Superconducting Stripline Resonators Research Articles

Superconducting stripline resonators at frequencies up to 50 GHz for microwave spectroscopy applications

Planar superconducting microwave resonators are commonly operated for various cryogenic applications, typically at frequencies between 2 and 15 GHz. But for certain applications, e.g. microwave spectroscopy to study the dynamics of charges and spins in solids, a wider spectral range is desired. Driving such microwave resonators at higher frequencies is challenging due to enhanced losses and reduced wavelength. Here we present superconducting stripline resonators operating at multiple frequencies as high as 50 GHz. These resonators are fabricated of Pb and can easily be adjusted to particular applications, including mK temperatures in a dilution refrigerator. Demonstrating such a resonator as a spectroscopic tool, we detect the superconducting transition of a Sn sample in a wide spectral range.

Microwave study of superconducting Sn films above and below percolation

The electronic properties of superconducting Sn films () change significantly when reducing the film thickness down to a few , in particular close to the percolation threshold. The low-energy electrodynamics of such Sn samples can be probed via microwave spectroscopy, e.g. with superconducting stripline resonators. Here we study Sn thin films, deposited via thermal evaporation—ranging in thickness between 38 and —which encompasses the percolation transition. We use superconducting Pb stripline resonators to probe the microwave response of these Sn films in a frequency range between 4 and at temperatures from down to . The measured quality factor of the resonators decreases with rising temperature due to enhanced losses. As a function of the sample thickness we observe three regimes with significantly different properties: samples below percolation, i.e. ensembles of disconnected superconducting islands, exhibit dielectric properties with negligible losses, demonstrating that macroscopic current paths are required for appreciable dynamical conductivity of Sn at GHz frequencies. Thick Sn films, as the other limit, lead to low-loss resonances both above and below Tc of Sn, as expected for bulk conductors. But in an intermediate thickness regime, just above percolation and with labyrinth-like morphology of the Sn, we observe a quite different behavior: the superconducting state has a microwave response similar to the thicker, completely covering films with low microwave losses; but the metallic state of these Sn films is so lossy that resonator operation is suppressed completely.

Signatures of Phase Transitions in the Microwave Response of YbRh2Si2

We used a spectroscopic microwave technique utilizing superconducting stripline resonators at frequencies between 3GHz and 15GHz to examine the charge dynamics of YbRh2Si2 at temperatures and magnetic fields close to the quantum critical point. The different electronic phases of this heavy-fermion compound, in particular the antiferromagnetic, Fermi-liquid, and non-Fermi-liquid regimes, were probed with temperature-dependent microwave measurements between 40 mK and 600 mK at a set of different magnetic fields up to 140 mT. Signatures of phase transitions were observed, which give information about the dynamic response of this peculiar material that exhibits field-tuned quantum criticality and pronounced deviations from Fermi-liquid theory.

Niobium stripline resonators for microwave studies on superconductors

Microwave spectroscopy is a powerful experimental tool to reveal information on the intrinsic properties of superconductors. Superconducting stripline resonators, where the material under study constitutes one of the ground planes, offer a high sensitivity to investigate superconducting bulk samples. In order to improve this measurement technique, we have studied stripline resonators made of niobium, and we compare the results to lead stripline resonators. With this technique we are able to determine the temperature dependence of the complex conductivity of niobium and the energy gap Δ(0) = 2.1 meV. Finally we show measurements at the superconducting transition of a tantalum bulk sample using niobium stripline resonators.

Surface-resistance measurements using superconducting stripline resonators

We present a method to measure the absolute surface resistance of conductive samples at a set of GHz frequencies with superconducting lead stripline resonators at temperatures 1-6 K. The stripline structure can easily be applied for bulk samples and allows direct calculation of the surface resistance without the requirement of additional calibration measurements or sample reference points. We further describe a correction method to reduce experimental background on high-Q resonance modes by exploiting TEM-properties of the external cabling. We then show applications of this method to the reference materials gold, tantalum, and tin, which include the anomalous skin effect and conventional superconductivity. Furthermore, we extract the complex optical conductivity for an all-lead stripline resonator to find a coherence peak and the superconducting gap of lead.

Efficient protocol of $$N$$ N -bit discrete quantum Fourier transform via transmon qubits coupled to a resonator

Based on the one- and two-qubit gates defined and generated via superconducting transmon qubits homogeneously coupled to a superconducting stripline resonator, we present a new physical protocol for implementing an $$N$$N-bit discrete quantum Fourier transform. We propose and illustrate a detailed experimental feasibility for realizing the algorithm. The average fidelity is computed to prove the success of this algorithm. Estimated time for implementing the protocol using the proposed scheme is compared with previous schemes. Estimates show that the protocol can be successfully implemented within the present experimental limits.

Simple scheme for multiqubit quantum controlled phase-flip gate with singlet-triplet spin qubits in nanowire double quantum dots

Abstract We propose an alternative scheme for one-step implementing three-qubit controlled phase-flip gate of spin qubits in spatially separated double quantum dots with a superconducting stripline resonator (SSR). Due to the switchable coupling effect between the double quantum dots and SSR, the present scheme could be easily generalized for multi-qubits. The feasibility of the present scheme is characterized by exact numerical simulations that incorporate various sources of experimental noise. Our results show the possibility to realize this proposed scheme within current experimental technologies.

Quantum phase transition of light in a one-dimensional photon-hopping-controllable resonator array

We give a concrete experimental scheme for engineering the insulator-superfluid transition of light in a one-dimensional (1-D) array of coupled superconducting stripline resonators. In our proposed architecture, the on-site interaction and the photon hopping rate can be tuned independently by adjusting the transition frequencies of the charge qubits inside the resonators and at the resonator junctions, respectively, which permits us to systematically study the quantum phase transition of light in a complete parameter space. By combining the techniques of photon-number-dependent qubit transition and fast read-out of the qubit state using a separate low-Q resonator mode, the statistical property of the excitations in each resonator can be obtained with a high efficiency. An analysis of the various decoherence sources and disorders shows that our scheme can serve as a guide to coming experiments involving a small number of coupled resonators.

Engineering two-mode squeezed states of cold atomic clouds with a superconducting stripline resonator

A scheme is proposed for engineering two-mode squeezed states of two separated cold atomic clouds positioned near the surface of a superconducting stripline resonator. Based on the coherent magnetic coupling between the atomic spins and a stripline resonator mode, the desired two-mode squeezed state can be produced via precisely control on the dynamics of the system. This scheme may be used to realize scalable on-chip quantum networks with cold atoms coupling to stripline resonators.

Bose–Hubbard dynamics of polaritons in a chain of circuit quantum electrodynamics cavities

We investigate a chain of superconducting stripline resonators, each interacting with a transmon qubit, that are capacitively coupled in a row. We show that the dynamics of this system can be described by a Bose–Hubbard Hamiltonian with attractive interactions for polaritons, superpositions of photons and qubit excitations. This setup, we envisage, is one of the first platforms where all the technological components that are needed to experimentally study chains of strongly interacting polaritons have already been realized. By driving the first stripline resonator with a microwave source and detecting the output field of the last stripline resonator, one can spectroscopically probe the properties of the system in the driven dissipative regime. We calculate the stationary polariton density and density–density correlations g(2) for the last cavity, which can be measured via the output field. Our results display a transition from a coherent to a quantum field as the ratio of on-site interactions to driving strength is increased.

Intermode dephasing in a superconducting stripline resonator

Supplementary information for the article "Intermode Dephasing in a Superconducting Stripline Resonator" (arXiv:0901.3110). The supplementary information is devoted to three main issues. In section I we describe the fabrication process; in section II we present the derivation of the Hamiltonian of the system and provide a more detailed discussion about the properties of the microbridges; in section III the hysteretic response of the resonator and the effect of heating are discussed.

Self-oscillations in a superconducting stripline resonator integrated with a dc superconducting quantum interference device

We study self-sustained oscillations in a Nb superconducting stripline resonator integrated with a dc superconducting quantum interference device (SQUID). We find that both the power threshold where these oscillations start and the oscillation frequency are periodic in the applied magnetic flux threading the SQUID loop. A theoretical model which attributes the self-sustained oscillations to a thermal instability in the dc-SQUID yields a good agreement with the experimental results. This flux dependant nonlinearity may be used for quantum state reading of a qubit-superconducting resonator integrated device.

Stochastic resonance with a single metastable state: Thermal instability in NbN superconducting stripline resonators

We study thermal instability in NbN superconducting stripline resonators. The system exhibits extreme nonlinearity near a bifurcation, which separates a monostable zone and an astable one. The lifetime of the metastable state, which is locally stable in the monostable zone, is measure near the bifurcation and the results are compared with a theory. Near bifurcation, where the lifetime becomes relatively short, the system exhibits strong amplification of a weak input modulation signal. We find that the frequency bandwidth of this amplification mechanism is limited by the rate of thermal relaxation. When the frequency of the input modulation signal becomes comparable or larger than this rate the response of the system exhibits sub-harmonics of various orders.

Signal amplification in NbN superconducting resonators via stochastic resonance

We exploit nonlinearity in NbN superconducting stripline resonators, which originates from local thermal instability, for studying stochastic resonance. As the resonators are driven into instability, small amplitude modulation (AM) signals are amplified with the aid of injected white noise. Simulation results based on the equations of motion for the system yield a good agreement with the experimental data both in the frequency and time domains.

Utilizing Nonlinearity in a Superconducting NbN Stripline Resonator for Radiation Detection

We study a microwave superconducting stripline resonator made of NbN on a sapphire substrate. A radiation detector (RD) having a thin meander shape is integrated into the resonator. We harness an extremely strong nonlinear instability occurring in the device in order to enhance its sensitivity to infrared radiation impinging on the RD. Characterization measurements yield a noise equivalent power of 34 fW/radicHz at a modulation frequency of 7.74 GHz. Such a device may be exploited for fast and sensitive radiation detection.

Prospects of employing superconducting stripline resonators for studying the dynamical Casimir effect experimentally

We discuss the prospects of employing an NbN superconducting microwave stripline resonator for studying the dynamical Casimir effect experimentally. Preliminary experiments, in which optical illumination is employed for modulating the resonance frequencies of the resonator, show that such a system is highly promising for this purpose. In addition, we discuss the undesirable effect of heating which results from the optical illumination, and show that degradation in noise properties can be minimized by employing an appropriate design.

Extreme nonlinear phenomena in NbN superconducting stripline resonators

We study giant nonlinear phenomena that emerge near a bifurcation threshold (BT) in a microwave superconducting stripline resonator. Above the BT the system becomes astable and self-sustained modulation of the reflected power off the resonator occurs. The giant nonlinearity manifests itself in an extremely high intermodulation gain, accompanied by a very strong noise squeezing and period doubling of various orders.

Bridge between two lengthscales

A 'real life' quantum computer requires well-protected qubits, as available in quantum optical systems, and scalability, usually the domain of solid-state devices. Polar molecules integrated with superconducting stripline resonators might offer the best of both worlds.

Fast Resonance Frequency Optical Modulation in Superconducting Stripline Resonator

Fast resonance frequency optical modulation of a superconducting stripline resonator is investigated. The experiments are performed using a novel device which integrates a hot electron detector (HED) into a superconducting stripline ring resonator. Frequency modulation is demonstrated by both applying dc current or voltage to the HED, and by applying optical illumination, with modulation frequencies of up to 4.2 GHz. Potential applications for such a device are in telecommunication, quantum cryptography, and biofluorescence

Dephasing due to intermode coupling in superconducting stripline resonators

The nonlinearity exhibited by the kinetic inductance of a superconducting stripline couples stripline resonator modes together in a manner suitable for quantum non-demolition measurement of the number of photons in a given resonator mode. Quantum non-demolition measurement is accomplished by coherently driving another resonator mode, referred to as the detector mode, and measuring its response. We show that the sensitivity of such a detection scheme is directly related to the dephasing rate induced by such an intermode coupling. We show that high sensitivity is expected when the detector mode is driven into the nonlinear regime and operated close to a point where critical slowing down occurs.