PDF (double-sided) - Physics Department, UCSB - University of ...

process of the qubits in two ways:
• If the circuit is driven with microwaves at a frequency that matches that
of the resonator, the resonator will begin accepting photons as described in
Chapter 3.3. This leads to complicated entangled states between the qubits
and the resonator that make it very hard to create a clean entanglement
only between the two qubits. Thus, the qubits need to be prepared in the
| 10 〉 state while they are biased at a frequency far away from the resonator.
• If both qubits are placed on resonance with the resonator at the same time,
the interaction between the three systems also leads to very complicated
dynamics that will prevent clean qubit-only entanglement. Therefore, the
qubits need to interact with the resonator one after the other to create the
state.
Overall, the entangling sequence consists of bringing the excited qubit on resonance
with the resonator for a time that yields half a swap operation and then
bringing the second qubit on resonance for a full swap time, as indicated in Figure
11.1b. The half-swap creates the entangled state | 10 〉 − i| 01 〉 between the
first qubit and the resonator, while the full-swap transfers the resonator’s share of
the entanglement into the other qubit, leaving the resonator in the ground state
and the two qubits in the state | 01 〉 + e iα | 10 〉. The phase factor e iα results from
243