We propose a scheme to enhance the light-matter coupling in a cavity QED system where two $\mathrm{\ensuremath{\Lambda}}$ atoms are weakly coupled to a single-mode cavity via multiphoton interaction. By introducing a second-order nonlinear (parametric) driving of the cavity, the original
N-photon exchanges between the atoms, and the cavity can be reduced to either an effective single- or two-photon transition depending on the odevity of
N, with the effective atom-field interaction strength being significantly enhanced. This results in an
N-dependent effective coupling strength on top of the exponential enhancement induced only by the parametric driving. As an example, we demonstrate that our proposal can be exploited for the preparation of high-fidelity steady-state entanglement. The proposed scheme could provide a feasible alternative for diverse applications in quantum technologies.
Cavity quantum electrodynamics (QED) serves as a fundamental platform for studying light-matter interactions at a single-particle level and has been extensively investigated in fundamental physics and quantum information. Recent development of parametrically squeezed techniques has demonstrated that they have the remarkable ability to exponentially enhance coherent atom-cavity coupling. However, the full extent to which these techniques can manipulate quantum optical phenomena requires further exploration. This work systematically investigates the influence of optical parametric amplification on single-photon excited atom-cavity systems within a parametrically driven cavity. In the proposed model, optical parametric amplification converts the driving photons into a squeezed cavity mode, which enhances the atom-cavity interaction into the strong coupling region. Through analytical derivation of atomic and cavity radiation spectra, we demonstrate that the optical parametric amplification induces splitting of atomic radiation spectra while exerting negligible effects on spectral intensity. Conversely, the cavity transmission spectrum exhibits both pronounced splitting and nonlinear intensity amplification. Notably, as driving field intensity approaches a critical intensity regime, the cavity radiation spectrum intensity is significantly enhanced. The underlying mechanism is parametric driving amplification, which converts the driving light into a squeezed cavity mode. When this squeezed mode is mapped back to the fundamental mode of the cavity through Bogoliubov squeezing transformation, the pump photons within the squeezed cavity mode are converted into the photons that contribute to the radiation spectrum of the cavity, thereby amplifying its intensity. This parametric enhancement method not only deepens the basic understanding of light-matter interactions, but also establishes a practical framework for improving the single-photon detection sensitivity in cavity-based quantum systems. These findings have broad prospects for quantum sensing and information processing applications.
We develop an approach for controllable single-photon transport between two remote one-dimensional coupled-cavity arrays, used as quantum registers, mediated by an additional one-dimensional coupled-cavity array, acting as a quantum channel. A single two-level atom located inside one cavity of the intermediate channel is used to control the long-range coherent quantum coupling between two remote registers, thereby functioning as a quantum switch. With a time-independent perturbative treatment, we find that the leakage of quantum information can in principle be made arbitrarily small. Furthermore, our method can be extended to realize a quantum router in multiregister quantum networks, where single-photons can be either stored in one of the registers or transported to another on demand. These results are confirmed by numerical simulations.
Integrating Rydberg-state control of atom-atom interactions with cavity control of atom-light interactions enables the combination of local entangling operations with photon-mediated long-range coupling, measurement, and communication. Such integration is challenging because electric fields generated by charges on cavity optics and by cavity-stabilizing actuators may disturb Rydberg-state coherence. Here, we couple a Rydberg tweezer array to a high-cooperativity optical cavity, suppressing the electric fields produced by cavity length actuation so that the residual field variation of about
3 mV/cm rms does not limit Rydberg coherence. We demonstrate two capabilities that neither system provides alone. First, we use Purcell-enhanced fluorescence to read out atoms directly in the ground-Rydberg basis within
7.5 μs, well within the Rydberg-state lifetime, with ground- and Rydberg-state detection infidelities of
3% and
5%, respectively, and with low atom loss. Second, we use Rydberg-Rydberg interactions to control collective light-atom scattering into the cavity mode. Specifically, we drive blockaded Rabi oscillations between a state with two ground-state atoms, which scatter collectively with a superradiant or subradiant rate controlled by the atomic positions, and an entangled state with a single Rydberg excitation, which scatters like a single atom. These capabilities open routes toward networked Rydberg processors, mid-circuit measurements in analog quantum simulators, and many-body quantum optics with entangled emitters coupled collectively to light.
The quantum nonlinear regime of optomechanics is reached when nonlinear effects of the radiation pressure interaction are observed at the single-photon level. This requires couplings larger than the mechanical frequency and cavity-damping rate, and is difficult to achieve experimentally. Here we show how to exponentially enhance the single-photon optomechanical coupling strength using only additional linear resources. Our method is based on using a large-amplitude, strongly detuned mechanical parametric drive to amplify mechanical zero-point fluctuations and hence enhance the radiation pressure interaction. It has the further benefit of allowing time-dependent control, enabling pulsed schemes. For a two-cavity optomechanical set-up, we show that our scheme generates photon blockade for experimentally accessible parameters, and even makes the production of photonic states with negative Wigner functions possible. We discuss how our method is an example of a more general strategy for enhancing boson-mediated two-particle interactions and nonlinearities.