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Craig M. Savage
Reader in Physics
ANU
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Publications 2004-now
mainly cold atoms and relativistic optics
ResearcherID |
Publications 1994-2003 |
Publications before 1994
Directional spatial structure of dissociated elongated molecular
condensates,
Magnus Ögren, C.M. Savage, K.V. Kheruntsyan, (2008).
ArXiv
Ultra-cold clouds of dimeric molecules can dissociate into quantum
mechanically correlated constituent atoms that are either bosons or fermions.
We theoretically model the dissociation of cigar shaped molecular condensates,
for which this difference manifests as complementary geometric structures of
the dissociated atoms.
Full abstract.
Ultra-cold clouds of dimeric molecules can dissociate into quantum
mechanically correlated constituent atoms that are either bosons or fermions.
We theoretically model the dissociation of cigar shaped molecular condensates,
for which this difference manifests as complementary geometric structures of
the dissociated atoms. For atomic bosons beams form along the long axis of the
molecular condensate. For atomic fermions beams form along the short axis. This
directional beaming simplifies the measurement of correlations between the
atoms through relative number squeezing.
Teaching Special Relativity using Virtual Reality,
Dominic McGrath, Craig Savage, Michael Williamson, Margaret Wegener and Tim McIntyre
Proceedings of the UniServe Science Symposium on Visualisation and Concept Development, October 2008.
Proceedings | Local copy
Learning Special Relativity is a highly anticipated experience for first year students; however, the
teaching and learning of Special Relativity are difficult tasks.
Full abstract.
Learning Special Relativity is a highly anticipated experience for first year students; however, the
teaching and learning of Special Relativity are difficult tasks. Special Relativity, while fundamentally and mathematically simple; has apparently bizarre implications and deals predominately with situations outside everyday experience. Understanding relativity requires one to accept that there is less that is absolute than was once believed and to accept a model of time and space that is strange and unfamiliar. As such, modifying everyday concepts of motion, time and space to
develop accurate constructs of the theory of Special Relativity is extraordinarily difficult. While Special Relativity is often featured in introductory physics courses, Scherr (2001) indicates many students fail to develop fundamental concepts in Special Relativity even after advanced instruction. To address these issues there has broad variety of efforts to determine the conceptual misunderstandings and develop activities to address them.
Real Time Relativity (RTR) is a virtual reality simulation of Special Relativity. Giving learners real
time control of how they explore and test the optical, spatial and time effects of near-light-speed
motion in a realistic environment enables a constructivist approach, previously unavailable, for
learning Special Relativity.
Given the hands-on nature of RTR, it has been incorporated into the experimental laboratories of
first year physics courses at the University of Queensland and the Australian National
University. These experiments enable students to explore relativistic effects without requiring
a detailed understanding of the theoretical framework. RTR experiments have been developed with an
active learning approach in which students learn by
developing, testing and refining their constructs with their peers. The RTR system and experiments
are currently being refined in a model inspired by the Physics Education Technology group at the
University of Colorado and
evaluated through a multimethods research approach. This
paper outlines our current point in a continuing development and evaluation project.
Atomic four-wave mixing via condensate collisions,
Aurélien Perrin, C. M. Savage, D. Boiron, V. Krachmalnicoff, C. I. Westbrook, Karen Kheruntsyan, New J. Phys. 10, 045021 (2008).
ArXiv |
New Journal of Physics
We perform a theoretical analysis of atomic four-wave mixing via a collision of two Bose-Einstein condensates of metastable helium atoms, and compare the results to a recent experiment.
Full abstract.
We perform a theoretical analysis of atomic four-wave mixing via a collision of two Bose-Einstein condensates of metastable helium atoms, and compare the results to a recent experiment. We calculate atom-atom pair correlations within the scattering halo produced spontaneously during the collision. We also examine the expected relative number squeezing of atoms on the sphere. The analysis includes first-principles quantum simulations using the positive P-representation method. We develop a unified description of the experimental and simulation results.
Time is money,
Craig Savage, Issue 18 of Cosmos, December 2007.
Cosmos
Time travel may be possible, but will it be affordable?
Quantum-field dynamics of expanding and contracting Bose-Einstein condensates,
S. Wuester, B.J. Dabrowska-Wuester, S.M. Scott, J.D. Close, C.M. Savage, Phys. Rev. A 77, 023619 (2008).
ArXiv |
Physical Review A |
doi:10.1103/PhysRevA.77.023619
We analyze the dynamics of quantum statistics in a harmonically trapped Bose-Einstein condensate, whose two-body interaction strength is controlled via a Feshbach resonance. From an initially non-interacting coherent state, the quantum field undergoes Kerr squeezing, which can be qualitatively described with a single mode model.
Full abstract.
We analyze the dynamics of quantum statistics in a harmonically trapped Bose-Einstein condensate, whose two-body interaction strength is controlled via a Feshbach resonance. From an initially non-interacting coherent state, the quantum field undergoes Kerr squeezing, which can be qualitatively described with a single mode model. To render the effect experimentally accessible, we propose a homodyne scheme, based on two hyperfine components, which converts the quadrature squeezing into number squeezing. The scheme is numerically demonstrated using a two-component Hartree-Fock-Bogoliubov formalism.
Spatial pair correlations of atoms in molecular dissociation,
C.M. Savage and K.V. Kheruntsyan, Phys. Rev. Lett. 99, 220404 (2007).
ArXiv |
Physical Review Letters
We perform first-principles quantum simulations of dissociation of trapped, spatially inhomogeneous Bose-Einstein condensates of molecular dimers using the positive-P representation method. Specifically, we study spatial pair correlations of atoms produced in dissociation and analyze different correlation measures after time of flight.
Full abstract.
We perform first-principles quantum simulations of dissociation of trapped, spatially inhomogeneous Bose-Einstein condensates of molecular dimers using the positive-P representation method. Specifically, we study spatial pair correlations of atoms produced in dissociation and analyze different correlation measures after time of flight. These include Glauber's density-density correlation and number-difference squeezing in spatial column densities which correspond to the experimental method of shot noise spectroscopy in absorption images. We find that the strength of the observable correlations may significantly degrade in systems with strong spatial inhomogeneity compared to the predictions of idealized uniform models. We show how binning of the signal can enhance the detectable correlations and lead to the violation of the classical Cauchy-Schwartz inequality.
Limits to the analogue Hawking temperature in a Bose-Einstein condensate,
S. Wuester and C.M. Savage, Phys. Rev. A 76, 013608 (2007).
ArXiv |
Physical Review A
Quasi-one dimensional outflow from a dilute gas Bose-Einstein condensate reservoir is a promising
system for the creation of analogue Hawking radiation. We use numerical modeling to show that
stable sonic horizons exist in such a system under realistic conditions, taking into account the
transverse dimensions and three-body loss.
Full abstract.
Quasi-one dimensional outflow from a dilute gas Bose-Einstein condensate reservoir is a promising
system for the creation of analogue Hawking radiation. We use numerical modeling to show that
stable sonic horizons exist in such a system under realistic conditions, taking into account the
transverse dimensions and three-body loss. We find that loss limits the achievable analogue Hawking
temperatures, with sodium condensates allowing the highest temperatures. A condensate of 30,000
atoms, with transverse confinement frequency of 6800 × 2pi Hz, yields horizon temperatures
of about 20 nK over a period of 50 ms. This is at least four times higher than for other atoms
commonly used for Bose-Einstein condensates.
Real Time Relativity: exploration learning of special relativity,
C. M. Savage, A. Searle, L. McCalman, American Journal of Physics 75, 791 (2007).
ArXiv |
American Journal of physics |
Google Scholar
Real Time Relativity is a computer program that lets students fly at relativistic speeds though a simulated world populated with planets, clocks, and buildings. The counterintuitive and spectacular optical effects of relativity are prominent, while systematic exploration of the simulation allows the user to discover relativistic effects such as length contraction and the relativity of simultaneity.
Full abstract.
Real Time Relativity is a computer program that lets students fly at relativistic speeds though a simulated world populated with planets, clocks, and buildings. The counterintuitive and spectacular optical effects of relativity are prominent, while systematic exploration of the simulation allows the user to discover relativistic effects such as length contraction and the relativity of simultaneity. We report on the physics and technology underpinning the simulation, and our experience using it for teaching special relativity to first year university students.
Quantum depletion of collapsing Bose-Einstein condensates,
S. Wuester, B.J. Dabrowska-Wuester, A.S. Bradley, M.J. Davis, P.B. Blakie, J.J. Hope, C.M. Savage, Phys. Rev. A 75, 043611 (2007).
ArXiv |
Physical Review A |
Google Scholar
We perform the first numerical three-dimensional studies of quantum field effects in the Bosenova experiment on collapsing condensates by E. Donley et al. [Nature 415, 39 (2002)] using the exact experimental geometry.
Full abstract.
We perform the first numerical three-dimensional studies of quantum field effects in the Bosenova experiment on collapsing condensates by E. Donley et al. [Nature 415, 39 (2002)] using the exact experimental geometry. In a stochastic truncated Wigner simulation of the collapse, the collapse times are larger than the experimentally measured values. We find that a finite temperature initial state leads to an increased creation of uncondensed atoms, but not to a reduction of the collapse time. A comparison of the time-dependent Hartree-Fock-Bogoliubov and Wigner methods for the more tractable spherical trap shows excellent agreement between the uncondensed populations. We conclude that the discrepancy between the experimental and theoretical values of the collapse time cannot be explained by quantum fluctuations or finite temperature effects.
Real Time Relativity,
C.M. Savage, A. C. Searle, L. McCalman, physics/0607223 (2006).
ArXiv |
HTML |
Google Scholar
Real Time Relativity is a computer program that allows the user to fly through a virtual world governed by relativistic physics.
Full abstract.
Real Time Relativity is a computer program that allows the user to fly through a virtual world governed by relativistic physics. The user controls a 'rocket' carrying a 'camera'. The rocket may be accelerated and steered, and the camera may be pointed in any direction. It takes advantage of the fact that video cards provide inexpensive data-parallel processing and are designed to perform rapid arithmetic on four-dimensional vectors.
First-principles quantum simulations of dissociation of molecular
condensates: Atom correlations in momentum space,
C.M. Savage, P. Schwenn, K.V. Kheruntsyan, Phys. Rev. A 74, 033620 (2006).
ArXiv |
Physical Review A |
Google Scholar
We investigate the quantum many-body dynamics of dissociation of a
Bose-Einstein condensate of molecular dimers into pairs of constituent bosonic
atoms and analyze the resulting atom-atom correlations.
Full abstract.
We investigate the quantum many-body dynamics of dissociation of a
Bose-Einstein condensate of molecular dimers into pairs of constituent bosonic
atoms and analyze the resulting atom-atom correlations. The quantum fields of
both the molecules and atoms are simulated from first principles in three
dimensions using the positive-P representation method. This allows us to
provide an exact treatment of the molecular field depletion and s-wave
scattering interactions between the particles, as well as to extend the
analysis to nonuniform systems. In the simplest uniform case, we find that the
major source of atom-atom decorrelation is atom-atom recombination which
produces molecules outside the initially occupied condensate mode. The unwanted
molecules are formed from dissociated atom pairs with non-opposite momenta. The
net effect of this process -- which becomes increasingly significant for
dissociation durations corresponding to more than about 40% conversion -- is to
reduce the atom-atom correlations. In addition, for nonuniform systems we find
that mode-mixing due to inhomogeneity can result in further degradation of the
correlation signal. We characterize the correlation strength via the degree of
squeezing of particle number-difference fluctuations in a certain
momentum-space volume and show that the correlation strength can be increased
if the signals are binned into larger counting volumes.
Through Einstein's Eyes,
A. C. Searle, C. M. Savage, P.A. Altin, F. H. Bennet, M. R. Hush, Australian Physics 42, 84 (2005).
ArXiv | ANU Eprint archive |
Google Scholar
We have developed a relativistically-accurate computer graphics code and have used it to produce photo-realistic images and videos of scenes where special relativistic effects dominate, either in astrophysical contexts or in imaginary worlds where the speed of light is only a few metres per second.
Full abstract.
We have developed a relativistically-accurate computer graphics code and have used it to produce photo-realistic images and videos of scenes where special relativistic effects dominate, either in astrophysical contexts or in imaginary worlds where the speed of light is only a few metres per second. The videos have been integrated into our under-graduate teaching programme for several years. Recently we took the next step, encouraging undergraduate students to use the code to explore relativity, develop their own videos, and eventually package them together into Through Einstein's Eyes, a multimedia CD.
Numerical Study of the stability of Skyrmions in Bose-Einstein Condensates,
S. Wüster, T.E. Argue and C. M. Savage, Phys. Rev. A 72, 043616 (2005).
ArXiv | Physical Review A |
Google Scholar
We show that the stability of three-dimensional Skyrmions in trapped Bose-Einstein condensates depends critically on scattering lengths, atom numbers, trap rotation and trap anisotropy.
Full abstract.
We show that the stability of three-dimensional Skyrmions in trapped Bose-Einstein condensates depends critically on scattering lengths, atom numbers, trap rotation and trap anisotropy. In particular, for the 87Rb |F=1,mf=-1>, |F=2,mf=1> hyperfine states stability is sensitive to the scattering lengths at the level of their present experimental uncertainties. In a cigar shaped trap, we find stable Skyrmions with as few as 2 x106 atoms, a number which scales with the inverse square root of the trap frequency. These can be stabilized against drift out of the trap by laser pinning.
Superradiant scattering from a hydrodynamic vortex,
T. R. Slatyer and C. M. Savage, Classical and Quantum Gravity 22, 3833 (2005).
ArXiv | Classical and Quantum Gravity |
Google Scholar
We show that sound waves scattered from a hydrodynamic vortex may be amplified. Such superradiant scattering follows from the physical analogy between spinning black holes and hydrodynamic vortices.
Full abstract.
We show that sound waves scattered from a hydrodynamic vortex may be amplified. Such superradiant scattering follows from the physical analogy between spinning black holes and hydrodynamic vortices. However a sonic horizon analogous to the black hole event horizon does not exist unless the vortex possesses a central drain, which is challenging to produce experimentally. In the astrophysical domain, superradiance can occur even in the absence of an event horizon: we show that in the hydrodynamic analogue, a drain is not required and a vortex scatters sound superradiantly. Possible experimental realization in dilute gas Bose-Einstein condensates is discussed.
Collapsing Bose-Einstein condensates beyond the Gross-Pitaevskii approximation,
S. Wüster, J. J. Hope, C. M. Savage, Phys. Rev. A 71, 033604 (2005).
ArXiv | Physical Review A |
Google Scholar
We analyse quantum field models of the bosenova experiment, in which 85Rb Bose-Einstein condensates were made to collapse by switching their atomic interactions from repulsive to attractive.
Full abstract.
We analyse quantum field models of the bosenova experiment, in which 85Rb Bose-Einstein condensates were made to collapse by switching their atomic interactions from repulsive to attractive. Specifically, we couple the lowest order quantum field correlation functions to the Gross-Pitaevskii function, and solve the resulting dynamical system numerically. Comparing the computed collapse times with the experimental measurements, we find that the calculated times are much larger than the measured values. The addition of quantum field corrections does not noticeably improve the agreement compared to a pure Gross-Pitaevskii theory.
Classical noise and flux: the limits of multi-state atom lasers,
N.P. Robins, C. M. Savage, J. J. Hope, J. E. Lye, C. S. Fletcher, S. A. Haine, J. D. Close, Phys. Rev. A 69, 051602 (2004).
ArXiv | Physical Review A |
Google Scholar
By direct comparison between experiment and theory, we show how the classical noise on a multi-state atom laser beam increases with increasing flux.
Full abstract.
By direct comparison between experiment and theory, we show how the classical noise on a multi-state atom laser beam increases with increasing flux. The trade off between classical noise and flux is an important consideration in precision interferometric measurement. We use periodic 10 microsecond radio-frequency pulses to couple atoms out of an F=2 87Rb Bose-Einstein condensate. The resulting atom laser beam has suprising structure which is explained using three dimensional simulations of the five state Gross-Pitaevskii equations.
ResearcherID |
Publications 1994-2003 |
Publications before 1994
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