Rubidium is a key element in the field of neutral atom quantum computing, offering a pathway to scalable and robust quantum information processing. Its unique properties and the ability to control them with high precision make it a valuable resource in both quantum computing and broader quantum research.
Beyond quantum computing, Rubidium has applications in other areas of quantum technology and physics. For example, Rubidium-based atomic clocks are among the most accurate timekeeping devices known. Rubidium is also used in Bose-Einstein condensate experiments and other studies of ultracold atoms.
For more information about the Rubidium element, the Royal Society of Chemistry lists its uses, properties, history, atomic data, oxidation states, isotopes, supply risks, pressure data, and temperature data. There are also links to a podcast and two videos about the Rubidium atom, as well as to the references for the page. For further reading, the Science Direct “Rubidium Atom” page offers chapter excerpts from books that may be of interest.
What is Rubidium
Rubidium is a chemical element with the symbol Rb and atomic number 37. It's a soft, silvery-white metallic element in the alkali metal group. It is the first element in the alkali metal group that is denser than water, with which it reacts very strongly. It is also the most volatile of the alkali metals, evaporating at temperatures as low as 150°C.
Rubidium has several isotopes. Some of them, such as Rubidium-87, have unique properties that make them valuable in quantum research, including quantum computing.
Properties of Rubidium
The quantum properties of Rubidium, such as its energy levels and transition frequencies, are well understood and can be precisely controlled. This allows for the implementation of quantum gates and the creation of entangled states. Rubidium's properties also make it useful in other quantum technologies, such as atomic clocks and quantum sensors.
One of the many desirable characteristics of Ribidium is that these computational, timing, and sensing applications can all be performed at room temperature. No spacious dilution refrigeration is required. For that matter, no spacious environmental shielding is required. This allows some Rubidium-based technologies to be miniaturized considerably. And without those protective layers, it becomes possible to illuminate the atoms with lasers such that a cloud of Rubidium vapor in a vacuum chamber can become “visible” to the naked eye.
Applications of Rubidium
Rubidium atoms are often used in the construction of neutral-atom quantum computers. The energy levels and hyperfine structure of Rubidium-87, in particular, make it suitable for trapping and manipulating as qubits. By using lasers and magnetic fields, Rubidium atoms can be cooled to near absolute zero and trapped in optical lattices, where they can be individually controlled and entangled.
It's worth noting that the largest publicly available quantum computer uses Rubidium neutral atoms as qubits. QuEra’s own “Aquila” device allows users to configure arrays with up to 256 of these neutral atom qubits. That’s just over double the number of qubits available with the next largest, non-exploratory, publicly available quantum computer.
Rubidium in Quantum Information Processing
Rubidium-based quantum computing offers some advantages, including the potential for scalability and long coherence times. Howe
ver, it also presents challenges, such as the need for precise control over the trapping and manipulation of individual atoms. Research and development in this area continue to explore ways to optimize the use of Rubidium in quantum computing.
A rubidium neutral atom array can be simulated at small scales with a tensor network. This has proven helpful in early attempts to verify the results of analog quantum computation. Although classical processing limits the scalability of these tensor networks, using them will help build confidence with proofs-of-concept that large-scale computation with Rubidium neutral atoms is accurate.
Learn more about how Rubidium can be used to build quantum computers here.