Unified model of ultracold molecular collisions

Croft, James; Bohn, John L.; Quéméner, Goulven

doi:10.1103/physreva.102.033306

Cited by 37 publications

(40 citation statements)

References 82 publications

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“…We see no evidence for collisional energy shifts, which would be observed by a change in the energies of the states when the density reduces over the course of each Ramsey measurement (see Supplementary Information). This is consistent with previous observations [25], and the absence of collisional energy shifts or decoherence may be expected as short-range collisions in the gas lead to loss of molecules with high probability [35][36][37][38]. Measurements of the coherence out to longer times will require confinement of the molecules to a 3D optical lattice [39] , optical tweezers [40][41][42], or the use of alternative trapping techniques such as a blue-detuned optical trap [43] to avoid losses from the optical excitation of two-molecule collision complexes [36,44].…”

supporting

confidence: 93%

Robust storage qubits in ultracold polar molecules

Gregory

Blackmore

Bromley³

et al. 2021

Preprint

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Quantum states with long-lived coherence are essential for quantum computation, simulation and metrology. The nuclear spin states of ultracold molecules prepared in the singlet rovibrational ground state are an excellent candidate for encoding and storing quantum information. However, it is important to understand all sources of decoherence for these qubits, and then eliminate them, in order to reach the longest possible coherence times. Here, we fully characterise the dominant mechanisms for decoherence of a storage qubit in an optically trapped ultracold gas of RbCs molecules using high-resolution Ramsey spectroscopy. Guided by a detailed understanding of the hyperfine structure of the molecule, we tune the magnetic field to where a pair of hyperfine states have the same magnetic moment. These states form a qubit, which is insensitive to variations in magnetic field. Our experiments reveal an unexpected differential tensor light shift between the states, caused by weak mixing of rotational states. We demonstrate how this light shift can be eliminated by setting the angle between the linearly polarised trap light and the applied magnetic field to a magic angle of arccos(1/√3)≈55°. This leads to a coherence time exceeding 6.9 s (90% confidence level). Our results unlock the potential of ultracold molecules as a platform for quantum computation.

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confidence: 93%

Robust storage qubits in ultracold polar molecules

Gregory

Blackmore

Bromley³

et al. 2021

Preprint

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“…Christianen et al [83] recently considered a lossy QDT model of such resonances. They concluded that if the complexes are lost rapidly once formed and Γs inc = d/2π, such that T s inc = 1 in equation ( 3), the loss rate is represented by y = 0.25, as opposed to the y = 1 implicit in the model of Croft et al [82]. The reasons for this apparent disagreement are not clear at present, but both methods rely on averaging over a large number of resonances.…”

Section: Resonance Widths and Lifetimes Of Collision Complexesmentioning

confidence: 99%

Complexes formed in collisions between ultracold alkali-metal diatomic molecules and atoms

Frye

Hutson

2021

New J. Phys.

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We explore the properties of 3-atom complexes of alkali-metal diatomic molecules with alkali-metal atoms, which may be formed in ultracold collisions. We estimate the densities of vibrational states at the energy of atom-diatom collisions, and find values ranging from 3.9 to 350 K$^{-1}$. However, this density does not account for electronic near-degeneracy or electron and nuclear spins. We consider the fine and hyperfine structure expected for such complexes. The Fermi contact interaction between electron and nuclear spins can cause spin exchange between atomic and molecular spins. It can drive inelastic collisions, with resonances of three distinct types, each with a characteristic width and peak height in the inelastic rate coefficient. Some of these resonances are broad enough to overlap and produce a background loss rate that is approximately proportional to the number of outgoing inelastic channels. Spin exchange can increase the density of states from which laser-induced loss may occur.

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“…All of the physics investigated above strongly depends on the capacity to fine-tune the dipolar length a dd and the two-body s-wave scattering length a s of an ultracold molecular gas. In addition, in contrast to atoms, ground-state molecules can also lead to two-body collisional losses, no matter if the molecules are chemically reactive or not [90,91]. As a result, the scattering length associated with molecular collisions becomes a complex quantity, with an imaginary part directly linked to the magnitude of the molecular losses [92].…”

Section: Controlling the Scattering Properties Of A Molecular Gasmentioning

confidence: 99%

Self-bound dipolar droplets and supersolids in molecular Bose-Einstein condensates

Schmidt,

Lassablière,

Quéméner

et al. 2021

Preprint

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Unified model of ultracold molecular collisions

Cited by 37 publications

References 82 publications

Robust storage qubits in ultracold polar molecules

Robust storage qubits in ultracold polar molecules

Complexes formed in collisions between ultracold alkali-metal diatomic molecules and atoms

Self-bound dipolar droplets and supersolids in molecular Bose-Einstein condensates

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