Spins in few-electron quantum dots
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Citations
Closed-loop control of a GaAs-based singlet-triplet spin qubit with 99.5% gate fidelity and low leakage.
Quantum Zeno Dynamics Through Stochastic Protocols
QFlow lite dataset: A machine-learning approach to the charge states in quantum dot experiments.
Flopping-mode electric dipole spin resonance
Transmission phase of a singly occupied quantum dot in the Kondo regime.
References
Quantum Computation and Quantum Information
Quantum Computation and Quantum Information
Spintronics: a spin-based electronics vision for the future.
Spintronics: Fundamentals and applications
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Frequently Asked Questions (18)
Q2. How can the authors deduce spin filling from excited-state spectroscopy?
Spin filling can also be deduced from excited-state spectroscopy without changing the magnetic field Cobden et al., 1998 , provided the Zeeman energy splitting EZ=2 EZ =g BB between spin-up and spin-down electrons can be resolved.
Q3. Why does the matrix element in Eq. 22 pick up another factor of EZ?
due to the effect of the Zeeman splitting, the matrix element in Eq. 22 picks up another factor of EZ assuming only single-phonon processes are relevant .
Q4. What is the simplest explanation for the hyperfine coupling?
Since both nuclear spins and the localized electron spin are quantum objects, the hyperfine coupling could in principle create entanglement between them if both the electron spin and nuclear spins had a sufficiently pure initial state; see Braunstein et al., 1999 .
Q5. What is the effect of electric fields on spin states?
Electric fields affect spins only indirectly, so generally spin states are only weakly influenced by their electric environment as well.
Q6. What is the main limitation on the fidelity of spin rotations in a quantum dot?
In fact, the nuclear field has been the main limitation on the fidelity of spin rotations in recent electron-spin resonance experiments in a quantum dot see Sec. IX.
Q7. How can the authors determine the total spin of the ground state?
by starting from zero electrons and thus zero spin and tracking the change in spin at subsequent electron transitions, the total spin of the ground state can be determined Willems van Beveren et al., 2005 .
Q8. how long would the effect of the nuclear field on the electron-spin interaction be suppresse?
If the effect of the nuclear field on the electron-spin coherence could be suppressed, the spin-orbit interaction would limit T2, to a value of 2T1 to first order in the spin-orbit interaction , which, is as the authors have seen, a very long time.
Q9. What is the phonon-induced transition rate between the renormalized states?
The phonon-induced transition rate between the renormalized states n , l , ↑ 1 and n , l , ↓ 1 is given by Fermi’s golden rule an analogous expression can be derived for relaxation from triplet to singlet states, or between other spin states := 2n,l1 nl↑
Q10. How many changes can lead to a spin blockade?
Sz of the ground state changes by more than 12 , which can occur due to many-body interactions in the dot, can lead to a spin blockade of the current Weinmann et al., 1995; Korkusiński et al., 2004 .
Q11. What is the probability that a triplet state is formed?
The probability that a triplet state is formed is given by 3 T / S+3 T , where the factor of 3 is due to the degeneracy of the triplets.
Q12. What is the effect of lock-in detection of GQPC on the pulse frequency?
The signal-to-noise ratio is enhanced significantly by lock-in detection of GQPC at the pulse frequency, thus measuring the average change in GQPC when a voltage pulse is applied Sprinzak et al., 2002 .
Q13. What is the amplitude of the current used to determine the spin filling?
If the tunnel rates for spin up and spin down are not equal, the amplitude of the current can be used to determine the spin filling.
Q14. How can the spin-orbit coupling be treated?
The authors now show that the same result follows from the quantum-mechanical description, where the spin-orbit coupling can be treated as a small perturbation to the discrete orbital energy-level spectrum in the quantum dot.
Q15. What is the full quantum description of nuclear spins?
the authors note that the full quantum description is required to analyze correlations between microscopic nuclear spin states and the single electron spin state, as, e.g., in a study of the entanglement between electron and nuclear spins.
Q16. How long does the spin-orbit length lSO mean?
In GaAs, estimates for vary from 103 to 3 103 m/s, and it follows that the spin-orbit length lSO = / m* is 1–10 m, in agreement with experimentally measured values Zumbühl et al., 2002 .
Q17. What is the error probability of a measurement on the state T?
The error probabilities are found to be =0.15 and =0.04, where is the probability that a measurement on the state S T yields the wrong outcome T S .
Q18. How can the sensitivity of the charge sensor be optimized?
The sensitivity of the charge sensor to changes in the dot charge can be optimized using an appropriate gate design Zhang et al., 2004 .