Scientists develop a new type of optical quantum computer

Scientists at the Institute of Physics of the University of Tartu have found a way to develop a new type of optical quantum computers. Central to the discovery are rare earth ions, which have certain characteristics and can act like quantum bits. This would give quantum computers super-fast computation speed and better reliability over earlier solutions. It is reported by Optics Communications.

Whereas in ordinary computers the units of information are binary digits or bits, in quantum computers the units of measure are quantum bits or qubits. In a conventional computer, information is mainly carried by electricity in memory cells consisting of field-effect transistors, but in a quantum computer, depending on the type of computer, information carriers are much smaller particles, such as ions, photons, and electrons.

Information about a qubit can carry a certain characteristic of this particle (for example, the spin of an electron or the polarization of a photon), which can have two states. Although the normal bit values ​​are 0 or 1, intermediate versions of these values ​​are also possible in the quantum bit. The intermediate state is called superposition. This property gives quantum computers the ability to solve problems

Researchers at the Institute of Physics of the University of Tartu have shown that microcrystals synthesized from mixed optical crystal matrices of fluorides doped with erbium, praseodymium and some other rare-earth ions can act as qubits, providing ultrafast optical quantum computing.

“When choosing ions, their electronic states with very different properties are of great importance. They must have at least two states in which the ionic interaction is very weak. These states are suitable for basic quantum logic operations with individual quantum bits. In addition, you need a state or states in which the ionic interaction is strong – they allow you to perform quantum logic operations with two or more qubits. All these states must have long lifetimes (milliseconds or microseconds), and optical transitions must be allowed between these states.”

Professor Vladimir Khizhnyakov, Member of the Estonian Academy of Sciences

Scientists say that until now, the detection of such electronic states of rare-earth ions was not considered possible, and therefore scientists did not look among them for such states that are suitable for qubits. Until now, mainly the spin states of atomic nuclei have been studied for the role of qubits. However, their frequency is a million times lower than the frequency of quantum bits. This is why quantum computers are also built around these qubits. And they will be significantly slower than computers with quantum bits based on electronic states.

The ultra-fast cycle time will help overcome one of the main obstacles to creating quantum computers. Qubits are very sensitive to their environment, so any interference from the environment can lead to errors in quantum computing.

“The coherence time of qubits, that is, the duration of a pure quantum state, is very short. The faster the computation cycle, the less interference from the environment in the work of the qubits.”

Professor Vladimir Khizhnyakov, Member of the Estonian Academy of Sciences

It has been established that the spectral hole burning method, previously developed at the Institute of Physics of the University of Tartu, can be used to select a set of qubits in a microcrystal acting as a computer copy. According to Khizhnyakov, today it is one of the most powerful methods of optical spectroscopy, which allows you to find those ions in a microcrystal that are most suitable for use as computer qubits.

Although it is still far from a real working quantum computer, researchers from the Laser Spectroscopy Laboratory of the University of Tartu have begun to create a pilot prototype of a quantum computer based on the new method. According to the researchers, they are on the eve of the presentation of the work of the basic elements of a new type of quantum computer.

Author: John Kessler
Graduated From the Massachusetts Institute of Technology. Previously, worked in various little-known media. Currently is an editor and developer of Free News.
Function: Director