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D-Wave Systems Inc.

D-Wave Systems Inc. D-Wave Systems Inc. THE QUANTUM COMPUTING COMPANY TM. A.M. Zagoskin (D-Wave Systems and UBC) A.Yu. Smirnov (D-Wave Systems) M.H.S. Amin (D-Wave Systems) Alec Maassen van den Brink (D-Wave Systems) E. Il’ichev (IPHT) A. Izmalkov (IPHT)

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D-Wave Systems Inc.

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  1. D-Wave Systems Inc. D-Wave Systems Inc. THE QUANTUM COMPUTING COMPANYTM A.M. Zagoskin (D-Wave Systems and UBC) A.Yu. Smirnov (D-Wave Systems) M.H.S. Amin (D-Wave Systems) Alec Maassen van den Brink (D-Wave Systems) E. Il’ichev (IPHT) A. Izmalkov (IPHT) M. Grajčar (Comenius University) Th. Wagner (IPHT) H.-G. Meyer (IPHT) Evidence for entangled states formation in a system of two coupled flux qubits Quantum Condensed Matter Meeting, Vancouver, January 2004

  2. D-Wave Systems Inc. 3JJ flux qubit Orlando et al. (1999); van der Wal et al. (2000)

  3. D-Wave Systems Inc. 3JJ flux qubit

  4. D-Wave Systems Inc. Coupled 3JJ flux qubits Majer et al. (2003) Izmalkov et al. (2003)

  5. D-Wave Systems Inc. Current experimental status of two-qubit entanglement NEC (!) - charge qubits Pashkin et al., Nature 421, 823 (2003) Yamamoto et al., Nature 425, 941 (2003) Maryland - CBJJ qubits Berkley et al., Science 300, 1548 (2003) Delft (?) - 3JJ qubits Majer et al., cond-mat/0308192 (2003)

  6. D-Wave Systems Inc. Impedance Measurement Technique Greenberg et al. (2002)

  7. D-Wave Systems Inc. Impedance Measurement Technique Voltage-current angle in the tank tan 

  8. D-Wave Systems Inc. Coherent tunneling in a 3JJ qubit: IMT dip Voltage-current angle in the tank: solid line is a fit for /h = 650 MHz 

  9. D-Wave Systems Inc. 3JJ flux qubit coupled to a tank circuit • Nb coil is prepared on oxidized Si substrates lithographically. • The line width of the coil windings was 2 m, with a 2 m spacing. • Various square-shape coils with between 20 and 150 m windings were designed. • External capacitance CT.

  10. h M  L C L T T D-Wave Systems Inc. Rabi spectroscopy Il’ichev et al. (2003)

  11. D-Wave Systems Inc. The voltage spectral density at different HF amplitudes at f=868  2 MHz

  12. D-Wave Systems Inc. Fit to the experimental data

  13. D-Wave Systems Inc. Two qubits inductively coupled to a resonance tank Sq = 80 m2 Lq = 39 pH Ic 400 nA EC 3.2 GHz Mab = 2.7 pH CT = 470 pF LT 130 nH fT = 20.139 MHz QT = 1680 (at 10 mK) Izmalkov et al., cond-mat/0312332(2003)

  14. D-Wave Systems Inc. Two qubits inductively coupled to a resonance tank Izmalkov et al. (2003)

  15. D-Wave Systems Inc. Two qubits inductively coupled to a resonance tank tan  -2 (QT/LT) (T) Izmalkov et al. (2003)

  16. D-Wave Systems Inc. Signature of entanglement Izmalkov et al. (2003); Smirnov, cond-mat/0312635 (2003)

  17. D-Wave Systems Inc. IMT dips (experiment) T = 10 (nominally), 50, 90, 160 mK Izmalkov et al. (2003)

  18. D-Wave Systems Inc. IMT dips (theory) T = 50, 90, 160 mK IMT deficit Izmalkov et al. (2003)

  19. D-Wave Systems Inc. Temperature dependence of IMT dips Squares: qubit a, triangles: qubit b, circles: coincident Izmalkov et al. (2003)

  20. D-Wave Systems Inc. Experimentally determined parameters a = 550 MHz b = 450 MHz Ia  Ib = Ip = 320 nA J = 420 MHz Izmalkov et al. (2003)

  21. D-Wave Systems Inc. Measure of entanglement Concurrence at the co-degeneracy point: C1 = C4 = 0.39 C2 = C3 = 0.97 For the equilibrium density matrix at 10 mK Ceq = 0.33 Izmalkov et al. (2003)

  22. D-Wave Systems Inc. Conclusions: • IMT approach allows to observe the signature of entanglement • in two coupled flux qubits • Quantitative agreement between the theory and experiment • confirms that the system is in an equilibrium mixture of entangled • two-qubit states • The quantitative measure of entanglement can be calculated • Only a lower limit on the appropriate coherence time can be • established • Rabi spectroscopy experiments on two qubits are under way

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