Controlling collisions between laser-cooled molecules and atoms
Lead Research Organisation:
Imperial College London
Department Name: Physics
Abstract
At temperatures around a millionth of a degree above absolute zero, atoms and molecules enter a new regime. All their motions follow the laws of quantum mechanics, and can be very precisely controlled. Researchers achieved this control for atoms some time ago, and it is now becoming possible for molecules too. This is important because molecules have much richer patterns of energy levels than atoms, and their complexity can be used for many applications in quantum science and technology. For example, they can be used as building blocks of a quantum computer and to simulate interacting quantum systems that cannot be simulated on a normal computer. They are also being used to study the fundamental symmetries of nature.
We are at the forefront of this field. We have a unique capability to laser-cool CaF molecules and Rb atoms to near the quantum regime and to confine them together in magnetic and magneto-optical traps. We have already used this for initial studies of CaF+Rb collisions in these environments.
Control of ultracold matter is achieved via collisions. Particularly important are resonant collisions, where the colliding pair can combine to form a larger molecule with no change in energy. Near such a resonance, a magnetic field can be used to control the collision: with only a small change in field, the interaction can be tuned to be attractive or repulsive, or even to zero so that the particles no longer see each other at all. Most of the properties of the ultracold gas depend on the interaction strength, which here can be controlled at will.
Our proposal is to locate these resonances for the prototype system CaF+Rb and use them for important applications. We will confine both the molecules and the atoms in an optical trap, where we can apply a controllable magnetic field. CaF+Rb is particularly suitable for this: both species have unpaired electron spins, so that the interactions between them are closely analogous to the well-understood case of pairs of alkali-metal atoms. We have exploited this similarity in a preparatory theoretical study, which has shown that suitable resonances will exist at easily accessible magnetic fields.
We will use the resonances to control how quickly the atoms and molecules come into thermal equilibrium. Then, by using the atoms as a coolant, we will bring the molecules further into the fully quantum regime. We will also use the resonances to form triatomic molecules in a controlled manner, and then characterise these new molecules spectroscopically. In these ways, we will bring the tools of quantum control to increasingly diverse and complex systems for the benefit of quantum science and technology.
We are at the forefront of this field. We have a unique capability to laser-cool CaF molecules and Rb atoms to near the quantum regime and to confine them together in magnetic and magneto-optical traps. We have already used this for initial studies of CaF+Rb collisions in these environments.
Control of ultracold matter is achieved via collisions. Particularly important are resonant collisions, where the colliding pair can combine to form a larger molecule with no change in energy. Near such a resonance, a magnetic field can be used to control the collision: with only a small change in field, the interaction can be tuned to be attractive or repulsive, or even to zero so that the particles no longer see each other at all. Most of the properties of the ultracold gas depend on the interaction strength, which here can be controlled at will.
Our proposal is to locate these resonances for the prototype system CaF+Rb and use them for important applications. We will confine both the molecules and the atoms in an optical trap, where we can apply a controllable magnetic field. CaF+Rb is particularly suitable for this: both species have unpaired electron spins, so that the interactions between them are closely analogous to the well-understood case of pairs of alkali-metal atoms. We have exploited this similarity in a preparatory theoretical study, which has shown that suitable resonances will exist at easily accessible magnetic fields.
We will use the resonances to control how quickly the atoms and molecules come into thermal equilibrium. Then, by using the atoms as a coolant, we will bring the molecules further into the fully quantum regime. We will also use the resonances to form triatomic molecules in a controlled manner, and then characterise these new molecules spectroscopically. In these ways, we will bring the tools of quantum control to increasingly diverse and complex systems for the benefit of quantum science and technology.
