Showing 1–16 of 16 results for author: Hope, J J

Dual Open Atom Interferometry for Compact and Mobile Quantum Sensing

Authors: Yosri Ben-Aïcha, Zain Mehdi, Christian Freier, Stuart S. Szigeti, Paul B. Wigley, Lorcán O. Conlon, Ryan Husband, Samuel Legge, Rhys H. Eagle, Joseph J. Hope, Nicholas P. Robins, John D. Close, Kyle S. Hardman, Simon A. Haine, Ryan J. Thomas

Abstract: We demonstrate an atom interferometer measurement protocol compatible with operation on a dynamic platform. Our method employs two open interferometers, derived from the same atomic source, with different interrogation times to eliminate initial velocity dependence while retaining precision, accuracy, and long term stability. We validate the protocol by measuring gravitational tides, achieving a p… ▽ More We demonstrate an atom interferometer measurement protocol compatible with operation on a dynamic platform. Our method employs two open interferometers, derived from the same atomic source, with different interrogation times to eliminate initial velocity dependence while retaining precision, accuracy, and long term stability. We validate the protocol by measuring gravitational tides, achieving a precision of 4.5 μGal in 2000 runs (6.7 h), marking the first demonstration of inertial quantity measurement with open atom interferometry that achieves long-term phase stability. △ Less

Submitted 18 January, 2025; v1 submitted 1 May, 2024; originally announced May 2024.

Journal ref: Phys. Rev. Lett. 133, 263403 - Published 27 December, 2024

Ultrafast, high repetition rate, ultraviolet, fiber based laser source: application towards Yb+ fast quantum-logic

Authors: Mahmood Irtiza Hussain, Matthew Joseph Petrasiunas, Christopher D. B. Bentley, Richard L. Taylor, Andre R. R. Carvalho, Joseph J. Hope, Erik W. Streed, Mirko Lobino, David Kielpinski

Abstract: Trapped ions are one of the most promising approaches for the realization of a universal quantum computer. Faster quantum logic gates could dramatically improve the performance of trapped-ion quantum computers, and require the development of suitable high repetition rate pulsed lasers. Here we report on a robust frequency upconverted fiber laser based source, able to deliver 2.5 ps ultraviolet (UV… ▽ More Trapped ions are one of the most promising approaches for the realization of a universal quantum computer. Faster quantum logic gates could dramatically improve the performance of trapped-ion quantum computers, and require the development of suitable high repetition rate pulsed lasers. Here we report on a robust frequency upconverted fiber laser based source, able to deliver 2.5 ps ultraviolet (UV) pulses at a stabilized repetition rate of 300.00000 MHz with an average power of 190 mW. The laser wavelength is resonant with the strong transition in Ytterbium (Yb+) at 369.53 nm and its repetition rate can be scaled up using high harmonic mode locking. We show that our source can produce arbitrary pulse patterns using a programmable pulse pattern generator and fast modulating components. Finally, simulations demonstrate that our laser is capable of performing resonant, temperature-insensitive, two-qubit quantum logic gates on trapped Yb$^+$ ions faster than the trap period and with fidelity above 99%. △ Less

Submitted 28 June, 2016; originally announced June 2016.

Journal ref: Optics Express Vol. 24, Issue 15, pp. 16638-16648 (2016)

Robustness of System-Filter Separation for the Feedback Control of a Quantum Harmonic Oscillator Undergoing Continuous Position Measurement

Authors: Stuart S. Szigeti, Sarah J. Adlong, Michael R. Hush, Andre R. R. Carvalho, Joseph J. Hope

Abstract: We consider the effects of experimental imperfections on the problem of estimation-based feedback control of a trapped particle under continuous position measurement. These limitations violate the assumption that the estimator (i.e. filter) accurately models the underlying system, thus requiring a separate analysis of the system and filter dynamics. We quantify the parameter regimes for stable coo… ▽ More We consider the effects of experimental imperfections on the problem of estimation-based feedback control of a trapped particle under continuous position measurement. These limitations violate the assumption that the estimator (i.e. filter) accurately models the underlying system, thus requiring a separate analysis of the system and filter dynamics. We quantify the parameter regimes for stable cooling, and show that the control scheme is robust to detector inefficiency, time delay, technical noise, and miscalibrated parameters. We apply these results to the specific context of a weakly interacting Bose-Einstein condensate (BEC). Given that this system has previously been shown to be less stable than a feedback-cooled BEC with strong interatomic interactions, this result shows that reasonable experimental imperfections do not limit the feasibility of cooling a BEC by continuous measurement and feedback. △ Less

Submitted 12 November, 2012; v1 submitted 11 November, 2012; originally announced November 2012.

Comments: 14 pages, 8 figures

Journal ref: Phys. Rev. A 87, 013626 (2013)

XMDS2: Fast, scalable simulation of coupled stochastic partial differential equations

Authors: Graham R. Dennis, Joseph J. Hope, Mattias T. Johnsson

Abstract: XMDS2 is a cross-platform, GPL-licensed, open source package for numerically integrating initial value problems that range from a single ordinary differential equation up to systems of coupled stochastic partial differential equations. The equations are described in a high-level XML-based script, and the package generates low-level optionally parallelised C++ code for the efficient solution of tho… ▽ More XMDS2 is a cross-platform, GPL-licensed, open source package for numerically integrating initial value problems that range from a single ordinary differential equation up to systems of coupled stochastic partial differential equations. The equations are described in a high-level XML-based script, and the package generates low-level optionally parallelised C++ code for the efficient solution of those equations. It combines the advantages of high-level simulations, namely fast and low-error development, with the speed, portability and scalability of hand-written code. XMDS2 is a complete redesign of the XMDS package, and features support for a much wider problem space while also producing faster code. △ Less

Submitted 16 July, 2012; v1 submitted 19 April, 2012; originally announced April 2012.

Comments: 9 pages, 5 figures

Journal ref: Comput. Phys. Commun. 184, 201-208 (2013)

Why momentum width matters for atom interferometry with Bragg pulses

Authors: Stuart S. Szigeti, John E. Debs, Joseph J. Hope, Nicholas P. Robins, John D. Close

Abstract: We theoretically consider the effect of the atomic source's momentum width on the efficiency of Bragg mirrors and beamsplitters and, more generally, on the phase sensitivity of Bragg pulse atom interferometers. By numerical optimization, we show that an atomic cloud's momentum width places a fundamental upper bound on the maximum transfer efficiency of a Bragg mirror pulse, and furthermore limits… ▽ More We theoretically consider the effect of the atomic source's momentum width on the efficiency of Bragg mirrors and beamsplitters and, more generally, on the phase sensitivity of Bragg pulse atom interferometers. By numerical optimization, we show that an atomic cloud's momentum width places a fundamental upper bound on the maximum transfer efficiency of a Bragg mirror pulse, and furthermore limits the phase sensitivity of a Bragg pulse atom interferometer. We quantify these momentum width effects, and precisely compute how mirror efficiencies and interferometer phase sensitivities vary as functions of Bragg order and source type. Our results and methodology allow for an efficient optimization of Bragg pulses and the comparison of different atomic sources, and will help in the design of large momentum transfer Bragg mirrors and beamsplitters for use in atom-based inertial sensors. △ Less

Submitted 18 December, 2011; v1 submitted 13 October, 2011; originally announced October 2011.

Comments: 25 pages, 11 figures

Quantum kinetic theory model of a continuous atom laser

Authors: G. R. Dennis, Matthew J. Davis, J. J. Hope

Abstract: We investigate the feasible limits for realising a continuously evaporated atom laser with high-temperature sources. A plausible scheme for realising a truly continuous atom laser is to outcouple atoms from a partially condensed Bose gas, whilst continuously reloading the system with non-condensed thermal atoms and performing evaporative cooling. Here we use quantum kinetic theory to model this sy… ▽ More We investigate the feasible limits for realising a continuously evaporated atom laser with high-temperature sources. A plausible scheme for realising a truly continuous atom laser is to outcouple atoms from a partially condensed Bose gas, whilst continuously reloading the system with non-condensed thermal atoms and performing evaporative cooling. Here we use quantum kinetic theory to model this system and estimate feasible limits for the operation of such a scheme. For sufficiently high temperatures, the figure of merit for the source is shown to be the phase-space flux. The dominant process limiting the usage of sources with low phase-space flux is the three-body loss of the condensed gas. We conclude that certain double-magneto-optical trap (MOT) sources may produce substantial mean condensate numbers through continuous evaporation, and provide an atom laser source with a narrow linewidth and reasonable flux. △ Less

Submitted 24 November, 2010; originally announced November 2010.

Comments: 28 pages, 5 figures

Feedback control of an interacting Bose-Einstein condensate using phase-contrast imaging

Authors: Stuart S. Szigeti, Michael R. Hush, Andre R. R. Carvalho, Joseph J. Hope

Abstract: The linewidth of an atom laser is limited by density fluctuations in the Bose-Einstein condensate (BEC) from which the atom laser beam is outcoupled. In this paper we show that a stable spatial mode for an interacting BEC can be generated using a realistic control scheme that includes the effects of the measurement backaction. This model extends the feedback theory, based on a phase-contrast imagi… ▽ More The linewidth of an atom laser is limited by density fluctuations in the Bose-Einstein condensate (BEC) from which the atom laser beam is outcoupled. In this paper we show that a stable spatial mode for an interacting BEC can be generated using a realistic control scheme that includes the effects of the measurement backaction. This model extends the feedback theory, based on a phase-contrast imaging setup, presented in \cite{Szigeti:2009}. In particular, it is applicable to a BEC with large interatomic interactions and solves the problem of inadequacy of the mean-field (coherent state) approximation by utilising a fixed number state approximation. Our numerical analysis shows the control to be more effective for a condensate with a large nonlinearity. △ Less

Submitted 3 September, 2010; originally announced September 2010.

Comments: 12 pages, 5 figures

Journal ref: S. S. Szigeti, M. R. Hush, A. R. R. Carvalho and J. J. Hope, Phys. Rev. A 82, 043632 (2010)

Pulsed pumping of a Bose-Einstein condensate

Authors: D. Döring, G. R. Dennis, N. P. Robins, M. Jeppesen, C. Figl, J. J. Hope, J. D. Close

Abstract: In this work, we examine a system for coherent transfer of atoms into a Bose-Einstein condensate. We utilize two spatially separate Bose-Einstein condensates in different hyperfine ground states held in the same dc magnetic trap. By means of a pulsed transfer of atoms, we are able to show a clear resonance in the timing of the transfer, both in temperature and number, from which we draw conclusi… ▽ More In this work, we examine a system for coherent transfer of atoms into a Bose-Einstein condensate. We utilize two spatially separate Bose-Einstein condensates in different hyperfine ground states held in the same dc magnetic trap. By means of a pulsed transfer of atoms, we are able to show a clear resonance in the timing of the transfer, both in temperature and number, from which we draw conclusions about the underlying physical process. The results are discussed in the context of the recently demonstrated pumped atom laser. △ Less

Submitted 29 June, 2009; v1 submitted 11 January, 2009; originally announced January 2009.

Comments: 5 pages, 5 figures, published in Physical Review A

Journal ref: Phys. Rev. A 79, 063630 (2009)

Quantum statistical measurements of an atom laser beam

Authors: M. K. Olsen, A. S. Bradley, S. A. Haine, J. J. Hope

Abstract: We describe a scheme, operating in a manner analogous to a reversed Raman output coupler, for measuring the phase-sensitive quadrature statistics of an atom laser beam. This scheme allows for the transferral of the atomic field statistics to an optical field, for which the quantum statistics may then be measured using the well-developed technology of optical homodyne measurement. We describe a scheme, operating in a manner analogous to a reversed Raman output coupler, for measuring the phase-sensitive quadrature statistics of an atom laser beam. This scheme allows for the transferral of the atomic field statistics to an optical field, for which the quantum statistics may then be measured using the well-developed technology of optical homodyne measurement. △ Less

Submitted 25 July, 2007; originally announced July 2007.

Comments: 4 pages, 2 fugures

Journal ref: Nuclear Physics A, 790, 733c (2007)

Teleportation of massive particles without shared entanglement

Authors: A. S. Bradley, M. K. Olsen, S. A. Haine, J. J. Hope

Abstract: We propose a method for quantum state transfer from one atom laser beam to another via an intermediate optical field, using Raman incoupling and outcoupling techniques. Our proposal utilises existing experimental technologies to teleport macroscopic matter waves over potentially large distances without shared entanglement. We propose a method for quantum state transfer from one atom laser beam to another via an intermediate optical field, using Raman incoupling and outcoupling techniques. Our proposal utilises existing experimental technologies to teleport macroscopic matter waves over potentially large distances without shared entanglement. △ Less

Submitted 1 June, 2007; originally announced June 2007.

Comments: 4 pages, 3 figures

Limit to non-destructive optical detection of atoms

Authors: J. J. Hope, J. D. Close

Abstract: All optical techniques used to probe the properties of Bose-Einstein condensates have been based on dispersion and absorption that can be described by a two-level atom. Both phenomena lead to spontaneous emission that is destructive. Recently, both were shown to lead to the same limit to the signal to noise ratio for a given destruction. We generalise this result to show that no single-pass opti… ▽ More All optical techniques used to probe the properties of Bose-Einstein condensates have been based on dispersion and absorption that can be described by a two-level atom. Both phenomena lead to spontaneous emission that is destructive. Recently, both were shown to lead to the same limit to the signal to noise ratio for a given destruction. We generalise this result to show that no single-pass optical technique using classical light, based on any number of lasers or coherences between any number of levels, can exceed the limit imposed by the two-level atom. This puts significant restrictions on potential non-destructive measurement schemes. △ Less

Submitted 28 August, 2003; originally announced August 2003.

Comments: 4 pages, 1 figure

The steady state of a pumped and damped atom laser

Authors: J. J. Hope, G. M. Moy, C. M. Savage

Abstract: This paper has been withdrawn, as further work has shown that an atom laser as described by the model herein does not have a steady state, so it doesn't matter much what it would look like. This paper has been withdrawn, as further work has shown that an atom laser as described by the model herein does not have a steady state, so it doesn't matter much what it would look like. △ Less

Submitted 14 May, 1998; v1 submitted 4 February, 1998; originally announced February 1998.

Comments: 1 postscript figure, uses revtex.sty This paper has been withdrawn, as further work has shown that an atom laser as described by the model herein *does not have a steady state*, so it doesn't matter much what it would look like

Report number: AN6353

Stimulation of Beta Decay due to a Bose-Einstein Condensate

Authors: J. J. Hope, C. M. Savage

Abstract: Nuclear processes can be stimulated by the presence of a macroscopic number of bosons in one of the final states. We describe the conditions necessary to observe the atom-stimulation of a beta decay process. The stimulation may be observable if it becomes possible to produce a Bose-Einstein condensate with the order of $10^{14}$ atoms in a trap. Nuclear processes can be stimulated by the presence of a macroscopic number of bosons in one of the final states. We describe the conditions necessary to observe the atom-stimulation of a beta decay process. The stimulation may be observable if it becomes possible to produce a Bose-Einstein condensate with the order of $10^{14}$ atoms in a trap. △ Less

Submitted 20 June, 1996; originally announced June 1996.

Comments: 7 pages, LaTeX, uses elsart.cls, home page at http://online.anu.edu.au/Physics/Welcome.html

An Atom Laser Based on Raman Transitions

Authors: G. M. Moy, J. J. Hope, C. M. Savage

Abstract: In this paper we present an atom laser scheme using a Raman transition for the output coupling of atoms. A beam of thermal atoms (bosons) in a metastable atomic state $|1 >$ are pumped into a multimode atomic cavity. This cavity is coupled through spontaneous emission to a single mode of another cavity for the ground atomic state, $|2 >$. Above a certain threshold pumping rate a large number of… ▽ More In this paper we present an atom laser scheme using a Raman transition for the output coupling of atoms. A beam of thermal atoms (bosons) in a metastable atomic state $|1 >$ are pumped into a multimode atomic cavity. This cavity is coupled through spontaneous emission to a single mode of another cavity for the ground atomic state, $|2 >$. Above a certain threshold pumping rate a large number of atoms, $N_2$, builds up in this single quantum state and transitions to the ground state of the cavity become enhanced by a factor $(N_2 + 1)$. Atoms in this state are then coupled to the outside of the cavity with a Raman transition. This changes the internal state of the atom and imparts a momentum kick, allowing the atoms to leave the system. △ Less

Submitted 24 March, 1997; v1 submitted 4 April, 1996; originally announced April 1996.

Comments: 8 pages, 4 postscript figures, uses RevTex, home page at http://online.anu.edu.au/Physics/Welcome.html (Some aspects of the exact physical model have changed from original version. Other general improvements included)

Stimulated Enhancement of Cross-Section by a Bose-Einstein Condensate

Authors: J. J. Hope, C. M. Savage

Abstract: This paper examines the feasibility of constructing an experiment which detects the atomic stimulation of a photon emission process. A beam of atoms (bosons) in an excited state is passed over an atomic trap which traps the atoms when they are in their internal ground state. When the trap contains a Bose-Einstein condensate, the cross-section for absorption of the atomic beam is increased. We ex… ▽ More This paper examines the feasibility of constructing an experiment which detects the atomic stimulation of a photon emission process. A beam of atoms (bosons) in an excited state is passed over an atomic trap which traps the atoms when they are in their internal ground state. When the trap contains a Bose-Einstein condensate, the cross-section for absorption of the atomic beam is increased. We examine a particular model in which this atom-stimulation is observable, and is also characterised by the emission of photons in a narrow cone in the direction of the atomic beam. △ Less

Submitted 26 February, 1996; originally announced February 1996.

Comments: 4 pages, two postscript figures, uses RevTex home page at http://online.anu.edu.au/Physics/Welcome.html

Report number: LP6025

Band Gaps for Atoms in Light based Waveguides

Authors: J. J. Hope, C. M. Savage

Abstract: The energy spectrum for a system of atoms in a periodic potential can exhibit a gap in the band structure. We describe a system in which a laser is used to produce a mechanical potential for the atoms, and a standing wave light field is used to shift the atomic levels using the Autler-Townes effect, which produces a periodic potential. The band structure for atoms guided by a hollow optical fibe… ▽ More The energy spectrum for a system of atoms in a periodic potential can exhibit a gap in the band structure. We describe a system in which a laser is used to produce a mechanical potential for the atoms, and a standing wave light field is used to shift the atomic levels using the Autler-Townes effect, which produces a periodic potential. The band structure for atoms guided by a hollow optical fiber waveguide is calculated in three dimensions with quantised external motion. The size of the band gap is controlled by the light guided by the fiber. This variable band structure may allow the construction of devices which can cool atoms. The major limitation on this device would be the spontaneous emission losses. △ Less

Submitted 11 October, 1995; v1 submitted 10 October, 1995; originally announced October 1995.

Comments: 7 pages, four postscript figures, uses revtex.sty, available through http://online.anu.edu.au/Physics/papers/atom.html

Report number: AJ5678