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Qubits in quantum computing

Scientists find gravity as key to optimal quantum computation

Scientists have been trying persistently to achieve significant success in the field of Quantum Computing but still, there is a huge scope of improvement if we go by the consensus.

But recently the arduous efforts of all the involved scientists have given them something to cheer at, as there is a claim that gravity a natural phenomenon which has been studied extensively will provide the pathway through which in-depth knowledge of quantum computing can be obtained. The scientific community is hailing these findings because there is a belief that quantum computing will bring a drastic change in the power and scale of computation. The study has been published in Physical Review Letters

The reason behind this linkage between gravity and quantum computing are the geometric rules which are used for finding the shortest distance between two points on a curved surface with respect to gravity in General Relativity. Those same geometric rules can be used for finding the most effective methods to process information in quantum computing.

These points of shortest travel – whether across a spherical planet or inside a quantum computing system – are known as geodesics. A noteworthy point regarding this discovery is that it involves a branch of quantum computing which is conformal field theory. Through this new study, there is a possibility of faster calculations in the above-mentioned branch of quantum computing.

Physicist Pawel Caputa who was involved in this discovery expounds that the process of finding minimal length on complexity geometry is equivalent to solving equations of gravity. So this explanation has made it transparent about how gravity is linked to discovery of quantum computing.

Looking at the other side, there is still a requirement where the reduction of error rates should take place. Along with this, scientists are looking to bring down the interference which hinders the computation process. The reason why quantum computing is thought as the future of computing because it functions on the concept of qubits which is also another form of information. The striking feature of a qubit is its ability to represent several states in contrast to binary digits which have only two states (0 and 1).

Therefore, along with this discovery, recent progress has made quantum computing to be more space efficient and significant improvement in accuracy has taken

All of this promises a bright future for the quantum computing field but the finding has been limited and thus it requires much deeper research which will help in finding its multidisciplinary applications.

Graphene

Researchers demonstrate working of quantum computers with help of graphene

A new material consisting of only one sheet of carbon atoms can give rise to new and unique designs of optical quantum computing devices. Researchers from the University of Vienna and Institute of Photonic Sciences, Barcelona have proved that tailored structures of graphene lead to the interaction of singular photons. The study has been published in the npj Quantum Information.

Photons interact with the environment to a very less degree, which makes it quite suitable for the storage and transmission of quantum information. However this same property makes it very difficult to interpret the information which has been stored in them.

For building a quantum photonic computer, it is essential for a photon to alter the state of second. This is called a quantum logic gate and a quantum computer requires millions of these. This can be achieved with the help of a ‘non-linear material’, in which there is interaction of two photons. But the standard non-linear materials are not efficient to construct a quantum logic gate.

However it has been recently understood that the nonlinear interactions can be highly improved with the help of plasmons. Plasmons make the light bind to the electrons which are located at the surface. Then these electrons facilitate a very strong interaction between the photons. In presence of these positives, a drawback is that the plasmons decay in the standard materials before the actual quantum effects can occur.

Philip Walther, from University of Vienna who led the team of researchers made a proposal to manufacture plasmons in the graphene material. Graphene has been only discovered in 2004 by Andre Geim and Konstantin Novoselov at University of Manchester. Though it was observed way back in 1962, it had not been independently isolated and studied then. For their work, the duo was awarded the Nobel Prize in Physics in 2010.

The unique arrangement of electrons in graphene leads to strong nonlinear interactions, which allows the plasmons to remain for a long duration. In the graphene quantum logic gate, scientists have demonstrated that if singular plasmons in nanoribbon are made from graphene, then it allows for the interaction of electrical fields of two plasmons in different nanoribbons. This makes way for quantum computation if each of the plasmons remain in their ribbons, since many gates can be applied to them.

Irati Alonso Calafell, who is the first author on this paper remarked that strong non linear interaction in graphene does not allow two plasmons to be in the same ribbon.

Simple Qubits

Scientists reversed time using quantum computer

Have you ever imagined the infused tea flowing back into the tea bag or a volcano from “erupting” in reverse? We cannot imagine about these things because we have learned about the second law of thermodynamics which states that the total entropy of an isolated system can never decrease over time. A group of researcher scientist from Russia teamed up with the scientist from the U.S. and Switzerland in order to challenge this fundamental law of energy.

The study’s lead author Gordey Lesovik who heads the Laboratory of the Physics of Quantum Information Technology at MIPT states that “This research is one of the series which adds up to violating the second law of thermodynamics which is closely associated with the notion of arrow of time that puts in position the one way direction of time from past to future.”

The physicists tried to understand if time could reverse itself for a tiny fraction of a second for a particle. They tried to do this by two methods – first by experimenting the electron in empty interstellar space.

Andrey Lebedev co-author from MIPT and ETH Zurich stated that “If we consider an electron in space and we begin to observe it, we can come to know the position of it. If not the position but at least the area can be decided since the laws of quantum mechanics don’t allow us to understand the exact position of the electron.”

The physicist then adds “The evolution of electron can be explained by Schrödinger’s equation. However, it makes no distinction between the past and the future, the region of space containing the electron will spread out very quickly. The uncertainty of the electron’s position is growing.”

Quantum mechanics travelling wavefunctions

Quantum mechanics travelling wavefunctions (Credit: Maschen/ wikimedia)

Valerii Vinokur, a co-author of the paper, from the Argonne National Laboratory, U.S. adds to the discussion that “Mathematically, it means that under a certain condition of transformation called complex conjugation, the equation will describe a smeared electron localizing back into a small region of space over the same time period. However, this is only possible theoretically and not practically.”

The second method of experimentation was done with the help of quantum computing instead of electrons, made out of two or three basic elements called superconducting qubits. They have four stages of the experiment.

The four stages are as follows:

  • Stage 1: Order
    In the first stage, like the electron was imagined to be localized in space, here, the qubit is initialized in a stage called the zero stage.
  • Stage 2: Degradation
    Similar to the electron being smeared out over an increasingly large region of space, the qubits leave the zero stage and become a complex pattern of zeros and ones.
  • Stage 3: Time Reversal
    In this stage similar to the electron being induced to fluctuation by microwave, here, a special program modifies the state of the quantum computer in such a way that it would then evolve “backward”, from chaos toward order.
  • Stage 4: Regeneration
    Again the evolution program starts from stage 2. Provided that the “kick “ has been launched successfully. The program reverses the state of qubits back into the past.
    It was observed that where two qubits were involved, the success rate was around 85 percent, but where 3 qubits or more than 3 qubits were involved more errors happened and it resulted in only 50 percent of the success rate.

Published Researchhttps://www.nature.com/articles/s41598-019-40765-6