Auxiliary Resonator Research Articles

Microwave quantum memcapacitor effect

Developing the field of neuromorphic quantum computing necessitates designing scalable quantum memory devices. Here, we propose a superconducting quantum memory device in the microwave regime, termed a microwave quantum memcapacitor. It comprises two linked resonators, the primary one is coupled to a Superconducting Quantum Interference Device, which allows for the modulation of the resonator properties through external magnetic flux. The auxiliary resonator, operated through weak measurements, provides feedback to the primary resonator, ensuring stable memory behavior. This device operates with a classical input in one cavity while reading the response in the other, serving as a fundamental building block toward arrays of microwave quantum memcapacitors. We observe that a bipartite setup can retain its memory behavior and gains entanglement and quantum correlations. Our findings pave the way for the experimental implementation of memcapacitive superconducting quantum devices and memory device arrays for neuromorphic quantum computing.

Selective active resonance tuning for multi-mode nonlinear photonic cavities

Resonant enhancement of nonlinear photonic processes is critical for the scalability of applications such as long-distance entanglement generation. To implement nonlinear resonant enhancement, multiple resonator modes must be individually tuned onto a precise set of process wavelengths, which requires multiple linearly-independent tuning methods. Using coupled auxiliary resonators to indirectly tune modes in a multi-resonant nonlinear cavity is particularly attractive because it allows the extension of a single physical tuning mechanism, such as thermal tuning, to provide the required independent controls. Here we model and simulate the performance and tradeoffs of a coupled-resonator tuning scheme which uses auxiliary resonators to tune specific modes of a multi-resonant nonlinear process. Our analysis determines the tuning bandwidth for steady-state mode field intensity can significantly exceed the inter-cavity coupling rate g if the total quality factor of the auxiliary resonator is higher than the multi-mode main resonator. Consequently, over-coupling a nonlinear resonator mode to improve the maximum efficiency of a frequency conversion process will simultaneously expand the auxiliary resonator tuning bandwidth for that mode, indicating a natural compatibility with this tuning scheme. We apply the model to an existing small-diameter triply-resonant ring resonator design and find that a tuning bandwidth of 136 GHz ≈ 1.1 nm can be attained for a mode in the telecom band while limiting excess scattering losses to a quality factor of 106. Such range would span the distribution of inhomogeneously broadened quantum emitter ensembles as well as resonator fabrication variations, indicating the potential for the auxiliary resonators to enable not only low-loss telecom conversion but also the generation of indistinguishable photons in a quantum network.

-Band Class-B VCO in 22 nm FD-SOI With Inductive Source Degeneration of the Tail Current Source

In this work, a voltage-controlled oscillator (VCO) in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> -band has been introduced that uses the proposed technique named “inductive source degeneration of the tail current source.” The contribution of this work is that the auxiliary resonator is placed differently than the conventional works so that it leads to a more compact solution without affecting the phase noise (PN). Based on the simulation results, for the same device sizes and power consumption, the proposed Class-B method reduces the PN by 1.5 dB than the conventional one at 1 MHz offset from 24 GHz center frequency. VCO has been fabricated on a die area of 0.026 mm2 in the 22 nm fully depleted silicon on insulator (FD-SOI) technology. The measurement was done in the free-running mode, and the results show a PN of −122.4 dBc/Hz at 10 MHz offset from the center frequency of 23.8 GHz. The power consumption of the VCO core is 14.4 mW with 1 V supply voltage. According to the measurement results, this work achieves <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\text {FoM}_{A}}$ </tex-math></inline-formula> , a figure of merit which considers the VCO core area, of −194.2 dBc/Hz at 10 MHz offset from the center frequency, featuring state-of-the-art among the CMOS VCOs in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> -band.

Integral equation analysis of multiport H‐plane microwave circuits by using 2D rectangular cavity Green's functions accelerated by the Ewald Method

An integral equation technique for the analysis of multiport H-plane microwave circuits composed of an unlimited number of arbitrarily shaped metallic and/or dielectric elements is proposed. The structure under study is divided into different regions after the application of the surface equivalence principle. Following this approach, the access waveguide ports are modelled by means of parallel plate Green's functions, whereas the central region is characterised by 2D rectangular cavity Green's functions. The use of this kind of Green's functions represents a novelty for solving H-plane integral equation problems. For the first time, the Ewald method has been employed in order to accelerate the computation of the 2D rectangular cavity Green's functions and their derivatives, needed in the integral equation. In addition, convergence studies show the numerical convenience of using the Ewald method to achieve a fast and accurate evaluation of these Green's functions. Results show that the analysis can be very efficient if the structure is segmented in a proper way based on fitting the cavity resonator within the geometry of the structure under analysis. In fact, all the walls of the structure that are coincident with the auxiliary resonator need not to be discretised during the numerical solution. Finally, several simulation examples of practical inductive microwave circuits are presented and discussed, showing a good agreement and higher computational efficiency when compared to results provided by commercial full-wave software tools and measurements.

Active tuning of dispersive waves in Kerr soliton combs.

Kerr soliton combs operate in the anomalous group-velocity dispersion regime through the excitation of dissipative solitons. The generated bandwidth is largely dependent on the cavity dispersion, with higher-order dispersion contributing to dispersive-wave (DW) generation that allows for power enhancement of the comb lines at the wings of the spectrum. However, the spectral position of the DW is highly sensitive to the overall cavity dispersion, and the inevitable dimension variations that occur during the fabrication process result in deviations in the DW emission wavelength. Here, we demonstrate active tuning of the DW wavelength, enabling post-fabrication spectral shaping of the soliton spectrum. We control the DW position by introducing a wavelength-controllable avoided mode crossing through actively tuning the resonances of a silicon nitride coupled microresonator via integrated heaters. We demonstrate DW tuning over 113 nm with a spectral power that can exceed the peak soliton spectral power. In addition, our modeling reveals buildup and enhancement of the DW in the auxiliary resonator, indicating that the mode hybridization arising from the strong coupling between the two resonators is critical for DW formation.

Coupling-induced microwave transmission transparency with quarter-wavelength superconducting resonators

&lt;sec&gt;The electromagnetic induced transparency (EIT) to atomic systems and its various applications have been extensively investigated, both theoretically and experimentally. In this paper, we study how to similarly verify these phenomena in the waveguide coupled to the transmission line resonators. By making use of real space quantum scattering theory, we calculate the transmission spectrum of the waveguide photons scattered by a single quarter-wavelength transmission line resonator. Our experimental results show that the resonant microwave transporting along the feedline is completely reflected by the resonator. This is similar to the situation of the light absorbed by the resonant atomic medium, and thus its transmission is significantly suppressed.&lt;/sec&gt;&lt;sec&gt;Like the EIT phenomena in atomic gas, wherein the resonant absorption can be significantly suppressed by applying a strong pumping light to control the optical properties of medium, the transport properties of the resonant microwave can be investigated by coupling it into an auxiliary quarter-wavelength resonator in this paper. If the frequency of the auxiliary quarter-wavelength resonator is different from the resonant frequency, the calculated transmission spectrum shows that the coupling with auxiliary quarter-wavelength resonator induces the complete transmission of the resonant microwave. This is one of the features of the EIT-like effect, and can be simply explained as the frequency renormalization of the coupling resonators. Also, by adjusting the coupling strength between the resonators, the width of the microwave transmission spectrum window can be manipulated. Our experimental observations verify such an argument, but the phase shift mutation (another typical signs of the EIT effect) of the resonant microwave cannot be observed. In physics, this is because the interference between the transmitted microwave and the reflected micowave with different frequencies does not take place in the coupling region between the two resonators.&lt;/sec&gt;&lt;sec&gt;It is expected that the effects with the complete EIT-like phenomena can be observed, in future, by fabricating the sample of two quarter-wavelength transmission line resonators with the same frequency, and thus the coupling between the two resonators can be controlled.&lt;/sec&gt;

Single-atom maser with an engineered circuit for population inversion

We present a blueprint for a maser with a single three-level transmon superconducting artificial atom. The system can be pumped coherently via a two-photon process, and to achieve high population inversion, the relaxation rate of the metastable state is increased via an auxiliary low-Q cavity coupled to a transition between the transmon excited states. We show numerically that such a maser can operate both in the intermediate coupling regime with super-Poissonian photon statistics and in the strong coupling regime, where the statistics is sub-Poissonian. For the former, the maser exhibits thresholdless behavior and for the latter, there is a well-defined pumping threshold. A useful side-effect of the auxiliary resonator is that it allows to overcome the photon blockade effect for the pump, which would otherwise prevent high photon population. Finally, we observe the bistability of the steady-state Wigner function and the self-quenching effect for some parameters.

Collective atomic correlations in absorptive optical bistability without adiabatic elimination: Exemplifying nonclassicality from a linearized treatment of fluctuations

We determine the incoherent spectrum, squeezing properties and second-order correlation function of the collective atomic degrees of freedom in absorptive optical bistability. This is accomplished via a linearized Fokker-Planck equation in the positive P representation, guided by the analysis of [H. J. Carmichael, Phys. Rev. A 33, 3262 (1986)] which does not resort to adiabatic elimination. We focus on the regimes of weak and strong intracavity excitation, addressing the good-cavity and bad-cavity limits as well as the limit of collective strong coupling. Adiabatic elimination of the intracavity field sustained by an auxiliary resonator coupled to the ensemble is used to probe the atomic correlations via the formation of a collective emission channel. We compare to the corresponding expressions for the forwards-scattered light with reference to experimental results, discussing key differences between the lower and upper branch of the steady-state semiclassical bistability curve. Our analysis is carried out around the stable states situated far away from the turning points, where analytical expressions can be obtained self-consistently, demonstrating a clear departure from classical behavior.

Detection of emitter-resonator coupling strength in the quantum Rabi model via an auxiliary resonator

In this paper, we propose a theoretical scheme to detect the emitter-resonator coupling strength in the ultra-strong coupling regime in the quantum Rabi model via introducing an auxiliary resonator. We demonstrate the total system as a two-mode Rabi model and obtain the ground state by the transformed rotating wave approximation, which is shown to be superior to the usually applied rotating wave approximation. Here, the coupling strength is detected by monitoring the average excitation number in the auxiliary resonator and the sensitivity of the detection scheme is discussed analytically.

Self-induced light trapping in nonlinear Fabry–Perot resonators

In the framework of the coupled mode theory we consider light trapping between two off-channel resonators which serve as self-adjusted Fano mirrors due to the Kerr effect. By inserting an auxiliary nonlinear resonator between the mirrors we achieve self-tuning of phase shift between the mirrors. That allows for the light trapping for arbitrary distance between the mirrors.

Multiphoton Controllable Transport between Remote Resonators

We develop a novel method for multiphoton controllable transport between remote resonators. Specifically, an auxiliary resonator is used to control the coherent long-range coupling of two spatially separated resonators, mediated by a coupled-resonator chain of arbitrary length. In this manner, an arbitrary multiphoton quantum state can be either transmitted through or reflected off the intermediate chain on demand, with very high fidelity. We find, on using a time-independent perturbative treatment, that quantum information leakage of an arbitrary Fock state is limited by two upper bounds, one for the transmitted case and the other for the reflected case. In principle, the two upper bounds can be made arbitrarily small, which is confirmed by numerical simulations.

Dual V-type resonators to enhance beam quality of Yb:YAG thin-disk lasers.

In this paper, the operating characteristics of a Yb:YAG thin-disk laser using double V-type resonators are reported. The laser maintained stable performance by independently activating either the main or the auxiliary V-type resonator depending on the pumping laser power. Experimental investigations revealed that by reducing the dynamic range in which the main resonator was used for stability and instead employing the auxiliary resonator, the laser beam quality factor M2 could be reduced from 40.2 to 32.3, representing a beam quality enhancement of approximately 20%.

All-optical stabilization of a soliton frequency comb in a crystalline microresonator.

We demonstrate the all-optical stabilization of a low-noise temporal soliton based microresonator based optical frequency comb in a crystalline resonator via a new technique to control the repetition rate. This is accomplished by thermally heating the microresonator with an additional probe laser coupled to an auxiliary optical resonator mode. The carrier-envelope offset frequency is controlled by stabilizing the pump laser frequency to a reference optical frequency comb. We analyze the stabilization by performing an out-of-loop comparison and measure the overlapping Allan deviation. This all-optical stabilization technique can prove useful as an actuator for self-referenced microresonator frequency combs.

Mid-infrared frequency comb generation in coupled silicon microring resonators

We propose and simulate an on-chip mid-IR frequency comb generator based on the four-wave mixing (FWM) effect in a coupled silicon microring resonator. The resonator is formed by suspended ridge waveguides that are designed to have low group-velocity dispersion. A continuous-wave pump laser coupled into the resonator excites other longitudinal modes of the resonator through FWM-based parametric oscillations. In comparison with the device based on a single-ring resonator, we numerically demonstrate that the pump threshold can be dramatically reduced by introducing an auxiliary ring resonator to compensate the phase mismatch between the pump and the generated comb components. The proposed frequency comb generator has a low pump threshold of ~40mW and a high efficiency of ~25% at the pump power of 100mW.

Ultraefficient Cooling of Resonators: Beating Sideband Cooling with Quantum Control

The present state of the art in cooling mechanical resonators is a version of sideband cooling. Here we present a method that uses the same configuration as sideband cooling-coupling the resonator to be cooled to a second microwave (or optical) auxiliary resonator-but will cool significantly colder. This is achieved by varying the strength of the coupling between the two resonators over a time on the order of the period of the mechanical resonator. As part of our analysis, we also obtain a method for fast, high-fidelity quantum information transfer between resonators.

Pulsed CO2laser with a mirror utilizing a four-wave interaction in an amplifying medium

An experimental investigation was made of the radiation parameters of a laser with a mirror based on a four-wave interaction, which was used as the exit reflector. Two four-wave interaction systems were used, one with counterpropagating reference waves inside an auxiliary resonator and the other without reference waves but with a self-intersecting beam that was reflected almost backward by the mirror. The pulse energy of the laser with a four-wave interaction mirror was 1 J and the output radiation had several angular components in the self-intersection plane. It was demonstrated that angular control of the laser beam may be achieved without adjusting the mirrors.

Stabilization of UHF oscillator frequency by use of an auxiliary resonator

The current interest in the frequency stabilization of uhf oscillators is directed toward the implementation of gyrotrons in active plasma diagnostics. Toward this end this paper demonstrates a method which permits consideration in general form of the effect of electron frequency shift on the frequency stability of uhf oscillators using an auxiliary high-Q resonator. The method is used to determine the parameters of a gyrotron model optimized from the viewpoint of frequency stabilization.

Copper vapor laser with a wavefront-reversing mirror induced in the active medium

A study was made of the operation of a copper vapor laser and a resonator with a dynamic wavefront-reversing mirror induced in the active medium by a four-wave interaction with pump waves excited in an auxiliary resonator. Radiation with a diffraction-limit divergence was generated in a resonator with a convex second mirror. The energy, time, and spectral characteristics of lasing were determined.

Computations of Frequencies and Intrinsic Q Factors of TE/sub 0nm/ Modes of Dielectric Resonators (Short Papers)

The Rayleigh-Ritz method is described, which is used to calculate the resonant frequencies and intrinsic Q factors due to dielectric losses of quasi TE/sub onm/ modes of dielectric resonators. Electromagnetic fields of an auxiliary post dielectric resonator are taken as an electrodynamics basis for approximate solutions of this problem. The method provides upper bounds for true resonant frequencies. Numerical results are compared with previously published complementary calculations. The influence of a dielectic substrate on resonant frequencies and intrinsic Q values is demonstrated.

Gyrator video filter IC with automatic tuning

A single-chip gyrator filter for separating the components of the video signal in a TV receiver is described which is suitable for mass production in a standard bipolar process (f/SUB T//spl ap/400 MHz). The 11 mm/SUP 2/ filter chip operates at frequencies up to 10 MHz, requires no tuning or alignment and has Q-factors which are stable with temperature. The IC contains an automatic tuning system which tunes the five resonators of the filter by aligning an auxiliary gyrator resonator with the crystal oscillator present in the color decoder of a TV receiver. Problems of matching the frequencies of the individual gyrator resonators are discussed, showing how alignment accuracy of 0.5 percent can be obtained when resistivities and specific capacitances have production spreads of at least 10 percent. Various gyrator circuit configurations are given which minimize the circuit complexity and, hence, the chip area. Computer aided design techniques for the filter using geometrically scaled models and macromodeling are presented and it is shown how a complete simulation of the chip led to a significant improvement in bandstop performance. Finally, the measured responses are presented and the filter performance is discussed in the light of present-day requirements.