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--></style><title>MIT Quantum Information Processing Seminar
Reminder</title></head><body>
<div>Today's MIT QIP seminar will take place on Monday, April 4th at
16:00 in 4-237, and features:</div>
<div><br></div>
<hr>
<div align="center"><font size="+2"><b>Superconductive Quantum
Computing at MIT Lincoln Laboratory and the MIT
Campus</b></font></div>
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<div align="center"><font size="+1"><i>by</i> Dr. William D. Oliver
(<i>MIT Lincoln Laboratory</i>)</font></div>
<div align="center"><br></div>
<div align="center"><u>ABSTRACT</u></div>
<div><br></div>
<blockquote>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.</blockquote>
<blockquote><br></blockquote>
<blockquote>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.</blockquote>
<blockquote><br></blockquote>
<blockquote>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.</blockquote>
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<hr>
<div>Next week's feature: John Clarke, Univ. of California at Berkeley
will speak on "Large-Inductance Superconducting Flux Qubits:
Coherent Oscillations and Controllable Coupling."</div>
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