In my last post I indicated that the fifty-year trend of doubling computer processing power every two years was coming to an end, and growth with the current integrated circuit technologies is expected to become almost flat by 2018. One of the possible ways around this limit is quantum computing. Quantum computers take advantage of the strange world of quantum mechanics.
This is the first in a series of planned posts to give a brief overview of quantum physics (with no math), a discussion of quantum computers, the potential impact of them especially as it pertains to data security, and the current state of development of quantum computers.
Most of us spend nearly all of our time in a Newtonian physical environment. If we drop something, it falls, and we can predict how long it will take to fall. We can throw a baseball with, depending on our skill, a reasonable expectation that we know where it will go. We know how long it will take for something to travel between two points, subject to understandable issues like traffic jams, construction, or weather. This works whether we are trying to drive to the grocery store or land a spacecraft on Mars.
But outside of this environment, things may work differently. At really high speeds, relativity has an effect. NASA scientists were able to measure this, admittedly very small, effect on the Apollo missions to the moon: the astronauts aged a tiny fraction of a second less the rest of us stuck on earth due to the speed of their travel to and from the moon. At very small sizes, quantum effects take over, and some of these effects may seem to be just weird.
One of these weird effects is the uncertainty principle: if you measure one aspect of a quantum particle you will not be able to measure another. At the quantum level, a policeman could determine how fast you were driving, but could not then determine where you were.
Superposition is the principle that a quantum object is actually in all possible states simultaneously all the time, until something checks it. You have probably heard of the “Schrodinger’s cat” thought experiment: place a live cat in a steel box along with a sealed vial of a highly poisonous gas, a hammer, and a very small amount of radioactive material, plus a very sensitive radioactive decay sensor (e.g., Geiger counter). If the sensor detects the decay of a single radioactive atom during the test period, a relay causes the hammer to fall on the vial of gas and the cat dies. If not, the cat lives. We cannot know the state of the cat until we actually break into the box and look, and in the quantum world the cat is both dead and alive, until we observe it. If you are a cat lover, then substitute “evil squirrel” for “cat” in this paragraph. Like most thought experiments, this one is technically flawed; a cat is not a quantum entity and “looking” at one cannot change it’s living state.
Quantum entanglement may be one of the strangest concepts in the weird quantum world. If two particles are entangled, then if you measure one property of one of the particles, then the same property of the other particle is identical. Measuring the property of the one particle fixes the property for the other particle, so if it is also measured it will always be the same as the first particle. Somehow, the second particle learns the result from the first particle, and this happens instantaneously over any distance. When the particles are far enough apart, this “learning” travels faster than the speed of light. However, you do not learn anything about another property of the entangled pair. Any other property still has all of its possible values on each particle, and there is no relation of that value between the particles. For example, assume these entangled quantum particles had two properties: color (red or green) and shape (cube or sphere). Then if you measured the shape of one of the particles and found it to be a cube, then the other particle would also be a cube. However, the color of each particle could be red or green independently.
As the current computer chip technology gets faster, the individual components on the chip of necessity get smaller and closer together. At the speed our current chips operate, the speed of light is too slow. We need to have components as close to each other as possible to minimize the time it takes a signal to travel between components. At this time, components may be the size of a molecule. Chips with this level of component density face three main challenges: high defect rates, process variation, and quantum effects. The first two challenges are simply the result of the closer tolerances in the actual manufacturing phase. The industry has been pushing these limits for the past couple of decades, resulting in the continuous development of more exacting, and more expensive, manufacturing methods as well as more stringent testing processes.
Quantum effects are not as easily overcome. They can cause high leakage currents and large variability in the device’s characteristics. As transistors get smaller, quantum superposition will make it impossible to distinguish between the two states of a transistor. The real barrier to unlimited performance increases in computers using today’s technology is the reality of the quantum universe.
The last word:
The two main national political conventions / carnivals are over. The Republican convention in Cleveland had no fence around the convention center, and fewer than 25 arrests for the entire four days. The Democratic convention in Philadelphia had an eight-foot tall fence around the convention arena, raised in part to twelve feet after the first night. There were more than 50 protestors cited and removed by police during the first day alone, and those protests were literally drowned out by several severe thunderstorms with gale-force winds.
Please do not jump to any conclusions from these data points. As I have said before, apparent correlation does not imply causation. The different results may be more due to the difference between Cleveland and Philadelphia, or the weather, then the political parties.
One clear distinction that is caused by the parties is the presence, or absence, of the US flag within the convention. For the first two days of the Democratic convention, there were no US flags within the convention center, a sports arena. The Democratic committee had all of the US flags removed, including the huge one that has always hung above the center in the arena. Apparently, it interfered with the balloons.
Alas, the American voter is left with the sad choice between a clown and a criminal.
Keep your sense of humor.