Physicists at the U.S. National Institute of Standards and Technology (NIST) have managed to trap 219 beryllium ions in strong electric and magnetic fields and confuse their properties at the quantum level using laser light. Several other techniques used by the scientists made it possible to read and manipulate the quantum information contained in these ions. All this turned this group of ions into a kind of quantum simulator, in the bowels of which quantum calculations, inaccessible to calculations on conventional computers, can be made.
Quantum entanglement is a “ghostly” phenomenon, which connects quantum characteristics and states of particles, which can be separated by any great distance. Any effect on one of the entangled particles instantly manifests itself in relation to other entangled particles as well. Scientists have already succeeded in entangling hundreds of thousands of photons of light and thousands of neutral atoms simultaneously at the quantum level. But this case is an absolute record for the number of simultaneously entangled ions.
The possibility of obtaining entangled ions in large quantities is of great importance for the field of quantum computing, which can be used to solve difficult problems of a certain kind, which are beyond the power of even the most powerful supercomputers. Each of the ions acts as a separate quantum bit (qubit) and a group of 10-20 qubits is not at all sufficient to perform complex quantum algorithms.
Instead of trapping ions one at a time, scientists used a tool called the Penning trap. Invented in 1959, this trap allows a large number of atoms or ions to be trapped and held, providing a way to measure the quantum characteristics of each individual ion. The Penning trap is based on a “grid” of strong electric and magnetic fields, which causes the ions to form a kind of two-dimensional crystal.
Once scientists were able to “trap” the amount of ions they needed, they used lasers to cool them to near absolute zero temperature. A pair of additional lasers allowed them to “strip” the neutral atoms, stripping them of several electrons on the upper electron layer, turning these neutral atoms into positively charged ions. In addition, the light from additional lasers allowed for the alignment of the rotational directions of the ions, the spin, and the entanglement of these ions at the quantum level.
The unique design of the Penning trap, developed by specialists at NIST, played a major role in this achievement. This trap gives scientists the ability to read the quantum state of each individual ion, in addition, it allows them to control the quantum state of the “ion crystal” as a whole.
It should be noted that this technology will be used in the future to simulate the behavior of ions of some magnetic materials, which entangle with each other under certain conditions naturally. And such unusual materials can point scientists to a new state of matter that is still unknown to scientists, and studying this state can lead to discoveries in the field of high-temperature superconductivity and in other areas that can have a huge impact on the development of modern science and technology.
The next step that NIST scientists intend to take is to implement a method to directly control the quantum state of each individual ion. If they succeed in doing this, they will have at their disposal a true quantum computer, whose “processor” consists of 200 entangled qubits. With this number of qubits, the computer will be able to execute very, very complex quantum algorithms, far ahead of any other existing computers.