We study the coherent control of microwave photons propagating in a superconducting waveguide consisting of coupled transmission line resonators, each of which is connected to a tunable charge qubit. While these coupled line resonators form an artificial photonic crystal with an engineered photonic band structure, the charge qubits collectively behave as spin waves in the low excitation limit, which modify the band-gap structure to slow and stop the microwave propagation. The conceptual exploration here suggests an electromagnetically controlled quantum device based on the on-chip circuit QED for the coherent manipulation of photons, such as the dynamic creation of laser-like output from the waveguide by pumping the artificial atoms for population inversion.

The microscopic approach quantum dissipation process presented by Yu and Sun [Phys. Rev., A49(1994) 592, A51(1995)1845] is developed to analyze the wave function structure of dynamic evolution of a typical dissipative system, a single mode boson soaked in a bath of many bosons. In this paper, the wave function of total system is explicitly obtained as a product of two components of the system and the bath in the coherent state representation. It not only describes the influence of the bath on the variable of the system through the Brownian motion, but also manifests the back-action of the system on the bath and the effects of the mutual interaction among the bosons of the bath. Due to the back-action, the total wave function can only be partially factorizable even for the Brownian motion can be ignored in certain senses, such as the cases with weak coupling and large detuning.PACS numbers: 03.65, 32.80, 42.50 1 1. Introduction: The typical microscopic treatment for the model of quantum dissipation is to consider a harmonic oscillator interacting with a many-oscillator bath (e.g., in [1][2][3][4][5][6]). This simple and rather conventional model has been used to completely clarify the relation between two different approaches for quantum dissipation process frequently appearing in the literature, i.e., the system plus bath model and the time-dependent effective Hamiltonian by Kanai and Calderora [7,8], since Yu and one (Sun) of the authors wrote down the total wave function explicitly in a form of direct product of the bath component and the system component [1,2]. In the discussion, because the mixed variables were chosen to describe the system and the bath, the wave function only manifested the influence of the bath on the system through the Brownian broadening of the width of the wave function for the system, but the back-action of the system on the bath was not discussed. If there indeed exists the back-action of the system on the bath, it is reasonable to expect that, for the individual particles constituting the bath, the mutual couplings among them can indirectly appear in a second order through coupling the system as an intermediate process.Another question is the relation between quantum and classical systems. In many real situations, the classical or macroscopic states can be represented by coherent states in the quantum optics and the macroscopic quantum mechanics. Therefore it is significant to study how the system with an initial coherent state evolves if it really has a macroscopic or classical meanings and to test if it can move in the classical orbits.In this paper, the back-action and mutual couplings with a simple model is studied and manifested in the coherent representation. In the presence of both the back-action and the indirect mutual coupling, we also consider the meaning of the wave function of the dissipative system governed by the effective Hamiltonian, which is also to be determined in this paper. A very interesting result is that a factorizable evolution represented by a prod...

Black phosphorus (BP) with a layered structure has been used gradually as a lubrication additive in the tribological area. In this study, BP powders are produced via an easy method of high-energy ball milling using red phosphorus as a raw material. Subsequently, BP nanosheets are prepared via liquid exfoliation in N-methyl pyrolidone solvent. The tribological behavior of BP nanosheets as water-based lubrication additives (BP-WL) is evaluated under Ti6Al4V (TC4)/GCr15 contact. The results suggest that the 70 mg/L BP-WL sample exhibits excellent lubrication performance, whose coefficient of friction (COF) and ball wear rate reduced by 32.4% and 61.1%, respectively, compared with those of pure water. However, as the load increased, the tribological properties of BP-WL reduced gradually because of the agglomeration of BP nanosheets. Based on tribological experiments and worn surface analysis, boundary lubrication mechanisms are proposed. The friction reduced, which is primarily attributed to the low interlaminar shear and adsorption of BP nanosheets. In addition, a tribochemical reaction film comprising TiO2, Al2O3, and Fe2O3 effectively protects the surface of titanium alloy/steel from wear. This new water-based lubrication additive can be used to process titanium alloys.

We have incorporated a single crystal silicon shunt capacitor into a Josephson phase qubit. The capacitor is derived from a commercial silicon-on-insulator wafer. Bosch reactive ion etching is used to create a suspended silicon membrane; subsequent metallization on both sides is used to form the capacitor. The superior dielectric loss of the crystalline silicon leads to a significant increase in qubit energy relaxation times. T1 times up to 1.6 µs were measured, more than a factor of two greater than those seen in amorphous phase qubits. The design is readily scalable to larger integrated circuits incorporating multiple qubits and resonators.PACS numbers: 85.25. Cp,77.22.Gm,74.50.+r The Josephson phase qubit is an attractive candidate for scalable quantum information processing in the solid state [1][2][3][4][5]. This qubit has achieved several important milestones, including realization of high-fidelity entangling gates in two and three qubit circuits [4], violation of a Bell's inequality [5], and full characterization of highly non-classical states in linear microwave resonators [6]. However, qubit performance is limited by relatively short coherence times, under 1 µs. It has been shown that the dominant energy relaxation mechanism is dielectric loss induced by a continuum of low-energy defect states in the amorphous thin films of the circuit [7]. In the most common approach to qubit realization, a ∼ 1 µm 2 Josephson junction is shunted by an external thin film capacitor of order 1 pF [8]; in this case, qubit T 1 is determined solely by the loss tangent of the bulk capacitor dielectric: T 1 = 1/ω 10 tan δ, where ω 10 /2π is the qubit frequency. There have been efforts to develop amorphous dielectrics with improved intrinsic (low-temperature, low power) loss for superconducting qubit applications [9]. An alternative approach is to incorporate crystalline, defectfree dielectrics into the qubit circuit. Molecular beam epitaxy techniques have been used to grow single-crystal Al 2 O 3 tunnel barriers on crystalline Re underlayers, and phase qubit circuits incorporating these barriers demonstrate a significant reduction in the density of spurious microwave resonances [10,11]. Moreover, there has been progress in the incorporation of epitaxial Josephson junctions into transmon qubits, although T 1 times were under 1 µs [12,13]. Other work involves the development of grown bulk crystalline Al 2 O 3 for phase qubit shunt capacitors [14]. However, the robust, repeatable growth of crystalline dielectrics for superconducting qubit circuits remains a daunting challenge.In this work, we demonstrate the realization of a Josephson phase qubit incorporating a crystalline silicon shunt capacitor. Silicon growth has been perfected over decades by the integrated circuit industry, and commercial-grade intrinsic silicon displays an internal quality factor in excess of 10 6 in the low-power, lowtemperature regime relevant to qubit operation. More- over, silicon-on-insulator (SOI) technology provides a path to the incorporation of...