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Dive into the research topics where M. H. G. de Miranda is active.

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Featured researches published by M. H. G. de Miranda.


Science | 2008

A High Phase-Space-Density Gas of Polar Molecules

Kang-Kuen Ni; S. Ospelkaus; M. H. G. de Miranda; Avi Pe'er; B. Neyenhuis; J. J. Zirbel; Svetlana Kotochigova; Paul S. Julienne; D. S. Jin; J. Ye

A quantum gas of ultracold polar molecules, with long-range and anisotropic interactions, not only would enable explorations of a large class of many-body physics phenomena but also could be used for quantum information processing. We report on the creation of an ultracold dense gas of potassium-rubidium (40K87Rb) polar molecules. Using a single step of STIRAP (stimulated Raman adiabatic passage) with two-frequency laser irradiation, we coherently transfer extremely weakly bound KRb molecules to the rovibrational ground state of either the triplet or the singlet electronic ground molecular potential. The polar molecular gas has a peak density of 1012 per cubic centimeter and an expansion-determined translational temperature of 350 nanokelvin. The polar molecules have a permanent electric dipole moment, which we measure with Stark spectroscopy to be 0.052(2) Debye (1 Debye = 3.336 × 10–30 coulomb-meters) for the triplet rovibrational ground state and 0.566(17) Debye for the singlet rovibrational ground state.


Science | 2008

Sr Lattice Clock at 1 x 10-16 Fractional Uncertainty by Remote Optical Evaluation with a Ca Clock

Andrew D. Ludlow; Tanya Zelevinsky; Gretchen K. Campbell; Sebastian Blatt; Martin M. Boyd; M. H. G. de Miranda; Michael J. Martin; Jan Thomsen; J. Ye; Tara M. Fortier; J. E. Stalnaker; Scott A. Diddams; Y. Le Coq; Zeb W. Barber; N. Poli; Nathan D. Lemke; K. M. Beck; Christopher W. Oates

Optical atomic clocks promise timekeeping at the highest precision and accuracy, owing to their high operating frequencies. Rigorous evaluations of these clocks require direct comparisons between them. We have realized a high-performance remote comparison of optical clocks over kilometer-scale urban distances, a key step for development, dissemination, and application of these optical standards. Through this remote comparison and a proper design of lattice-confined neutral atoms for clock operation, we evaluate the uncertainty of a strontium (Sr) optical lattice clock at the 1 × 10–16 fractional level, surpassing the current best evaluations of cesium (Cs) primary standards. We also report on the observation of density-dependent effects in the spin-polarized fermionic sample and discuss the current limiting effect of blackbody radiation–induced frequency shifts.


Science | 2010

Quantum-State Controlled Chemical Reactions of Ultracold Potassium-Rubidium Molecules

S. Ospelkaus; Kang-Kuen Ni; D. Wang; M. H. G. de Miranda; B. Neyenhuis; Goulven Quéméner; Paul S. Julienne; John L. Bohn; D. S. Jin; J. Ye

Colliding in the Cold Chemical reactions occur through molecular collisions, which, in turn, are governed by the distributions of energy in each colliding partner. What happens when molecules are cooled so that they no longer have sufficient energy to collide? Ospelkaus et al. (p. 853; see the Perspective by Hutson) explored this question by preparing a laser-cooled sample of potassium rubidium (KRb) diatomics with barely any residual energy in any form (translational, rotational, vibrational, or electronic). By monitoring heat release over time, evidence was gathered for exothermic atom exchange reactivity through quantum mechanical tunneling. As predicted by theory, these reactions were exquisitely sensitive to the molecular states, with rates changing by orders of magnitude on varying minor factors such as nuclear spin orientation. Reactions mediated by quantum mechanical tunneling are observed, even in a sample of molecules cooled almost to a standstill. How does a chemical reaction proceed at ultralow temperatures? Can simple quantum mechanical rules such as quantum statistics, single partial-wave scattering, and quantum threshold laws provide a clear understanding of the molecular reactivity under a vanishing collision energy? Starting with an optically trapped near–quantum-degenerate gas of polar 40K87Rb molecules prepared in their absolute ground state, we report experimental evidence for exothermic atom-exchange chemical reactions. When these fermionic molecules were prepared in a single quantum state at a temperature of a few hundred nanokelvin, we observed p-wave–dominated quantum threshold collisions arising from tunneling through an angular momentum barrier followed by a short-range chemical reaction with a probability near unity. When these molecules were prepared in two different internal states or when molecules and atoms were brought together, the reaction rates were enhanced by a factor of 10 to 100 as a result of s-wave scattering, which does not have a centrifugal barrier. The measured rates agree with predicted universal loss rates related to the two-body van der Waals length.


Nature | 2010

Dipolar collisions of polar molecules in the quantum regime

Kang-Kuen Ni; S. Ospelkaus; D. Wang; Goulven Quéméner; B. Neyenhuis; M. H. G. de Miranda; John L. Bohn; J. Ye; D. S. Jin

Ultracold polar molecules offer the possibility of exploring quantum gases with interparticle interactions that are strong, long-range and spatially anisotropic. This is in stark contrast to the much studied dilute gases of ultracold atoms, which have isotropic and extremely short-range (or ‘contact’) interactions. Furthermore, the large electric dipole moment of polar molecules can be tuned using an external electric field; this has a range of applications such as the control of ultracold chemical reactions, the design of a platform for quantum information processing and the realization of novel quantum many-body systems. Despite intense experimental efforts aimed at observing the influence of dipoles on ultracold molecules, only recently have sufficiently high densities been achieved. Here we report the experimental observation of dipolar collisions in an ultracold molecular gas prepared close to quantum degeneracy. For modest values of an applied electric field, we observe a pronounced increase in the loss rate of fermionic potassium–rubidium molecules due to ultracold chemical reactions. We find that the loss rate has a steep power-law dependence on the induced electric dipole moment, and we show that this dependence can be understood in a relatively simple model based on quantum threshold laws for the scattering of fermionic polar molecules. In addition, we directly observe the spatial anisotropy of the dipolar interaction through measurements of the thermodynamics of the dipolar gas. These results demonstrate how the long-range dipolar interaction can be used for electric-field control of chemical reaction rates in an ultracold gas of polar molecules. Furthermore, the large loss rates in an applied electric field suggest that creating a long-lived ensemble of ultracold polar molecules may require confinement in a two-dimensional trap geometry to suppress the influence of the attractive, ‘head-to-tail’, dipolar interactions.


Physical Review Letters | 2007

Coherent Optical Phase Transfer over a 32-km Fiber with 1 s Instability at 10 − 17

Andrew D. Ludlow; M. H. G. de Miranda; J. E. Stalnaker; Scott A. Diddams; J. Ye

The phase coherence of an ultrastable optical frequency reference is fully maintained over actively stabilized fiber networks of lengths exceeding 30 km. For a 7-km link installed in an urban environment, the transfer instability is 6 x 10{-18} at 1 s. The excess phase noise of 0.15 rad, integrated from 8 mHz to 25 MHz, yields a total timing jitter of 0.085 fs. A 32-km link achieves similar performance. Using frequency combs at each end of the coherent-transfer fiber link, a heterodyne beat between two independent ultrastable lasers, separated by 3.5 km and 163 THz, achieves a 1-Hz linewidth.


Physical Review Letters | 2010

Controlling the Hyperfine State of Rovibronic Ground-State Polar Molecules

S. Ospelkaus; Kang-Kuen Ni; Goulven Quéméner; B. Neyenhuis; Dajun Wang; M. H. G. de Miranda; John L. Bohn; J. Ye; D. S. Jin

We report the preparation of a rovibronic ground-state molecular quantum gas in a single hyperfine state and, in particular, the absolute lowest quantum state. This addresses the last internal degree of freedom remaining after the recent production of a near quantum degenerate gas of molecules in their rovibronic ground state, and provides a crucial step towards full control over molecular quantum gases. We demonstrate a scheme that is general for bialkali polar molecules and allows the preparation of molecules in a single hyperfine state or in an arbitrary coherent superposition of hyperfine states. The scheme relies on electric-dipole, two-photon microwave transitions through rotationally excited states and makes use of electric nuclear quadrupole interactions to transfer molecular population between different hyperfine states.


Physical Review A | 2013

Power-broadening-free correlation spectroscopy in cold atoms

H. M. Florez; L. S. Cruz; M. H. G. de Miranda; R. A. de Oliveira; J. W. R. Tabosa; Marcelo Martinelli; D. Felinto

We report a detailed investigation on the properties of correlation spectra for cold atoms under the condition of Electromagnetically Induced Transparency (EIT). We describe the transition in the system from correlation to anti-correlation as the intensity of the fields increases. Such transition occurs for laser frequencies around the EIT resonance, which is characterized by a correlation peak. The transition point between correlation and anti-correlation is independent of power broadening and provides directly the ground-state coherence time. We introduce a method to extract in real time the correlation spectra of the system. The experiments were done in two distinct magneto-optical traps (MOT), one for cesium and the other for rubidium atoms, employing different detection schemes. A simplified theory is introduced assuming three-level atoms in


international frequency control symposium | 2008

Strontium optical lattice clock: 10 −16 uncertainty

A. D. Ludlow; Gretchen K. Campbell; S. Blatt; Martin M. Boyd; T. Zelevinsky; Michael J. Martin; M. H. G. de Miranda; Jan Thomsen; J. Ye; Tara M. Fortier; J. E. Stalnaker; Scott A. Diddams; Christopher W. Oates

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Laser Spectroscopy - The XVIII International Conference on ICOLS 2007Laser Spectroscopy - Proceedings of the XVIII International Conference on ICOLS 2007 | 2008

Sr Optical Clock with High Stability and Accuracy

Leo W. Hollberg; J. C. Bergquist; Mark Kasevich; A. D. Ludlow; Sebastian Blatt; Micah Boyd; Gretchen K. Campbell; Michael J. Martin; M. H. G. de Miranda; Tanya Zelevinsky; J. Ye; T. M. Foetier; J. E. Stalnaker; Scott A. Diddams; Christopher W. Oates; Zeb W. Barber; N. Poli

configuration interacting with a laser with stochastic phase fluctuations, providing a good agreement with the experimental observations.


Nature Physics | 2011

Controlling the quantum stereodynamics of ultracold bimolecular reactions

M. H. G. de Miranda; A. Chotia; B. Neyenhuis; Dajun Wang; Goulven Quéméner; S. Ospelkaus; John L. Bohn; J. Ye; D. S. Jin

We report on the improved characterization and operation of an optical frequency standard based on nuclear-spin-polarized, ultracold neutral strontium confined in a one dimensional optical lattice. We implement a remote optical carrier phase link between JILA and NIST Boulder campus, permitting high precision evaluation of the Sr system with other optical standards. Frequency measurement against a free-space Ca standard enables determination of systematic shifts of the Sr standard at or below 1 x 10-16 fractional uncertainty. We observe a density-dependent shift of the clock transition and its dependence on excited state fraction, with a zero crossing of the shift. We perform a 50-hour-long absolute frequency measurement of the strontium transition referenced to the NIST-F1 Cs fountain standard. This yields a value for the Sr clock transition frequency with a fractional uncertainty of 8.6 x 10-16, limited by the H-maser and Cs standards used. This represents our fifth, and the most accurate, measurement of the 87Sr clock frequency.

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J. Ye

National Institute of Standards and Technology

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B. Neyenhuis

University of Colorado Boulder

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D. S. Jin

University of Colorado Boulder

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S. Ospelkaus

National Institute of Standards and Technology

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Kang-Kuen Ni

National Institute of Standards and Technology

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Christopher W. Oates

National Institute of Standards and Technology

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Goulven Quéméner

University of Colorado Boulder

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Gretchen K. Campbell

National Institute of Standards and Technology

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J. E. Stalnaker

National Institute of Standards and Technology

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John L. Bohn

University of Colorado Boulder

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