# Encryption schemes could become history as MIT announces a 5-atom quantum computer

Researchers from MIT and the University of Innsbruck in Austria have created the world’s first five-atom quantum computer which could decipher the security of traditional encryption schemes.

More than two decades after Peter Shor, the Morss Professor of Applied Mathematics at MIT, created a quantum algorithm which calculates the prime factors of a large number more efficiently than a classical computer, researchers from MIT and the University of Innsbruck in Austria reported that they have designed a quantum computer from five atoms in an ion trap.

Unlike traditional computing, where numbers are represented by 0s or 1s, quantum computing is all about “qubits” (atomic-scale units), which can be at the same time 0 and 1. The researchers’ discovery is fascinating because even though it usually takes roughly 12 qubits to factor the number 15, their attempt to reduce the number to just five qubits, each represented by one atom only, has been successful. In a paper published in early March in the journal *Science*, the team announced that they have created a quantum computer from five atoms in an ion trap which uses laser pulses to carry out Shor’s algorithm on each atom, to correctly factor the number 15. The success of Shor’s algorithm depended on a computer with a large number of quantum bits.

## New quantum computer factors numbers in a scalable way

According to the team of researchers, the system is created in such a way that more atoms and lasers can be added to build a faster and larger quantum computer which can factor much larger numbers. The results of this new quantum computer represent the first scalable implementation of the algorithm created in 1994.

Isaac Chuang, professor of physics and professor of electrical engineering and computer science at MIT explained that “now it’s much more an engineering effort, and not a basic physics question.” Chuang, a pioneer in the field of quantum computing, designed a quantum computer 15 years ago based on one molecule which could be held in superposition and manipulated with nuclear magnetic resonance to factor the number 15. Although the results -published in *Nature*– represented the first experimental realization of Shor’s algorithm, the system was not scalable and it became more problematic to control it as more atoms were added.

The team of researchers have now come up with a new, scalable quantum system for factoring numbers efficiently. Each atom can be held in a superposition of two distinct energy states at the same time. They use laser pulses to perform “logic gates,” (or components of Shor’s algorithm) on four of the five atoms. The results are stored, forwarded, extracted and recycled through the fifth atom, thereby executing Short’s algorithm in parallel, with fewer qubits than is usually required. The team also managed to maintain the quantum system stable by holding the atoms in an ion trap, where they removed an electron from every atom, thereby charging it. The researchers held each atom in place with an electric field to “know exactly where the atom is in space,” Chuang explained. “Then we do that with another atom, a few microns away – [a distance] about 100th the width of a human hair. By having a number of these atoms together, they can still interact with each other because they’re charged.” The interaction allows the team to perform logic gates and realize the primitives of the Shor factoring algorithm. “The gates we perform can work on any of these kinds of atoms, no matter how large we make the system,” the professor added.

While Chuang’s team worked out the quantum design in principle, his colleagues at the University of Innsbruck created an experimental apparatus based on his methodology. The quantum system was directed to factor the number 15 and, without any prior knowledge of the answers, the system returned the correct factors, with a confidence exceeding 99 percent.

## Encryption schemes could become obsolete

Chuang opined that nation states probably do not want to publicly store their secrets using encryption which relies on factoring as a hard-to-invert problem. “Because when these quantum computers start coming out, you’ll be able to go back and un-encrypt all those old secrets,” he concluded.

Although the MIT professor said that “it might still cost an enormous amount of money to build [a quantum computer]” and warned that you won’t “be putting it on your desktop anytime soon,” some countries are taking this matter -that a functional quantum computer may decipher traditional RSA encryption- seriously. In early 2016, the U.S. National Security Agency (NSA) published an FAQ with regard to this scenario.

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