2014/11/20 by Jared Lolli, Alexandre Baksic, Dávid Nagy +4 · 61 citations
Computer Science · Physics and Astronomy · #Boson #Cavity quantum electrodynamics #Circuit quantum electrodynamics #Coupling (piping) #Field (mathematics) #Ground state #Lamb shift #Master equation #Open quantum system #Phase qubit #Photon #Physics #Quantum #Quantum Information and Cryptography #Quantum and electron transport phenomena #Quantum electrodynamics #Quantum mechanics #Qubit #Strong Light-Matter Interactions #Vacuum state #cond-mat.mes-hall #quant-ph
paper · pdf · doi:10.1103/physrevlett.114.183601
published in Physical Review Letters 114(18), 183601 (American Physical Society)
arxiv created 2014/11/20 · openalex publication_date 2015/05/06 · arxiv updated 2015/09/07 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We investigate theoretically how the spectroscopy of an ancillary qubit can probe cavity (circuit) QED ground states containing photons. We consider three classes of systems (Dicke, Tavis-Cummings, and Hopfield-like models), where nontrivial vacua are the result of ultrastrong coupling between N two-level systems and a single-mode bosonic field. An ancillary qubit detuned with respect to the boson frequency is shown to reveal distinct spectral signatures depending on the type of vacua. In particular, the Lamb shift of the ancilla is sensitive to both ground state photon population and correlations. Backaction of the ancilla on the cavity ground state is investigated, taking into account the dissipation via a consistent master equation for the ultrastrong coupling regime. The conditions for high-fidelity measurements are determined.