Preparation of a Pure Molecular Quantum Gas

Herbig, Jens; Kraemer, T.; Mark, Manfred J.; Weber, T.; Chin, Cheng; Nägerl, Hanns‐Christoph; Grimm, Rudolf

doi:10.1126/science.1088876

Cited by 393 publications

(429 citation statements)

References 31 publications

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“…Assuming a perfect filling of the two-atom Mott shell at the centre of the trap, taking into account the efficiencies for molecule production and state transfer and factoring in weak extra loss during sample purification, 85(3)% of the central lattice sites are occupied. We detect the molecules in |1 by reversing the Feshbach state transfer sequence, dissociating the molecules at the Feshbach resonance and detecting the resulting atoms by standard absorption imaging 29 .…”

Section: Methodsmentioning

confidence: 99%

An ultracold high-density sample of rovibronic ground-state molecules in an optical lattice

et al. 2010

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Control over all internal and external degrees of freedom of molecules at the level of single quantum states will enable a series of fundamental studies in physics and chemistry 1,2 . In particular, samples of ground-state molecules at ultralow temperatures and high number densities will facilitate new quantum-gas studies 3 and future applications in quantum information science 4 . However, high phase-space densities for molecular samples are not readily attainable because efficient cooling techniques such as laser cooling are lacking. Here we produce an ultracold and dense sample of molecules in a single hyperfine level of the rovibronic ground state with each molecule individually trapped in the motional ground state of an optical lattice well. Starting from a zero-temperature atomic Mott-insulator state 5 with optimized double-site occupancy 6 , weakly bound dimer molecules are efficiently associated on a Feshbach resonance 7 and subsequently transferred to the rovibronic ground state by a stimulated four-photon process with >50% efficiency. The molecules are trapped in the lattice and have a lifetime of 8 s. Our results present a crucial step towards Bose-Einstein condensation of groundstate molecules and, when suitably generalized to polar heteronuclear molecules, the realization of dipolar quantumgas phases in optical lattices [8][9][10] .Recent years have seen spectacular advances in the field of atomic quantum gases. Ultracold atomic samples have been loaded into optical lattice potentials, enabling the realization of strongly correlated many-body systems and the direct observation of quantum phase transitions with full control over the entire parameter space 5 . Molecules with their higher level of complexity are expected to have a crucial role in future-generation quantumgas studies. For example, the long-range dipole-dipole force between polar molecules gives rise to nearest-neighbour and next-nearest-neighbour interaction terms in the extended BoseHubbard Hamiltonian and should thus lead to unusual many-body states in optical lattices in the form of striped, checkerboard and supersolid phases [8][9][10] .An important prerequisite for all proposed molecular quantumgas experiments is the capability to fully control all internal and external quantum degrees of freedom of the molecules. For radiative and collisional stability, the molecules need to be prepared in their rovibronic ground state, that is, the lowest vibrational and rotational level of the lowest electronic state, and preferably in its energetically lowest hyperfine sublevel. As a starting point for the realization of new quantum phases, the molecular ensemble should be in the ground state of the many-body system. Such state control is possible only at ultralow temperatures and sufficiently high particle densities. Although versatile non-optical cooling and slowing techniques have recently been developed for molecular ensembles 11 and photo-association experiments with atoms in magneto-optical traps have reached the rovibrational ground sta...

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Section: Methodsmentioning

confidence: 99%

An ultracold high-density sample of rovibronic ground-state molecules in an optical lattice

et al. 2010

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“…This will open new areas for investigation, much as frequency conversion provided for in quantum and nonlinear optics. We note here that photoassociation is not the only possible method which can be used to form coupled atomic and molecular condensates, with Feshbach resonance techniques having been successfully used [21][22][23][24], although this technique would not normally be expected to produce the population oscillations predicted for photoassociation superchemistry.…”

Section: Introductionmentioning

confidence: 99%

Fock-state dynamics in Raman photoassociation of Bose-Einstein condensates

2004

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By stochastic modeling of the process of Raman photoassociation of Bose-Einstein condensates, we show that, the farther the initial quantum state is from a coherent state, the farther the one-dimensional predictions are from those of the commonly used zero-dimensional approach. We compare the dynamics of condensates, initially in different quantum states, finding that, even when the quantum prediction for an initial coherent state is relatively close to the Gross-Pitaevskii prediction, an initial Fock state gives qualitatively different predictions. We also show that this difference is not present in a single-mode type of model, but that the quantum statistics assume a more important role as the dimensionality of the model is increased. This contrasting behavior in different dimensions, well known with critical phenomena in statistical mechanics, makes itself plainly visible here in a mesoscopic system and is a strong demonstration of the need to consider physically realistic models of interacting condensates.

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“…In the first experimental successes re-ported for heteronuclear molecular KRb [36] and homonuclear molecular Cs 2 [37], researchers started with quantum degenerate atomic gases and created ultracold molecules in the absolute rovibrational ground state of the electronic ground (singlet) potential via a coherent process that consists of two main steps. First, a Feshbach resonance is used to convert pairs of free atoms to weakly bound molecules [43,44,45,46]. Then, these weakly bound molecules are transferred coherently to the rovibrational ground state via STImulated Raman Adiabatic Passage (STIRAP) [47].…”

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confidence: 99%

New frontiers for quantum gases of polar molecules

et al. 2016

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The field of ultracold quantum matter has burgeoned over the last few decades, thanks to the growing capabilities for atomic systems to be probed and manipulated with exquisite control. Researchers can now precisely create and study quantum manybody states that are effectively isolated from the external environment. Much of the work in ultracold matter has focused on systems of alkali or alkaline-earth atoms, mainly due to their ease of cooling. Extending this precise control to molecules has seen rapidly increasing interest and activity, as molecules possess additional degrees of freedom that make them useful for tests of fundamental physics, studying ultracold chemistry and collisions, and engineering qualitatively new types of quantum phases and quantum many-body systems. Here, we review one particularly fruitful research direction: the creation and manipulation of ultracold bialkali molecules. The recent success in creating a quantum gas of polar molecules opens many exciting research opportunities. Atomic, Molecular, and Optical (AMO) systems offer experimentalists the ability to precisely control interactions in a quantum many-body system [1,2], and a rich set of experiments has already been performed. Some prominent examples include studies of the BEC-BCS crossover in two-component Fermi gases [3,4,5] and the superfluid-Mott insulator transition in ultracold bosons loaded into a 3D optical lattice [6]. Neutral atomic systems normally have point-like contact interactions that can be parametrized with a single quantity, the scattering length a, which can be tuned via a Feshbach resonance [2]. In recent years, systems with long-range and anisotropic interactions have garnered much attention. One natural example is the dipolar interaction between polar molecules, which is the focus of this Review. Of course, many other experimental platforms are also being pursued that feature long-range interactions, including highly magnetic atoms [7,8], trapped ions The dipolar interaction exhibits several important attributes. First, the energy scales in dipolar systems are usually much larger than those in typical atomic alkali systems, making it easier to study interaction-driven structural properties and non-equilibrium dynamics. Second, and perhaps more importantly, the anisotropic and long-range nature of the interaction allows for the realization of novel quantum phases, especially when the spatial dimensions of the system can be varied with optical lattices. Some of these engineered systems may find relevance to outstanding problems in condensed-matter physics [13,14]; moreover, qualitatively new types of physics can emerge in the presence of long-range interactions [15,16,17,18,19,20,21]. As a specific example of a unique feature of long-range interactions, a spin-1/2 Hamiltonian can be encoded based on a pair of oppositeparity rotational states where dipolar interactions give rise to a direct spin exchange coupling between molecules [22,23]. With this scheme implemented in an optical lattice, many-body spin dynam...

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Preparation of a Pure Molecular Quantum Gas

Cited by 393 publications

References 31 publications

An ultracold high-density sample of rovibronic ground-state molecules in an optical lattice

An ultracold high-density sample of rovibronic ground-state molecules in an optical lattice

Fock-state dynamics in Raman photoassociation of Bose-Einstein condensates

New frontiers for quantum gases of polar molecules

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