We describe the fabrication and measurement of microwave coplanar waveguide resonators with internal quality factors above 10 7 at high microwave powers and over 10 6 at low powers, with the best low power results approaching 2 × 10 6 , corresponding to ∼ 1 photon in the resonator. These quality factors are achieved by controllably producing very smooth and clean interfaces between the resonators' aluminum metallization and the underlying single crystal sapphire substrate. Additionally, we describe a method for analyzing the resonator microwave response, with which we can directly determine the internal quality factor and frequency of a resonator embedded in an imperfect measurement circuit.High quality factor microwave resonators provide critical elements for superconducting electromagnetic radiation detectors 1 , quantum memories 2,3 , and quantum computer architectures 4 . Good performance and stability can be achieved for such applications using aluminum resonators patterned on sapphire substrates. Aluminum is a favored material due to its robust oxide and reasonable transition temperature, and sapphire provides an excellent substrate due to its very low microwave loss tangent 5 δ ∼ 10 −8 and its chemical inertness. However, the quality factors measured in such resonators is lower than expected; recent simulations 6 and experiments 7 suggest that the unexplained loss arises mostly from imperfections at the metal-substrate interface. Using an experimental apparatus with minimal stray magnetic fields and infrared light at the sample 8 , here we show that careful substrate preparation and cleaning yields aluminumon-sapphire resonators with significantly higher internal quality factors Q i . We also introduce a new method for evaluating the resonator microwave response.The aluminum for the resonators was deposited on cplane sapphire substrates in one of three deposition systems: A high vacuum DC sputter system (base pressure P base = 6 × 10 −8 Torr), a high vacuum electron-beam evaporator (P base = 5 × 10 −8 Torr) or an ultra-high vacuum (UHV) molecular beam epitaxy (MBE) system (P base = 6 × 10 −10 Torr) with electron-beam deposition. The sapphire substrates were first sonicated in a bath of acetone then isopropanol followed by a deionized water rinse. For the sputter-deposited and e-beam evaporated samples, we further cleaned the substrates prior to Al de-

The von Neumann architecture for a classical computer comprises a central processing unit and a memory holding instructions and data. We demonstrate a quantum central processing unit that exchanges data with a quantum random-access memory integrated on a chip, with instructions stored on a classical computer. We test our quantum machine by executing codes that involve seven quantum elements: Two superconducting qubits coupled through a quantum bus, two quantum memories, and two zeroing registers. Two vital algorithms for quantum computing are demonstrated, the quantum Fourier transform, with 66% process fidelity, and the three-qubit Toffoli-class OR phase gate, with 98% phase fidelity. Our results, in combination especially with longer qubit coherence, illustrate a potentially viable approach to factoring numbers and implementing simple quantum error correction codes.

Notes on 113 fungal taxa are compiled in this paper, including 11 new genera, 89 new species, one new subspecies, three new combinations and xx reference specimens. A wide geographic and taxonomic range of fungal taxa are detailed. In the Ascomycota the new genera Angustospora (Testudinaceae), Camporesia (Xylariaceae), Clematidis, Crassiparies (Pleosporales genera incertae sedis), Farasanispora, Longiostiolum (Pleosporales genera incertae sedis), Multilocularia (Parabambusicolaceae), Neophaeocryptopus (Dothideaceae), Parameliola (Pleosporales genera incertae sedis), and Towyspora (Lentitheciaceae) are introduced. Newly introduced species are Angustospora nilensis, Aniptodera

We find that stray infrared light from the 4 K stage in a cryostat can cause significant loss in superconducting resonators and qubits. For devices shielded in only a metal box, we measured resonators with quality factors Q = 10 5 and qubits with energy relaxation times T1 = 120 ns, consistent with a stray light-induced quasiparticle density of 170-230 µm −3 . By adding a second black shield at the sample temperature, we found about an order of magnitude improvement in performance and no sensitivity to the 4 K radiation. We also tested various shielding methods, implying a lower limit of Q = 10 8 due to stray light in the light-tight configuration.Quantum information processing in superconducting circuits is performed at very low temperatures, so energy loss due to quasiparticles is expected to vanish because their density diminishes exponentially with decreasing temperature. As energy relaxation times saturate for superconducting quantum circuits and planar resonators, reaching values on the order of 1-10 µs [1-4], recent experiments have suggested that this may be due to excess non-equilibrium quasiparticles; measurements on phase qubit coherence [5,6], tunneling in charge qubits [7], resonator quality factors [3,4] and quasiparticle recombination times [8,9] are compatible with an excess quasiparticle density on the order of 10-100 µm −3 , possibly arising from stray light, cosmic rays, background radioactivity, or the slow heat release of defects.In this Letter, we demonstrate that stray infrared light gives significant loss in resonators and qubits, and is sometimes the dominant limitation in our present experiments. We also show quantitatively how a combination of infrared shielding techniques removes the influence of stray infrared light, and that the required shielding is beyond what is generally used. The effectiveness of the various techniques is investigated by methodically changing and testing them. With our new light-tight setup, the quality factors of Al superconducting resonators improve dramatically by a factor of 20, as shown in Fig. 1. We also show that shielding improves phase qubit coherence.Loss in a superconducting resonator with frequency f is controlled by the quasiparticle density n qp [10] (for kT ≪ hf )with ∆ the energy gap, D(E F ) the two-spin density of states, and α the kinetic inductance fraction, which depends on geometry. Importantly, excess quasiparticles can limit quality factors, in particular at the low temperatures at which resonators and qubits are operated.Measurements on the temperature dependence of resonator quality factors indicate the presence of an additional loss term, as shown in Fig. 1. Here we plot quality factors of coplanar waveguide (CPW) Al resonators. The open symbols are measured when simply placing the sample in a sample box in a cryostat, with no special measures against stray light. Above a temperature of 200 mK the quality factors decrease exponentially, consistent with a thermal quasiparticle density (dashed line, Eq. 1). At low temperatures a plateau ...

Losses in superconducting planar resonators are presently assumed to predominantly arise from surfaceoxide dissipation, due to experimental losses varying with choice of materials. We model and simulate the magnitude of the loss from interface surfaces in the resonator, and investigate the dependence on power, resonator geometry, and dimensions. Surprisingly, the dominant surface loss is found to arise from the metalsubstrate and substrate-air interfaces. This result will be useful in guiding device optimization, even with conventional materials.