Recent experiments in gate defined GaAs quantum dots have demonstrated that these systems are well-suited for coherent manipulation of the electron spin degree of freedom.1 Two electron spin states have been prepared, manipulated, and measured using all electrical techniques.2 Coherent single spin rotations have been achieved using conventional electron spin resonance and spin-orbit mediated electrically driven spin resonance.3,4 Microwave reflectometry has been used to measure the conductance of a quantum point contact charge sensor, enabling spin-state read out on microsecond timescales.5,6 Futher advances in this area will hinge on the development of new and integrated methods for quantum control. The demonstration of elementary quantum gates based on electron spin will require the integration of single spin rotations, exchange gates, and fast readout.7 In addition, it is desirable to transfer quantum information over large distances, either directly, or by coupling stationary qubits to "flying" qubits.8
1. R. Hanson et al., Rev. Mod. Phys. 79, 1217 (2007).
2. J. R. Petta et al., Science 309, 2180 (2005).
3. F. H. L. Koppens et al., Nature 442, 766 (2006).
4. F. H. L. Koppens et al., Science 318, 1430 (2007).
5. R. J. Schoelkopf et al., Science 280, 1238 (1998).
6. D. J. Reilly et al., Appl. Phys. Lett. 91, 162101 (2007).
7. D. Loss and D. P. Divincenzo, Phys. Rev. A 57, 120 (1998).
8. J. Majer et al., Nature 449, 443 (2007).
9. J. M. Kikkawa and D. D. Awschalom, Nature 397, 139 (1999).
Coherent spin transport has been demonstrated in bulk systems using optical techniques.9 However, experiments have not determined how spin-orbit and hyperfine interactions will affect the coherence of single electron spins as they are shuttled in tightly confined multiple quantum dot systems. Towards this goal, we are fabricating devices to investigate coherent spin transport in GaAs quantum dots. We will investigate mechanisms for spin decoherence during transport in these multiple quantum dot systems, and in particular, methods of extending coherence through fast gate control techniques.
References1. R. Hanson et al., Rev. Mod. Phys. 79, 1217 (2007).
2. J. R. Petta et al., Science 309, 2180 (2005).
3. F. H. L. Koppens et al., Nature 442, 766 (2006).
4. F. H. L. Koppens et al., Science 318, 1430 (2007).
5. R. J. Schoelkopf et al., Science 280, 1238 (1998).
6. D. J. Reilly et al., Appl. Phys. Lett. 91, 162101 (2007).
7. D. Loss and D. P. Divincenzo, Phys. Rev. A 57, 120 (1998).
8. J. Majer et al., Nature 449, 443 (2007).
9. J. M. Kikkawa and D. D. Awschalom, Nature 397, 139 (1999).
Gate defined double quantum dot fabricated from a GaAs/AlGaAs 2-dimensional electron gas wafer. The number of electrons in the double quantum dot is determined by measuring the quantum point contact charge sensor conductance, gS. Trapped electrons are coupled to ~106 lattice nuclei through the contact hyperfine interation.2