Modern Physics

Quantum computer

Quantum computers are machines capable of using information contained in particles, such as atoms and electrons, and even in light to solve complex problems.

A quantum computer is a machine capable of manipulating information stored in quantum systems , such as electron spins (electron magnetic field), energy levels of atoms , and even photon polarization . In these computers, the fundamental units of information, called “quantum bits” (in Portuguese, quantum bits), are used in order to solve calculations or simulations that would take processing times impractical in electronic computers, such as those used today.

Some quantum computers will be able to use the photons of light as quantum bits.

Quantum computers work with a logic quite different from that of classical computers: quantum bits can have the values ​​0 and 1 simultaneously, as a result of a quantum phenomenon called quantum superposition . These values ​​represent the binary code of computers and are, in a way, the language understood by machines.

Quantum computers have proved to be the newest answer in Physics and Computing to the problems related to the limited potential of electronic computers. The processing speed and capacity of these computers are closely related to the size of their components. In this way, its miniaturization is an inevitable process .

The limit of electronic computers

In 1965, American chemist Gordon Earle Moore predicted that, every 18 months , the number of transistors used in electronic chips would increase by approximately 100% . In 2017, the American technology company IBM managed to produce a chip the size of a fingernail, with approximately 30 billion 5 nm transistors ( 1 nanometer = 10 -9 m). With that, the company showed that, even if not very accurate, Moore ‘s prediction remains valid to this day, but will reach its limit sooner than we imagined.

Integrated circuits like the ones in the photo are made of transistors, which are present in processors, calculators, cell phones, etc.

The problem starts when it is no longer possible to decrease one of the smallest and most important components of processors, the transistor . It is in this small device that all information is read, interpreted and processed. When dealing with very small scales , such as interatomic distances , Physics is no longer as predictable as it is in macroscopic systems , starting to behave randomly , in a probabilistic way , subject to the properties of Quantum Physics .

What is a quantum computer for?

Quantum computers will definitely not serve the same purposes as classical computers, so we shouldn’t expect or worry about the technologies being used today being discontinued . One of the possible uses of quantum computers is to factor large numbers in order to discover new prime numbers. Even for today’s most powerful supercomputers, this is a difficult and time-consuming task. Theoretically, quantum computers could run it much faster.

Large prime numbers , with 128 or even 256 digits, are used to encrypt bank passwords, logins and e-mail passwords, in order to prevent someone from intercepting them and being able to decipher their contents.

Theoretically, these computers are good at working with many variables simultaneously , unlike current computers, which have many limitations for performing this type of task. In this way, it is expected that quantum computers can be used to simulate extremely complex systems, such as biological , meteorological , astronomical , molecular systems, etc.

A classical computer that reads three bits can provide one combination possibility, while the quantum computer can present up to eight possibilities.

The “ease” of quantum computers in dealing with complex systems is related to the nature of quantum bits: while an electronic bit can only take the value 0 or 1 , quantum bits can have both values ​​at the same time . In this way, a single quantum bit has a numerical equivalence of 2 electronic bits . It doesn’t seem like much, but with just 10 quantum bits, we would produce a computer with a capacity of 1024 bits (2 10 = 1024), whereas most home computers today run on 64-bit systems .

What are the limitations of a quantum computer?

Despite representing a significant leap from classical computers, quantum computers also have their limitations . The quantum behavior of bits is only achieved under very sensitive conditions. Thus, it is necessary to keep them at very low temperatures , close to absolute zero , using sophisticated nitrogen or liquid helium refrigeration systems. Any variations in these temperature conditions, no matter how small, can harm or even interrupt its proper functioning.

Other factors, such as external magnetic fields and electromagnetic waves emitted by nearby devices, can interfere with the quantum behavior of extremely sensitive particles used to store information, such as electrons and atoms .

The D-Wave quantum computer

Founded in 1999, the Canadian company D-Wave claims to have produced the first commercial quantum computer . In 2017, the company put up for sale a quantum computer called 2000Q , which reportedly features an incredible 2000 quantum bits. To acquire it, however, it is necessary to pay something between 15 million dollars .

This company divides the opinions of the scientific community, as there are groups of physicists and computer scientists who believe that the machine is not 100% quantum, but a hybrid computer capable of using both quantum and electronic bits simultaneously .

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