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Your search keyword '"Levitin, L."' showing total 104 results
Start Over Author "Levitin, L." Publication Type Academic Journals
104 results on '"Levitin, L."'

2. QUEST-DMC superfluid 3He detector for sub-GeV dark matter

Author

Autti, S., Casey, A., Eng, N., Darvishi, N., Franchini, P., Haley, R. P., Heikkinen, P. J., Jennings, A., Kemp, A., Leason, E., Levitin, L. V., Monroe, J., March-Russel, J., Noble, M. T., Prance, J. R., Rojas, X., Salmon, T., Saunders, J., Smith, R., Thompson, M. D., Tsepelin, V., West, S. M., Whitehead, L., Zavjalov, V. V., and Zmeev, D. E.

Published
2024
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7. Quantum bath suppression in a superconducting circuit by immersion cooling.

Author

Lucas, M., Danilov, A. V., Levitin, L. V., Jayaraman, A., Casey, A. J., Faoro, L., Tzalenchuk, A. Ya., Kubatkin, S. E., Saunders, J., and de Graaf, S. E.

Subjects
SUPERCONDUCTING circuits, SUPERCONDUCTING resonators, DECOHERENCE (Quantum mechanics), IMMERSION in liquids, DEGREES of freedom, HEAT sinks
Abstract

Quantum circuits interact with the environment via several temperature-dependent degrees of freedom. Multiple experiments to-date have shown that most properties of superconducting devices appear to plateau out at T ≈ 50 mK – far above the refrigerator base temperature. This is for example reflected in the thermal state population of qubits, in excess numbers of quasiparticles, and polarisation of surface spins – factors contributing to reduced coherence. We demonstrate how to remove this thermal constraint by operating a circuit immersed in liquid 3He. This allows to efficiently cool the decohering environment of a superconducting resonator, and we see a continuous change in measured physical quantities down to previously unexplored sub-mK temperatures. The 3He acts as a heat sink which increases the energy relaxation rate of the quantum bath coupled to the circuit a thousand times, yet the suppressed bath does not introduce additional circuit losses or noise. Such quantum bath suppression can reduce decoherence in quantum circuits and opens a route for both thermal and coherence management in quantum processors. Removing excess energy (cooling) and reducing noise in superconducting quantum circuits is central to improved coherence. Lucas et al. demonstrate cooling of a superconducting resonator and its noisy environment to sub-mK temperatures by immersion in liquid 3He. [ABSTRACT FROM AUTHOR]

Published
2023
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17. Minimal sets of turns for breaking cycles in graphs modeling networks

Author

Levitin, L., Karpovsky, M., and Mustafa, M.

Subjects
Computer networks -- Design and construction, Information networks -- Design and construction, Graph theory -- Usage, High performance computing -- Analysis, Bridge/routers -- Usage, Bridge/router, Internetworking device, ISDN router, Business, Computers, Electronics, Electronics and electrical industries
Published
2010

33. Superconductivity in AuNiGe Ohmic contacts to a GaAs-based high mobility two-dimensional electron gas.

Author

Beauchamp, C. B., Dimitriadis, S., Nicholls, J. T., Levitin, L. V., Casey, A. J., See, P., Creeth, G., Waldie, J., Farrer, I., Beere, H. E., and Ritchie, D. A.

Subjects
TWO-dimensional electron gas, ELECTRON gas, ELECTRON mobility, OHMIC contacts, SUPERCONDUCTIVITY, SCANNING electron microscopes, OHMIC resistance
Abstract

To cool a high mobility two-dimensional electron gas (2DEG) at a GaAs–AlGaAs heterojunction to milliKelvin temperatures, we have fabricated low resistance Ohmic contacts based on alloys of Au, Ni, and Ge. The Ohmic contacts have a typical contact resistance of R C ≈ 0.8 Ω at 4.2 K, which drops to 0.2 Ω below 0.9 K. Scanning electron microscope images establish that the contacts have the same inhomogeneous microstructure that has been observed in previous studies. Measurements of the contact resistance R C , the four-terminal resistance along the top of a single contact, and the vertical resistance RV all show that there is a superconductor in the Ohmic contact, which can be turned completely normal with a magnetic field of 0.15 T. We briefly discuss how this superconductivity may be affecting the electrical transport measurements of 2DEGs, especially how it may hinder the cooling of electrons in a 2DEG below 0.1 K. [ABSTRACT FROM AUTHOR]

Published
2020
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46. Fabrication of microfluidic cavities using Si-to-glass anodic bonding.

Author

Zhelev, N., Abhilash, T. S., Bennett, R. G., Smith, E. N., Ilic, B., Parpia, J. M., Levitin, L. V., Rojas, X., Casey, A., and Saunders, J.

Subjects
MICROFLUIDIC devices, SEMICONDUCTOR wafer bonding, MICROFABRICATION, PHASE diagrams, ANODES, LOW temperatures
Abstract

We demonstrate the fabrication of ∼1.08 μm deep microfluidic cavities with characteristic size as large as 7 mm × 11 mm or 11 mm diameter, using a silicon-glass anodic bonding technique that does not require posts to act as separators to define cavity height. Since the phase diagram of 3He is significantly altered under confinement, posts might act as pinning centers for phase boundaries. The previous generation of cavities relied on full wafer-bonding which is more prone to failure and requires dicing post-bonding, whereas these cavities are made by bonding a pre-cut piece of Hoya SD-2 glass to a patterned piece of silicon in which the cavity is defined by etching. Anodic bonding was carried out at 425 °C with 200 V, and we observe that pressurizing the cavity to failure (>30 bars pressure) results in glass breaking, rather than the glass-silicon bond separation. In this article, we discuss the detailed fabrication of the cavity, its edges, and details of the junction between the coin silver fill line and the silicon base of the cavity that enables a low internal-friction joint. This feature is important for mass coupling torsional oscillator experimental assays of the superfluid inertial contribution where a high quality factor (Q) improves frequency resolution. The surface preparation that yields well-characterized smooth surfaces to eliminate pinning sites, the use of transparent glass as a cover permitting optical access, low temperature capability, and attachment of pressure-capable ports for fluid access may be features that are important in other applications. [ABSTRACT FROM AUTHOR]

Published
2018
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