Polymers offer unique avenues for the structural control of materials on the nanoscopic length scale for the production of nanoporous media, membranes, lithographic templates, and scaffolds for assemblies of electronic materials. [1±4] With structures on this length scale, quantum properties of electronic materials are exhibited even at elevated temperatures. The natural length scale of polymer chains and their morphologies in the bulk lie precisely at these length scales and, as such, there is a substantial effort to produce, characterize and use polymeric nanostructures. The ease of processing polymers adds to the attractiveness of polymer-based nanostructures. In comparison to the time-intensive process of sequential writing of nanoscale patterns, nanostructure formation by self-assembly is highly parallel and inherently fast. Block copolymers are ideal materials in this respect, since, due to the connectivity of two chemically distinct chains, the molecules self-assemble into ordered morphologies with a size scale limited to molecular dimensions. Of particular interest are block copolymers that form cylindrical microdomains, since the elimination of the minor component transforms the material into an array of nanopores.A prerequisite for the use of copolymers is the control over the orientation of the microdomains. In particular, for cylindrical microdomains, an orientation normal to the substrate surface is desirable. Two different approaches are used to this end. In thin films, random copolymers anchored to a substrate can be used to produce a neutral surface. [5] For entropic reasons, the microdomains orient normal to the substrate surface. [6] In a second approach, electric fields were used to orient the cylindrical microdomains parallel to the field lines. [7±10] The approach relies on the orientation-dependent polarization energy induced when an anisotropic body is placed in an electric field. An anisotropic microphase structure will orient such that the interfaces between the two blocks are aligned parallel to the electric field.In this article it is shown that cylindrical microdomains of a copolymer film can be used to generate an array of ordered nanoscopic pores with well-controlled size, orientation, and structure. To this end, selective etching procedures and a characterization of the samples by quantitative analysis of the X-ray scattering along with electron (EM) and atomic force microscopies (AFM) are described. The processes outlined are shown to be operative over a very large range in sample thickness ranging from 40 nm up to several micrometers. The resulting nanoporous films are promising candidates as membranes with specific transport properties and as templates for electronic and magnetic nanostructured materials. Figures 1A and 1B show AFM images obtained from a 40 nm±thick film prepared on a neutral substrate after annealing. Cylinders standing perpendicular to the substrate are clearly discernable, particularly in the phase image, since the height variations are very small. Polystyr...

Polymers offer unique avenues for the structural control of materials on the nanoscopic length scale for the production of nanoporous media, membranes, lithographic templates, and scaffolds for assemblies of electronic materials.[1±4] With structures on this length scale, quantumproperties of electronic materials are exhibited even at elevated temperatures. The natural length scale of polymer chains and their morphologies in the bulk lie precisely at these length scales and, as such, there is a substantial effort to produce, characterize and use polymeric nanostructures. The ease of processing polymers adds to the attractiveness of polymer-based nanostructures. In comparison to the time-intensive process of sequential writing of nanoscale patterns, nanostructure formation by self-assembly is highly parallel and inherently fast. Block copolymers are ideal materials in this respect, since, due to the connectivity of two chemically distinct chains, the molecules self-assemble into ordered morphologies with a size scale limited to molecular dimensions. Of particular interest are block copolymers that form cylindrical microdomains, since the elimination of the minor component transforms the material into an array of nanopores. A prerequisite for the use of copolymers is the control over the orientation of the microdomains. In particular, for cylindrical microdomains, an orientation normal to the substrate surface is desirable. Two different approaches are used to this end. In thin films, random copolymers anchored to a substrate can be used to produce a neutral surface.[5] For entropic reasons, the microdomains orient normal to the substrate surface.[6] In a second approach, electric fields were used to orient the cylindrical microdomains parallel to the field lines.[7±10] The approach relies on the orientation-dependent polarization energy induced when an anisotropic body is placed in an electric field. An anisotropic microphase structure will orient such that the interfaces between the two blocks are aligned parallel to the electric field. In this article it is shown that cylindrical microdomains of a copolymer film can be used to generate an array of ordered nanoscopic pores with well-controlled size, orientation, and structure. To this end, selective etching procedures and a characterization of the samples by quantitative analysis of the X-ray scattering along with electron (EM) and atomic force microscopies (AFM) are described. The processes outlined are shown to be operative over a very large range in sample thickness ranging from 40 nm up to several micrometers. The resulting nanoporous films are promising candidates as membranes with specific transport properties and as templates for electronic and magnetic nanostructured materials.Figures 1A and 1B show AFM images obtained from a 40 nm±thick film prepared on a neutral substrate after annealing. Cylinders standing perpendicular to the substrate are clearly discernable, particularly in the phase image, since the height variations are very small. Polystyrene (PS...

A novel approach to highly ordered and modular nanoelectrode arrays (NEAs) has been developed using block copolymer self-assembly. Variable scan rate cyclic voltammetry studies were performed to characterize the NEA. At low scan rates, the NEA behaves similar to a macroelectrode, while at high scan rates the nanoelectrodes act independently. This is an important feature for real-time in vivo sensing and other electroanalytical applications.

Efficient detection of magnetic fields is central to many areas of research and technology. High-sensitivity detectors are commonly built using direct-current superconducting quantum interference devices or atomic systems. Here we use a single artificial atom to implement an ultrasensitive magnetometer with micron range size. The artificial atom, a superconducting two-level system, is operated similarly to atom and diamond nitrogen-vacancy centre-based magnetometers. The high sensitivity results from quantum coherence combined with strong coupling to magnetic field. We obtain a sensitivity of 3.3 pT Hz À 1/2 for a frequency of 10 MHz. We discuss feasible improvements to increase sensitivity by one order of magnitude. The intrinsic sensitivity of this detector at frequencies in the 100 kHz-10 MHz range compares favourably with direct-current superconducting quantum interference devices and atomic magnetometers of equivalent spatial resolution. This result illustrates the potential of artificial quantum systems for sensitive detection and related applications.

We report experiments on superconducting flux qubits in a circuit quantum electrodynamics (cQED) setup. Two qubits, independently biased and controlled, are coupled to a coplanar waveguide resonator. Dispersive qubit state readout reaches a maximum contrast of 72 %. We find intrinsic energy relaxation times at the symmetry point of 7 µs and 20 µs and levels of flux noise of 2.6 µΦ0/ √ Hz and 2.7 µΦ0/ √ Hz at 1 Hz for the two qubits. We discuss the origin of decoherence in the measured devices. These results demonstrate the potential of cQED as a platform for fundamental investigations of decoherence and quantum dynamics of flux qubits.PACS numbers: 85.25. Cp, 42.50.Dv , 03.67.Lx, 74.78.Na Superconducting qubits are one of the main candidates for the implementation of quantum information processing [1] and a rich testbed for research in quantum optics, quantum measurement, and decoherence [2]. Among various types of superconducting qubits, flux-type superconducting qubits have unique features. Strong and tunable coupling to microwave fields enables fundamental investigations in quantum optics [3][4][5] and relativistic quantum mechanics [6]. The large magnetic dipole moment is a key ingredient in flux noise measurements [5], sensitive magnetic field measurements [8], microwave-optical interfaces [9], and hybrid systems formed with nanomechanical resonators [10]. Finally, flux qubits have a large degree of anharmonicity which is an advantage for fast quantum control [11]. Progress on these diverse research avenues has been hampered by relatively low and irreproducible coherence times compared to other types of superconducting qubits.In the last decade, circuit quantum electrodynamics (cQED) [12,13] has become increasingly popular. In cQED, resonators provide a controlled electromagnetic environment protecting qubits from energy relaxation. In addition, resonators are used for qubit state measurement [2] and as quantum buses for qubit-qubit coupling [15]. In this letter, we present an implementation of cQED with flux qubits strongly coupled to a superconducting coplanar waveguide resonator. The qubits and the resonator are made of aluminum. Local biasing and control lines provide a mean to implement fast single qubit gates as well as controlled two-qubit interactions. We measure energy relaxation times around 10 µs, an improvement over previous experiments with flux qubits coupled to coplanar waveguide resonators [16,17], and comparable with the longest measured to date on flux qubits [5,18]. We characterize in detail the decoherence of the flux qubits coupled to the resonator. Based on decoherence measurements, we extract levels of flux noise of 2.6 µΦ 0 / √ Hz and 2.7 µΦ 0 / √ Hz at 1 Hz for the two qubits. We also present a spectroscopic measurement of a resonator-mediated qubit-qubit coupling, which is relevant for implementation of two-qubit gates. These results demonstrate the versatility of cQED with flux qubits, and its potential for further understanding and improvements of decoherence of these qubits.T...