Multimode Cavity Research Articles

Implementation of universal two- and three-qubit quantum gates in a cavity QED

We propose two schemes to directly implement the iSWAP and Fredkin gates by passing an atom across a multi-mode cavity QED. We have combined three types of qubits: the flying photonic qubits, the atomic qubits and the dual-rail-encoded qubits. First, we have studied the interaction of multi-level atom with multi-mode fields in a cavity by using the shore’s method. Next we have calculated the probabilities of the states of the interest as well as the fidelity of theses two schemes. An appropriate interaction times, allow us to accomplish these two gates.

Ultrasensitive, real-time trace gas detection using a high-power, multimode diode laser and cavity ringdown spectroscopy.

We present a simplified cavity ringdown (CRD) trace gas detection technique that is insensitive to vibration, and capable of extremely sensitive, real-time absorption measurements. A high-power, multimode Fabry-Perot (FP) diode laser with a broad wavelength range (Δλlaser∼0.6 nm) is used to excite a large number of cavity modes, thereby reducing the detector's susceptibility to vibration and making it well suited for field deployment. When detecting molecular species with broad absorption features (Δλabsorption≫Δλlaser), the laser's broad linewidth removes the need for precision wavelength stabilization. The laser's power and broad linewidth allow the use of on-axis cavity alignment, improving the signal-to-noise ratio while maintaining its vibration insensitivity. The use of an FP diode laser has the added advantages of being inexpensive, compact, and insensitive to vibration. The technique was demonstrated using a 1.1W (λ=400 nm) diode laser to measure low concentrations of nitrogen dioxide (NO2) in zero air. A sensitivity of 38 parts in 1012 (ppt) was achieved using an integration time of 128ms; for single-shot detection, 530ppt sensitivity was demonstrated with a measurement time of 60μs, which opens the door to sensitive measurements with extremely high temporal resolution; to the best of our knowledge, these are the highest speed measurements of NO2 concentration using CRD spectroscopy. The reduced susceptibility to vibration was demonstrated by introducing small vibrations into the apparatus and observing that there was no measurable effect on the sensitivity of detection.

Nonthermal Plasma System for Marine Diesel Engine Emission Control

A nonthermal plasma reactor (NTPR) using two 2.45-GHz microwave (MW) generators for the abatement of nitrogen oxides ( ${\text {NO}}_{\text {x}}$ ) and sulfur ( ${\text {SO}}_{\text {x}}$ ) contained in the exhaust gas of a 200-kW marine diesel engine was built and tested. Numerical analysis based on a nonthermal plasma kinetics model for the abatement of ${\text {NO}}_{\text{x}}$ and ${\text{SO}}_{\text{x}}$ from marine diesel engine exhaust gas was performed. A generic kinetic model that implements electron collisions and plasma chemistry has been developed for applications involving low-temperature (50–100 K) nonthermal plasma. Abatement efficiencies of ${\text {NO}}_{\text{x}}$ and ${\text {SO}}_{\text{x}}$ were investigated for a range of mean electron energies, which directly impact on the rate constants of electron collisions. The simulation was conducted using the expected composition of exhaust gas from a typical two-stroke, slow-speed marine diesel engine. The simulation results predict that mean electron energy of 0.25–3.2 eV gives abatement efficiency of 99% for ${\text {NO}}_{\text{x}}$ and ${\text {SO}}_{\text{x}}$ . The minimum residence time required was found to be 80 ns for the mean electron energy of 1 eV. Multimode cavity was designed using COMSOL multiphysics. The NTPR performance in terms of ${\text {NO}}_{\text{x}}$ and ${\text {SO}}_{\text{x}}$ removal was experimentally tested using the exhaust from a 2-kW lab scale, two-stroke diesel engine. The experimental results also show that the complete removal of NO is possible with the MW plasma (yellow color) generated. However, it was found that generating required MW plasma is a challenging task and requires further investigation.

Tunable two-axis spin model and spin squeezing in two cavities**Project supported by the National Natural Science Foundation of China (Grant Nos. 11422433, 11447028, 61227902, 11434007, and 61275211), the Natural Science Foundation of Zhejiang Province, China (Grant No. LY13A040001), and the Scientific Research Foundation of the Education Department of Zhejiang Province, China (Grant No. Y201122352).

Multi-mode cavities have now attracted much attention both experimentally and theoretically. In this paper, inspired by recent experiments of cavity-assisted Raman transitions, we realize a two-axis spin Hamiltonian in two cavities. This realized Hamiltonian has a distinct property that all parameters can be tuned independently. For proper parameters, the well-studied one- and two-axis twisting Hamiltonians are recovered, and the scaling of N−1 of the maximal squeezing factor can occur naturally. On the other hand, in the two-axis twisting Hamiltonian, spin squeezing is usually reduced when increasing the atomic resonant frequency ω0. Surprisingly, we find that by combining with the dimensionless parameter χ (> −1), this atomic resonant frequency ω0 can enhance spin squeezing greatly. These results are beneficial for achieving the required spin squeezing in experiments.

Effect of load on the heating efficiency and temperature uniformity in multi-mode cavity applicators

ABSTRACTIn this paper, we investigate the effect of load size, geometry and properties on microwave heating efficiency and heating uniformity during microwave processing of materials using multi-mode cavity applicators. For this purpose, a numerical technique based on finite element method and implemented using COMSOL Multiphysics package is deployed to compute heating efficiency expressed in terms of power absorbed by the material divided by the input power. Both field variations and resulting temperature evolutions are computed for each size and shape studied. Results show that heating efficiency and temperature uniformity are dependent on the size, the geometry and the properties of the material to be treated and can be controlled to a large extent by just changing these material characteristics without the need of external impedance matching components. The model is experimentally validated and good agreement between the theoretical and experimental results is obtained.

Multiple Fano-Like Transmission Mediated by Multimode Interferences in Spoof Surface Plasmon Cavity-Waveguide Coupling System

Many efforts have been devoted to the design of photonic microcavities and the utilization of them in optical sensing, imaging, optomechanics, lasing, and micromanipulation. Cavities supporting spectrally close multiple resonance modes can favor energy exchange among the modes and the ambient, enabling nontrivial coherent dynamics that are useful in wave manipulation. Coupling between multimode cavities with multiple waveguides is a significant theme for optical, terahertz, and microwave signal control, but remains largely unexplored. Here we present a phenomenological modeling based on the coupled mode theory (CMT) that fully accounts for the interplays between such a cavity and surrounding waveguide structures in a generic situation with asymmetric coupling rates between the guiding channels and the resonant modes. It is shown that the waveguide-cavity couplings are crucial for the energy steering between the modes and their far-field radiation and provide flexible control over waveguide transmission featured with a multiple Fano line profile. Numerical simulations were conducted for a spoof plasmonic cavity waveguides system working at sub-GHz band to demonstrate these effects. The results are in good agreement with the CMT prediction.

54 Gbit/s OOK transmission using single‐mode VCSEL up to 2.2 km MMF

Successful 54 Gbit/s on–off keying (OOK) transmission over 2.2 km of multimode OM4 fibre is demonstrated. The decisive advantages of the single mode over multimode vertical cavity surface emitting laser (VCSEL) in transmission experiments are shown.

Study on stability of electric field in multimode microwave heating cavity

Microwave heating has been widely used and the heating uniformity is related to the characteristics of electric field. In this paper, we investigate the stability of electric field in a multimode microwave cavity by analyzing the spectrum and the condition number of integral equation. Results show that the stability of the electric field is mainly dependent on microwave frequency, the permittivity of heating object and cavity geometrical parameters. Particularly, when the heating object has a low loss factor, the electric field is generally unstable. Namely, a tiny shift of the parameters mentioned above will result in dramatic changes of electric field distribution. Besides, the instability of the electric field increases with the lower loss, the higher microwave frequency or the larger permittivity of the heating object.

Origin and implications of anA2-like contribution in the quantization of circuit-QED systems

By placing an atom into a cavity, the electromagnetic mode structure of the cavity is modified. In Cavity QED, one manifestation of this phenomenon is the appearance of a gauge-dependent diamagnetic term, known as the $A^2$ contribution. Although in atomic Cavity QED, the resulting modification in the eigenmodes is negligible, in recent superconducting circuit realizations, such corrections can be observable and may have qualitative implications. We revisit the canonical quantization procedure of a circuit QED system consisting of a single superconducting transmon qubit coupled to a multimode superconducting microwave resonator. A complete derivation of the quantum Hamiltonian of an open circuit QED system consisting of a transmon qubit coupled to a leaky transmission line cavity is presented. We introduce a complete set of modes that properly conserves the current in the entire structure and present a sum rule for the dipole transition matrix elements of a multi-level transmon qubit coupled to a multi-mode cavity. Finally, an effective multi-mode Rabi model is derived with coefficients that are given in terms of circuit parameters.

Adiabatic passage mediated by plasmons: A route towards a decoherence-free quantum plasmonic platform

We show that the interaction of surface plasmons with quantum emitters can be described by an effective model that has the same structure as a lossy multimode cavity quantum electromagnetic interaction. This allows the coherent manipulation of quantum emitters dressed by surface plasmons at the nanoscale. We show that strong coupling in quantum plasmonics can be used to mediate efficiently the interaction between emitters via a decoherence-free channel, immune to the strong plasmon dissipation. Efficient and robust population transfer, as well as the deterministic generation of entanglement between emitters are numerically shown. These results pave the way for an efficient use of the quantum plasmonic platform beyond its inherent losses.

A Technique for Localized Rapid Soot Oxidation Using Metal Aided Microwave Radiation

The regeneration of soot filter using microwave heating has several drawbacks, which include non-uniform regeneration, ineffective on very small soot thickness, and could lead to excessive heating, which damages the filter that is loaded with high layer of soot. This paper proposes a novel technique for localized rapid heating and oxidation of any thickness of solid soot, and saving of the consumed microwave energy. This technique was applied by inserting a metal in the accumulated soot, located inside a closed multi-mode microwave cavity, attached to a mono-mode waveguide, connected with a magnetron with a capacity of 2.45 GHz and 800 W. The electric field, generated heat, and temperature variation with time till the attaining of the oxidation temperature of the soot during microwave heating were simulated. The simulation methodology is based on the concept of electromagnetic-thermal energy conversion by coupling Maxwell with heat transfer equations. Finite element method was used with frequency domain for electromagnetic analysis and time domain for thermal analysis. In agreement with experimental results, the predicted microwave heating time to attaining the soot ignition/oxidation temperature was reduced from 8.5 to 0.3 seconds. Based on the presented technique, metallic electrodes can be inserted on the soot filter surfaces as local heating electrodes to enhance the microwave heating of the soot filter regeneration.

Half-Mode Substrate-Integrated-Waveguide Cavity-Backed Slot Antenna on Cork Substrate

A wideband half-mode substrate-integrated-waveguide cavity-backed slot antenna covering all Unlicensed National Information Infrastructure (U-NII) radio bands (5.15-5.85 GHz) is designed, fabricated, and validated. By a half-mode implementation of a multimoded cavity with nonresonant slot, a compact ultrawideband antenna is obtained with very stable radiation characteristics, owing to the excellent antenna/platform isolation. Cork material is applied as antenna substrate, making the proposed antenna suitable for integration into floors or walls. In free-space conditions, an impedance bandwidth of 1.30 GHz (23.7%), a radiation efficiency of 85%, a front-to-back ratio of 15.0 dB, and a maximum gain of 4.3 dBi at 5.50 GHz are measured. Performance is also validated when the antenna is deployed on various dielectric or conducting platforms and underneath different dielectric superstrates. Only the latter slightly detunes the antenna's impedance bandwidth. Yet, the complete frequency band of interest remains covered, owing to additional design margins incorporated in the requirements. Its compactness, unobtrusive integration potential, and stable high performance in different environments make this antenna topology an ideal candidate for Internet of Things applications.

Coherent optical propagation properties and ultrahigh resolution mass sensing based on double whispering gallery modes cavity optomechanics

Whispering gallery mode (WGM) cavities due to their high quality factors, small mode volumes, and simple fabrications, have potential applications in photonic devices and ultrasensitive mass sensing. Cavity optomechanic systems based on WGM cavities have progressed enormously in recent years due to the fact that they reveal and explore fundamental quantum physics and pave the way for potential applications of optomechanical devices. However, WGM based cavity optomechanics still lies in a single optical mode coupled to a single mechanical mode. Here in this paper, in order to reveal more quantum phenomena and realize remarkable applications, we present a typical multimode cavity optomechanical system composed of two WGM cavities, of which one WGM cavity is an optomechanical cavity driven by a pump laser and a probe laser and the other cavity is an ordinary WGM cavity only driven with a pump laser. The two WGM cavities are coupled with each other via exchanging energy, and the coupling strength depends on the distance between the two cavities. With the standard method of quantum optics and the quantum Langevin equations, the coherent optical spectra are derived. The coherent optical propagation properties and the phenomenon of optomechanically induced transparency based slow-light effect are demonstrated theoretically via manipulating the coupling strength of the two cavities. The results based on the two-WGM cavity optomechanical system are also compared with those based on the single cavity optomechanical system, and the results indicate that the cavity-cavity coupling plays a key role in the system, which indicates a quantum channel, and influences the width of the transparency window. We further theoretically propose a mass sensor based on the double WGM cavity optomechanical system. To implement mass sensing, the first step is to determine the original frequency of the resonator. With adjusting the detuning parameters and the cavity-cavity coupling strength, a straightforward method to measure the resonance frequency of the WGM optomechanical resonator is proposed. The resonance frequency of the mechanical resonator can be determined from the probe transmission spectrum, and the coupling strength between the two cavities will enhance both the line width and the intensity, which will be beneficial to implementing mass sensing. The mass of external nanoparticles deposited onto the WGM optomechanical cavity can be measured conveniently by tracking the mechanical resonance frequency shifts due to the fact that mass changes in the probe transmission spectrum. Compared with those of single-cavity optomechanical mass sensors, the mass sensitivity and resolution are improved significantly due to the cavity-cavity coupling. This double WGM cavity optomechanical system provides a new platform for exploring the on-chip applications in optical storage and ultrahigh resolution sensing devices.

Nucleation and crystallization of tailing-based glass-ceramics by microwave heating

The effect of microwave radiation on the nucleation and crystallization of tailing-based glass-ceramics was investigated using a 2.45 GHz multimode microwave cavity. Tailing-based glass samples were prepared from Shandong gold tailings and Guyang iron tailings utilizing a conventional glass melting technique. For comparison, the tailing-based glass samples were crystallized using two different heat-treatment methods: conventional heating and hybrid microwave heating. The nucleation and crystallization temperatures were determined by performing a differential thermal analysis of the quenched tailing-based glass. The prepared glass-ceramic samples were further characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, thermal expansion coefficient measurements, and scanning electron microscopy. The results demonstrated that hybrid microwave heating could be successfully used to crystallize the tailing-based glass, reduce the processing time, and decrease the crystallization temperature. Furthermore, the results indicated that the nucleation and crystallization mechanism of the hybrid microwave heating process slightly differs from that of the conventional heating process.

Techno-Economic Comparison of Silicon Photonics and Multimode VCSELs

Recent technical and commercial milestones in Silicon Photonics technology including its introduction into commercial foundries, and successful integration of most optical components, as well as the choice of single mode fiber in some mega data centers have prompted the speculation that Si photonics is the new low cost solution for optical interconnects and that it may replace multi-mode vertical cavity surface emitting lasers (MM VCSEL). We show that the dominant technology has to offer the lowest cost for the single channel transceiver application, which represents 90% of the data center market and which historically dominates sales. We show that Si photonics is currently significantly more expensive than MM VCSEL for single channel, but that it can make a successful entry into the four channel single mode market with significant growth, capturing 20% of the data center market. We discuss the challenges with Si/InP integration; i.e., hybrid lasers for breaking the cost barrier and to enter the market. We show that both MM VCSEL and Si photonics technologies can operate at 50 Gb/s. We discuss the transmission reach limitations of Si photonics and MM VCSEL and show an example of reach extension for 100 Gb/s using MM VCSEL to 300 m of MM fiber. In addition we show that MM VCSEL has fundamentally lower power consumption than Si photonics and is a good candidate for super-computing applications.

Beyond Strong Coupling in a Multimode Cavity

The study of light-matter interaction has seen a resurgence in recent years, stimulated by highly controllable, precise, and modular experiments in cavity quantum electrodynamics (QED). The achievement of strong coupling, where the coupling between a single atom and fundamental cavity mode exceeds the decay rates, was a major milestone that opened the doors to a multitude of new investigations. Here we introduce multimode strong coupling (MMSC), where the coupling is comparable to the free spectral range (FSR) of the cavity, i.e. the rate at which a qubit can absorb a photon from the cavity is comparable to the round trip transit rate of a photon in the cavity. We realize, via the circuit QED architecture, the first experiment accessing the MMSC regime, and report remarkably widespread and structured resonance fluorescence, whose origin extends beyond cavity enhancement of sidebands. Our results capture complex multimode, multiphoton processes, and the emergence of ultranarrow linewidths. Beyond the novel phenomena presented here, MMSC opens a major new direction in the exploration of light-matter interactions.

Theoretical scheme for the realization of the sphere-coherent motional states in an atom-assisted optomechanical cavity

A theoretical scheme for the realization of the sphere-coherent motional states in an optomechanical cavity in the presence of a two-level atom is proposed. To this end, the analogy between an atom-assisted optomechanical cavity and a laser-driven trapped-ion system is used. This analogy provides us with a theoretical tool to show how sphere-coherent states can be generated for the motional degree of freedom of the macroscopic mechanical oscillator from atom-field-mirror interactions in a multi-mode optomechanical cavity. Some nonclassical properties of the generated state of the mechanical oscillator, including the degree of quadrature squeezing and the negativity of the Wigner distribution are studied. We also examine the effects of the dissipation mechanisms involved in the system under consideration, including the atomic spontaneous emission and the damping of the motion of the mechanical oscillator, on the generated motional sphere-coherent states.

Ultra fast microwave-assisted leaching for the recovery of copper and tellurium from copper anode slime

The decomposition of copper anode slime heated by microwave energy in a sulfuric acid medium was investigated. Leaching experiments were carried out in a multi-mode cavity with microwave assistance. The leaching process parameters were optimized using response surface methodology (RSM). Under the optimized conditions, the leaching efficiencies of copper and tellurium were 99.56% ± 0.16% and 98.68% ± 0.12%, respectively. Meanwhile, a conventional leaching experiment was performed in order to evaluate the influence of microwave radiation. The mechanism of microwave-assisted leaching of copper anode slime was also investigated. In the results, the microwave technology is demonstrated to have a great potential to improve the leaching efficiency and reduce the leaching time. The enhanced recoveries of copper and tellurium are believed to result from the presence of a temperature gradient due to the shallow microwave penetration depth and the superheating at the solid-liquid interface.

Numerical investigation of the flat band Bloch modes in a 2D photonic crystal with Dirac cones

A numerical method combining complex-k band calculations and absorbing boundary conditions for Bloch waves is presented. We use this method to study photonic crystals with Dirac cones. We demonstrate that the photonic crystal behaves as a zero-index medium when excited at normal incidence, but that the zero-index behavior is lost at oblique incidence due to excitation of modes on the flat band. We also investigate the formation of monomodal and multimodal cavity resonances inside the photonic crystals, and the physical origins of their different line-shape features.

An adjustable-length cavity and Bose–Einstein condensate apparatus for multimode cavity QED

We present a novel cavity QED system in which a Bose–Einstein condensate (BEC) is trapped within a high-finesse optical cavity whose length may be adjusted to access both single-mode and multimode configurations. We demonstrate the coupling of an atomic ensemble to the cavity in both configurations and measure that the single-atom, -mode cooperativity exceeds unity. The atoms are confined either within an intracavity far-off-resonance optical dipole trap or a crossed optical dipole trap via transversely oriented lasers. Multimode cavity QED provides fully emergent and dynamical optical lattices for intracavity BECs, in that the process of atomic self-organization may be described as a continuous symmetry breaking phase transition resulting in the emergence of a compliant lattice with phonon-like excitations. Such systems will enable explorations of quantum soft matter, including superfluid smectics, superfluid glasses, and spin glasses as well as neuromorphic associative memory.