What the hell is going on inside a quantum computer?

Quantum computers are computers that are expected to perform large-scale calculations that cannot be achieved by conventional computers (classical computers) by using quantum mechanics for calculations. Physics Today , a scientific media, explains some of the functions of quantum computers.

What's under the hood of a quantum computer?

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Quantum computers, unlike classical computers that use bits that can only take '0' or '1' states, have the smallest unit of quantum information 'qubits ' that can take both '0' and '1' states. It is a computer that uses it to perform calculations. In classical physics, either '0' or '1' was definitely determined, whereas in the quantum state, '0' or '1' is probabilistically determined only after observation, and quantum computers. Then, complex information is expressed using this vague superposition state.

An example of a computer that realizes qubits is the ' ion trapped quantum computer '. An ion trapped quantum computer uses an electromagnetic field to confine ions in space and store qubits as a stable electronic state of particles. The ion trap type quantum computer is a quantum computer that can perform operations with the highest accuracy currently known.


IBM Research

However, quantum computers have the problem of being 'error-prone.' All kinds of environmental factors such as thermal fluctuation , electromagnetic radiation, and magnetic field can cause the qubit to deviate from its intended state. This information degradation is called 'decoherence ' and can occur in an instant even when the computer is kept at low temperature to reduce thermal fluctuation.

'Quantum error correction' is a method to correct errors caused by decoherence. Quantum computer performs error correction, which is also used in classical computers, and quantum error correction is indispensable when performing complex multi-bit calculations.

Also, in classical computers, the compiler that receives the higher-level instructions of the task to be executed converts the instructions into operations performed by the underlying hardware, but the same is done in quantum computers. That is the mechanism called 'transpiler ', which determines how to execute a series of logical operations while considering the connection between qubits. It is difficult to physically rearrange the qubits, but by swapping the states of the two qubits, efficient rearrangement is performed.

Various studies are progressing on quantum computers, but they are still complicated and not easy to construct. However, with access to quantum computers provided by Amazon and Microsoft, it is expected that the range of activities of quantum computers will continue to expand.

in Science, Posted by log1p_kr