Abstract
Qubit-qubit interactions can significantly boost quantum coherence times for Bell states. The coherence-time enhancements are, however, not monotonic and there exists a phase where further increasing the interaction is unhelpful. A resonator in a suggested circuit QED-type implementation of the Tavis-Cummings (Dicke) model, is shown to shift this transition point depending on the number of loaded photons. This allows the resonator to amplify the coherence enhancements in certain regimes. The interactions also induce unusual collapse and revival-type behavior for the entanglement dynamics. An exact open quantum system's formalism–(quasi-Hamiltonians for the Dicke model) shows how a Bell state singlet-triplet qubit in a resonator can be protected against noise from randomly fluctuating two-level systems. Simple circuit level details are given for flux qubits.
- Received 25 October 2013
- Revised 29 September 2014
DOI:https://doi.org/10.1103/PhysRevA.91.012317
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