[QIP-Sem] MIT Quantum Information Processing Seminar Announcement

[QIP-Sem Mailing List]

Next week's MIT QIP seminar will take place on Monday, April 4th at 
16:00 in 4-237, and features:


Superconductive Quantum Computing at MIT Lincoln Laboratory and the MIT Campus

by Dr. William D. Oliver (MIT Lincoln Laboratory)

ABSTRACT

MIT Lincoln Laboratory has a superconductor-based quantum computing 
(QC) program comprising experimental, theoretical, and fabrication 
efforts aimed at demonstrating and improving single-qubit figures of 
merit (e.g., Rabi fringe contrast, decoherence times), with a 
longer-term vision towards coupled qubits and, ultimately, 
demonstrations of the subsystem integration required for scalable 
quantum computing.

We begin this talk with a presentation of our QC efforts during the 
past 12 months with our collaborators at the MIT campus; the focus 
will be qubit measurement and fabrication. MIT Lincoln Laboratory 
designed, implemented, and automated a time-resolved 
persistent-current-qubit readout in the MIT dilution refrigerator 
capable of nanosecond-scale resolution measurements. We used this 
readout to map the qubit energy-band diagram, match it to simulation, 
and demonstrate multi-photon transitions. We also have preliminary, 
albeit weak, Rabi oscillation data; we understand and will discuss 
what limits the oscillations for this particular qubit design. In 
addition, we have fabricated and prototyped a resonant-circuit-based 
qubit readout with the explicit aim of reducing qubit decoherence.

In parallel, we have reassessed and refocused our qubit fabrication 
at MIT Lincoln Laboratory. We will present the results of this 
reassessment: a new deep-submicron qubit fabrication process (DSM-1). 
DSM-1 is a fully-planarized Nb-trilayer process which provides 
high-yield and reproducible structures, including Josephson 
junctions, capacitors, inductors, and resistors. It was specifically 
designed to realize the more sophisticated ancillary circuits 
required for improved qubit readout and decoherence times which are 
difficult to realize using the conventional shadow-evaporation 
approach. Using the DSM-1 process, we have demonstrated Josephson 
junctions smaller than 100 nm and critical current densities ranging 
from 30 A/cm2 to 10 KA/cm2. We have also fabricated and begun testing 
at 15 mK qubits using the DSM-1 process. We will discuss why these 
new DSM qubits should exhibit improved decoherence times.
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