Zeno physics in ultrastrong-coupling circuit QED

Abstract

We study the Zeno and anti-Zeno effects in a superconducting qubit interacting strongly and ultrastrongly with a microwave resonator. Using a model of a frequently measured two-level system interacting with a quantized mode, we predict different behaviors and total control of the Zeno times depending on whether the rotating-wave approximation can be applied in the Jaynes-Cummings model, or not. We exemplify showing the dependence of our results with the properties of the initial field states.

Detecting ground-state qubit self-excitations in circuit QED: A slow quantum anti-Zeno effect

“…Like previous proposals for probing the ultrastrong coupling limit, 17,18 the anti-Zeno dynamics in this paper is supported by the counter-rotating terms in the qubit-resonator interaction, using the ground-state excitations of these systems as a seed. The phenomenon is absent in the limit of RWA in Jaynes-Cummings models.…”

“…II C and, in particular, to the exponential law from Eq. (12). For strong couplings, decoherence amounts to random modulations of the qubitcavity energy levels without significantly affecting populations |c i | 2 .…”

“…As we will show in the following sections, in the case of a qubit and a single harmonic oscillator, this translates into a state that is a superposition of a deexcited qubit and a vacuum, with other states in which the qubit, the oscillator, or both are populated with excitations and photons, respectively. 10,12,13 This is a completely non-RWA effect, which requires large values of the coupling to be observed. More precisely, the excitation probability grows approximately as p e ∝ (g/ω) 2 , and g has to become comparable to the energies of photonhω or of qubithω 0 , making the interaction dynamics both very strong and very fast.…”

Effect of the third level on time evolution of the spontaneous upper level decay due to counter-rotating terms

“…The time evolution of an atomic spontaneous decay in a vacuum reservoir has attracted a lot of attention in recent years, where the Zeno and anti-Zeno effects can be realized [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. For the time evolution, the rotating wave approximation (RWA) cannot be applied, because the counter rotating terms (CRTs) have great influence.…”

Zeno dynamics in wave-packet diffraction spreading

“…This includes the unavoidable perturbation of the observed system, which acquires the form of Zeno-type effects when its evolution is repeatedly monitored along time [1][2][3]. Zeno effects can be found at least in three forms: proper Zeno effect (the evolution is slowed down) [1][2][3][4], anti-Zeno effect (the evolution is speeded up) [5][6][7][8][9][10][11][12], and inverse-Zeno effect (the evolution is guided by gradually changing measurements) [13][14][15][16]. Remarkably, the Zeno effects have crossed the quantum-classical border [13,14,[17][18][19].…”