It is demonstrated that a thin-film Fabry-Perot superconducting resonator can be used to reveal the Little-Parks (LP) effect even at temperatures much lower than the critical temperature. A pair of parallel nanowires is incorporated into the resonator at the point of a supercurrent antinode. As magnetic field is ramped, the Meissner current develops, changing the kinetic inductance of the wires and, correspondingly, the resonance frequency of the resonator, which can be detected. The LP oscillation are revealed as a periodic set of distorted parabolas observed in the transmission of the resonator and corresponding to the states of the wire loop having different vorticities. We also report a direct observation of single and double phase slip events and their statistical analysis.
We demonstrate the operation of superconducting coplanar microwave resonators in a very large frequency range up to 50 GHz. The resonators are fabricated from niobium thin films on sapphire substrates and optimized for these high frequencies by small chip sizes. We study numerous harmonics of the resonators at temperatures between 1.5 K and 6 K, and we determine quality factors of up to 25000 at 1.5 K. As an example for spectroscopy applications of such resonators we detect the superconducting transition of a bulk tin sample at multiple probing frequencies.
We report on the on-chip detection of microwaves in the frequency range around 100GHz. For the purpose of detection, we employ a discrete transport channel triggered in a superconducting single-electron transistor by photon-assisted tunneling of quasiparticles. The technique is successfully applied to observe the spectrum of the dressed states of a model cQED system consisting of a superconducting coplanar resonator coupled to a quantum Josephson oscillator. The dressed states appear as typical resonance anticrossing exhibiting, in our case, an expectedly wide frequency splitting corresponding…
The complex dielectric constant $\hatε = ε_1 + i ε_2$ of SrTiO$_3$ reaches high values $ε_1 \approx 2*10^{4}$ at cryogenic temperatures, while the dielectric losses ($ε_2$) are much stronger than for other crystalline dielectrics. SrTiO$_3$ is a common substrate for oxide thin films, like the superconducting LaAlO$_3$/SrTiO$_3$ system, but the large $ε_1$ and $ε_2$ restrict high-frequency quantum devices on SrTiO$_3$. Here we present superconducting coplanar Nb resonators on SrTiO$_3$, which we successfully operate in a distant-flip-chip geometry at frequencies that exceed 1 GHz. We find a pro…
Dielectric measurements on insulating materials at cryogenic temperatures can be challenging, depending on the frequency and temperature ranges of interest. We present a technique to study the dielectric properties of bulk dielectrics at GHz frequencies. A superconducting coplanar Nb resonator is deposited directly on the material of interest, and this resonator is then probed in distant-flip-chip geometry with a microwave feedline on a separate chip. Evaluating several harmonics of the resonator gives access to various probing frequencies, in the present studies up to 20 GHz. We demonstrate t…
Generating entanglement between microwave photons and qubits in multiple cavities coupled by a superconducting qutrit
讨论了如何利用超导量子比特耦合的四个\textrm{microwave}共振器\textrm{(a.k.a. cavities)}产生纠缠相干态。我们还展示了四个超导量子位嵌入四个不同谐振器\textrm{can be created with this scheme}的GHZ态\textrm{that}。原则上，可以扩展\textrm{the proposed method}以创建$n$谐振器的纠缠相干态，并制备分布在量子网络中的$n$腔上的$n$量子位的Greenberger-Horne-Zeilinger（GHZ）态。此外，注意，由耦合器量子比特耦合的四个谐振器可以用作基本电路块以构建二维量子网络，这对于可扩展的量子信息处理是有用的。
We have fabricated planar amorphous Indium Oxide superconducting resonators ($T_c\sim2.8$ K) that are sensitive to frequency-selective radiation in the range of 7 to 10 GHz. Those values lay far below twice the superconducting gap that worths about 200 GHz. The photons detection consists in a shift of the fundamental resonance frequency. We show that the detected frequency can be adjusted by modulating the total length of the superconducting resonator. We attribute those observations to the excitation of higher-order resonance modes. The coupling between the fundamental lumped and the higher o…
A semiconductor transmon with an epitaxial Al shell fully surrounding an InAs nanowire core is investigated in the low $E_J/E_C$ regime. Little-Parks oscillations as a function of flux along the hybrid wire axis are destructive, creating lobes of reentrant superconductivity separated by a metallic state at a half-quantum of applied flux. In the first lobe, phase winding around the shell can induce topological superconductivity in the core. Coherent qubit operation is observed in both the zeroth and first lobes. Splitting of parity bands by coherent single-electron coupling across the junction …
