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DESCRIPTION:Olivier Pfister\, University of Virginia\n\nQuantum computing h
as attracted much attention over the past sesquidecade because it makes in
teger-factoring easy\, even though that has been a historically (if not pr
ovably) hard mathematical problem [1]. Another major interest is the expon
ential speedup of quantum simulations [2]. The physical implementation of
nontrivial quantum computing is an exciting\, if daunting\, experimental c
hallenge\, epitomized by the issues of decoherence and scalability of the
quantum registers and processors. In this talk\, I will present a novel sc
heme for realizing a scalable quantum register of potentially very large s
ize\, entangled in a "cluster" state\, in a remarkably compact physical sy
stem: the optical frequency comb (OFC) defined by the eigenmodes of a sing
le optical resonator. The classical OFC is well known as implemented by th
e femtosecond\, carrier-envelope-phase- and mode-locked lasers which have
redefined time/frequency metrology and ultraprecise measurements in recent
years [3\,4]. The quantum version of the OFC is then a set of harmonic os
cillators\, or "Qmodes\," whose amplitude and phase are analogues of the p
osition and momentum mechanical observables. The quantum manipulation of t
hese continuous variables for one or two Qmodes is a mature field. Recentl
y\, we have shown theoretically that the nonlinear optical medium of a sin
gle optical parametric oscillator (OPO) can be engineered\, in a sophistic
ated but already demonstrated manner\, so as to entangle\, in constant tim
e\, the OPO's OFC into a cluster state of arbitrary size\, suitable for on
e-way quantum computing over continuous variables [5\,6]. I will describe
the mathematical proof of this result and report on our progress towards i
ts experimental implementation at the University of Virginia.

\n\n[
1] P. W. Shor\, “Algorithms for quantum computation: discrete logarithms
and factoring\,” in Proceedings\, 35th Annual Symposium on Foundations
of Computer Science\, S. Goldwasser\, ed.\, pp. 124–134 (IEEE Press\, Lo
s Alamitos\, CA\, Santa Fe\, NM\, 1994).

\n\n[2] R. P. Feynman\,
Simulating Physics With Computers\,” Int. J. Theor. Phys. 21\, 467 (198
2).

\n\n[3] J. L. Hall\, “Nobel Lecture: Defining and measuring o
ptical frequencies\,” Rev. Mod. Phys. 78\, 1279 (2006)

\n\n[4] T.
W. Hänsch\, “Nobel Lecture: Passion for precision\,” Rev. Mod. Phys.
78\, 1297 (2006).

\n \n[5] N. C. Menicucci\, S. T. Flammia\, and
O. Pfister\, “One-way quantum computing in the optical frequency comb\,
Phys. Rev. Lett. 101\, 130501 (2008).

\n \n[6] S. T. Flammia\, N
. C. Menicucci\, and O. Pfister\, “The optical frequency comb as a one-w
ay quantum computer\,” J. Phys. B\, 42\, 114009 (2009).

\n
DTSTART:20101029T200000Z
LOCATION:Physics Building\, Room 204
SUMMARY:Quantum computing over the rainbow
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