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Realization of qubit and electron entangler with

NanoTechnology

Realization of qubit and electron entangler with

NanoTechnology EmilieEmilie DupontDupont

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Plan

1. Quantum computing2. Realization of a QUantum

Bit.3. Why an electron entangler is

needed ?4. Experimental setup

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Quantum computing

Cryptography: perfectly secure communication.

Searching, especially algorithmic searching

Simulating quantum-mechanical systems efficiently.

Efficiency: factorising a 300 digits number in 1 sec / 150,000 years for a classical computer

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Quantum computing

A. Aspect et al, PRL 49, 1804 (‘82) A. Aspect, Nature 398, 189 ('99)

Quantum operator useful for factoring + security

Entanglement : 1 measure instantaneously know other

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Quantum Qubit

artificial atom AlGaAs heterostructure :

depleting a 2DEG inside create a quantum dot

With gate : controlling the energy level of e- in the dots

D. Berman, N. B. Zhitenev, and R. C. D. Berman, N. B. Zhitenev, and R. C. Ashoori Ashoori

Phys. Rev. Lett. Phys. Rev. Lett. 8282, 161 (1999), 161 (1999)

van der Wiel et van der Wiel et alal Rev. Mod. Phys. Rev. Mod. Phys. 7575, 1 (2003) , 1 (2003)

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Quantum Qubit

Double dots = qubit: leads on resonance + choice of gate voltage: (0,1) or (1,0)

spin qubit: 1 e- out of resonance

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Electron Entangler

Superconducting lead = source of Cooper pairs

Correlated e- on the dots but spatially separated =

EPR pairsBut noise effect

É. Dupont and K. Le Hur Phys. Rev. B É. Dupont and K. Le Hur Phys. Rev. B 7373, 045325 (2006), 045325 (2006)

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Operation on Qubit

Novel entanglement mechanisms based on the prolific combination of charge and spin qubits.

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. K. Le Hur, P. Recher, É. Dupont, and D. Loss Loss

Phys. Rev. Lett. Phys. Rev. Lett. 9696, 106803 (2006), 106803 (2006)

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Measurements and Experimental setup

SC + Carbon Nanotubes easier and same conclusion

Samuelson, Sukhorukov, Büttiker, PRB 61, R16303 ('00) PRB 70, 115330 ('04)

C. Bena, S. Vishveshawara, L. Balents,

M. Fisher PRL 89, 037901 ('02)

Measure of the spin state of the electron with a beam-splitter

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Conclusion

Can create an EPR pair but affected by

noise.

Can control spin entanglement by the

state of charge qubit.

Experimentaly feasible (CNT…).