Dispersive readout of a weakly coupled qubit via the parity-time-symmetric phase transition

Abstract

For some cavity-quantum-electrodynamics systems, such as a single electron spin coupled to a passive cavity, it is challenging to reach the strong-coupling regime. In such a weak-coupling regime, the conventional dispersive readout technique cannot be used to resolve the quantum states of the spin. Here we propose an improved dispersive readout method to measure the quantum states of a weakly coupled qubit by harnessing either one or two auxiliary cavities linearly coupled to the passive cavity containing the qubit. With appropriate parameters in both cases, the system excluding the qubit can exhibit a parity-time-symmetric phase transition at the exceptional point (EP). Because the EP can amplify the perturbation induced by the qubit and the parity-time symmetry can narrow the linewidths of the peaks in the transmission spectrum of the passive cavity, we can measure the quantum states of the weakly coupled qubit via this transmission spectrum. Owing to the weak coupling between the qubit and the passive cavity, the backaction due to the measurement of the qubit can also be reduced in comparison with the conventional dispersive readout technique in the strong-coupling regime.

8 pages, 4 figures

References in corpus (13)

• Making Sense of Non-Hermitian Hamiltonians
• The physics of exceptional points
• Beyond the Jaynes-Cummings model: circuit QED in the ultrastrong coupling regime
• Quantum technologies with hybrid systems
• Observation of the Bloch-Siegert Shift in a Qubit-Oscillator System in the Ultrastrong Coupling Regime
• $\mathcal{P}\mathcal{T}$-Symmetry-Breaking Chaos in Optomechanics
• Tunable coupling engineering between superconducting resonators: from sidebands to effective gauge fields
• Input-output theory for spin-photon coupling in Si double quantum dots
• Spectroscopic properties of inhomogeneously broadened spin ensembles in a cavity
• Tunable and Switchable Coupling Between Two Superconducting Resonators
• Dispersive read-out of ferromagnetic resonance for strongly coupled magnons and microwave photons
• Dispersive readout of valley splittings in cavity-coupled silicon quantum dots
• Dispersive readout of adiabatic phases

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• Gain-Loss Coupled Systems
• Work statistics in non-Hermitian evolutions with Hermitian endpoints
• Resonant-amplified and invisible Bragg scattering based on spin coalescing modes