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A picosecond is one-trillionth of a second. It is a measure of time that comes into play with types of technology such as lasers, microprocessors, and other electronic components that operate at extremely fast speeds. Nuclear physics research also involves measurements that approach the range of the picosecond, as well as related nuclear medicine imaging using positron emission tomography (PET).
Personal computers are gradually approaching the speed where a single calculation can be performed in a picosecond. A home computer with a microprocessor that runs at three gigahertz performs at three billion cycles per second. This means it is actually taking about 330 picoseconds to perform a single binary operation.
Supercomputers in the United States and China already exceed picosecond per operation speeds. One of the fastest supercomputers in the US can do 360 trillion operations per second, which is slightly faster than one operation per picosecond. China revealed a supercomputer in 2010 that was capable of performing 2.5 petaflops per second, or 2.5 quadrillion operations every second, meaning that every picosecond, it optimally performs 2,500 calculations.
Lasers designed to operate in the picosecond range emit light pulses every one to several tens of picoseconds in time. There are several types of laser designs that can operate at these speeds, including bulk solid state lasers, mode-locked fiber lasers, and Q-switched lasers. Each model is built upon the picosecond diode, which can be mode-locked or gain switched, changing pulse rates from nanosecond speeds which are in billionths of a second, to at least ten times faster into the 100s of picoseconds range.
Though such ultra-fast lasers are hard to imagine, an even faster level of models exists. A picosecond pulse laser is 1,000 times slower than a femtosecond laser. This makes picosecond designs less cutting edge, and considerably more economical for uses such as the micro-machining of components. Both types of lasers have similar levels of performance for the jobs with which they are tasked.
In the nuclear medicine field, a PET machine builds up an image through gamma rays interacting with scintillating crystals to produce Compton electrons at optimal speeds of around 170 picoseconds. In reality, this is usually much slower and takes about 1 to 2 nanoseconds in length per emission particle. Time of flight PET (TOFPET) research is attempting to reduce the actual flight time down to below 300 picoseconds, through improvements in photodetectors, the scintillating crystals themselves, and associated electronics. Though these speed rates are incredibly fast already, reconstructing an image of human body regions from these emissions is a slow, time-consuming process that often takes several days to complete.