Quantum Mechanics: Note 7

Quantum Applications Since the development of quantum theory in the early 1900’s and quantum based technology in the mid to late 1900’s, our society has become totally dependent on quantum mechanics. Some current technology that could not be created without an understanding of quantum mechanics include: The Laser Laser is an acronym for “light amplification by stimulated emission of radiation.” By understanding the way electrons jump between energy levels, we can harness the emitted photons and send them through a gain medium (something that makes them more intense). Lasers are used everywhere from communication devices to retail bar code scanners. The Semiconductor and Transistors Semiconductors are special type of conductors that allow electricity to flow through them in one direction over a crystalline lattice. The flow of the electrons can only be described with quantum mechanics. If made into a diode, light will be given off as electrons travel from a region of high to low potential. This is known as a light emitting diode (LED). Transistors are basically a semiconductor device used to amplify or switch electric current on or off. Transistors are the basis of all modern electronics (including computers) and could not be created without semiconductors. The number of transistors within a dense integrated circuit doubles about every two years, something known as Moore’s Law. Superconductors Superconduction is a phenomenon when a piece of material has absolutely no resistance to electric current AND expels all magnetic fields when it is cooled past some critical temperature. These types of materials allow large electric currents to flow through a superconducting material without any increase in temperature. This also allows magnets to levitate above superconducting material due to the Meissner Effect.

Quantum Mechanics: Note 7 Future Application: Quantum Computers Currently, all computers run on “bits” of information. These bits are coded in binary, which means they are recorded as either a 1 or a 0. Quantum computers will use the principle of superposition when reading quantum bits (or qubits). Qubits can be a 1 AND a 0 at the same time, until they are observed. If a qubit can be in two states at the same time, then two qubits can be in four states at the same time (11, 10, 01, 00). Three qubits can be in eight states at the same time (111, 110, 101, 100, 011, 010, 001, 000). In general, n qubits can be in 2n states at the same time, whereas a classical computer can only be in one state at a time. By allowing qubits to be in many states at once, a quantum computer can compute much more quickly and with tremendously more power than a classical computer. What is it Good For? Factoring It is very difficult for a classical computer to factor large numbers. Factoring is important when sending secure messages. A message is created and turned into a numerical code. The first half of the message is multiplied with the second half of the message to produce one, humongous number. That number is sent to another computer where it is to be factored into the two individual numbers so the code can be interpreted. This is the way security work on current computers. On a large enough quantum computer, it can check all possible factors that could make a number at the same time. This allows it to break any code instantly because the qubits can be in many states at the same time. Making New Drugs/Materials If qubits can be in many states at the same time, they can be applied to chemistry. Quantum computers can be used to create new molecules. They can simulate the function of the drugs and the way they interact with the human body. This has the possibility to create drugs that are more effective with little side effects. We also have the opportunity to design new materials with crystalline structures that allow them to be lightweight but durable. Weather Forecasting Weather systems are very complex and chaotic. This is the reason why it is difficult for an average weather reporter to predict an accurate forecast. Quantum computer will be more accurate in the simulation of weather systems, allowing for forecasts that reflect what will actually happen which ultimately could save lives (from tornadoes or hurricanes).