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via:博客园 time:2018/3/10 15:49:31 readed:221

In this year, held in Losangeles at the annual meeting of the American Physical Society, Google put a big move, released the world's first 72 qubit quantum computer general Bristlecon, 1% low error rate, flat deals with Google before the 9 qubit universal quantum computer. The processor not only helps scientists to explore quantum simulation, but also can be used in quantum optimization and quantum machine learning.

Google related personnel said:

We think cautiously and optimistically that Bristlecone can achieve quantum hegemony (Quantum Supremacy).

Google's latest quantum processor Bristlecon

With regard to this quantum computer, we can understand the following concepts:

**Quantum hegemony**

As we all know, the computing power of a quantum computer is much more than the ability of the most advanced supercomputer. Some experts believe that this can be a big step in the development of quantum chips, and quantum is arranged in two dimensional layout, making the control system more complex. This is closer to the requirement for the implementation of the surface coding, that is, the ability to manipulate the quantum of the quantum system to perform useful computing. Google staff believe that the new processor will not only achieve quantum hegemony, but also Google has developed a benchmark test tool to measure whether the quantum computer has reached the standard of quantum hegemony. This test can apply a random single quantum circuit to a processor and measure the output of a classic simulation.

**Bristlecone**

This computer is developed by Google Quantum AI Lab (AI Google), based on the nine bit matrix developed by Google researchers, similar to the shape of pineal, so it is named Bristlecone (Hu Weisong). The goal of Google quantum AI laboratory is to build quantum computers that can be used to solve real world problems. Their research strategy is to explore short-term solutions in a system compatible with large-scale, general-purpose, and error correcting quantum computers.

The chip structure schematic diagram, each "X" represents a qubit, adjacent to the nearest qubits.

In order to allow a quantum processor to run an algorithm other than the classic simulation algorithm, it will certainly require more quantum bits (qubit), but it needs more. Most importantly, the processor must maintain a low error rate in read and logic operations such as single and double qubit gates.

**Qubit**

Qubits are the quantum analog forms of digital bits, and are the smallest units of information processing by traditional computers. However, the digital bits are binary and can only be selected between 0 and 1. The qubits can exist in the superimposed state (its value can be 0, 1, or other combinations). If it is a N qubit, it can theoretically store the data of 2^N at the same time. For example, 250 qubits can be stored in 2^250, which is more than all known cosmos. When a quantum computer performs operations, it can calculate the mathematical operation of 2^N at the same time, which is equivalent to the repetition of the calculation of the 2^N by the classical computer. It can be seen that quantum computers can save a lot of time and computing units, allowing quantum computers to query databases, decompose large prime numbers, or create complex scientific models, and are more efficient and accurate than supercomputers.

Qubit number

But creating a large quantum computer is not just as simple as putting a pile of qubits together. Creating a qubit array is a challenging task. Usually, special materials are needed, expensive laser settings and / or extreme environmental conditions are needed to create a successful and normal operation, depending on whether the qubits are based on ions, spin semiconductors, or Google based processors or superconducting circuits.

It should be noted that qubit itself is very sensitive to noise environment interference. Non ideal environment may cause the qubit state problem, so it is very easy to make mistakes. With the minimum error rate is between the qubits array to create powerful quantum computer powerful physicist and one of the biggest obstacles.

**error rate**

Because the quantum state is very unstable, only 50 qubits are far from enough, because the quantum entanglement of quantum bits will be wrong. Only enough quantum bits and low error rates can realize the real meaning of quantum hegemony.

Install Bristlecone

By using the 72 qubit matrix of a quantum computer (9 qubit universal quantum computer and before) can achieve a 1% bit double door error reading error rate and 0.6% single qubit error rate, the rate of 0.1%. A quantum bit gate is a quantum gate (also called quantum logic) that is basic, operating a quantum circuit of a small number of qubits. It is the basis of a quantum circuit, like the relationship between a traditional logic gate and a general digital line. A common quantum gate performs a logical operation on one or two qubits, resulting in a single output.

**The quantum computer may break the bitcoin**

At present, quantum computers are applied only in the field of scientific research. But if Google labs say that Bristlecone can achieve quantum hegemony, the virtual currency based on block chain technology will probably be cracked.

According to the principle of the majority in the block chain, once the miners have 51% of the power, other follow-up miners will not be able to continue to obtain bitcoins. In the future, with the growth of quantum bits of quantum computer, the asymmetric cryptographic algorithm used in block chain, that is, public key cryptosystem will also be threatened by more.

By using a quantum computer, you can use the public key to infer the private key in reverse operation. Everyone's private key is easily inferred by a quantum computer. Motherboard, a foreign medium, thinks a 4000 quantum computer can break up the block chain. In other words, which person or team makes and applies such a quantum computer first can solve and verify every transaction, and all the cryptographic currencies that will be generated in the future will be monopolized by them. The trust system for encrypted currencies will be broken down. See the FreeBuf feature article for more details:Quantum computing moves from concept to reality, and whether public key encryption is in danger.

In a strict sense, the advent of quantum computers will threaten all the encryption of the existing system, and will rewrite the security of the entire financial and banking industry.

However, many scientists believe that quantum computers do not take the place of classical computers. Because of the computational characteristics of the quantum computer, it can only be used in a few fields, and the scope of the classical computer is far beyond the quantum computer.

However, every block chaining technology developer should also be vigilant. The emergence of Google's quantum computer indicates that the future block chain field will be changed dramatically.

**Reference sources:**

Http://www.freebuf.com/articles/database/139347.html

Https://motherboard.vice.com/en_us/article/pam958/bristlecone-google-quantum-computer-72-qubits

Https://zh.wikipedia.org/wiki/ quantum gate(quantum gate)

Https://research.googleblog.com/2018/03/a-preview-of-bristlecone-googles-new.html

Https://www.cnbeta.com/articles/tech/704777.htm

* Author: AngelaY, reprint please indicate from FreeBuf.COM

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