Cooling a single atom in an optical tweezer to its quantum ground state (1209.2087v2)

Abstract: We report cooling of a single neutral atom to its three-dimensional vibrational ground state in an optical tweezer. After employing Raman sideband cooling for tens of milliseconds, we measure via sideband spectroscopy a three-dimensional ground-state occupation of ~90%. We further observe coherent control of the spin and motional state of the trapped atom. Our demonstration shows that an optical tweezer, formed simply by a tightly focused beam of light, creates sufficient confinement for efficient sideband cooling. This source of ground-state neutral atoms will be instrumental in numerous quantum simulation and logic applications that require a versatile platform for storing and manipulating ultracold single neutral atoms. For example, these results will improve current optical tweezer experiments studying atom-photon coupling and Rydberg quantum logic gates, and could provide new opportunities such as rapid production of single dipolar molecules or quantum simulation in tweezer arrays.

• The paper demonstrates achieving approximately 90% three-dimensional quantum ground-state occupation of a single 87Rb atom using Raman sideband cooling.
• The methodology employs a far-off-resonant optical tweezer with sequential stimulated Raman transitions and optical pumping to lower vibrational energy.
• The results improve control of spin and motional states, paving the way for high-fidelity quantum logic operations and scalable quantum systems.

Cooling a Single Atom in an Optical Tweezer to Its Quantum Ground State

This paper presents an experimental paper focused on cooling a single neutral rubidium atom to its three-dimensional vibrational quantum ground state within an optical tweezer. By utilizing Raman sideband cooling, the researchers have achieved a notable three-dimensional ground-state occupation of approximately 90%. In this concise analysis, the methodology, results, and implications of this work are examined, highlighting its contribution to the field of quantum simulation and computation with neutral atoms.

Methodology

The experimental setup includes a highly focused optical tweezer formed using a far-off-resonant laser beam to trap a single 87Rb atom. Following the trapping, optical cooling is initiated using Raman sideband cooling. This technique reduces the atom's vibrational energy by iterating through two main processes: a stimulated Raman transition that reduces the vibrational state by one quantum, and a subsequent optical pumping step that returns the atom to its initial spin state. The dual step ensures that entropy is transferred from the atom to the external environment, ultimately pushing the atom towards its vibrational ground state.

Results

The experiment showcases a significant asymmetry in the sideband spectra post cooling, indicative of a well-defined ground-state population. Specifically, the radial dimensions achieved a ground-state occupation probability of 97%, while the axial dimension's occupation reached 93%. Collectively, these achievements represent a considerable advancement as they culminate in a three-dimensional ground-state population probability of around 90%.

The experiment further demonstrated coherent control of the spin and motional states of the atom, a critical factor for applications in high-fidelity quantum logic operations. The process allows for refined quantum state manipulation, paving the way for quantum operations previously plagued by thermal motion issues, such as atom-photon interactions and Rydberg quantum logic gates.

Implications

From a practical standpoint, achieving such a high ground-state occupation within optical tweezers enhances the feasibility of several quantum technologies. It could significantly improve atom-photon coupling schemes and enhance the fidelity of quantum gates, thereby benefiting quantum computing protocols that rely on high coherence and precise quantum state control. Moreover, this level of control is foundational for quantum simulators aimed at exploring novel many-body physics and interactions not easily accessible through traditional methods.

Looking forward, the ability to cool and coherently manipulate single atoms in optical tweezers offers promising avenues for the on-demand creation of dipolar molecules, critical in quantum chemistry and condensed matter simulations. With precise control, constructing multi-qubit systems using optical tweezer arrays becomes viable, potentially leading to innovations in reconfigurable quantum networks and facilitating explorations into strongly correlated systems under non-equilibrium conditions.

Conclusion

This body of work presents a crucial step in the manipulation and control of atom-based quantum systems. The successful application of Raman sideband cooling to a single neutral atom's motional state within an optical tweezer not only broadens the range of feasible quantum experiments but also represents a reliable pathway to scalable quantum systems. As the landscape of quantum technologies expands, such techniques will play a pivotal role in advancing both theoretical exploration and practical implementations, offering insights into the quantum mechanical fundamentals that underpin future technological developments.