Criticism. Essay. Fiction. Science. Weather.
NASA space probes like the Mars rovers Spirit
, the spacecraft currently orbiting Saturn, manipulate quantum tunneling of electrons in order to record data. The technology they use provides high-density, re-writable, non-volatile, radiation-proof, energy-efficient storage -- it's ideal for spacecraft. It's also the basis for inexpensive techno gadgets like flash drives
Flash memory, used in such drives, is cheap because it relies on 40-year-old transistor technology called MOSFET
. MOSFETs dominate the electronics industry. Tens to hundreds of thousands of MOSFETs make up the microprocessor you are probably using right now. They're also in cell phones, stereos, cars, etc, etc. Even the new iPhone uses MOSFETs.
To demonstrate a flash MOSFET in action, I will make a conceit: bees will stand in for electrons. Flowers, which attract bees, will stand in for positive charges. Honeycomb wax and boring blue wax will stand in for two types of silicon semiconductor. Finally, dirt will stand in for a thin dielectric membrane.
In its ready state, this little MOSFET garden has bees on one side. They can fly in and out of their honeycomb. They want to visit the flowers on the other side, but blue wax and dirt are in the way.
A gardener wants to store data, so he puts a bouquet of new flowers on the dirt. The bees can smell them and get motivated to make honeycomb wax out of nearby blue wax. They are rewarded for their effort because soon they can fly across the garden to the flowers on the right.
Since the dirt layer is very thin and there are lots of bees flying past it -- and since bees are really a superposition many quantum states -- odds are that one bee will spontaneously appear on the top side of the dirt!
In real transistors, the process of an electron jumping a barrier in this way is called "hot electron injection." It's a good thing the gardener made a special cave just to hold hot-injected bees.
When the gardener removes his bouquet from the dirt, bees on the left won't smell flowers anymore. They'll lose interest and let the honeycomb degrade until it turns back into boring blue wax. The hot-injected bee will be stuck.
Later, another gardener wants to read the data stored in the garden. She takes the flowers on the right and puts them on the dirt. Nothing happens. That angry, trapped bee is preventing other bees from working on the blue wax. It is canceling out the effect of the flowers.
Since the second gardener observes no bees flying out the right side, she knows that someone else has stored data under the dirt.
The second gardener consults the first, and they decide that the garden was nicer without an angry bees trapped in the dirt. But how to let them out? They've both tried putting flowers in the dirt, and that's what trapped the bee in the first place.
Gardeners to the end, they decide that flowers are still the answer -- tons of flowers. They gather up all the flowers they can find and dump them all over the dirt. They smell good, and the trapped bee gets terribly excited. Bees on the left get excited, too, and start making honeycomb.
Since the trapped bee is so excited, and since it now has somewhere to go -- and since it's a superposition of quantum states -- it spontaneously appears on the left side of the dirt!
Once the gardeners pick all their flowers out of the dirt, the garden will be back in its ready state.
Real flash drives must erase groups of transistors by discharging a large voltage across all of them at once. They accumulate charge using the same mechanism as a camera's flash circuit, so that's their name.
Data storage by hot electron injection is a neat trick. But storage is a relatively easy application of quantum mechanics. The job of a flash drive is usually to sit still and never forget. A greater challenge will be to employ quantum mechanics in the critical, dynamic part of a computer: the processor.
Indeed, quantum processors have been promised in the coming decades. They will gain great speed by representing information as a superposition of bits, called qbits. They may enjoy tiny size by replacing MOSFETs, which always seem too big
, with things like single Beryllium ions.
Also, they may run cool by replacing wires, which tend to heat up, with teleporters