A new construction of quantum chips can become a basis of future computers

ElectronicJune 27, 2015

The quantum computers which are today a more theoretical concept, than practical, in the future will be capable of calculating difficult mathematical models which will be too hard even to the most powerful modern supercomputers. Calculations of similar models can bring many areas of science, including chemistry, biology, materials science, etc. to a new level. But development of quantum computing technologies is slowed down by the scientists and engineers who are simply not able to provide manipulation with a large number of quantum bits, qubits in which quantum information is stored and processed.

Nevertheless, scientists continue to work in the direction of creating quantum computing systems, and recently the group of Technological research institute of Georgia (Georgia Tech Research Institute) and the Honeywell International company managed to develop the quantum chip with a new construction which allows to place a rather large number of electrodes through which it will be possible to write down and read out information from qubits on its square.

“To set a quantum condition of the system consisting of 300 qubits it is required 2^300 numerical values, and it is more, than quantity of protons in part of the Universe known to us. According to the restrictions imposed by the known Gordon Moore law, people will never be able to create the classical computing system capable of processing such an amount of information” – Nicholas Guiz (Nicholas Guise), one of the researchers says, – “And these restrictions define why by means of ordinary computers it is impossible to construct mathematical model not of the most difficult quantum system”.

Concerning a role of qubits of the quantum computer there are some applications, one of which are the ions of some chemical elements concluded in a trap of laser light in a vacuum chamber. Unfortunately, the scalability of such approach is very limited as the trap lattice in which knots ions qubits settle down, is created by means of the electrodes brought to edges of the quantum chip. And the quantity of such electrodes is limited to length of edges in a chip (perimeter).

In the chip created by the GTRI/Honeywell team, this problem is solved by means of using new micro and nanoproductions which allow getting a large number of electrodes on a chip crystal, having left its top part open for easy access of light of the laser. The basis of a design of the chip is borrowed at the electronic BGA (ball grid array) components design. The matrix of tiny spheres contacts allows to bring electrodes directly from a back surface of the chip to its top surface that gives a very high rate of density of packing electric connections. Besides, researchers released additional chip surface space, having replaced flat superficial condensers with the condensers of trench type carried to the edges of a chip crystal.

Such steps, driven at the release of additional free space, allowed to realize technology of the very exact focusing of light of the laser that, in turn, allows to quickly address each separate qubit and to initiate performance of certain quantum operations.

Now prototypes of quantum chips with the development of technology became more perfect and capable to catch and hold ions qubits in traps. “Ions are very sensitive things with their external electric fields and electromagnetic noise from other sources influence. Besides, the particle of the wrong material, the size in some micron which got to the wrong place can destroy an ionic trap. And when we created the first BGA matrixes of traps, we were pleasantly surprised that they functioned also, and even it is better than the most high-quality traps created in the traditional ways” – Nicholas Guiz says.

Now the work with a matrix of ionic traps demands the whole room filled with the difficult and bulky equipment in which some qualified specialists work. However, after the solution of a number of technical problems nothing will stir miniaturization of this technology to the level of a very compact system which can become “the standard block” for creation of the quantum computing systems capable to be scaled to any level of complexity.

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