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D-Wave Systems Inc. THE QUANTUM COMPUTING COMPANY TM

D-Wave Systems Inc. THE QUANTUM COMPUTING COMPANY TM. A.M. Zagoskin (D-Wave Systems and UBC). Tunable coupling of superconducting qubits. A. Blais (Yale University) A. Maassen van den Brink (D-Wave Systems) A.Yu. Smirnov (D-Wave Systems). Quantum Mechanics on the Large Scale, Banff,

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D-Wave Systems Inc. THE QUANTUM COMPUTING COMPANY TM

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  1. D-Wave Systems Inc. THE QUANTUM COMPUTING COMPANYTM A.M. Zagoskin (D-Wave Systems and UBC) Tunable coupling of superconducting qubits A. Blais (Yale University) A. Maassen van den Brink (D-Wave Systems) A.Yu. Smirnov (D-Wave Systems) Quantum Mechanics on the Large Scale, Banff, April 12-17, 2003

  2. D-Wave Systems Inc. Direct coupling of superconducting qubits Capacitive coupling- CBJJ qubits Capacitive coupling - charge qubits Blais, Maassen van den Brink, and Zagoskin, PRL 90 (2003) 127901 Johnson et al., PRB 67 (2003) 020509(R) Pashkin et al., Nature 421 (2003) 823

  3. D-Wave Systems Inc. Direct coupling of superconducting qubits Inductive coupling - 3JJ qubits Makhlin, Schön, and Shnirman, Rev.Mod.Phys. 73 (2001) 357 Il’ichev et al. (2003)

  4. D-Wave Systems Inc. Direct coupling of superconducting qubits Inductive+ coupling - 3JJ qubits Paauw et al. (2002)

  5. D-Wave Systems Inc. Direct coupling of superconducting qubits Inductive+ coupling - 3JJ qubits Akisato, quant-ph_0303128 (2002)

  6. D-Wave Systems Inc. Coupling through a resonant tank circuit b a

  7. D-Wave Systems Inc. Coupling through virtual states Coupled phase qubits Coupled charge qubits Makhlin, Schön, and Shnirman, Rev.Mod.Phys. 73 (2001) 357

  8. D-Wave Systems Inc. Qubit-qubit entanglement in cavity QED Rauschenbeutel et al., Science 288 (2000) 2024

  9. D-Wave Systems Inc. Superconducting tanks and qubits Ilichev et al., cond-mat/0303433 (2003)

  10. D-Wave Systems Inc. Superconducting tanks and qubits Ilichev et al., cond-mat/0303433 (2003)

  11. D-Wave Systems Inc. Tunable inductance Assuming 1, we obtain

  12. D-Wave Systems Inc. Mediated coupling Blais, Maassen van den Brink, and Zagoskin, PRL 90 (2003) 127901 Plastina and Falci, cond-mat/0206586 (2002)

  13. D-Wave Systems Inc. Tuning a large Josephson junction Moderate response to bias current. Weak sensitivity to bias noise. Fine tuning.

  14. D-Wave Systems Inc. Coupled CBJJs Qubit Blais, Maassen van den Brink, and Zagoskin, PRL 90 (2003) 127901

  15. D-Wave Systems Inc. CBJJ qubit coupled to a tunable bus Josephson frequency Coupling parameter In the {|0q1b>, |1q0b>}-subspace (in resonance)

  16. D-Wave Systems Inc. Coherent qubit-bus oscillations If Cj=6 pF, Cc=25 fF, Ic=21 A, Ibias=20.8 A, there are three levels in each well (interlevel spacing ~1 GHz), and coherent oscillations have period T=h/~40 ns.

  17. D-Wave Systems Inc. Two-qubit operations:

  18. D-Wave Systems Inc. Two-qubit operaions: Ib Ib,2 Ib,decouple Ib,1 Ib,1

  19. D-Wave Systems Inc. Decoupling of CBJJ qubit from the bus Decoupling is achieved if decrease the bus current to Ibias=20.43 A. The “degenerate” eigenstates are 0.999|0q1b>+0.007|1q0b>+o(10-3) 0.007|0q1b>+0.999|1q0b>+o(10-3)

  20. D-Wave Systems Inc. Additional noise in CBJJ qubit-bus system Noise source: bias current fluctuations:

  21. D-Wave Systems Inc. Additional noise in CBJJ qubit-bus system In resonance, For T = 25 mK, R = 560 k, CJ = 6 pF, Cc = 25 fF, Ic=20 A T1,2 ~ 1 ms

  22. D-Wave Systems Inc. Quality of coupled CBJJ qubits Blais, Maassen van den Brink, and Zagoskin, PRL 90 (2003) 127901

  23. D-Wave Systems Inc. Quality of coupled CBJJ qubits Blais, Maassen van den Brink, and Zagoskin, PRL 90 (2003) 127901

  24. D-Wave Systems Inc. Coupled “quantroniums” Blais, Maassen van den Brink, and Zagoskin, PRL 90 (2003) 127901

  25. D-Wave Systems Inc. Phase qubits coupled through a resonator Ic CJ Ib IT CT LT M2 M1 I1 I2 Smirnov and Zagoskin, cond-mat/0207214 (2002)

  26. D-Wave Systems Inc. Phase qubits coupled through a resonator If both qubits are in a degeneracy point and near resonance: Jaynes-Cummings Hamiltonian Smirnov and Zagoskin/cond-mat/0207214 (2002)

  27. D-Wave Systems Inc. Qubit + tank 1 2

  28. D-Wave Systems Inc. Qubit + tank For a 3JJ phase qubit with Iq~450 nA, L~25 pH, fT~1 GHz the frequency of the corresponding coherent oscillations is f0~0.1 GHz.

  29. D-Wave Systems Inc. State pump

  30. D-Wave Systems Inc. State pump

  31. D-Wave Systems Inc. State pump

  32. D-Wave Systems Inc. State pump

  33. D-Wave Systems Inc. State pump

  34. D-Wave Systems Inc. State pump

  35. D-Wave Systems Inc. State pump

  36. D-Wave Systems Inc. State pump

  37. D-Wave Systems Inc. State pump

  38. D-Wave Systems Inc. Equal qubits, equal couplings 1 3,4 2 No “classical” entanglement!

  39. D-Wave Systems Inc. (Teleportation)1/2 For n=0 there are only three constituent states:

  40. D-Wave Systems Inc. (Teleportation)1/2 Starting from the state in=|0>(a|11>+b|01>) | 02>, after time t1/2= 2-1/2/ we reach the state out=|0> | 01>( -a|12>+b|02>)

  41. D-Wave Systems Inc. (Teleportation)1/2

  42. D-Wave Systems Inc. (Teleportation)1/2

  43. D-Wave Systems Inc. (Teleportation)1/2

  44. D-Wave Systems Inc. (Teleportation)1/2

  45. D-Wave Systems Inc. (Teleportation)1/2

  46. D-Wave Systems Inc. (Teleportation)1/2

  47. D-Wave Systems Inc. (Teleportation)1/2

  48. D-Wave Systems Inc. Photon-splitting and qubit-qubit entanglement If instead start from the state ’in=|1>|01>|02>, and after tB = 2-3/2/ the Bell state of two qubits is formed: For the above choice of parameters and Q=1000 the decay time in the tank ~ 1 s, while tB ~ 1 ns

  49. D-Wave Systems Inc. Phase-charge duality The previous results apply to capacitively coupled charge qubits. Plastina and Falci, cond-mat/0206586 (2002)

  50. D-Wave Systems Inc. Phase-charge vocabulary

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