Quantum computers, arithmetic miracles in the works


Quantum computers, which can do more than classical computers, are still under development. A big challenge – because quantum states are fragile. Qubits interact with their environment. Stopping them is difficult, even with precise lasers in vacuum chambers. Any noise in the system leads to “decoherence”: the superposition is destroyed and the computer loses information. A few errors are normal because quantum computers work with probabilities. Without the strict rules of the binary system. But decoherence disturbs so much that the result is no longer unambiguous. When a qubit enters the state of decoherence, the system of entangled qubits collapses.

On the other hand, error correction helps – for which there are several options. One option is full error correction. Then typical errors such as “bit flips” would no longer be a problem for the quantum computer. A qubit suddenly changes into the wrong state. To do this, the quantum computer needs both the so-called “logical” qubits for calculations and a large number of normal qubits for corrections: around 100 correction qubits for one logical qubit. The result would be an extremely reliable and useful quantum computer.

Another possibility would be to suppress the noise in the data caused by errors. The “Noisy Intermediate-Scale Quantum Computer” is designed to do just that. However, it is still a work in progress – and probably does not solve the problem in all cases. Or you can use a new qubit source that is less sensitive to noise. For example, “topological particles” that can store information better. However, some of the particles only exist in theory. Therefore, this approach will probably be years or decades away.

Sycamore is considered a major breakthrough – how big is a matter of debate

Despite all the difficulties, quantum computing has made some significant achievements. In 2019, Google tested a simulation: The 54-qubit quantum computer “Sycamore” calculated the probabilities of different outcomes – a million times within four minutes. Sycamore works very differently from the quantum computer that IBM used to prove Shor’s algorithm. The device cools down the superconducting circuits to such an extent that the current flowing through them behaves like a quantum mechanical system. One of the currently leading methods for building a quantum computer. Also popular: ion traps. The energy levels stand for different qubit states.

Sycamore is considered a major breakthrough. However, how big is a matter of debate. According to Google, it was the first quantum advantage presented: that is, a quantum computer solves a task that computers cannot solve. According to Google, even the best supercomputer in the world would have needed 10,000 years. IBM has denied this claim.

Serious quantum computers are still out of reach. But governments and the world’s largest companies are investing billions in the quantum computing race. The question is: how do quantum computers change our view of what a computer is? How is our networked world changing? And when?



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