Quantum computers are often seen in Sci-Fi movies like I, Robot and Eagle Eye as computers with capabilities beyond those of present day computers. The computer named Becky in Eagle Eye was especially memorable, attempting to kill government officials including the president by hacking into high security systems.
How were quantum computers able to express feelings and hack into everything in these movies? Today, I’d like to introduce you to the world of quantum computers.
Definition and Mechanism of Quantum Computers
Quantum computers are computers that process data using the principles of quantum mechanics such as entanglement and superposition. They are also called ‘future computers’ that surpass super computers by using quantum mechanics as their computing element.
It was Richard Feynman, a theoretical physicist in the US, who discovered the potential and necessity of quantum computers in 1982, and David Deutsch from Oxford University defined it in more specifics. Let’s take a look at the mechanism of quantum mechanics utilized in quantum computers.
Quantum computers make use of two basic phenomena: quantum superposition and entanglement. Quantum superposition is when electrons are held in an arbitrary state until protons are measured, and quantum entanglement describes an entire group of protons entering a fixed state when one of the entangled protons is observed.
These physical phenomena may be quite complicated to grasp. Let’s think about the cat experiment from Erwin Schrodinger, an Austrian physicist, famously known as Schrodinger’s cat.
Let’s say there’s a sealed box with potassium cyanide and a cat in it. Until we open the box and take a look inside, we wouldn’t know if the cat is dead or alive. This means that until the moment we open the box we cannot know whether the cat is dead or not, and that the situation is fixed simultaneously when the observation is made.
Based on these two phenomena, quantum computers use qubit, a unit at a quantum state, for calculations. Unlike in digital computers that use bits, in two states of 0 and 1, quantum computers use qubit with four states: 00, 01, 10, and 11. A qubit can be 0 or 1, and 0 and 1 can both exist as well.
Therefore, quantum computing means it’s processing in a state where the decision of whether something is at 0 or 1 can’t be made. The computing speed goes up in the form of , and if there are 512 qubits the speed is going to be as fast as .
D-Wave, the First Commercial Quantum Computer
Quantum computer D-Wave
In 2011, D-Wave System launched a 128 qubit quantum computer D-Wave 1 as the first commercial quantum computer, and 512 qubit D-Wave 2 in 2013. Its price was set at $10 million and Lockheed Martin, Google, and NASA were some of the first buyers of their new product.
Because D-Wave uses a superconductor made of niobium, it has to be used at a temperature of absolute zero (-273℃). The photo above makes it look like it’s a giant computer, but the actual computer inside is as small as a human fist. The outer part of the computer is made of a liquid helium cooling system which keeps it at the absolute zero degree and also lowers noise.
Unlike the quantum computer defined by David Deutsch, it works based on quantum annealing phenomenon to solve optimization (NP-complete) problems. Quantum annealing here means the process of electrons finding the most stable state called the ground state while the risen temperature of the object is dropping.
Pros and Cons of D-Wave
According to Google’s D-Wave benchmark in January of 2014, quantum computers show much higher speed in solving optimization problems compared to general PCs. Although there are reports that say its speed is sometimes slower than PCs, they seem to be faster than PCs, on average, to solve optimization problems involving data with regularity.
D-WAVE has three big cons.
First, despite being called the world’s first commercial quantum computer, it’s a shame that D-Wave is not considered a real quantum computer at the same time. This is because it’s designed to have an external computer read the processing results from the quantum CPU. Some may refer to it as just a “half-quantum” computer which consists of the regular workstation with a qubit CPU on the side.
Second, the CPU generates heat while operating, and the noise made while running the cooler to lower the temperature can create computing errors. The size of the computer is also quite large due to the big cooling unit on top to stabilize the temperature of absolute zero.
Finally, D-Wave is made based on the tunnel effect of quantum annealing unlike the formerly defined quantum computers. The tunnel effect here means the phenomenon where a particle stochastically tunnels through the energy barrier higher than its own potential energy. As a result, its computing speed is not overwhelmingly faster than in existing computers except for in particular calculating operations.
Prospects of Quantum Computers
Quantum computers still don’t have a lot of algorithms that solve general problems, so it only uses certain algorithms for specific operations such as prime factorization or Fourier transform.
Once the technology is found that can maintain algorithms and qubits to solve these problems and find a room temperature superconductor through which electric resistance gets close to zero at room temperature, quantum computers will become popular enough for us to see them in our daily lives.
There are new materials and products utilizing quantum mechanics these days, including TVs using quantum dots. When this kind of quantum communication is used in our lives, tapping and data interception will become impossible. I think the day when we’ll see these technologies go beyond our imagination and appear in our real lives is not so far away.
I look forward to seeing more quantum computers in the future.
Written by Deok Lee, University student reporter for LG CNS
 http://navercast.naver.com/contents.nhn?rid=122&contents_id=31579 [back to the article]
 D-Wave experiment report (https://plus.google.com/+QuantumAILab/posts/DymNo8DzAYi) [back to the article]
 http://www.dongascience.com/sctech/view/720 [back to the article]