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Figure 9.3: Spectroscopy of Coupled Qubits – a) Far off: Initially the flux bias
crosstalk will probably place the qubits off resonance. b) Closer: As the flux bias
is corrected, the resonance peaks move closer. c) Splitting: When the qubits are
on resonance, the coupling causes them to split.
one-dimensional spectroscopy scan introduced above. If it is run on all qubits
simultaneously, it will show each qubit’s resonance peak in the presence of all
other qubits’ biases. If the operating biases of all qubits are then adjusted to set
the resonance frequency of all qubits to the same value, the qubits will begin to
couple. This can sometimes be seen in a splitting of the response peak in the
spectroscopy sweep, as shown in Figure 9.3c.
9.2.3 Swaps
The next step is to examine the time dynamics from the qubits’ interaction.
This can be achieved with a sweep that is essentially a multi-qubit T 1 experiment,
except that only one of the involved qubits is prepared in the | 1 〉-state with a
π-pulse, while all other qubits remain in the ground state.
In addition to the
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