaAs dot at 1 Tesla magnetic field, spin relaxation time is 1 ms. At 2 Tesla magnetic field, it is ...

• 2 ms

• 0.5 ms

• 0.25 ms

• 0.03 ms

Which function of the strain tensor enters the deformation-potential electron-phonon interaction Hamiltonian?

• determinant

• eigenvectors

• trace

• Pfaffian

In a Ramsey experiment, the first pulse kicks the qubit polarisation vector to...

• the South Pole of the Bloch sphere

• the North Pole of the Bloch sphere

• the Equator of the Bloch sphere

• the center of the Bloch sphere

Which is the primary source of electron-spin-qubit dephasing in GaAs?

• electron-phonon interaction

• spin-orbit interaction

• the Ramsey mechanism

• hyperfine interaction

How many pulses do you need for a single run of a Ramsey experiment?

• 1

• 2

• 3

• 4

How many pulses do you need for a single run of a Spin Echo experiment?

• 1

• 2

• 3

• 5

What are the characteristic time dependencies of spin-qubit relaxation and dephasing in GaAs?

• relaxation: exponential decay, dephasing: Gaussian decay

• relaxation: Gaussian decay, dephasing: exponential decay

• both show exponential decay

• both show Gaussian decay