(과학) 한 발짝 다가선 콴텀 컴퓨팅(양자 컴퓨터작업)

출처: http://www.bbc.com/news/science-environment-32534763

1 May 2015

Step forward for quantum computing 한 발 다가선 콴텀 컴퓨팅 (양자 컴퓨터작업?)

By Paul RinconScience editor, BBC News website

IBM wants quantum computers to help design new drugs and materials 아이비엠은 양자컴퓨터가 신약이나 신물질을 개발하는데 도움이 되기를 바란다

Scientists have made progress towards correcting the errors that are expected to affect quantum computing. 과학자들이 양자 컴퓨터작업에 영향을 끼칠 것으로 보이는 에러들을 교정하는데 있어 진보를 했다

Quantum computers could offer a massive performance boost over conventional types, but progress toward commercially useful machines has been slow. 양자 컴퓨터는 기존 컴퓨터보다 훨씬 대량의 작업을 수행할 수 있으나, 상업화로의 길은 너무 느리다. 

Now, scientists from IBM's Watson Research Center have successfully demonstrated a new method for correcting errors on a quantum circuit. 아이비엠의 앗슨 연구센터의 과학자들은 성공적으로 양자회로에서 발견된 에러를 교정하는 새로운 방법을 시연했다.

Details are published in the journal Nature Communications. 상세한 사항은 저널 네이쳐 회보에 실렸다.

The basic units of information in classical computers are called "bits" and are stored as a string of 1s and 0s. But their equivalents in a quantum system - qubits - can be both 1s and 0s at the same time. 기존 컴퓨터에서는 정보의 기본 단위가 "비트"로 1이나 0으로 저장된다. 그러나 양자체제에서는 1과 0이 동시에 저장가능하다.

In theory, this should give quantum machines much greater computational power than conventional types. 이론상으로, 이런 체제는 기존 형태(의 컴퓨터)보다 훨씬 많은 입력작업을 수행할 수 있는 힘을 양자 기계(=컴퓨터)에 실어준다.

But quantum information is fragile, and errors in calculations carried out in a quantum system can creep in through interference from factors such as heat, electromagnetic radiation and defects in materials.

Controlling or removing such errors is one of the great challenges for harnessing the power of quantum computing.

Scaling up

The IBM team was able to detect and measure two key types of quantum error (called bit-flip and phase-flip) that will occur in any real quantum computer.

"Up until now, researchers have been able to detect bit-flip or phase-flip quantum errors, but never the two together," said co-author Jay Gambetta.

The team demonstrated its error-protection protocols on a quantum circuit consisting of a square lattice of four superconducting qubits on a chip roughly one-quarter inch square.

IBM claims the square shape of the circuit makes it more scalable than the linear arrays that have been used by other groups.

Prof Alan Woodward, a computing expert from the University of Surrey, UK, said the work represented a step forward, but was a "significant evolution" rather than a "revolution".

"We all know that error correction is very important in quantum computing because of the inherent errors that are caused by the way qubits tend to operate, but this isn't the first time it's been addressed," he told BBC News.

For example, an American team of physicists published a separate protocol for quantum-error detection just last month.

But Prof Woodward said: "What we're seeing is the move from the drawing board to actual implementation.

"This is the first time we have seen groups actually implementing real hardware which is then proven experimentally to have significant error correction properties."

"Which architecture, if any, actually wins out remains to be seen. Each has pros and cons but at the moment there isn't really an obvious winner."

But he said the "dark horse in the race" was topological quantum computing, an architecture that is intrinsically more fault-tolerant. A team at the University of California, Santa Barbara, has been working on this method, and is being backed in its efforts by Microsoft.