Physicists Have Created A 256-qubit Analog Quantum Computer
Physicists have created an analog quantum computer based on 256 qubits, which can solve complex scientific problems. A description of the development is available in the scientific journal Nature.
"Our experiments have shown that two-dimensional arrays of cold atoms are a promising platform for programmable quantum simulators with hundreds of qubits. We hope that the size of this system, its accuracy, and controllability can be significantly increased," the researchers write.
There are two approaches to the development of quantum computers – classical and adiabatic. In the first case, the computing device is similar in principle to conventional digital computers. An adiabatic quantum computer is easier to create than a classical one. But its working principles are closer to analog computers of the beginning of the last century, designed to solve one specific problem.
The adiabatic quantum computer, which was created by physicists under the guidance of Professor Mikhail Lukin of Harvard University, is devoid of these shortcomings. It contains 256 qubits at once – quantum memory cells. In this case, their role is played by the so-called Rydberg atoms. These are atoms of rubidium-87-an alkali metal, the last electron of which is "moved" a long distance from the nucleus through laser radiation pulses or radio waves. Due to this, the size of the atom increases by about a million times.
Such quantum objects are much easier to control than other particles. At the same time, they have another useful property. They repel each other and at the same time can interact with each other at long distances. Earlier, Lukin and his colleagues have already used this feature of Rydberg atoms to create a universal 51-qubit quantum computer.
Scientists used the same technologies to create an analog computer-based on several hundred qubits, the principles of which can be flexibly changed. This approach has allowed physicists to conduct much more complex and curious calculations and experiments related to the study of quantum mechanics.
This computer is a set of Rydberg atoms that are arranged in a two-dimensional lattice. They are held in place inside a special laser trap. During calculations, scientists adjust the operation of each qubit with laser flashes, after which they allow them to interact with each other.
Lukin and his colleagues conducted several experiments to study quantum phase transitions, as well as quantum fluctuations of particles and interactions of light and matter, using this approach.
Physicists have tested some theories that describe these phenomena with the help of these calculations. They also discovered several previously unknown states of matter that are potentially interesting from the point of view of quantum computing.
Soon, physicists plan to improve the quality of their quantum simulators significantly. So far, this is hindered by the fact that the quantum state of qubits is destroyed periodically due to random collisions between Rydberg atoms and single gas molecules that remain in the vacuum chamber. If all of them can be pumped out, scientists will be capable of increasing the number of qubits simultaneously and improve the quality of control over their condition.