Whether we like to admit it or not, science and technology are full of "hypes", developments with extraordinary potential and spectacular promises that never materialize. Cold fusion and graphene are two good examples, but if we look closely at the giants of the market, we discover that they can't stop talking about quantum computers. What do they want to do with them? How does a quantum computer work? Today we'll explore the answers to those questions.
Ones, zeros... and something more
Our digital life is an endless dance of ones and zeros. This article, the browser you use, your operating system. Photos, videos, music, games, work, exams. Love? Money? Neither do they escape bits. Beyond some specific conditions that can "change" a bit spontaneously and sow chaos, the truth is they work, and they've served us well.
The development of computing in recent decades has been focused on processing more bits, and at greater speed. However, our advances are quickly approaching physical limits we cannot escape. With components approaching the size of an atom, quantum physics is our main enemy... but what if we turn it into an ally? Welcome to the quantum computer.
How a quantum computer works
(Editor's note: subtitles in Spanish)
In general terms, the idea of a quantum computer is to use quantum properties to perform operations. In a conventional computer, the bit is the smallest unit of information, with 0 and 1 as possible states. But in a quantum computer we have the qubit (quantum bit), which can be 0, 1... or a proportion of both. That leads us to the famous quantum superposition: As long as it is not observed-evaluated-measured, the qubit is in superposition, but once you do something with it, it must collapse to one of its definitive states. Schrödinger's cat, with bits.
Yes, but it's even more complicated...
To the previous paragraph we must add the concept of quantum entanglement. Basically it's a connection or link that makes a qubit react to a change in the state of another qubit. This reaction is instantaneous, and is not affected by the distance separating the qubits. Why is this important? Because by measuring an entangled qubit, we can calculate the properties of its partner without having to make an additional observation.
However... everything we've said so far is the "simple version" of the quantum computer. Scott Aaronson, professor of computer science at the University of Texas (Austin) and one of the most important experts in quantum computing, explains that quantum mechanics works with amplitudes. And the qubit is a bit with an amplitude for 0, and another for 1. One of the fundamental goals of quantum computers is that all amplitudes that lead us to wrong results cancel each other out, and the remaining amplitudes serve to reach the correct answer.
To achieve this, current quantum computer designs depend on superconductivity. The size of the chip is not much larger than a traditional processor, and it uses a series of "coils" in which two quantum states of current flow. The coils can interact with each other with the help of Josephson junctions, giving rise to the generation of entangled states. The interaction between qubits is completely programmable, and for all this to work, the system must be brought to a temperature very close to absolute zero.
The Problem
When the first laser was built in 1960, its creator Theodore Maiman defined it as "a solution looking for a problem". And from a certain point of view, we can say the same about the quantum computer. We have a fairly solid idea of its potential, but it must not only make a leap in quality, but also in quantity.
The best quantum computers have an average of 50 qubits. Google's Sycamore quantum processor has a total of 53 qubits, and the Chinese system Jiuzhang reached 76. However, experts recognize that exponential growth is needed, with computers made up of hundreds of thousands of qubits to generate useful work and solve broad-spectrum problems.
The first thing that comes to mind is a kind of "quantum Moore's law", but it wouldn't be enough: While Moore's law doubled the number of transistors every 18-24 months, quantum computers must double their number of qubits every twelve months or less. What does that mean? Ten years, at least.
Quantum computer: Applications and challenges
Obviously, there are plenty of reasons to face all the challenges that quantum computing throws in our direction. From advanced simulations of molecules to economic projections, including new branches in education, medicine and security, quantum computers will create many markets, and we must prepare for them.
https://old.neoteo.com/supremacia-cuantica-google-que-significa/The security aspect deserves a chapter of its own: Under the right conditions (think millions of qubits), a quantum computer could pulverize the RSA cryptosystem, and if that happens... we better have a good alternative in place.
