DWave Systems Inc.

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D-Wave Systems Inc. THE QUANTUM COMPUTING
COMPANYTM
Continuous observation of Rabi oscillations in a
Josephson flux qubit
E. Il'ichev, N. Oukhanski, A. Izmalkov, H.-G.
Meyer (IPHT-Jena) Th. Wagner (Friedrich
Schiller U.) M. Grajcar (Comenius
U.) A.Yu. Smirnov, Alec Maassen van den Brink,
M.H.S. Amin (D-Wave Systems) A.M. Zagoskin
(D-Wave Systems and UBC)
CIAR Quantum Materials Program Meeting Vancouver,
May 16-19, 2003
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D-Wave Systems Inc. THE QUANTUM COMPUTING
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Idea of the experiment Rabi spectroscopy

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D-Wave Systems Inc. THE QUANTUM COMPUTING
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Idea of the experiment Rabi spectroscopy
H
S
Voltage
ltSxgt ? sin(wRt)sin(? t) ltSygt ? sin(wRt)cos(?
t) ltSzgt ? cos(wRt)

?R?Ahf
Resonant circuit Rabi spectrum
Frequency
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D-Wave Systems Inc. THE QUANTUM COMPUTING
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Three-junction flux qubit coupled to a tank
circuit
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D-Wave Systems Inc. THE QUANTUM COMPUTING
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Nb technology for the tank circuit coil
T. May et al. Rev.Sci.Instrum., 74 March 2003
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D-Wave Systems Inc. THE QUANTUM COMPUTING
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Three-junction 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.
• We use an external capacitance CT.

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D-Wave Systems Inc. THE QUANTUM COMPUTING
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The voltage spectral density at different HF
amplitudes at f868 ? 2 MHz
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Normalized spectral density (background
subtracted)
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Theoretical expression for the tank voltage
spectrum
E.Ilichev et al., preprint , cond-mat /0303433
(2003)
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D-Wave Systems Inc. THE QUANTUM COMPUTING
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Fit to the experimental data
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D-Wave Systems Inc. THE QUANTUM COMPUTING
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Conclusions
Rabi oscillations were demonstrated in a
three-junction flux qubit New method (Rabi
spectroscopy) developed continuous
observation Tank protects the qubit from external
noise Weak tank-qubit coupling ? Large coherence
time
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D-Wave Systems Inc. THE QUANTUM COMPUTING
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Further research directions
Ilichev et al. (2003)
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D-Wave Systems Inc. THE QUANTUM COMPUTING
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Further research directions

• Demonstrate entanglement in a two-qubit system
• Determine parameters of two-qubit system coupled
  to a control/readout circuit
• Optimize circuit parameters
• Establish criteria for demonstrating entanglement
  in a four-qubit circuit
• Demonstrate entanglement in a four-qubit circuit
• Determine and optimize parameters of four-qubit
  system coupled to a control/readout circuit
• Demonstrate quantum error correction in a
  four-qubit circuit.