Is it possible to have a computer upload a movie, open several Internet browsers, and download an album of music, all within a millisecond? Many scientists would say yes. The theory of creating a computer capable of almost anything has been around since 1981, when Paul Benioff, a physicist at the Argonne National Laboratory, applied quantum theory (a branch of physics explaining the interactions between matter and energy at atomic or subatomic levels) to computers. Since then, quantum computers have gone a long way, coming out of science fiction and into the real world, as scientists are currently developing early prototypes. One way of measuring the superior performance of quantum computers is through FLOPS (floating-point operations per second). A current PC’s output is measured in gigaflops (billions of floating-point operations per second), but David Deutsch of Oxford University believes a consumer quantum computer would be able to run at about 10 teraflops, or trillions of floating-point operations per second. That means a quantum computer would be around 1,000 times faster than our current models! The next logical step in technology would be to expand our limits of speed and availability by developing a quantum computer, but is it possible within our lifetime, and would it be worthwhile?
Before we dive into quantum and the quantum computer, a relatively short background of the modern computer is necessary. What is widely regarded at the blueprint of the modern computer emerged in the 1930s, when Alan Turing developed a theoretical device called a Turing machine. The device contains a tape of unlimited length that is divided into squares, which hold either a 1, 0, or nothing at all. These 1’s and 0’s make up binary code, the language of modern-day computers. Turing thought a read-write device could then read this sequence of 0’s and 1’s, translate it, and perform the instructions given.
This binary tape principle is the core of modern-day computers and the rough basis of a quantum computer. However, as the foundation of quantum computers, the main points of quantum theory must be discussed as well. Quantum theory states, first of all, that energy consists of units, rather than a constant wave. Second, energy and matter may behave like particles or waves at any given time. Third, particle movement is random and unpredictable. Lastly, the measurements of two complementary values of a particle (such as position and momentum) are imperfect; the more precise one value is, the more flawed the other will be.
In 1981, Paul Benioff applied the quantum theory to computers, envisioning the creation of a normal computer with quantum principles, or “quantum computer.” In 1984, David Deutsch published a paper about a computer based solely on quantum rules that is now widely viewed as the basis and start of quantum computing. A decade later, Berthiaume and Brassard proved that a quantum computer would theoretically be faster than a current classical computer, due to the parallelism of the quantum computer, which allows it to perform two calculations simultaneously.
So, how exactly does the application of quantum theory to computers enhance their performance? The quantum computer, unlike the current computer, which uses a silicon chip, would use atomic and molecular power as the memory and processor. The atoms, photons, and molecules would form what is called a qubit, which is similar to a gigabyte of memory space. Classic computers have a tape sequence of 0’s and 1’s which cannot exist in both states. With a quantum computer, the tape can be 0 and 1 at the same time. This is called superposition, and it is what gives a quantum computer the ability to make today's fastest supercomputer look like Windows 1.
To explain superposition, we may use the famous example of Schrodinger’s cat (cat lovers, you may want to skip this part). Take a living cat and place it into a thick box. Right now, the cat is quite obviously alive. Then put a sealed bottle of cyanide into the box, and close the box. Now, we no longer know if the cat is alive or dead. According to superposition, the cat can now be considered dead and alive. However, once we open the box, that superposition is lost, and the cat will be either dead or alive.
The drawback to superposition is that while one can easily examine the insides of current computers without disturbing the silicon chips and wires, examining a qubit would cause it to lose the ability of superposition. To assist in understanding with this problem, scientists devised a way of indirectly making measurements, called entanglement. In quantum physics, if an atom is left alone, it will spin in every direction. Physicists take two atoms that are spinning in all directions and apply an outside force. The first atom will choose one spin, or value. At the same time, the second atom will choose the opposite spin, or value, of the first. This way, scientists know the value of the qubits without looking at them.
Now that we have some background information, it’s finally time to see how the world is getting it done. In 2007, Canadian company D-Wave manipulated a 16-qubit quantum computer. D-Wave had the computer solve sudoku puzzles and other pattern matching problems. The company claimed to be able to have practical quantum computers by 2008, but was unable to achieve that goal. On October 4, 2010, researchers at UC Santa Barbara were able to entangle 3 qubits of information. Although it is far away from the goal of a 30-qubit consumer quantum computer, the entanglement of 3 qubits was a major step towards constructing a practical quantum computer.
Recently, a new method for quantum computing has been proposed. Up to this point, most quantum computers have been created using neutral atoms as a processor, which are much harder to control than polar atoms. Neutral atoms cannot be manipulated easily; there is no way to attract them due to their lack of charge. Meanwhile, the charged nature of polar atoms makes them much easier to influence, but they can only be useful when cooled to a few millionths of a degree above absolute zero. Elena Kuznetsova, a researcher in University of Connecticut’s Department of Physics, recently discovered a way to control polar atoms in computers more easily. Kuznetsova was able to break down the molecules with a laser without compromising the data, allowing the processor’s results to be read with less effort. This is the equivalent of being given a pie and figuring out the recipe by scanning it versus virtually taking it apart.
To avoid individual particles altogether, physicists at Bell Laboratories have devised another method of creating a quantum computer, which uses anyons, particle-like structures that exist in two dimensions, or quasiparticles, which are entities that behave as particles. If anyons are manipulated to twist into braids, they would be much more resistant to disturbances than individual particles, reducing the chance of data and calculation corruption. Unfortunately, the anyons can only store quantum information and stay together on 2-D sheets. At 3-D, the anyons easily unravel and data would be lost. The team has yet to announce whether they were able to successfully produce braided anyons, but the research could be a major step in creating a practical quantum computer.
Why should we make the switch from current PCs to quantum computers? One reason would be the depleting amount of silicon in the world. China recently announced that the levels of mineable silicon are dwindling, which means fewer resources to produce the iPhone, Xbox, LCD TV, GPS, or iMac. Quantum computers, however, use subatomic particles instead of silicon in a processor--crisis averted. Also, a quantum computer is billions of times faster than a normal PC, a major tool for scientists and the military, as well as a huge plus for gamers, Hulu users, and movie downloads. An algorithm that would normally take years for a classic computer to solve would take mere seconds for a quantum computer, meaning knowledge would be gained faster than ever. The creation of a practical quantum computer would also mean better homeland security.
Police occasionally trace calls by using triangulation techniques, but tracing takes some time, leaving windows for criminals to leave a message and still be concealed. Quantum computing would leave no such window of opportunity for criminals, improving the effectiveness of triangulation. Also, quantum computers would work wonders with sonar technology, aerial combat, and missile tracking, making it a highly useful “upgrade.”
So, it’s time to answer the questions from the beginning: is it possible and is it worthwhile to create a quantum computer? We have seen that a quantum computer would be 1000x faster than a current consumer PC, thus speeding everything up, from downloads, to missile tracking, to saving the world from a technological breakdown due to low silicon reserves. We have seen that, with time, it is possible to entangle and manipulate 30 qubits. A quantum computer, though seemingly a fantastical device, is indeed possible and undoubtedly worthwhile. The development of a practical quantum computer may be decades away, but it is definitely possible within most of our lifetimes.
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