What is a Quantum Computer?
Bomb news in the field of quantum computing. Leaked, then withdrawn, but never denied or officially confirmed about the world of Quantum Computer.
Last week a paper entitled Quantum supremacy using a programmable superconducting processor appeared on the NASA website, Quantum Supremacy using a programmable superconducting processor.
The article remained online for a few hours (fortunately some pious souls saved it) but it was enough to generate an avalanche of comments, controversies, controversies, suppositions and hopes among the community of professionals about this “futuristic” technology.
This is the gist: Sycamore, Google’s quantum computer, would have succeeded in achieving the so-called quantum supremacy, that is to say, within a few minutes, and for the first time in the world, a series of operations that traditional computers would take tens of thousands of years to play. We tried to understand, with the help of an expert, how much to trust, because it is such an important news and what could change in the future if confirmed.
What is a Quantum Computer and How it Works?
Let’s start with the basics, also to clear the field of ambiguity and misunderstanding. A quantum computer exploits some of the most bizarre and counterintuitive properties of quantum mechanics to obtain computing power far superior to that of a classic computer (and supercomputer).
As everyone knows, the minimum unit of information of a conventional processor is the bit, a binary entity that can assume the values zero and one depending on the passage of current.
For their part, quantum processors use qubits, usually subatomic particles like photons or electrons, which instead can store much more information: “Traditional processors,” says Tommaso Calarco, director of the Jara-Institute Quantum Information and president of the European Quantum Flagship Network, “admit only two states, zero and one, linked to the passage or non-passage of current, that is, a flow of electrons. In quantum processors, instead, every single electron carries information, which greatly amplifies the computing power. “
The laws of quantum mechanics, in fact, postulate (among other things) that each particle is subject to the so-called superposition principle, that is – to put it roughly – can be found simultaneously, with different probabilities, in several different states. “
The superposition principle allows to overcome the on / off dualism and to convey much more information: a quantum particle can simultaneously represent more states”. The qubit, in short, allows to parallelize the calculations, that is to carry out many, many operations simultaneously.
Quantum Computers will not replace traditional computers for now
Attention: what has been said so far probably does not mean that in the near future the classical processors will definitely retire. For most conventional operations they will still be the most efficient and economical option: using a quantum computer to render a video or to shoot down video game monsters would be like shooting a fly with a cannon.
The case of sectors such as materials science, or the pharmaceutical industry, or particle physics is different: in these scenarios a quantum processor could really completely change – and forever – the rules of the game, making vast technological advances possible. scope and difficult to predict.
Quantum Computer: Where are We Now?
These months represent a crucial phase in the history of quantum computer development. Just a few days before the Google leak, IBM announced that next October it will allow engineers, physicists and computer scientists to remotely access a 53 qubit quantum computer, the most powerful ever built by the company and the largest ever made available for external use.
The news has come to fulfillment of efforts that have been going on for years: in 2017, as we told you, IBM scientists were able to successfully simulate a 56 qubit quantum computer inside a traditional processor with 4.5 terabytes of memory .
For its part, instead, Google has available Sycamore, a 54 qubit computer (one of which does not seem to work as it should, and therefore 53 are used), and another 72 qubit system, which at the moment has turned out however. too difficult to control.
All because quantum systems are extremely delicate, and particularly susceptible also to imperceptible external interference (thermal and electromagnetic, for example): “To give an idea of the enormous difficulty of managing and controlling quantum computers”, Calarco explains, ” you can think of qubits as members of an orchestra called to play Beethoven’s ninth symphony. But each musician must be able to do it with boxing gloves in his hands and a helmet on his head. And in a room kept at ninety degrees of temperature. It is a very, very difficult task ”.
Quantum Supremacy vs Quantum Advantage
What does Quantum Supremacy Mean?
“In itself, this is a very simple concept,” says Calarco. “It means being able to solve, with a quantum computer, a calculation that a traditional computer would not be able to solve, at least in a reasonable time”.
In this case, Sycamore has succeeded in demonstrating that a sequence of random numbers is really random (a mathematically very complex problem) in about three minutes and twenty seconds; Summit, the most powerful (traditional) supercomputer in the world, would take about 10 thousand years.
“The problem solved by Sycamore, in itself, is completely useless, or rather it is purely academic. Its importance is linked to the fact that being able to solve it proves once and for all that we have achieved quantum supremacy. It’s the crowning glory of what we thought was just a dream, and now we actually know it to be feasible ”.
The next step, Calarco explains, will be to move from quantum supremacy to the quantum advantage, that is to the effective design of algorithms to be played by the quantum computers of the future. It is as if at this moment we have shown that it is possible to build a very fast car, but we still lack roads, gas stations, infrastructures. And above all departures and destinations.
“It is the same as was for 3D Printing, we ar still far too early to imagine all the applications. They could be really exterminated, and amazing. The next steps are first of all to further improve the hardware, arriving to precisely control systems with 100 or more qubits, and then work on the development of algorithms that allow us to arrive at the quantum advantage “. The future awaits us.
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