Superradiant phase transition in the ultrastrong-coupling regime of the two-photon Dicke model

Garbe, Louis; Egusquiza, I. L.; Solano, E.; Ciuti, Cristiano; Coudreau, Thomas; Milman, P.; Felicetti, Simone

doi:10.1103/physreva.95.053854

Cited by 83 publications

(100 citation statements)

References 72 publications

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“…Indeed, in a finite-component system quantum-control techniques could be applied without implementing complex non-local operations, as it is the case for many-body systems. In addition, our study paves the way to the application of other criticalities appearing in quantum-optical models [20,[31][32][33] in quantum metrology. Finally, by focusing on the time-scaling and on a finite-component system, our analysis challenges the standard framework in which the fundamental resources needed to achieve metrological quantum advantage are assessed [34][35][36][37].…”

Section: Analysis Of Resourcesmentioning

confidence: 92%

Critical Quantum Metrology with a Finite-Component Quantum Phase Transition

et al. 2020

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Physical systems close to a quantum phase transition exhibit a divergent susceptibility, suggesting that an arbitrarily-high precision may be achieved by exploiting quantum critical systems as probes to estimate a physical parameter. However, such an improvement in sensitivity is counterbalanced by the closing of the energy gap, which implies a critical slowing down and an inevitable growth of the protocol duration. Here, we design different metrological protocols that make use of the superradiant phase transition of the quantum Rabi model, a finite-component system composed of a single two-level atom interacting with a single bosonic mode. We show that, in spite of the critical slowing down, critical quantum optical systems can lead to a quantum-enhanced time-scaling of the quantum Fisher information, and so of the measurement sensitivity.In a system close to a critical point, small variations of physical parameters may lead to dramatic changes in the equilibrium state properties. The possibility of exploiting this sensitivity for metrological purposes is well known, and it has already been applied in classical devices, e.g. in superconducting transition-edge sensor [1]. Besides, the development of quantum metrology has extensively shown that quantum states can outperform their classical counterparts for sensing tasks [2]. Therefore, a question naturally arises: what sensitivity can be achieved using interacting systems close to a quantum-critical point? In the last few years, this question has attracted growing interest and it has been addressed by different methods [3][4][5][6][7][8][9]. These studies may be roughly divided in two classes.The first approach, which we will call the "dynamical" paradigm [5,7], focus on the time evolution induced by a Hamiltonian close to a critical point. In this approach, one prepares a probe system in a suitably chosen state, lets it evolve according to the critical Hamiltonian, and finally measures it. This bear close similarity to the standard interferometric paradigm of quantum metrology [2]. On the other hand, the "static" approach [3, 6] is based on the equilibrium properties of the system. It consists in preparing and measuring the system ground state in the unitary case, or the system steady-state when open quantum systems are considered. In proximity of the phase transition the susceptibility of the equilibrium state diverges, and so it does the achievable measurement precision. Unfortunately, the time required to prepare the equilibrium state diverges as well, both in the unitary [10] and in the driven-dissipative case [11,12], a behavior called critical slowing down. Only very re-cently, it has been demonstrated that for a large class of spin models these two approaches are formally equivalent [9], and that they both make it possible to achieve the optimal scaling limit of precision with respect to system size and to measurement time. These results were obtained considering spin systems that undergo quantum phase transitions in the thermodynamic limit, where the numb...

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Section: Analysis Of Resourcesmentioning

confidence: 92%

Critical Quantum Metrology with a Finite-Component Quantum Phase Transition

et al. 2020

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“…Finally, the USC regime seems a promising field in which to investigate the effect of local dissipation for ensembles with N ≫ 1, as using PIQS one can retain the full nonlinearity of the TLSs beyond the usually explored dilute-excitation regime [250,306].…”

Section: Discussionmentioning

confidence: 99%

Open quantum systems with local and collective incoherent processes: Efficient numerical simulations using permutational invariance

et al. 2018

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The permutational invariance of identical two-level systems allows for an exponential reduction in the computational resources required to study the Lindblad dynamics of coupled spin-boson ensembles evolving under the effect of both local and collective noise. Here we take advantage of this speedup to study several important physical phenomena in the presence of local incoherent processes, in which each degree of freedom couples to its own reservoir. Assessing the robustness of collective effects against local dissipation is paramount to predict their presence in different physical implementations. We have developed an open-source library in Python, the Permutational-Invariant Quantum Solver (PIQS), which we use to study a variety of phenomena in driven-dissipative open quantum systems. We consider both local and collective incoherent processes in the weak, strong, and ultrastrong-coupling regimes. Using PIQS, we reproduced a series of known physical results concerning collective quantum effects and extended their study to the local driven-dissipative scenario. Our work addresses the robustness of various collective phenomena, e.g., spin squeezing, superradiance, quantum phase transitions, against local dissipation processes. arXiv:1805.05129v5 [quant-ph]

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“…For higher values of the coupling parameter, the model becomes unbounded from below. This behavior results in a nontrivial phase diagram in the many-body limit [56].…”

Section: Introductionmentioning

confidence: 99%

Two-photon quantum Rabi model with superconducting circuits

Felicetti¹,

Rossatto²,

Rico³

et al. 2018

Phys. Rev. A

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137

168

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We propose a superconducting circuit to implement a two-photon quantum Rabi model in a solid-state device, where a qubit and a resonator are coupled by a two-photon interaction. We analyze the input-output relations for this circuit in the strong coupling regime and find that fundamental quantum optical phenomena are qualitatively modified. For instance, two-photon interactions are shown to yield single-or two-photon blockade when a pumping field is either applied to the cavity mode or to the qubit, respectively. In addition, we derive an effective Hamiltonian for perturbative ultrastrong two-photon couplings in the dispersive regime, where twophoton interactions introduce a qubit-state-dependent Kerr term. Finally, we analyze the spectral collapse of the multi-qubit two-photon quantum Rabi model and find a scaling of the critical coupling with the number of qubits. Using realistic parameters with the circuit proposed, three qubits are sufficient to reach the collapse point.

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Superradiant phase transition in the ultrastrong-coupling regime of the two-photon Dicke model

Cited by 83 publications

References 72 publications

Critical Quantum Metrology with a Finite-Component Quantum Phase Transition

Critical Quantum Metrology with a Finite-Component Quantum Phase Transition

Open quantum systems with local and collective incoherent processes: Efficient numerical simulations using permutational invariance

Two-photon quantum Rabi model with superconducting circuits

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