News for September 2009

Joint QuantumInstitute

ψA Summer ofOutreach:Students fromMiddle School to College, High-schoolTeachers andREU Dayspages 3-5

Hacking theQuantumAt DEFCONAnd More:Entangled Statespage 6

UpcomingWorkshop:

Ultracold Group IIAtomsSept. 17-19University of Marylandfor details, seejqi.umd.edu/workshop.html

A New JQI Fellow and a Distinguished VisitorThis month JQI welcomes two arrivals who bring additional strength and depthto the Institute’s inventory of talent.

One is the newest JQI Fellow, Gretchen Campbell, who will be a staff physicist at the National Institute of Standards and Technology (NIST) starting September 15. She received her Ph.D from MIT, where she worked in Wolf-gang Ketterle’s and Dave Prichard’s lab and studied rubidium Bose-Einstein condensates in optical lattices.

Most recently, Campbell was at JILA, a partner-ship between NIST and the University of Colorado, where she was a research associ-ate in the Jun Ye group. Among other pursuits, she was engaged in the effort to develop a strontium optical lattice clock -- and in the construction of a novel experimental apparatus that is used to explore elec-tronic transitions in strontium atoms. The frequency of such transitions is the fun-damental basis of modern timekeeping.

The world’s master clocks, as well as the

international standard for the duration of the second, rely on the natural frequency at which cesium atoms oscillate between two quantum conditions: a ground state and an excited state. At present, the sec-ond is defined as the time it takes a cesi-um-133 atom to complete 9,192,631,770 cycles between these states. That fre-

quency falls into the microwave range of the electromagnetic spectrum.

The best existing cesium clocks, such as NIST’s F-1, have an accuracy of a few parts in 10 quadrillion (1016), but that is not suf-ficiently exact for the increasingly precise demands of 21st-cen-tury science and tech-nology. So researchers are exploring numer-

ous alternatives for higher accuracy.

One very promising idea is to use an atomic transition that occurs about a hundred thousand times faster -- a frequency in the optical range of EM radiation. Among the optimal candidate atoms is strontium.

continued on page 2

JQI Fellow Gretchen Campbell

Campbell and Carmichael from p. 1

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At JQI, Campbell will continue research, begun in the Ye group, into using an array of strontium atoms confined in an optical lattice -- a sort of grid pat-tern formed by the intersection of two or more laser beams -- as a platform for quantum simulations of many-body physics problems and as a potential clock mechanism.

One extremely difficult aspect of this work involves exploiting a transition, artificially induced by numer-ous lasers acting in concert, that appears to be very stable. Creating, controlling and measuring that transition require exquisitely delicate manipulation of nuclear spin states using lasers and related apparatus.

In addition, Campbell will continue the investigations begun at NIST by departing JQI Fellow Kris Helmer-son into the behavior of Bose-Ein-stein condensates in toroid (do-nut-shaped) configurations. That arrangement has advantages for certain kinds of study. For example, an ordinary BEC has a substantial density gradient, thinning out from the center to the edges. A toroidal BEC has a much more uniform den-sity. In addition, it provides a closed loop in which atoms can move or forces can propagate, allowing a wide range of effects.

The Kiwi Connection

The second arrival this month is Professor Howard Carmichael of the University of Auckland (New Zea-land) Physics Department. Carmi-chael, an expert in cavity quantum electrodynamics and a Fellow of both the American Physical Society and the Optical Society of America, holds the Dan Walls Chair in Theoretical Physics. He is spending a sabbatical year at JQI, where he will work with many Fellows including Luis Orozco, whom Car-michael met years ago when both were at the Univer-sity of Texas at Austin.

His current research is concentrated in two areas, which he describes as follows:

Quantum Trajectory Theory

“Quantum trajectory theory treats the open systems

encountered in quantum optics according to a scat-tering scenario, in which the inputs are classical fields (external fields) and the outputs are classical stochas-tic processes that model the scattered fields after detection (after their measurement).

“The mapping from inputs to outputs is provided by a quantum stochastic process that is set up to ac-count for a particular measurement strategy (e.g., photon counting, homodyne/heterodyne detection, etc.). Both the formal theory and its applications are under study. Recent work includes the development of a novel measurement scheme to correlate the quadrature amplitudes of an electromagnetic field,

applications of this scheme in cavity quantum electrodynamics, and the modelling of multimode aspects of collective radiative phenomena (super-radiance).

Entanglement and Correlation in Composite Systems

“Quantum optics has traditionally concerned itself with uniquely quantum mechanical aspects of optical phenomena (e.g., photon antibunching and squeezing, violations of Bell inequalities). Attention in recent years has been focused on applications of these quantum features of light to novel schemes for processing information (so-called quantum information science). Entangled states are central to the proposed information processing proto-cols.

“Current work is directed towards understanding entangled states, and the contextual correlations they describe, in the broadest sense, i.e.,we are concerned with the physics of composite quantum systems in general. Specific interests include measures of en-tanglement for open systems, and schemes for the generation and manipulation of this entanglement. Continuous variable entanglement is of particular interest. It has been suggested by others that this form of entanglement can be accounted for within stochastic electrodynamics. The suggestion is being assessed. A quantum trajectory theory of continuous variable teleportation is being developed for compar-ison with the stochastic electrodynamics proposal.”

Visiting Professor Howard Carmichael

Summer Outreach 1: H.S. Teachers

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Physics in Focus: On June 26, 2009, JQI’s Physics Frontier Center conducted a day-long workshop on optics in the classroom for local-area high school physics teachers, using instructional materials from the Optical Society of America. The first half of the event was devoted to demonstrations and discussion of techniques to illustrate optical phenomena. The second half involved a tour of several JQI laboratories to see some of the ways in which quantum optics is employed in ongoing research.

Clockwise from left: PFC Co-Director Luis Orozco works with Faiz Mohideen of Largo (MD) High School. PFC Co-Director Bill Phillips with Mohideen and Sarah Wendel of Parkdale High School (Riverdale, MD). Postdoc Steve Olmschenk explains an ex-periment to Wendel and Herb Edelstein of Richard Montgomery High School (Rockville, MD).

Above left: Wendel and Sederik Rice, of Bowie (MD) High School experiment with laser demonstrations for classroom use. Above right: JQI Co-Director Steve Rolston takes questions after a presentation on techniques and materials for teaching optics. Other participating teachers were: Christopher Hahn of Linganore High School (Ijamsville, MD); Jasper Layne of Largo (MD) High School; and Yau-Jong Twu, Eleanor Roosevelt High School (Greenbelt, MD).

Summer Outreach 2: REU Projects

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2009 Summer Research Experience for Inter-national Undergraduates: Three undergradu-ate students spent ten weeks working with JQI researchers this summer.

Two were from Mexico -- Jorge Gomez (Uni-versidad de Guadalajara) and Diego Quiñones (Universidad Autónoma de San Luis Potosí). They were selected by the division of Quantum Information of Sociedad Mexicana de Fisica (Mexican Physical Society) after a national com-petition and worked in the group of JQI Fellow Luis Orozco, shown in top and bottom photos.

The third student -- Douglas Onyago, originally from Kenya -- is an undergraduate at Williams College in Massachusetts. He contacted JQI after learning of opportunities at the Annual Meeting of the National Society of Black Physi-cists and the National Society of Hispanic Physi-cists in Nashville, TN where JQI and its Physics Frontier Center had a booth. Onyago (at right in center photo) worked in the group of JQI Fel-low Trey Porto (at left in center photo).

Gomez (center in bottom photo) worked with JQI graduate student Dong Sheng (left in photo) on a “Magnetic field sensor and feed-back system for precise spectroscopy in an atom trap”.

Quiñones (at right in top photo) worked with JQI researcher Jonathan Hood (center of photo) on “Analysis of a Microwave Cavity and Antenna for driving a Parity Violating Transition”. Onyago worked with JQI student Creston Herold (not shown) on “Atomic beam collimators for Rb/Yb experiment.”

Their stay was supported by JQI, which thanks the REU MRSEC site at UMD for its hospitality in facilitating the students’ stay and making them part of the group.

All photos were taken at the final poster ses-sion for the REU MRSEC in August 2009.

Photos courtesy of Julie Callis/MRSEC

Summer Outreach 3: H.S. Students

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Getting the Point: This summer, the Chris Monroe group added two high-school seniors to its lab team: Grace Young and Jennifer Wang. Their job was to test a “parabolic dish” trap in which individual 5-micron hol-low polystyrene spheres are confined and irradiated by laser light. The spheres serve as a point source, scat-tering light in all directions. When a sphere is placed at the focus of the dish, more than half its light emerges vertically and can be collimated and routed to a fiber.

Eventually, the group willuse the trap configura-tion to hold a single atom, thereby achiev-ing very high collec-tion efficiency of single photons. The arrange-ment can then be put to use in other experi-ments. In particular, the group may replace the dust particle with a tiny chunk of diamond dusk containing a nitrogen-vacancy (NV) point defect. Such defects act somewhat like indi-vidual atoms, emitting single photons and per-mitting storage of spin qubits. NVs are “dirtier” sources than individual atoms, but are considerably cleaner than most other solid-state systems. And they can operate at room temperature in air.

Above: Students Grace Young (left) of The Potomac School and Jennifer Wang of Montgomery Blair High School manipulate the trap.

Right: A minuscule polystyrene sphere scatters red laser light from its position in the trap.

Below left: Photons scatter at all angles from the spheres, but the parabolic disk reflects and redirects the majority of the photons, which exit in a verti-cal direction. This makes it possible to dramatically improve the collection efficiency of the apparatus.

Below right: The Monroe group often meets at Ben’s Chili Bowl, the legendary eatery on U Street in the District of Columbia. Young and Wang are in the front row, second and third from the right.

sphere point source

“Number fluctuations and en-ergy dissipation in sodium spinor condensates,” Y. Liu, E. Gomez, S. Maxwell, L. Turner, E. Tiesinga, and P. Lett, Phys. Rev. Lett. 102, 225301 (2009)

“Collisional cooling of ultracold-atom ensembles using Feshbach resonances,” L. Mathey, Eite Ties-inga, Paul S. Julienne, and Charles W. Clark, Phys. Rev. A 80, 030702(R) (2009)

“Low-noise amplification of a con-tinuous variable quantum state,” R. C. Pooser, A. M. Marino, V. Boyer, K. Jones and P. Lett, Phys. Rev. Lett. 103, 010501 (2009)

“Precision Measurement of the Lifetime of the P_1/2 level of Yb+,” S. Olmschenk, D. Hayes, D. N. Mat-sukevich, P. Maunz, D. L. Moehring, K. C. Younge, C. Monroe, Phys. Rev. A 80, 022502 (2009)

“Large Scale Quantum Computa-tion in an Anharmonic Linear Ion Trap,” G.-D. Lin, S.-L. Zhu, R. Islam, K. Kim, M.-S. Chang, S. Korenblit, C. Monroe, and L.-M. Duan, Europhys-ics Letters 86, 60004 (2009)

“Counterflow and paired super-fluidity in one-dimensional Bose mixtures in optical lattices,”A. Hu, L. Mathey, I. Danshita, E. Tiesinga, C.J. Williams, and C.W. Clark, Phys. Rev. A 80, 023619 (2009)

“Topological insulators and met-als in atomic optical lattices,” T. D.

Stanescu, V. Galitski, J. Y. Vaishnav, C. W. Clark, and S. Das Sarma, Phys. Rev. A 79, 053639 (2009)

“Blackbody-radiation shift in a 88Sr+ ion optical frequency stan-dard,” Dansha Jiang, Bindiya Arora, Marianna S. Safronova and Charles W. Clark, J. Phys. B: At. Mol. Opt. Phys. 42, 154020 (2009)

Papers Accepted

“Quantum and classical dynamics of a Bose-Einstein condensate in alarge-period optical lattice,” J.H. Huckans, I.B. Spielman, B. La-burthe Tolra, et al. , accepted at Physical Review A.

“Frequency and temperature dependence of the anomalous ac Hall conductivity in a chiral p_x+ip_y superconductor with impurities,” Roman M. Lutchyn, Pavel Nagornykh, and Victor M. Yakovenko, accepted at Physical Review B and selected as an Edi-tors’ Suggestion.

JQI in VJAQF: Four JQI papers are included in the first issue of the Virtual Journal of Atomic Quantum

Fluids (http://vjaqf.aip.org/aqf ). VJAQF is the sixth and latest in the series of Virtual Journals co-pub-lished by the American Physical Society and the American Institute of Physics. The four papers are:

“Photon burst detection of single atoms in an optical cavity,”M. L. Terraciano, R. Olson Knell, D. G. Norris, J. Jing, A. Fernández & L. A. Orozco, Nature Physics 5, 480 - 484 (2009)

“Rapid production of 87Rb Bose-Einstein condensates in a com-bined magnetic and optical potential,” Y.-J. Lin, A. R. Perry, R. L. Compton, I. B. Spielman, and J. V. Porto, Phys. Rev. A 79, 063631 (2009)

“Number Fluctuations and Energy Dissipation in Sodium Spinor Condensates,” Y. Liu, E. Gomez, S. E. Maxwell, L. D. Turner, E. Tiesinga, and P. D. Lett, Phys. Rev. Lett. 102, 225301 (2009)

“Raman processes and effective gauge potentials,” I.B. Spielman,Phys. Rev. A 79, 063613 (2009)

Recent Publications

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Photo captions

Above, left to right: Alan Mink (JQI), Jemellie Galang (JQI), Ilya Gerhardt (NUS), Joshua Bienfang (JQI), Christina Brown (JQI) and Alessandro Restelli (JQI). Not shown: JQI Fellow Charles Clark. At right: Correlated photons as seen with the naked eye by visitors to the JQI/NUS live demonstration of quantum random number generation, Bell violation and quantum hacking. Here, parametric down-conversion annihilates violet photons from a salvaged HD-DVD diode (central spot), resulting in correlated photons emitted on opposing sides of the rings above. Image: Matthew Stits

Entangled States: Way Out West

“Hack the Quantum” is the title of the presentation staged at this year’s DEFCON hackers’ convention in Las Vegas, July 30-Aug. 2, by researchers from JQI and the Centre for Quantum Technologies, National University of Singapore (NUS). The description: “With a hands-on Bell-o-meter for entangled photons you can convince yourself that there are quantum effects beyond classical physics: a real qubit is offered to the participant who achieves the strongest violation of a Bell inequality. We also present a fresh attack that breaks many current quantum crypto systems, and demonstrate a photon-based quantum random number generator.”

Hack theQuantum

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Arrivals: NRC Postdoctoral Re-search Associate Amy Cassidy has joined NIST. She is seen in the photo at left, between JQI Fellow Paul Julienne and another NRC Postdoc-toral Research Associate, Ludwig Mathey, in the NIST dining hall on August 20, 2009.

Former Monroe group member Steve Olmschenk has joined the Laser Cooling and Trapping Group at NIST, where he will work with JQI Fellows Bill Phillips, Paul Lett, Trey Porto and Ian Spielman.

Emily Edwards is now a postdoc in the Monroe group, which has also added two new graduate students: David Hucul and Crystal Senko.

Departures: Former JQI/NIST postdoc Yingmei Liu has taken a faculty position at Oklahoma State University and Raphael Pooser, also a NIST postdoc, took a fel-lowship at Oak Ridge National Lab.

Former Monroe group Research Scientist Peter Maunz has taken a Research Scientist position at Duke Univer-sity, and Ming-Shien Chang is joining the faculty at the Academica Sinica, Taipei, Taiwan.

Entangled States: Going Places

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At left:

Hans Peter Büchler of the University of Stuttgart and JQI Fellows Ian Spielman and Charles Clark confer at the Work-shop on Quantum Gauge Theories and Ultracold Atoms, Sant Benet, Spain, September 3, 2009

Edwards

Chang

Maunz

Olmschenk

Liu

Pooser

Macroscopic Phase Transition: The DARPA Optical Lattice Emulator program at JQI has advanced to Phase II. JQI fellows Chris Monroe, Trey Porto, Ian Spielman and Sankar Das Sarma continue their work on the quantum simulation of materials and intractable systems using atoms and ions controlled by optical lattices.

The Phase II program, funded at approximately $3 million per year under PI Monroe, includes 16 PIs at 10 institutes. Work at JQI will use trapped ions to simulate intractable models of quantum magnetism, study atomic mixtures in optical lattices, implement a simulation of

fractional quantum statistics, and advance the theory of topological quantum manipulations that emerge in such systems.

Upcoming Meeting: The kick-off meeting for “Quantum-Optical Circuits of Hybrid Quantum Memories,” the newly announced project funded by the Department of De-fense’s Multidisciplinary University Research Initiative, will be held on October 1 and 2 at the University of Maryland’s Kim Engi-neering Building, Room 1105. This MURI is led by Chris Monroe, with JQI co-PIs Edo Waks and Jake Taylor.

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 InstituteCSS (Bldg. 224) Room 2207University of MarylandCollege Park, MD 20742E-mail: jqi_info@squid.umd.edu

Entangled States, continuedIan Spielman