Experiments to probe the basic quantum properties of motional degrees of freedom of mechanical systems have developed rapidly over the last decade. One promising approach is to use hybrid electromechanical systems incorporating superconducting qubits and microwave circuitry. However, a critical challenge facing the development of these systems is to achieve strong coupling between mechanics and qubits while simultaneously reducing coupling of both the qubit and mechanical mode to the environment. Here we report measurements of a qubit-coupled mechanical resonator system consisting of an ultra-high-frequency nanoresonator and a long coherence-time superconducting transmon qubit, embedded in a superconducting coplanar waveguide cavity. It is demonstrated that the nanoresonator and transmon have commensurate energies and transmon coherence times are one order of magnitude larger than for all previously reported qubit-coupled nanoresonators. Moreover, we show that numerical simulations of this new hybrid quantum system are in good agreement with spectroscopic measurements and suggest that the nanoresonator in our device resides at low thermal occupation number, near its ground state, acting as a dissipative bath seen by the qubit. We also outline how this system could soon be developed as a platform for implementing more advanced experiments with direct relevance to quantum information processing and quantum thermodynamics, including the study of nanoresonator quantum noise properties, reservoir engineering, and nanomechanical quantum state generation and detection.

Molybdenum oxide thin films find diverse applications as catalysts, gas sensors, and electrochromic devices. Such films are produced mainly by reactive sputtering and thermal evaporation but other techniques such as chemical vapor deposition and electrochemical deposition have been used. In the present work, the feasibility of an alternative method for the production of molybdenum oxide films using a molybdenum filament heated in a rarefied oxygen atmosphere is demonstrated. The filament heating current, I F , and the oxygen flow rate, F O 2 , are the key deposition parameters and their effect on the deposition rate, R, was investigated. For I F ) 12.5 A, an increase in the R-value from 7.5 to 31 nm/min was observed as F O 2 was increased from 6.0 to 21 sccm. To characterize the chemical bonds, infrared spectroscopy, using both unpolarized and p-polarized infrared beams, and X-ray photoelectron spectroscopy (XPS) were employed. Line shape analysis of the Mo(3d) XPS peak revealed that the Mo atoms were in mixed valence states, Mo 6+ and Mo 5+ , with a high predominance of the former over the latter, thus indicating an oxygen-deficient MoO 3 film. From Rutherford backscattering spectroscopic analysis of the films, an average O/Mo atomic ratio of 2.9 was calculated, consistent with the XPS results. A combination of the XPS and RBS results and the data of other investigators on the oxidation of molybdenum suggests that the film is formed from MoO 2 and MoO 3 species desorbed from the Mo filament. The optical gap, E g , was determined from transmission UV-visible spectra of the films. An average E g value of 3.03 eV was found. The electrochromic properties of the films were investigated for Li + intercalation using an electrochemical cell. A coloration efficiency of 19.5 cm 2 /C at a wavelength of 700 nm was observed.

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Superconducting metamaterials are a promising resource for quantum information science. In the context of circuit QED, they provide a means to engineer on-chip, novel dispersion relations and a band structure that could ultimately be utilized for generating complex entangled states of quantum circuitry, for quantum reservoir engineering, and as an element for quantum simulation architectures.Here we report on the development and measurement at millikelvin temperatures of a particular type of circuit metamaterial resonator composed of planar superconducting lumped-element reactances in the form of a discrete left-handed transmission line (LHTL) that is compatible with circuit QED architectures. We discuss the details of the design, fabrication, and circuit properties of this system. As well, we provide an extensive characterization of the dense mode spectrum in these metamaterial resonators, which we conducted using both microwave transmission measurements and laser scanning microscopy (LSM). Results are observed to be in good quantitative agreement with numerical simulations and also an analytical model based upon current-voltage relationships for a discrete transmission line. In particular, we demonstrate that the metamaterial mode frequencies, spatial profiles of current and charge densities, and damping due to external loading can be readily modeled and understood, making this system a promising tool for future use in quantum circuit applications and for studies of complex quantum systems.

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We present the design of a reflective stop-band filter based on quasi-lumped elements that can be utilized to introduce large dc and low-frequency voltage biases into a low-loss superconducting coplanar waveguide (CPW) cavity. Transmission measurements of the filter are seen to be in good agreement with simulations and demonstrate insertion losses greater than 20 dB in the range of 3 to 10 GHz. Moreover, transmission measurements of the CPW's fundamental mode demonstrate that loaded quality factors exceeding 10 5 can be achieved with this design for dc voltages as large as 20 V and for the cavity operated in the single-photon regime. This makes the design suitable for use in a number of applications including qubit-coupled mechanical systems and circuit QED.The integration of bias circuitry into high-quality (lowloss) microwave cavities for controlling embedded components is an important technical issue for a range of topics that includes research with qubit-and cavity-coupled mechanical systems,[1-10] circuit QED, [11,12] and quantum dynamics of nonlinear systems. [13,14] In these scenarios, the applied potentials and currents serve a variety of functions such as maintaining a device's operating state or establishing tunable electrostatic interactions between devices. However, if not carefully engineered, the introduction of the requisite circuitry can degrade the quality of a cavity through increased external circuit loading and radiative losses,[15] which generally have a detrimental effect on the given application.In recent years, several solutions to this problem have been developed for dc biasing of superconducting coplanar waveguide (CPW) cavities. These cavities play an important role in the applications mentioned above due to their large electric field density [16,17] and high intrinsic quality factors ( 10 6 ).[18] The solutions put forth for biasing such cavities utilize either half-wavelength or quarter-wavelength traces for band-stop filtering or highimpedance isolation of the bias circuitry's connections to the cavities. [19,20] This has enabled operation of biased CPWs with loaded quality factors in the range of 10 3 -10 4 for several applications. [12,14,19,21] However, the reliance on wavelength-specific isolation geometries results in a narrow band of controlled isolation around a specific operating frequency, which could be problematic in instances where multiple devices with different or tunable energy scales are integrated into the cavity and thus require broadband isolation. Important examples of this include proposed techniques for the dispersive read-out of a qubit-coupled nanoresonator embedded inside a CPW cavity. [2,3] For such techniques to be feasible, the qubit and CPW, which can be detuned in energy by several GHz, should have linewidths comparable to or smaller than the nanoresonator-qubit coupling strength, which is controlled by a large dc voltage (∼ 10 s V); this requires both the CPW and qubit to be well-isolated at their respective energies from the bias circuitry. Here we re...

Method to prepare suspended multilayer graphene (MLG) flakes and to form highly conductive (contact resistivity of ∼0.1 kΩ μm2) and tight mechanical connection between MLG and metal electrodes is described. MLG flakes prepared from natural graphite were precisely deposited over tungsten electrodes using dielectrophoresis, followed by high-temperature thermal annealing in high-vacuum. Considerable strain induced in the suspended part of flakes was revealed by Raman imaging.

The effects of ion irradiation on the composition, structure, compactness, and surface hardness of polyorganosiloxane films synthesized by plasma-enhanced chemical vapor deposition were investigated as a function of the ion mass and fluence. The films were obtained from a glow discharge plasma of a hexamethyldisiloxane (HMDSO)−O2−Ar mixture, and the irradiations were carried out with 170 keV He+, Ne+, Ar+, and Kr+ ions at fluences between 1 × 1014 and 1 × 1016 cm-2. To characterize the film elemental composition, two ion-beam analysis techniques were used:  Rutherford backscattering spectroscopy (RBS) and forward recoil spectroscopy (FRS). The ion-beam-induced hydrogen loss from the films was significant. For the He+-irradiated samples, a H loss of about 50% with respect to the pristine or unirradiated film was observed for the highest fluence. The surface hardness measurements, performed with a nanoindenter, in films irradiated at a fluence of 1 × 1016 cm-2 were 8.1, 6.0, 4.7, and 1.6 GPa for He+, Ne+, Ar+, and Kr+, respectively. To examine the ion-induced structural transformations in the films, infrared reflection−absorption spectroscopy (IRRAS) was employed. From analysis of the spectra of the irradiated samples several conclusions could be drawn. For example, as the ion fluence increased, (i) the densities of methyl- and Si−O-related groups changed, (ii) film disorder increased, and (iii) groups such as Si−CH2−Si, and Si−OH, which were not present in the pristine film, were formed at lower fluences but disappeared when the latter attained their highest values. Furthermore, some of the absorption peaks that appeared at low fluences and increased with increasing fluence strongly indicate formation of carbon domains in the film. Finally, differences in the ion-induced modifications produced by the different ion species were analyzed in terms of the electronic and nuclear collisions of the ions traversing the film using the well-known SRIM simulation program.