The world of theoretical physics has been the domain of geniuses like Stephen Hawking and fictional characters such as The Big Bang Theory’s Sheldon Cooper. But now companies like Google (GOOG), IBM (IBM), and Intel (INTC) are building quantum computer systems, that may soon outperform even the fastest supercomputers in the world. So, it’s a good time to learn some basic quantum computing terms and concepts.
It’s physics
Quantum Computing is based on Quantum Physics. Quantum Physics is the arm of modern physics that explains the nature and behavior of matter and energy on the atomic and subatomic levels. It is also called quantum theory and quantum mechanics. Quantum computers use quantum physics to compute.
Before quantum physics, “classical” physics explained the world around us (calculations of speeds, rotations, weights, forces …). Then came Einstein who explained the “infinitely large”, the universe, time, big bang, black holes… But the classic mechanics did not explain everything and this is where quantum physics, steps in. The world of atoms, the infinitely small, does not work like the world that we, humans, see every day. The algebra story problems about a ball bouncing off a wall at 37 degrees and landing 43 feet away no longer apply in the world of quantum physics. Quantum computing devices use these newly discovered properties to perform computations using quantum bits, or qubits.
Classical computers
Pierre Pinna at IPFCOnline explains that the “classical” computer sitting on your desk, manipulates information (software, texts, pictures, videos, etc.). Inside your laptop, this information is made up of “1” and “0”. All computers have one (or more) micro-processors that manipulate the “0” and “1”, by applying the basic operations (addition, subtraction, multiplication) to “order” the 1’s and 0’s into software, texts, pictures, videos, etc.
The 1’s and 0’s are physically created by electric current inside transistors. Each transistor can be on or off, which indicates the 1 or 0 to be used to compute the next step in a program.
When the transistor is open, the electric current does not pass through the transistor and we say that we are in the state “0” and conversely if the transistor is closed, the electrical current can pass through it, we are in state “1”. The transistors inside the CPU can be combined into logic gates to perform logic operations like “OR”, “XOR”, “AND.” The classical computers 1’s and 0’s are called “bits.”
Quantum computers
Quantum computers also handle “1” and “0” just like your laptop. But the information is no longer manipulated by transistors but by atomic and subatomic particles (electrons, protons, ions, photons, neutrons, etc.). You know, the stuff they taught in Mr. Birchmeier’s high school science class. Quantum computers don’t use bits; they use quantum bits (qubits). And that’s where quantum computing gets interesting – the subatomic world does not work like the physical world we live in. Quantum physics explains how the subatomic world works.
Tristan Greene at TNW writes that qubits have extra functions that bits don’t. Instead of only being represented as a 1 or 0, qubits can actually be both at the same time. Mr. Greene writes that qubits, when unobserved, are considered to be “spinning.” Instead of referring to these types of “spin qubits” using ones or zeros, they’re measured in states of “up,” “down,” and “both.”
The IPFCOnline article explains that to better understand all of this, we must see each particle as a wave and not a single physical element. The particles are then characterized by their “spin” to create a state called superposition.
Mr. Greene at TNW writes that quantum superposition in qubits can be explained by flipping a coin. We know that the coin will land in one of two states: heads or tails. This is how classical computers think. While the coin is still spinning in the air, the coin is actually in both states at the same time. Essentially until the coin lands, it has to be considered both heads and tails simultaneously.
Quantum computing use superposition
Superposition is based on Observation theory. Observation theory basically says the universe acts one way when we’re looking, another way when we aren’t. Mr. Pinna at IPFCOnline writes that with superposition, while we do not know what the state of any object is, it is actually in all possible states simultaneously, as long as we don’t look to check. To illustrate this theory, we can use the famous and somewhat cruel analogy of Schrodinger’s Cat using a cat in a box as being both alive and dead at the same time.
All of these sub-atomic activities make the quantum computer very sensitive to disturbances from the outside world. When quantum computers are disturbed they become unstable, and revert to “classical computers.” In order to keep the quantum properties of the system, it must be protected from the outside world. According to the article, this is typically done by cooling the quantum computer to temperatures very close to absolute zero (-273.145°C – colder than in space). Another factor when working with qubits is noise. The more qubits a system has, the more errors you get.
All of these factors make working with qubits incredibly difficult. These challenges are made worse by the unsustainable amount of electricity currently needed to generate quantum computing results. Reports are that one quantum computer burns about 20 megawatts of electricity — enough to power 20,000 households.
Therefore, the current state-of-the-art quantum computing theoretical speed gain is limited by the cost, size, and instability of the system. Right now, quantum computers aren’t worth the trouble and money they take to build and operate. A quantum computer is not going to run MS Word on your desktop.
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Ralph Bach has been in IT long enough to know better and has blogged from his Bach Seat about IT, careers, and anything else that catches his attention since 2005. You can follow him on LinkedIn, Facebook, and Twitter. Email the Bach Seat here.