Realization of qubit and electron entangler with Nano

Realization of qubit and electron entangler with Nano. Technology Emilie Dupont 1

Plan 1. Quantum computing 2. Realization of a QUantum Bit. 3. Why an electron entangler is needed ? 4. Experimental setup 2

Quantum computing l Efficiency: factorising a 300 digits number in 1 sec / 150, 000 years for a classical computer Cryptography: perfectly secure communication. l Searching, especially algorithmic searching l Simulating quantum-mechanical systems efficiently. l 3

Quantum computing l Entanglement : 1 measure instantaneously know other l Quantum operator useful for factoring + security A. Aspect et al, PRL 49, 1804 (‘ 82) A. Aspect, Nature 398, 189 ('99) 4

Quantum Qubit l artificial l atom Al. Ga. As heterostructure : D. Berman, N. B. Zhitenev, and R. C. Ashoori depleting Phys. Rev. Lett. 82, 161 (1999) a 2 DEG inside create a quantum dot l With gate : controlling the energy level of e- in the dots van der Wiel et al Rev. Mod. Phys. 75, 1 (2003) 5

Quantum Qubit l Double dots = qubit: leads on resonance + choice of gate voltage: (0, 1) or (1, 0) l spin qubit: 1 e- out of resonance 6

Electron Entangler l Superconducting lead = source of Cooper pairs l Correlated e- on the dots but spatially separated = EPR pairs l But noise effect É. Dupont and K. Le Hur Phys. Rev. B 73, 045325 (2006) 7

Operation on Qubit l Novel entanglement mechanisms based on the prolific combination of charge and spin qubits. l The spin entanglement can be controlled by the charge qubit. (Effect of charge noise will be neglected) K. Le Hur, P. Recher, É. Dupont, and D. Loss Phys. Rev. Lett. 96, 106803 (2006) 8

Measurements and Experimental setup l SC + Carbon Nanotubes easier and same conclusion C. Bena, S. Vishveshawara, L. Balents, M. Fisher PRL 89, 037901 ('02) l Measure of the spin state of the electron with a beam-splitter 9 Samuelson, Sukhorukov, Büttiker, PRB 61, R 16303 ('00) PRB 70, 115330 ('04)

Conclusion l Can create an EPR pair but affected by noise. l Can control spin entanglement by the state of charge qubit. l Experimentaly feasible (CNT…). 10