Will quantum computers replace traditional computers?

Last year, Google first proved the superiority of quantum computers over traditional architecture computers in experiments. It also attracted the public's attention to quantum computers. But can quantum computers really replace traditional computers? This should start with the principle of quantum computer.

The binary data representation of traditional computers is deterministic. For example, in a digital circuit, a transistor has only two states-conducting or non-conducting. But the quantum computer can't determine which state it is in. Quantum can have two states: topspin and backspin. But before being observed, quantum can be in two states at the same time.

Therefore, two qubits are expressed as α | 0 >:+β|1>; Where α and β represent amplitude. Where | 0> and |1>; Can be represented by a vector:

Please continue to discuss the specific physical principles of quantum computing: how quantum computers work.

At this time, we know that a qubit needs two amplitudes to represent the state before being observed. From this, it is deduced that the 2-bit qubit is represented as C0 | 00 >；; +c 1 | 0 1 & gt； +C2 | 10 & gt； +C3 | 1 1 & gt； N-bit qubits need the amplitude of 2 to the nth power to represent them.

The gate operation of qubits (similar to the gate operation of digital circuits in traditional computers) is realized by changing these two amplitudes. The following is a (non-comprehensive) list of gate operations for quantum computers:

The matrix on the right is the basic unit of quantum bit operation. Take Pauli-X as an example: Not-gate operates on a single qubit, specifically, α and β are exchanged into β | 0 >; +α| 1 & gt； .

At present, quantum computer is still immature, and most of the algorithms about quantum computer are simulated by traditional computers. QuEST is a quantum computing simulation library, which supports multithreading, distributed computing and GPU acceleration. The advantages and disadvantages of Quest are written in the thesis QuEST and high performance simulation of quantum computer. You can have a look if you are interested.

Learn how single door operation works. How do so many doors operate?

Parallel operation of two gate operations:

Serial operation of two gates:

Now you have a general understanding of the principle of quantum computing, but if you want to use quantum computing to help you complete an algorithm, you need to design the quantum bit states determined after calculation, such as | 0 >; Or |1>; (that is, α is 0 or β is 0) is measurable and meaningful.

Therefore, according to the professor in How Quantum Computers Work, quantum computers are only faster than traditional computers in some parallel algorithms, such as cracking passwords. But if you just need to surf the Internet and write articles, traditional computers have more advantages. Therefore, quantum computers will not be a substitute for traditional computers in the future, but will be used as a computing aid.

If there are any inaccuracies, please correct and discuss them!