Investigation of the spin-cavity polaritons (SCP) is important since they play decisive role for the creating long-storage quantum memories and optical interfaces, polaritonic chemistry and for the elaborating of masers, especially those which operate at room temperature being of the great significance for a lot of different applications. In this report, we suggest almost completely classical model for the description of the polaritonic peaks conditioned both by free and forced Rabi oscillations of the SCP system. Our investigation is based on the linearized coupled differential equations we derived semi-classically for the magnetization component of the transition of the spin triplet states and the varying field in a cavity, when the empty cavity is exactly tuned to the transition. The normal frequencies of this system of equations were found and the corresponding graphs were constructed for the appropriate values of the parameters. It is shown that the increase of the spin-photon coupling can cause both pushing apart normal frequencies at a mutual decay rate (which is the known effect), and merging together normal decay rates at a mutual frequency (which is the predicted here effect). Polariton peaks observable by the cavity transmission function and by electron paramagnetic resonance (EPR) in the form of absorption and dispersion signals were also investigated and corresponding graphs were constructed. At that, instead of a transition of spin triplet states, a variety of other two-level systems (atoms, molecules, excitons and so on) can act as emitters. Since the value of the spin-photon coupling is of great interest for applied scientists, obtaining this value by comparing our results with experimental data is of great importance.
Investigation of the spin-cavity polaritons (SCP) is important since they play decisive role for the creating long-storage quantum memories and optical interfaces, polaritonic chemistry and for the elaborating of masers, especially those which operate at room temperature being of the great significance for a lot of different applications. In this report, we suggest almost completely classical model for the description of the polaritonic peaks conditioned both by free and forced Rabi oscillations of the SCP system. Our investigation is based on the linearized coupled differential equations we derived semi-classically for the magnetization component of the transition of the spin triplet states and the varying field in a cavity, when the empty cavity is exactly tuned to the transition. The normal frequencies of this system of equations were found and the corresponding graphs were constructed for the appropriate values of the parameters. It is shown that the increase of the spin-photon coupling can cause both pushing apart normal frequencies at a mutual decay rate (which is the known effect), and merging together normal decay rates at a mutual frequency (which is the predicted here effect). Polariton peaks observable by the cavity transmission function and by electron paramagnetic resonance (EPR) in the form of absorption and dispersion signals were also investigated and corresponding graphs were constructed. At that, instead of a transition of spin triplet states, a variety of other two-level systems (atoms, molecules, excitons and so on) can act as emitters. Since the value of the spin-photon coupling is of great interest for applied scientists, obtaining this value by comparing our results with experimental data is of great importance.
Investigation of the spin-cavity polaritons (SCP) is important since they play a decisive role in creating long-storage quantum memories and optical interfaces, polaritonic chemistry, and masers, especially those which operate at room temperature, being of great significance for a lot of different applications. In this report, we suggest an almost completely classical model for the description of the polaritonic peaks conditioned both by free and forced Rabi oscillations of the SCP system. Our investigation is based on the linearized coupled differential equations we derived semi-classically for the magnetization component of the transition of the spin triplet states and the varying field in a cavity when the empty cavity is exactly tuned to the transition. The normal frequencies of this system of equations were found, and the corresponding graphs were constructed for the appropriate values of the parameters. It is shown that the increase in the spin-photon coupling can cause both the pushing apart of normal frequencies at a mutual decay rate (which is the known effect) and the merging together of normal decay rates at a mutual frequency (which is the predicted effect here). Polariton peaks, observable by the cavity transmission function and by EPR in the form of absorption and dispersion signals, were also investigated, and corresponding graphs were constructed. At that, instead of a transition of spin triplet states, a variety of other two-level systems (atoms, molecules, excitons, and so on) can act as emitters. Since the value of the spin-photon coupling is of great interest for applied scientists, obtaining this value by comparing our results with experimental data is of great importance.
The emerging field of cavity spintronics utilizes the cavity magnon polariton (CMP) induced by magnon Rabi oscillations. In contrast to a single-spin quantum system, such a cooperative spin dynamics in the linear regime is governed by the classical physics of harmonic oscillators. It makes the magnon Rabi frequency independent of the photon Fock state occupation, and thereby restricts the quantum application of CMP. Here we show that a feedback cavity architecture breaks the harmonic-oscillator restriction. By increasing the feedback photon number, we observe an increase in the Rabi frequency, accompanied with the evolution of CMP to a cavity magnon triplet and a cavity magnon quintuplet. We present a theory that explains these features. Our results reveal the physics of cooperative polariton dynamics in feedback-coupled cavities, and open up new avenues for exploiting the light-matter interactions.
Abstract The strong coupling regime is essential for efficient transfer of excitations between states in different quantum systems on timescales shorter than their lifetimes. The coupling of single spins to microwave photons is very weak but can be enhanced by increasing the local density of states by reducing the magnetic mode volume of the cavity. In practice, it is difficult to achieve both small cavity mode volume and low cavity decay rate, so superconducting metals are often employed at cryogenic temperatures. For an ensembles of N spins, the spin–photon coupling can be enhanced by N N through collective spin excitations known as Dicke states. For sufficiently large N the collective spin–photon coupling can exceed both the spin decoherence and cavity decay rates, making the strong-coupling regime accessible. Here we demonstrate strong coupling and cavity quantum electrodynamics in a solid-state system at room-temperature. We generate an inverted spin-ensemble with N ~ 1015 by photo-exciting pentacene molecules into spin-triplet states with spin dephasing time T2∗∼3 T 2 * ~ 3 μs. When coupled to a 1.45 GHz TE01δ mode supported by a high Purcell factor strontium titanate dielectric cavity ( Vm∼0.25 V m ~ 0.25 cm3, Q ~ 8,500), we observe Rabi oscillations in the microwave emission from collective Dicke states and a 1.8 MHz normal-mode splitting of the resultant collective spin–photon polariton. We also observe a cavity protection effect at the onset of the strong-coupling regime which decreases the polariton decay rate as the collective coupling increases.
The ability to establish coherent communication channels is key for scaling up quantum devices. Here, we engineer interactions between distant polaritons, hybrid spin-photon excitations formed at different lumped-element superconducting resonators within a chip. The chip consists of several resonator pairs, slightly detuned in frequency to make them addressable, capacitively coupled within each pair and inductively coupled to a common readout line. They interact locally with samples of PTMr and Tripak− organic free radicals, deposited onto their inductors, which provide model S=1/2, g≃2 spin ensembles. Frequency-dependent microwave transmission experiments, performed at very low temperatures, measure polariton frequencies as a function of magnetic field in different scenarios. When only one resonator within a pair hosts a molecular sample, the results evidence that spins couple remotely to the empty LER as well as to the local cavity mode. If both resonators interact with a spin ensemble, the magnetic field tunes the polariton frequencies relative to each other, on account of the different spin-photon interactions at each LER. When polaritons are brought into mutual resonance, an avoided level crossing emerges that gives direct spectroscopic evidence for a coherent polariton-polariton interaction mediated by the circuit. Pump-probe experiments reveal that the excitation of a polariton within a connected pair is felt, thus it can be read out, by the other one. These observations, backed by model calculations, illustrate the control and detection of distant photon-photon and spin-spin correlations and entanglement in a scalable modular chip.
We study the energy level structure of the Tavis-Cumming model applied to an ensemble of independent magnetic spins s=1/2 coupled to a variable number of photons. Rabi splittings are calculated and their distribution is analyzed as a function of photon number nmax and spin system size N. A sharp transition in the distribution of the Rabi frequency is found at ${n}_{\text{max}}\ensuremath{\approx}N$. The width of the Rabi frequency spectrum diverges as N at this point. For increased number of photons nmax>N, the Rabi frequencies converge to a value proportional to nmax. This behavior is interpreted as analogous to the classical spin-resonance mechanism where the photon is treated as a classical field and one resonance peak is expected. We also present experimental data demonstrating cooperative, magnetic strong coupling between a spin system and photons, measured at room temperature. This points toward quantum computing implementation with magnetic spins, using cavity quantum-electrodynamics techniques.
The polarization dependence of nonequilibrium transitions in a multistable cavity-polariton system is studied under nanosecond-long resonant optical excitation at normal and magic angle incidences with various polarizations of the pump beam. The temporal correlations between the frequency, intensity, and optical polarization of the intracavity field, which all undergo sharp threshold-like changes due to the spin-dependent interaction of cavity polaritons, are visualized. The observed dynamics cannot be reproduced within the conventional semiclassical model based on the Gross-Pitaevskii equations. To explain the observed phenomena, it is necessary to take into account the unpolarized exciton reservoir that brings on an additional blue shift of bright excitons, the same for the ${\ensuremath{\sigma}}^{+}$ and ${\ensuremath{\sigma}}^{\ensuremath{-}}$ polarization components. This model explains the effect of polarization instability under both pulsed- and continuous-wave resonant excitation conditions, consistently with the spin ring pattern formation that has recently been observed under Gaussian-shaped excitation.