Dispersive regime of circuit QED : Photon-dependent qubit dephasing and relaxation rates

By M. Boissonneault, Jay M. Gambetta, Alexandre Blais. 2008

270 citations recorded by the source corpus.

Superconducting electrical circuits can be used to study the physics of cavity quantum electrodynamics (QED) in new regimes, therefore realizing circuit QED. For quantum-information processing and quantum optics, an interesting regime of circuit QED is the dispersive regime, where the detuning between the qubit transition frequency and the resonator frequency is much larger than the interaction strength. In this paper, we investigate how nonlinear corrections to the dispersive regime affect the measurement process. We find that in the presence of pure qubit dephasing, photon population of the resonator used for the measurement of the qubit act as an effective heat bath, inducing incoherent relaxation and excitation of the qubit. Measurement thus induces both dephasing and mixing of the qubit, something that can reduce the quantum nondemolition aspect of the readout. Using quantum trajectory theory, we show that this heat bath can induce quantum jumps in the qubit state. Nonlinear effects can also reduce the achievable signal-to-noise ratio of a homodyne measurement of the voltage.

Subfields: Artificial Intelligence, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/88fab15b89295d483a70377e9c24c38f4ebd0cee

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Citations in the corpus

Microwave photonics with superconducting quantum circuits (2017, unknown): “up to first order in g/∆, by applying the Schrieffer-Wolff transformation U = exp[g(a†σ−− aσ+)/∆] to eliminate the linear-order term aσ+ +a †σ− [5, 6, 359, 360] (see Appendix B.”
Circuit QED: Superconducting Qubits Coupled to Microwave Photons (2015, background): “This back-action effect leads to a broadening of the spectroscopic line width of the qubit (Schuster et al., 2005; Schuster et al., 2007b; Ithier et al., 2005; Lupascu et al., 2005; Boissonneault et al., 2008; Boissonneault et al., 2009).”
Low-Disorder Microwave Cavity Lattices for Quantum Simulation with Photons (2012, background): “For quantum information processing it is often preferable to operate within this limit because the qubit will not directly absorb cavity photons [12], furthermore the Purcell effect on the qubit is weaker when the qubit is energetically far away from the cavity [85].”
Fast universal control of an oscillator with weak dispersive coupling to a qubit (2021, background): “We find that, up to 2000 oscillator photons, there is no appreciable heating out of |g〉 when displacing the cavity state, indicating that the dressed dephasing rate is small [73].”
Two-photon and three-photon blockades in driven nonlinear systems (2012, unknown): “[18, 28] in the circuit QED context).”
Rapid High-Fidelity Single-Shot Dispersive Readout of Superconducting Qubits (2017, background): “Additionally, the mixing rates of the qubit states during measurement may also depend on higher order transmon states [37, 38], as well as, the power spectrum of the flux noise Γ↑↓ ∝ (ndrive/ncrit)Nf (±∆), where Nf is the flux noise power at detuning ±∆ [39].”
Rapid High-fidelity Multiplexed Readout of Superconducting Qubits (2018, background): “Second, qubit state mixing between the ground and excited states due to the readout tone [46] and rethermalization causes an error with probability P (e|0) = 0.”