Deterministic Down-Converter and Continuous Photon-Pair Source within the Bad-Cavity Limit

Multiple-photon bundle emission in the n-photon Jaynes-Cummings model

We study the multiple-photon bundle emission in the n-photon Jaynes-Cummings model composed of a two-level system coupled to a single-mode optical field via the n-photon exciting process. Here, the two-level system is strongly driven by a near-resonant monochromatic field, and hence the system can work in the Mollow regime, in which a super-Rabi oscillation between the zero-photon state and the n-photon state can take place under proper resonant conditions. We calculate the photon number populations and the standard equal-time high-order correlation functions, and find that the multiple-photon bundle emission can occur in this system. The multiple-photon bundle emission is also confirmed by investigating the quantum trajectories of the state populations and both the standard and generalized time-delay second-order correlation functions for multiple-photon bundle. Our work paves the way towards the study of multiple-photon quantum coherent devices, with potential application in quantum information sciences and technologies.

Near-field enhancement of optical second harmonic generation in hybrid gold-lithium niobate nanostructures

Nanophotonics research has focused recently on the ability of nonlinear optical processes to mediate and transform optical signals in a myriad of novel devices, including optical modulators, transducers, color filters, photodetectors, photon sources, and ultrafast optical switches. The inherent weakness of optical nonlinearities at smaller scales has, however, hindered the realization of efficient miniaturized devices, and strategies for enhancing both device efficiencies and synthesis throughput via nanoengineering remain limited. Here, we demonstrate a novel mechanism by which second harmonic generation, a prototypical nonlinear optical phenomenon, from individual lithium niobate particles can be significantly enhanced through nonradiative coupling to the localized surface plasmon resonances of embedded gold nanoparticles. A joint experimental and theoretical investigation of single mesoporous lithium niobate particles coated with a dispersed layer of ~10 nm diameter gold nanoparticles shows that a ~32-fold enhancement of second harmonic generation can be achieved without introducing finely tailored radiative nanoantennas to mediate photon transfer to or from the nonlinear material. This work highlights the limitations of current strategies for enhancing nonlinear optical phenomena and proposes a route through which a new class of subwavelength nonlinear optical platforms can be designed to maximize nonlinear efficiencies through near-field energy exchange.

Quantum switching between nonclassical correlated single photons and two-photon bundles in a two-photon Jaynes-Cummings model

We propose a scheme to realize a two-photon Jaynes-Cummings model for a single atom inside an optical cavity. It is shown that the interplay of a laser detuning and atom (cavity) pump (driven) field gives rise to the strong single photon blockade, two-photon bundles, and photon-induced tunneling. With the cavity driven field, strong photon blockade occurs in the weak coupling regime, and switching between single photon blockade and photon-induced tunneling at two-photon resonance are achievable via increasing the driven strength. By turning on the atom pump field, quantum switching between two-photon bundles and photon-induced tunneling at four-photon resonance are realized. More interestingly, the high-quality quantum switching between single photon blockade, two-photon bundles, and photon-induced tunneling at three-photon resonance is achieved with combining the atom pump and cavity driven fields simultaneously. In contrast to the standard two-level Jaynes-Cummings model, our scheme with generating a two-photon (multi-photon) Jaynes-Cummings model reveals a prominent strategy to engineer a series of special nonclassical quantum states, which may pave the way for investigating basic quantum devices to implement in quantum information processing and quantum networks.

Antibunched single-photon/photon-pair emission with coupled Jaynes-Cummings model

Herein, we propose a coupled Jaynes-Cummings model for the preparation of strong antibunched single photons and antibunched correlated photon pairs. Using the effective Hamiltonian method, we obtained the expression for the correlation function and then presented the optimal conditions for conventional/unconventional photon blockade. The results showed that on one hand, an intersection point exists between conventional photon blockade and unconventional photon blockade and that the performance of the single photon at the intersection point is better. On the other hand, under the condition of unconventional photon blockade, the photons produced by each Jaynes-Cummings system are strongly correlated with each other.

Parity-Symmetry-Protected Multiphoton Bundle Emission

We demonstrate symmetry protected multiphoton bundle emission in the cavity QED system under the ultrastrong coupling regime. Our proposal only enables the super-Rabi oscillations with periodic generation of even correlated photons in the cavity, which is realized by combining the laser driven flip of qubit and the symmetry conserved transitions induced by Rabi interaction with parity symmetry. Combined with dissipation, only 2n-photon bundle emissions are allowed, due to the almost perfect suppression of bundle emissions with odd correlated photons. Meanwhile, the corresponding purities are significantly enhanced by the parity symmetry. This work extends multiphoton bundle emission to the ultrastrong coupling regime, and offers the prospect of exploring symmetry-protected multiphoton physics.

Quantum Non-Gaussian Photon Coincidences

Photon coincidences represent an important resource for quantum technologies. They expose nonlinear quantum processes in matter and are essential for sources of entanglement. We derive broadly applicable criteria for quantum non-Gaussian two-photon coincidences that certify a new quality of photon sources. The criteria reject states emerging from Gaussian parametric processes, which often limit applications in quantum technologies. We also analyze the robustness of the quantum non-Gaussian coincidences and compare it to the heralded quantum non-Gaussianity of single photons based on them.

Bright Sub-Poissonian Light through Intrinsic Feedback and External Control

Balancing nonlinear gain and loss automatically generates sub-Poissonian light, through negative feedback, when the gain is significantly reduced (increased) by the addition (subtraction) of a single photon. We show that micromaser trapping states can provide the necessary feedback in the presence of photon loss and, with the addition of external parametric control, realize a photon number on the order of 100 and a Mandel Q parameter of -0.998, i.e., number squeezing of 27 dB.

N-Phonon Bundle Emission via the Stokes Process

We demonstrate theoretically the bundle emission of n strongly correlated phonons in an acoustic cavity QED system. The mechanism relies on Stokes resonances that generate super-Rabi oscillations between states with a large difference in their number of excitations, which, combined with dissipation, transfer coherently pure n-phonon states outside of the cavity. This process works with close to perfect purity over a wide range of parameters and is tunable optically with well-resolved operation conditions. This broadens the realm of quantum phononics, with potential applications for on-chip quantum information processing, quantum metrology, and engineering of new types of quantum devices, such as optically heralded n-phonon guns.