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Role of Nano-devices in Quantum Information 2004-NCU

Role of Nano-devices in Quantum Information 2004-NCU. (1)Quantum information (2)Nano-devices (SETs) (3)Single photon sources-I (4)Single photon sources-II David M. T. Kuo ( 郭明庭 ). Papers. 1-1 Quantum computer. 000 001 010 100 011 101 110 111. Three qubit register , 8 states

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Role of Nano-devices in Quantum Information 2004-NCU

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  1. Role of Nano-devices in Quantum Information2004-NCU (1)Quantum information (2)Nano-devices (SETs) (3)Single photon sources-I (4)Single photon sources-II David M. T. Kuo(郭明庭)

  2. Papers

  3. 1-1 Quantum computer 000 001 010 100 011 101 110 111 • Three qubit register , 8 states • 500 qubits 8 classical registers How many classical registers! Quantum operation could compute not just on one machine state, as serial computers do, but on machine states at once

  4. 1-1-1 Quantum logical gates • Quantum “or”,”and”, “not”, and “exclusive” gates • Based on Quantum mechanics Quantum statistics Quantum field theory Quantum transport theory Reference: Quantum computation and quantum information theory, Macchiavello, Palma, and Zeilinger July/1999 Reversible vs irreversible Classical logical gates

  5. 1-2 What else? Future, 10-15 ys Quantum information • Quantum computer • Quantum entanglement manipulation. • Teleportation • Quantum cryptograph • Quantum dot of nanometer scale Material science is crucial, nanodevices play an important role.

  6. 2 Nano-devices • State of the art Nano-meter Manipulate the internal degree of freedom of electron ( photon ) such as spin (polarization). Sexy topics, Spintronics/Photonics Fabricate nanoscale materials, Quantum dots (artificial atoms) Chyi’s team makes QDs.

  7. 2-0 Feature size Integrated circuit history Feature size NCU NTRS Roadmap Transition region Quantum devices Atomic dimensions 1960 1980 2000 2020 2040

  8. 2-1 SETs (nano-device I) Dreammakeambition become true • Single electron transistors • MIT (Bell Lab) fabricated the first SET operating at very low temperature. • Recently, Prof Li. P. W’s team has made SET working at room temperature. • SET is a Key device to read/write QUANTUM INFORMATION. (Appl, Phys. Lett. 85, 1532 (2004)) 5nm Pauli exclusion principle, and Coulomb blockade. 100nm State of the art based on novel tech.

  9. 2-1-1 Li. P. W. (SETs) Appl, Phys. Lett 85,1532 (2004). USA -1 team Jap - 2 teams Taiwan- 1 team

  10. 2-1-2 non-equilibrium problem Keldysh Green function method USA (UIUC,Gordon Baym, (1960)) Keldysh (Soviet) (1964) H. Haug (Germany) • P. Jauho (USA) • China 3-5 teams • Taiwan 1 team

  11. 2-1-3 SETs at high temperature Ge SiO2 Confinement effect

  12. 2-1-4 Coulomb interaction E3 E2 E1

  13. 2-1-4 Tunneling current

  14. 2-1-5 Tunneling current

  15. 2-1-6Tunneling current

  16. 2-1-7 Differential Conductance

  17. 2-2SPG (nano-device II) • Prof. Chyi’s team fabricates InAs/GaAs quantum dot. • Prof. Hsu’s team (department of physics) measures P.L spectrum from a single QD and second order correlation function showing anti-bunching. 4nm 12nm Optical pumping meV

  18. 2-2-1 Quantum cryptograph(BB84 PROTOCAL) C. H. Bennett, and G. Brassard, Proc. Internet, Conf. Computer Systems and Singal Processing, Banggalore, p175 (1984) • For polarizations 0, 90, 45, 135 • Sender • Receiver t Announce type of measurement, but not results . secret 1 1 0 0 key 1

  19. 2-2-2 Polarization Light polarized at angle Vertical polarization filter What is polarization for a single photon?

  20. 2-2-3 Quantum states(Qs) Number state or FOCK state • 2.1Objects p p 6 e e 6

  21. 2-3 Single photon generator Electrons Holes Z.L. Yuan et al., Science, 295, 102 (2002)

  22. Conductance band Гe Гr Гh n i p 2-3-1Schematic diagram Valence band Energy (eV)

  23. 2-3-2 Spontaneous emission (SE) • Matter - Vacuum interaction • Without Vacuum, without SE e Interband dipole h k

  24. 2-3-3 Free space • Emission at random direction • The spontaneous transition probability F Dipole Photon density of states Electric inter-band dipole moment

  25. 2-3-4 Purcell effect • Cavity • Spontaneous emission can be inhibited or enhanced c F b The spontaneous transition probability a ,where Q and V are, respectively, the quality factor and volume of cavity.

  26. 2-3-5 Manipulate single photon Cavity manipulates the polarization and direction of propagation of a single photon • State of the Art k Can QD itself as a cavity?

  27. 3-1 SPG-I, How many peaks? Very small InAs Dots X;exciton peak Biexciton Intensity of light J

  28. 3-2 Exciton, trion and biexciton

  29. 3-3 Coulomb Energy Biexciton P-trion N-trion

  30. 3-4 Spectrum Complex

  31. 3-5 Oscillator strength

  32. 4-1 SPG-2, Keldysh Green function

  33. 4-2 Spontaneous emission spectrum

  34. 4-3 Intensity

  35. 4-3-1 Hsu’s team (SPG)Optical pumping

  36. 4-4 Experimental and theoretical result Science 295, 102 (2002)

  37. 4-5 Anti-bunching • Electrically driven single photon source B 1 A

  38. Summary • State of the art ( Design of cavity with optimization) • Manipulation of entanglement of two photons • Material science (Room temperature) Ge, Si ,GaAs or… Integrated team; Physics, EE, Material, Chemistry, and CS.

  39. Take advantage of your strength and work on your weakness, then you will be very successful. 1000 Most cited Physicist, 1981-1997, Out of over 500, 000 (Examined) http://www.sst.nrel.gov, Chang, Y. C. ranked 110.

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