A physicist told how scientists make diamonds in quantum computers

© Personal archive of Dennis Skatevideos Sukachev, a physicist from the Russian quantum centerA physicist told how scientists make diamonds in quantum computers© Personal archive of Denis Sukachev

. Physicist Denis Sukachev of the Russian quantum center told about how the Russian and American scientists are trying to turn diamonds into quantum computers, and explain why these computing devices are already a reality and not just science fiction.

Qubits represent both memory and compute modules of a quantum computer, which can simultaneously store and a Boolean zero and unit, thanks to the laws of quantum physics. Combine multiple qubits into a single computing system allows you to quickly solve mathematical or physical problems, finding answers to who, with the help of methods of brute force would take time comparable to the lifetime of the Universe.

Denis Sukachev and many other scientists under the leadership of Mikhail Lukin of Harvard University have been working on the creation of qubits on the basis of the so-called «defective» diamonds. The interest in them is due to the two most important advantages of diamond — qubits based on them fairly easily make and receive, and they are able to work at room temperature.

The «heart» of the compute module is defect — atom of nitrogen or other element, «wormed» into the interior of carbon atoms. Similar defects scientists call «jobs,» or NV-centers, because the addition of an atom of nitrogen in the diamond creates a crystal lattice is a special empty space with unusual properties. At this point, the carbon atom is missing, but it has all the properties of the atom, which was at this point in relatively «frozen» state.

Scientists have learned to use the spin — direction of rotation — of the electrons of the nitrogen atom and its nucleus to store information inside the defect and for processing data inside of a qubit for a very long time.

This week, the domestic and foreign physicists have described the creation of the technology to mass produce qubits, the basic computational modules and memory of quantum computers, «printing» them in diamonds.

Technology of introduction of nitrogen to NV centers, SiV and silicon centers are in essence the same. And those and others can be formed during the growth of diamond, and by means of ion implantation.

The first method allows us to centers with better spectral properties — they don’t flicker, don’t insults, and the frequency of the radiation is stable for several hours. «Implantirovannykh» centers yield «natural» defects in quality, but their production technology allows us to control where they will be located. This is very important in cases when we want to force them to interact with photons in a predictable manner and put them to the impurity molecules or nanoobjects.

In turn, we made a choice in favor of silicon centers because they remain stable spectral properties when placed in such impurity molecules or nanoobjects, which is not typical for nitrogen «competitors».

If we take the silicon center and place it in the photonic resonator inside of the diamond that the number of photons increase significantly, which should lead to an increase in frequency of generation of entanglement.

Now we are working to create long-term quantum memory on the basis of silicon centers. To do this, we cool them to a temperature of about 20 millikelvins, 200 times less than the boiling point of liquid helium. At these temperatures the carbon atoms completely «frozen», so that collective oscillations of the atoms in the crystal lattice of the diamond, interfere with the operation of the quantum memory, the so-called phonons, completely disappear.

— Make it to diamond qubits competition of their superconducting counterparts, and that will be the basis of the first commercial quantum computers?

— The main advantage of the «diamond qubits» over their superconducting counterparts, in my opinion, is that you can use them to create a «long» quantum memory due to the possibility of transfer of a qubit on the nuclear spin.

In addition, the defects are able to glow in the optical range, which greatly simplifies the process of transferring data across large distances due to the fact that we can use for these purposes high-quality fiber.