QSIT Student Presentations Quantum Dot Spin QuBits Quantum Devices for Information Technology Anastasia Varlet ETH - 05/04/12 Outline I. Double Quantum Dot ∣S〉 II. The Logical Qubit ∣↓↑〉 ∣↑↓〉 ∣T 〉 0 III. Experiments Anastasia Varlet ETH - 05/04/12 I. Double Quantum Dot 1. Reminder : Quantum Dot (QD) AlGaAs/GaAs heterostructure → 2DEG at the interface. [1] T. Ihn, Semiconductor Nanostructures (2009), Oxford University Press. [2] Hanson et al.,Coherent manipulation of single spins in SC (2008), Nature 453, 1043 Anastasia Varlet 1/14 ETH - 05/04/12 I. Double Quantum Dot 1. Reminder : Quantum Dot (QD) S D Picture from: [3] Ciorga et al., Electrically-defined island → top gates on a 2DEG Phys. Rev. B 61 (2000) 2 tunable parameters : - source and drain bias - plunger gate voltage PG Anastasia Varlet 2/14 ETH - 05/04/12 I. Double Quantum Dot 1. Reminder : Quantum Dot (QD) S D Picture from: [3] Ciorga et al., Electrically-defined island → top gates on a 2DEG Phys. Rev. B 61 (2000) 2 tunable parameters : - source and drain bias - plunger gate voltage PG [4] Hanson et al., Spins in few-electron QDs (2007), Rev. Mod. Phys., Vol. 79, No. 4 Anastasia Varlet 2/14 ETH - 05/04/12 I. Double Quantum Dot 1. Reminder : Quantum Dot (QD) S D Picture from: [3] Ciorga et al., Electrically-defined island → top gates on a 2DEG Phys. Rev. B 61 (2000) 2 tunable parameters : - source and drain bias - plunger gate voltage PG [4] Hanson et al., Spins in few-electron QDs (2007), Rev. Mod. Phys., Vol. 79, No. 4 Anastasia Varlet 2/14 ETH - 05/04/12 I. Double Quantum Dot 2. Double Quantum Dot [5] Picture from: [5] Petta et al., Electrically-defined island → top gates on a 2DEG Science 309 (2005) 2 tunable parameters : - source and drain bias - plunger gate voltages [4] V L V R [1] T. Ihn, Semiconductor Nanostructures (2009), Oxford University Press. Anastasia Varlet 3/14 ETH - 05/04/12 I. Double Quantum Dot 3. Two-electron regime [3] Picture from: [3] Petta et al., A Quantum Point Contact is used to determine Science 309 (2005) the charge state in the dots. [4] [3] V L V R [1] T. Ihn, Semiconductor Nanostructures (2009), Oxford University Press. Anastasia Varlet 4/14 ETH - 05/04/12 I. Double Quantum Dot 3. Two-electron regime [5] Picture from: [5] Petta et al., A Quantum Point Contact is used to determine Science 309 (2005) the charge state in the dots. [3] Anastasia Varlet 5/14 ETH - 05/04/12 I. Double Quantum Dot 3. Two-electron regime [3] [5] [4] Hanson et al., Spins in few-electron QDs (2007), Rev. Mod. Phys., Vol. 79, No. 4 ∆V ε = η∆V Anastasia Varlet 6/14 ETH - 05/04/12