Sub-cycle switch-on of ultrastrong light–matter interaction

Günter, G.; Anappara, Aji A.; Hees, Jakob; Sell, Alexander; Biasiol, G.; Sorba, L.; Liberato, Simone De; Ciuti, Cristiano; Tredicucci, Alessandro; Leitenstorfer, Alfred; Huber, Rupert

doi:10.1038/nature07838

Cited by 546 publications

(525 citation statements)

References 26 publications

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“…However, there is still no connection between the individual carrier pairs, which have random phases with respect to the driving field. In the ultrastrong-coupling regime 2 , where B 1 ≈ B 0 , the spin-Dicke effect sets in 3 , which is equivalent in form to the familiar optical Dicke effect [5][6][7] . The driving field now defines the Bloch sphere axis, voiding the rotating-wave approximation 26 .…”

Section: Lettersmentioning

confidence: 99%

The spin-Dicke effect in OLED magnetoresistance

et al. 2015

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Pairs of charge-carrier spins in organic semiconductors constitute four-level systems that can be driven electromagnetically 1 . Given appropriate conditions for ultrastrong coupling 2 -weak local hyperfine fields B hyp , large magnetic resonant driving fields B 1 and low static fields B 0 that define Zeeman splittingthe spin-Dicke e ect, a collective transition of spin states, has been predicted 3 . This parameter range is challenging to probe by electron paramagnetic resonance spectroscopy because thermal magnetic polarization is negligible. It is accessed through spin-dependent conductivity that is controlled by electron-hole pairs of singlet and triplet spin-permutation symmetry without the need of thermal spin polarization 4 . Signatures of collective behaviour of carrier spins are revealed in the steady-state magnetoresistance of organic light-emitting diodes (OLEDs), rather than through radiative transitions. For intermediate B 1 , the a.c.-Zeeman e ect appears. For large B 1 , a collective spin-ensemble state arises, inverting the current change under resonance and removing power broadening, thereby o ering a unique window to ambient macroscopic quantum coherence.Macroscopic phase coherence is a hallmark of many exotic states of matter such as superconductivity, ferromagnetism or BoseEinstein condensation. Such coherence may also emerge between two-level systems, where it is mediated by electromagnetic fields, as described by the Dicke effect in collisional narrowing 5 and superradiance 6 . Collective behaviour may already arise within a pair of interacting two-level systems 7 , an observation that can potentially be extended to the prototypical two-level system of an electron spin. For pairs of charge-carrier spins in organic semiconductors, with driving fields B 1 exceeding the hydrogen-induced random local hyperfine field 1 B hyp and approaching the magnitude of the static magnetic field B 0 , a collective macroscopic spin phase has been predicted to emerge 3 . Under these conditions, when the spin-Rabi splitting becomes comparable to the Zeeman splitting, the electromagnetic field links individually resonant spin pairs together, forming a spin-Dicke state analogous to that in the dipolar Dicke effect [5][6][7] . These macroscopic effects are observable through measurements of electronic recombination rates, which depend on spin-permutation symmetry of the pair 8 .We monitor the electron-hole recombination current in an OLED, where positive and negative charges are injected into a thin film of an organic semiconductor from opposite electrodes. As the charges drift through the material, they can capture each other on intermolecular length scales owing to weak dielectric screening. These weakly coupled intermolecular electron-hole pairs 9 can ultimately recombine on individual molecules to form a molecular excited state, or exciton, which gives rise to electroluminescence. The subsequent discussion focuses on carrier pairs and not on excitons, which have spin S = 0 or 1. Because the carriers possess spi...

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Section: Lettersmentioning

confidence: 99%

The spin-Dicke effect in OLED magnetoresistance

et al. 2015

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“…Although the Hamiltonian of a realistic atom-cavity system contains so-called counterrotating terms allowing the simultaneous creation ior annihilation of an excitation in both atom and cavity mode, these terms can be safely neglected for small normalized coupling rates g/ω r . However, when g becomes a significant fraction of ω r , the counterrotating terms are expected to manifest, giving rise to exciting effects in QED.The ultrastrong coupling regime is difficult to reach in traditional quantum optics, but was recently realized in a solid-state semiconductor system 19,20 . There, quantitative deviations from the Jaynes-Cummings model have been observed, but a direct experimental proof of its breakdown by means of an unambiguous feature is still missing.…”

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confidence: 99%

“…The ultrastrong coupling regime is difficult to reach in traditional quantum optics, but was recently realized in a solid-state semiconductor system 19,20 . There, quantitative deviations from the Jaynes-Cummings model have been observed, but a direct experimental proof of its breakdown by means of an unambiguous feature is still missing.…”

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confidence: 99%

“…While these experiments are well described by the renowned Jaynes-Cummings model 16 , novel physics is expected when g reaches a considerable fraction of ωr. Promising steps towards this so-called ultrastrong coupling regime 17,18 have recently been taken in semiconductor structures 19,20 . Here, we report on the first experimental realization of a superconducting circuit QED system in the ultrastrong coupling limit and present direct evidence for the breakdown of the Jaynes-Cummings model.…”

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Circuit quantum electrodynamics in the ultrastrong-coupling regime

et al. 2010

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In cavity quantum electrodynamics (QED) 1-3 , light-matter interaction is probed at its most fundamental level, where individual atoms are coupled to single photons stored in three-dimensional cavities. This unique possibility to experimentally explore the foundations of quantum physics has greatly evolved with the advent of circuit QED 4-13 , where on-chip superconducting qubits and oscillators play the roles of two-level atoms and cavities, respectively. In the strong coupling limit, atom and cavity can exchange a photon frequently before coherence is lost. This important regime has been reached both in cavity and circuit QED, but the design flexibility and engineering potential of the latter allowed for increasing the ratio between the atom-cavity coupling rate g and the cavity transition frequency ωr above the percent level 8,14,15 . While these experiments are well described by the renowned Jaynes-Cummings model 16 , novel physics is expected when g reaches a considerable fraction of ωr. Promising steps towards this so-called ultrastrong coupling regime 17,18 have recently been taken in semiconductor structures 19,20 . Here, we report on the first experimental realization of a superconducting circuit QED system in the ultrastrong coupling limit and present direct evidence for the breakdown of the Jaynes-Cummings model. We reach remarkable normalized coupling rates g/ωr of up to 12 % by enhancing the inductive coupling of a flux qubit 21 to a transmission line resonator using the nonlinear inductance of a Josephson junction 22 . Our circuit extends the toolbox of quantum optics on a chip towards exciting explorations of the ultrastrong interaction between light and matter.In the strong coupling regime, the atom-cavity coupling rate g exceeds the dissipation rates κ and γ of both, cavity and atom, giving rise to coherent light-matter oscillations and superposition states. This regime was reached in various types of systems operating at different energy scales [1][2][3][23][24][25] . At microwave frequencies, strong coupling is feasible due to the enormous engineerability of superconducting circuit QED systems 4,5 . Here, small cavity mode volumes and large dipole moments of artificial atoms 26 enable coupling rates g of about 15 1 % of the cavity mode frequency ω r . Nevertheless, as in cavity QED, the quantum dynamics of these systems follows the Jaynes-Cummings model, which describes the coherent exchange of a single excitation between the atom and the cavity mode. Although the Hamiltonian of a realistic atom-cavity system contains so-called counterrotating terms allowing the simultaneous creation ior annihilation of an excitation in both atom and cavity mode, these terms can be safely neglected for small normalized coupling rates g/ω r . However, when g becomes a significant fraction of ω r , the counterrotating terms are expected to manifest, giving rise to exciting effects in QED.The ultrastrong coupling regime is difficult to reach in traditional quantum optics, but was recently realized in a solid-stat...

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“…Parametric driving is increasingly used as an experimental tool in diverse contexts, e.g. , in the generation of Floquet topological insulators [8], improved measurement fidelity with squeezed quantum states [9,10] and unconventional phenomena in cavity QED [11].A prime example of a system exhibiting light-matter collective phenomenon is the Dicke model [12]. Here, a bosonic/cavity mode is coupled to a large number of twolevel atoms.…”

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Dynamical many-body phases of the parametrically driven, dissipative Dicke model

Читра

Zilberberg

2015

Phys. Rev. A

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The dissipative Dicke model exhibits a fascinating out-of-equilibrium many-body phase transition as a function of a coupling between a driven photonic cavity and numerous two-level atoms. We study the effect of a time-dependent parametric modulation of this coupling, and discover a rich phase diagram as a function of the modulation strength. We find that in addition to the established normal and super-radiant phases, a new phase with pulsed superradiance which we term dynamical normal phase appears when the system is parametrically driven. Employing different methods, we characterize the different phases and the transitions between them. Specific heed is paid to the role of dissipation in determining the phase boundaries. Our analysis paves the road for the experimental study of dynamically stabilized phases of interacting light and matter.PACS numbers: 42.50. Pq, 05.30.Rt, 32.80.Qk, 42.65.Yj Experimental progress in control and manipulation of light-matter quantum systems has generated a growing interest in many-body phenomena out of equilibrium [1]. Well established examples of such systems include ultracold atomic or ionic quantum gases in high finesse optical cavities [2], semiconductor microcavities in the strong coupling regime [1,3], and superconducting qubits in microwave resonators [4,5]. The engineered interplay between light and matter in these systems has led to the observation of a host of fascinating collective phases and quantum phase transitions including superfluidity in polaritons [6] and the super-radiant Dicke phase transition in a Bose-Einstein condensate (BEC) coupled to an optical cavity [7].A defining feature of many of these systems is that they are inherently driven and subject to dissipation. Driven dissipative systems are usually treated within a rotating frame formalism. This effectively renders the problem time-independent with the important feature that the asymptotic steady states are necessarily out of equilibrium. However, parametric driving of the system often does not allow the usual rotating frame simplifications. Consequently, the resulting interplay between interactions, dissipation, and parametric driving, could lead to novel and exotic steady-state physics that has no counterpart in the undriven case. Parametric driving is increasingly used as an experimental tool in diverse contexts, e.g. , in the generation of Floquet topological insulators [8], improved measurement fidelity with squeezed quantum states [9,10] and unconventional phenomena in cavity QED [11].A prime example of a system exhibiting light-matter collective phenomenon is the Dicke model [12]. Here, a bosonic/cavity mode is coupled to a large number of twolevel atoms. It exhibits a Z 2 symmetry breaking quantum phase transition from a normal phase (NP), where all the atoms are in their ground state and the cavity is empty, to a super-radiant phase (SP), where the atoms are excited and the cavity is in a coherent state. This model has recently been realized by coupling the external degree of freedom of a BE...

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Sub-cycle switch-on of ultrastrong light–matter interaction

Cited by 546 publications

References 26 publications

The spin-Dicke effect in OLED magnetoresistance

The spin-Dicke effect in OLED magnetoresistance

Circuit quantum electrodynamics in the ultrastrong-coupling regime

Dynamical many-body phases of the parametrically driven, dissipative Dicke model

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