Optical Tweezers, also known as optical traps, are a scientific tool that uses highly focused laser beams to manipulate microscopic particles, including individual atoms and molecules. In the field of quantum computing, optical tweezers are used to trap and control neutral atoms, enabling their use as qubits and facilitating quantum operations.
Optical tweezers offer advantages such as high spatial resolution, flexibility in trapping configurations, and the ability to manipulate individual atoms without physical contact. However, they also present challenges, including the need for precise alignment and calibration, sensitivity to environmental noise, and potential heating effects on the trapped particles.
Beyond quantum computing, optical tweezers applications include physics, biology, and materials science. They are used to study molecular interactions, cellular mechanics, and nanoscale phenomena. Research into optical tweezers continues to explore new trapping techniques, applications in quantum simulation, and integration with other quantum technologies.
An Optical Tweezer represents a powerful and versatile tool in quantum computing and broader scientific research. By enabling the precise control and manipulation of individual atoms, they contribute to the development of neutral-atom quantum computers and provide insights into fundamental quantum behavior.
In quantum computing, optical tweezers are used to trap individual neutral atoms in specific locations, forming a lattice or array of qubits. These trapped atoms can be manipulated using additional laser beams to perform quantum gates and create entangled states. Optical tweezers provide a flexible and precise method for controlling neutral-atom qubits, making them a valuable tool in neutral-atom quantum computing.
We reflect a laser beam off a spatial light modulator to create an array of many optical tweezers that each “trap” an individual qubit.
Note that only a few lasers are required to trap dozens or even hundreds of atoms. In fact, they only use one laser. In total, QuEra Computing’s own “Aquila” quantum computer uses only 7 lasers to trap and control 256 atoms.
The atoms can be shuttled around by moving the tweezer.
A paper titled “A quantum computation architecture using optical tweezers”by Christof Weitenberg, Stefan Kuhr, Klaus Mølmer, and Jacob F. Sherson from the Max-Planck-Institut f¨ur Quantenoptik, the University of Strathclyde, and the University of Aarhus, mentions how it is possible to move atoms around in what is called, “shuttling,” something that has been experimentally demonstrated by a team of researchers from Harvard, QuEra Computing, MIT, and the University of Innsbruck.
The working principle of optical tweezers involves the use of a tightly focused laser beam to create an electric field gradient that exerts forces on neutral particles. When a particle is placed near the focus of the laser beam, it experiences forces that draw it towards the center of the beam. By carefully controlling the laser's properties, researchers can trap and manipulate the particle with high precision.
The Atom Computing article also notes how the term “tweezers” is a bit of a misnomer. The visualization of the term suggests two lasers are coming in from the sides and holding an atom in place like something you would hold with grooming tweezers. Instead, an optical tweezer works more like a tractor beam out of a popular science fiction movie franchise, such as Star Trek and Star Wars, except that it is real and holding only an individual atom in place.
The Weitenberg, et al., paper delves deeper into this topic with both illustrations and mathematics. Although it gets very technical, much of it is written in language suitable for general audiences. And to follow up on the “tractor beam” analogy, Figure 1 of this paper provides a helpful illustration which is neither personal hygiene nor science fiction, but actual science.