Ring-shaped BECs
Hold Promise for
Future Atomtronics
Institute News for
October-November 2010
JQI scientists recently published a paper in
Physical Review A, discussing the thermal phase
A ring-shaped Bose-Einstein condensate,
fluctuations of ring-shaped Bose-Einstein conuseful for atomtronics.
densates.* The publication can be seen as one
Home Team of the first theory papers under the Atomtronics
MURI (Multidisciplinary University Research Initiative), a collaboration kicked off on September
Kicks Off
Atomtronics 27, 2010 and headed by JQI Fellow Ian Spielman.
MURI
page 2
Quantum
Entrepreneurship
Seminar
page 4
As part of the prestigious MURI program (funded by the U.S. Department of Defense and awarded to a number of JQI scientists this past July), the research investigates atomtronics: an exciting
new field that seeks to create ultra-cold atom systems that resemble electronic devices such as
transistors and diodes, and surpass them in functionality. Atomtronics may play a critical role in
the future as an interface between quantum information processors and present-day electronics.
continued, page 3
NIST Researchers Create
‘Quantum Cats’ Made of Light
Researchers at the National Institute of Standards and Technology (NIST) have created “quantum cats” made of photons
(particles of light), boosting prospects for manipulating light
in new ways to enhance precision measurements as well as
computing and communications based on quantum physics.
NIST research associate Thomas
Gerrits at the laser table used to
The NIST experiments, described in a paper co-authored by
create “quantum cats” made of
JQI fellow Alan Migdall,* produced light pulses that each poslight.
sessed two exactly opposite properties—specifically, opposite
phases, as if the peaks of the light waves were superimposed on the
troughs. Physicists call this an optical Schrödinger’s cat. NIST’s quantum
cat is the first to be made by detecting three photons at once and is one
continued, page 5
For JQI research news, see http://jqi.umd.edu, updated daily.
Home Team Kicks Off Atomtronics MURI
During the summer of 2010, the JQI learned that it
would receive a Multidisciplinary University Research
Initiative (MURI) award from the U.S. Army Research
Office, the fourth such award for the JQI from the
Department of Defense during the past three years.
The MURI program funds research teams to attack
multidiscipinary problems, at a level of about $1M/
year for three to five years.
MURI includes seven other JQI senior investigators (Gretchen Campbell, Charles Clark, Sankar Das
Sarma, Victor Galitski, Bill Phillips, Trey Porto, Steve
Rolston) plus Eugene Demler of Harvard University,
Martin Zwierlein and Ike Chuang of MIT, and Jay
Vaishnav of Bucknell University. It was launched at a
day-long kickoff meeting at the University of Maryland Conference Center on September 27 and featured research presentations by many of the investigators. Among the headline results reported there
were the observation of the longest-lasting known
supercurrents in a ring trap, by JQI Fellow Gretchen
Campbell, and the production of a system of three
quantum degenerate gases (6Li, 40K and 41K) by
Martin Zwierlein.
The theme of this year’s MURI is “atomtronics”: the
search for alternative modalities to electronics, in
which atoms replace electrons as the vehicles of action and information.
Led by JQI Fellow Ian Spielman, the Atomtronics
Deep in thought: Eugene
Demler (left) and Ian Spielman
Left to right: Karina Jimenez-Garcia, Jennifer Johnson, Luis Orozco, Jeff Grover
Striking a pose: Steve Rolston (left)
and Luis Orozco
22
Ring-shaped BECs, from p. 1
The research effort is an epitome of the interdisciplinary teamwork required under the MURI. A collaboration between experimentalists
and theorists, the research brought together the efforts of a number of JQI
associates: Fellows Gretchen Campbell, Bill Phillips and Charles Clark;
graduate student Anand Ramanathan;
and postdocs Kevin Wright, Sergio Muniz, and Ludwig Mathey, lead author
of the paper.
phase fluctuations occur and identifies the regime
where phase coherence is preserved. The phase
coherence is likely a central ingredient
in the technology of atomtronics in
the superfluid ring, and therefore it is
important to characterize the regime
under which coherence can be maintained.
“In the future we plan on adding circuit
elements, such as repulsive barriers, to
Fig. 2. Strong constructive our superfluid ring,” explains Gretchen
A ring-shaped Bose-Einstein condeninterference for a phase Campbell. “Understanding how phase
sate (BEC) is used as the first building
fluctuations can affect the behavior
coherent BEC.
block in the circuits of atomic systems,
of the superfluid will be essential for
in a way that can mimic conventional
those activities.”
electronic circuits—and go beyond
them. In this approach, the ring-shaped
An experimental realization of the
condensate plays the critical role of a
ideas presented in the paper is sug“superfluid wire.” Just as current flows
gested by an interference experiment
without dissipation in a superconductthat would show the effect of reduced
ing wire, persistent flow of a condensate
phase coherence. Here, the atoms
can be created in a superfluid wire. Thus,
would be released from the trap as
the ring-shaped condensate constitutes
shown in Fig. 1 (below, right). As they
Fig. 3. Suppressed interfer- approach the center of the ring, the
a “superfluid circuit.”
ence for a phase fluctuat- atoms can either show significant
ing BEC.
However, because of the elongated
constructive interference for a phase
shape of the condensate, the system
coherent BEC (Fig. 2) or suppressed
reflects some features of one-dimensional systems.
interference (Fig. 3). This suppression of interference
Specifically, the phase coherence across the system
would be the smoking gun for strong phase fluctuacan be destroyed, due to the importance of phase
tions in the condensate.
fluctuations in low-dimensional systems. The paper
characterizes the circumstances under which these
* Phys. Rev. A 82, 033607 (2010).
Fig. 1. An experimental setup for
creating a toroidal Bose-Einstein
condensate. The toriodal trap is
created by combining two laser
beams. The first beam, referred
to as the “sheet beam,” confines
the atoms tightly in the vertical
direction. The second beam has
a ring-shaped intensity profile.
The combination of these beams
creates the ring shaped condensate
shown to the right, where red corresponds to high density and blue represents the background level. This
design might be used to confirm the reduced phase coherence predicted in the paper.
23
Quantum Entrepreneurship Seminar
JQI held a Quantum Entrepreneurship Seminar at
NIST on October 19, 2010, featuring a talk by Rainer
Kunz on “Commercializing Ultracold and Cold
Atom Technologies,” interspersed by lively discussion with JQI students, postdocs and Fellows.
Jr. Chaired Professor in the Department of Electrical,
Computer and Energy Engineering at the University
of Colorado at Boulder, is the wife of Dana Anderson, a JILA Fellow who has pioneered the development of compact apparatus for the production of
Bose-Einstein condensates (at the 2010 APS March
Meeting in Portland, OR, Anderon’s research group
caused a sensation by demonstrating BEC production in a portable apparatus in the exhibit hall). A
casual conversation between Rainer and Zoya led
to the foundation of ColdQuanta in 2007. In 2010,
ColdQuanta will likely return its first year of profitable operation, based in part on commercial sales.
Rainer Kunz, President and CEO of ColdQuanta,
Inc., is a seasoned business executive with over 20
years of experience in management, sales, business
development, and software development, including positions at AltoCom, Apple, General Magic and
Apollo Computer.
With no professional training in quantum physics,
but a fascination with the subject, Rainer met Zoya
Popović when they were both serving as judges at a
middle-school science fair. Zoya, the Hudson Moore
Rainer offered much practical advice to those interested in forming startup companies.
Postdocs and graduate students meet with Rainer Kunz, CEO and co-founder of ColdQuanta,
Inc., after his Quantum Entrepreneurship Seminar, October 19, 2010. Left to right: Yu-Ju Lin, Kai
Le, Elizabeth Goldschmidt, Karl Nelson, Amy Cassidy, Anand Ramanathan, Rainer Kunz, Brenton
Knuffman, Adam Steele and Joffrey Peters.
24
Quantum Cats, from p. 1
of the largest and most well-defined cat states ever
made from light. (Larger cat states have been created in different systems by other research groups,
including one at NIST.)
Depending on the number of subtracted photons,
the remaining light is in a state that is a good approximation of a quantum cat, says Gerrits—the
best that can be achieved because nobody has been
able to create a “real” one, by, for instance, the quantum equivalent to superimposing two weak laser
beams with opposite phases.
A “cat state” is a curiosity of the quantum world,
where particles can exist in “superpositions” of two
opposite properties simultaneously. The “cat” is a
reference to German physicist Erwin Schrödinger’s
famed 1935 theoretical notion of a cat that is both
alive and dead simultaneously.
NIST conducts research on novel states of light because they may enhance measurement techniques
such as interferometry, used to measure distance
based on the interference of two light beams. The
research also may contribute to quantum computing—which may someday solve some problems that
are intractable today—and quantum communications, the most secure method known for protecting
the privacy of a communications channel. Larger
quantum cats of light are needed for accurate information processing.
“This is a new state of light, predicted in quantum
optics for a long time,” says NIST research associate Thomas Gerrits, lead author of the paper. “The
technologies that enable us to get these really good
results are ultrafast lasers, knowledge of the type of
light needed to create the cat state, and photon detectors that can actually count individual photons.”
The NIST team created their optical cat state by using an ultrafast laser pulse to excite special crystals
to create a form of light known as a squeezed vacuum, which contains only even numbers of photons.
A specific number of photons were subtracted from
the squeezed vacuum using a device called a beam
splitter. The photons were identified with a NIST
sensor that efficiently detects and counts individual
photons (see “NIST Detector Counts Photons With
99 Percent Efficiency,” NIST Tech Beat, Apr. 13, 2010.)
* “Generation of optical coherent state superpositions
by number-resolved photon subtraction from squeezed
vacuum,” T. Gerrits, S. Glancy, T. Clement , B. Calkins, A.
Lita, A. Miller, A. Migdall, S.W. Nam, R. Mirin and E. Knill,
Phys. Rev. A 82, 031802 (2010).
Media Contact: Laura Ost, [email protected],
303-497-4880
These colorized plots of electric field values indicate how closely the NIST “quantum cats” (left)
compare with theoretical predictions for a cat state (right). The purple spots and alternating blue
contrast regions in the center of the images indicate the light is in the appropriate quantum state.
Credit: Gerrits/NIST
25
Publications
“Phases of a Two-Dimensional Bose Gas in an Optical Lattice,” K. Jiménez-García, R.L. Compton, Y.-J. Lin,
W.D. Phillips, J.V. Porto, I.B. Spielman, Phys. Rev. Lett.
105, 110401 (2010).
“Creation and manipulation of Feshbach resonances
with radio-frequency radiation,” Thomas M. Hanna,
Eite Tiesinga, Paul S. Julienne, New J. Phys. 12,
083031 (2010).
“Phase fluctuations in anisotropic Bose-Einstein
condensates: From cigars to rings,” L. Mathey, A.
Ramanathan, K.C. Wright, S.R. Muniz, W.D. Phillips,
Charles W. Clark, Phys. Rev. A 82, 033607 (2010).
“Universal rates for reactive ultracold polar molecules in reduced dimensions,” Andrea Micheli, Zbigniew Idziaszek, Guido Pupillo, Mikhail A. Baranov,
Peter Zoller, Paul S. Julienne, Phys. Rev. Lett. 105,
073202 (2010).
“Quantum simulation and phase diagram of the
transverse-field Ising model with three atomic spins,” “Interactions between Rydberg-dressed atoms,” J.E.
E.E. Edwards, S. Korenblit, K. Kim, R. Islam, M.-S.
Johnson, S.L. Rolston, Phys. Rev. A 82, 033412 (2010).
Chang, J.K. Freericks, G.-D. Lin, L.-M. Duan, C. Monroe, Phys. Rev. B 82, 060412 (2010).
“Theory and applications of atomic and ionic polarizabilities,” J. Mitroy, M.S. Safronova, Charles W. Clark,
“The rotating-wave approximation: consistency and J. Phys. B: At. Molec. Phys. 43, 202001 (2010).
applicability from an open quantum system analysis,” Chris Fleming, N.I. Cummings, Charis Anastopou- “Improved Timing Resolution Single-Photon Deteclos, B.L. Hu, J. Phys. A: Math. Theor. 43, 405304 (2010). tors in Daytime Free-Space Quantum Key Distribution With 1.25 GHz Transmission Rate,” A. Restelli, J.C.
“Observation of Ground-State Quantum Beats in
Bienfang, C.W. Clark, I. Rech, I. Labanca, M. Ghioni,
Atomic Spontaneous Emission,” D.G. Norris, L.A. Oro- S. Cova, IEEE Journal of Selected Topics in Quanzco, P. Barberis-Blostein, H.J. Carmichael, Phys. Rev.
tum Electronics, DOI: 10.1109/JSTQE.2010.2040710
Lett. 105, 123602 (2010).
(2010).
Entangled States
Chris Monroe was the lone experimentalist at the Benasque Workshop on Quantum Coherence and Decoherence (Benasque, Spain). During this international workshop on quantum decoherence, set deep in the Pyrenees Mountains Monroe spoke on quantum simulation of magnetism with ever larger atomic spin chains.
The 2010 European Conference on Trapped Ions (Durham, UK) featured three invited talks from the JQI Ion
Trap Group. Chris Monroe presented an historical perspective on trapped ion physics and quantum information over the last two decades; Wes Campbell spoke about the ultrafast and ultraclean manipulation of individual atoms using laser pulses; and Emily Edwards spoke on the use of trapped ion crystals for the quantum
simulation of magnetism.
6
Entangled States, from p. 7
Paul Julienne visited Austria, Poland, and the UK
where he gave numerous invited talks at various
conferences titled “Ultracold Polar Molecules in
Gases and Lattices,” and “Cold Collisions of Atoms,
Molecules, and Ions.” During the trip Julienne visited the University of Innsbruck, Austria and met
with Rudolph Grimm, Peter Zoller, Christoph Naegerl, Guido Pupillo, and Florian Schreck to continue
collaborative projects on ultracold atoms and
molecules.
Susan Clark, a new JQI Postdoctoral Fellow, joins JQI following her PhD at Stanford, where
she conducted research with
semiconductor quantum dots in
the group of Y. Yamomoto. Here
she will join the JQI Ion Trap
Group and apply her knowledge of ultrafast semiconductor control to the generation
of entanglement of large ion
crystals. Susan is also a triathalon competitor and an
accomplished flautist, who has performed the very
difficult Flute Sonata by S. Prokofiev.
High School standouts Grace Young (left) and Jennifer Wang (right) returned for an abbreviated summer
stint in the JQI Ion Trap Laboratory of C. Monroe (see
Sept. 2009 JQI newsletter). This summer, Grace and
Jennifer designed and constructed a macroscopic
trap from a polished aluminum paraboloid, with
help from JQI grad student David Hayes and postdoc Qudsia Quraishi. In this trap, they successfully
confined individual grains of diamond dust, for the
efficient collection of photons from the nitrogen-vacancy (NV) defects in the diamond. NV-diamond has
become an attractive solid-state host for quantum
bits for applications in quantum information science.
Both young women commence their college studies
at MIT this Fall.
The 2010 Michigan Quantum Summer School,
partially supported by JQI, was held in the first two
weeks of August with several JQI students in
attendance. This biennial school mirrors the famous
symposia held at the University of Michigan from
1928-1942, as quantum foundations are again on
center stage now in the 21st century with the new
field of Quantum Information Science promising
to exploit quantum phenomena for gains in the
processing and communication of information.
This year, the school concentrated on the topics of
quantum simulation and quantum metrology, and
featured several lectures by JQI fellows Luis Orozco
and Chris Monroe.
On September 8-9, Bill Phillips visited Amherst College in
Amherst, MA to give the “Five
College Colloquium” series
on “What’s New in Physics.”
Members of the communities
of Amherst College, University
of Mass. at Amherst, Smith
College, Mount Holyoke College, and Hampshire College
attended his lecture: “Time,
Einstein, and the Coolest Stuff
in the Universe.” Phillips also
gave a seminar at Amherst on
“Spinning Atoms with Light: a new twist on deBroglie wave optics.”
On September 15, Joshua Bienfang was honored
as the finalist of the 2010 Science and Environment
Medal during the Service to America Medals ceremony at the Andrew W. Mellon Auditorium, Washington, DC.
Left to right: Patrick Gallagher, Director,
NIST; Susan Solomon, National Oceanic
and Atmospheric Administration (NOAA),
2010 Career Achievement Medal; Joshua
Bienfang, JQI, 2010 Science and Environment Medal Finalist; Jane Lubchenco,
Administrator of NOAA. Photo credit: JQI.
7
Entangled States, from p. 8
Ian Spielman was honored as one of Popular Science
magazine’s “Brilliant 10” scientists of 2010. The full
story is available online: ”Ian Spielman, the Control
Freak .”
Ludwig Mathey gave an invited talk at Stony Brook
University entitled, “Many-Body Physics of Bosonic
Mixtures in 1D.”
On October 23-24, the JQI assembled at Booth 1108
on Wilson Plaza for the nation’s inaugural USA Science and Engineering Festival. The festival, aimed
to promote science and technology among young
children and students, was manned ‘round the clock
by a number of JQI fellows and researchers.
The October 2010 issue of Optics and Photonics
News (OPN) featured back-to-back articles authored
by JQI researcher Jemellie Galang (UMD) and
former researcher Danny Rogers (NIST). OPN is
the membership magazine of the Optical Society of
America, with a circulation of 16,000. The October issue can be found online at http://www.osa-opn.org/
Archives/BackIssue.aspx?j=OPN&v=21&i=10.
During October 11-15, several JQI fellows attended
the Kavli Institute of Theoretical Physics Conference
on “Frontiers of Ultracold Atoms and Molecules.”
Bill Phillips, as one of the conference organizers,
gave a brief history of the field in the way of opening remarks which was followed by invited talks by
Sankar DasSarma (“Interesting Quantum Phases at
the Frontiers of Cold Atom Physics: Perspectives of
a Condensed Matter Theorist”) and Ian Spielman
(“Spin Orbit Coupling in a BEC”).
JQI researcher Tom Hanna explains levitation of
magnets by superconductors to junior colleagues.
From October 27-29 the JQI, in collaboration with
the NIST Information Technology Laboratory, organized a workshop entitled “From Quantum Information and Complexity to Post-Quantum Information Security.” With more than 90 participants
from across the globe, the conference was the first
of its kind, bringing physicists, mathematicians, and
computer scientists together to look at the connection between physical systems, computability, and
approaches to cryptography in the era of quantum
information. For a list of the conference talks, please
see http://jqi.umd.edu/workshop/2010-quantuminformation.html.
On October 4, Bill Phillips gave the Boris Jacobsohn
Memorial Lecture as part of the Physics Colloquium
at the University of Washington.
JQI researcher Wes Campbell (left) discusses magnetic levitation while Zaheil
Kim (right) demonstrates a principle of
fiber-optic communication using a laser
and piece of plexiglass.
In addition, on October 25, Phillips visited the students of Dos Pueblos High School in Goleta, CA, and
gave an invited talk titled “Time, Einstein, and the
Coolest Stuff There Is.” The students were part of an
engineering class taught by Amir Abo-Shaeer, the
recent recipient of the MacArthur “genius prize” for
his work at the school.
8
Entangled States, from p. 8
Chris Monroe is co-PI with 6 others in a 5-year program to develop a new type of quantum computer architecture based on trapped ions. The project, entitled “MUSIQC: Modular Universal Scalable Ion-tap Quantum
Computer,” is a $15M program funded by IARPA (Intelligence Advanced Research Projects Activity). Local
quantum gate operations within small atom crystals will be accomplished via the Coulomb interaction, and
the crystals will be connected over larger distance through a photonic interface.
Concept of a large-scale quantum computer as envisioned by MUSIQC.
Charles Clark attended the 9th World Conference on Neutron Radiography, Kwa Maritane, South Africa,
October 3-8. In addition Clark, with co-inventors Michael Coplan (IPST) and Alan Thompson (NIST), was
awarded U.S. Patent 7,791,045 on September 7, for “Apparatus and Method for Detecting Slow Neutrons by
Lyman Alpha Radiation.”
JQI is a joint venture of the University of
Maryland and the National Institute of
Standards and Technology, with support
from the Laboratory for Physical Sciences.
Joint Quantum Institute
CSS (Bldg. 224) Room 2207
University of Maryland
College Park, MD 20742
E-mail: [email protected]
9