When a short pulse of light arrives, it usually appears as a symmetrical curve, which is statistically like a bell curve. The leading edge of this curve must not exceed the speed of light, but the main body bulge, that is, the peak of the pulse, can be tilted forward or backward, and will arrive faster or slower than usual.
Using four-wave mixing, the researchers sent a 200-second-long "seed" pulsed laser into a heated optoelectronic component that contained an atomic helium gas phase, as well as a separate "pump" beam with different frequencies, all from seed pulses. . This gas phase amplifies the seed pulse, shifting the peak and tilting forward so that it can exceed the speed of light. At the same time, there are photons from the incoming beam that interact with the gas phase to produce a second pulse called a "conjugation" because of its mathematical relationship with the seed pulse. The propagation of its peaks can also be accelerated or slowed down, depending on how the laser is tuned and the internals of the gain medium.
Researchers at the National Institute of Standards and Technology (NIST: NaTIonal InsTItute of Standards and Technology) have developed a novel method for making "superluminal" pulsed light. In a sense, they travel faster than light. Faster. This technique, called four-wave mixing, reshapes part of the light pulse so that they reach somewhere ahead of time, where they would have arrived, when they passed through the vacuum without change. Will also arrive. This new method can be used to improve the timing of communication signals, as well as to explore quantum-related propagation. Their results were published in the Physical Review Letters on April 26th, entitled "STImulated GeneraTIon of Superluminal Light Pulses via Four-Wave Mixing."
According to Einstein's special theory of relativity, light travels in a vacuum with a universal speed limit. No information can travel faster than light.
But there is still a loophole. When a short pulse of light arrives, it usually appears as a symmetrical curve, which is statistically like a bell curve. The leading edge of this curve must not exceed the speed of light, but the main body bulge, that is, the peak of the pulse, can be tilted forward or backward, and will arrive faster or slower than usual.
Recent experiments have produced a "uninformed" superluminal pulse because the leading edge of the amplified pulse attenuates or cuts off its back end. This method produces a lot of noise and obviously does not increase the speed significantly. Four-wave mixing produces cleaner, less noisy pulses that can increase speed more because of “re-phasing†or rearranging the light waves that make up the pulse.
Using four-wave mixing, the researchers sent a 200-second-long "seed" pulsed laser into a heated optoelectronic component containing a rubidium gas phase and a separate "pump" beam with different frequencies. From the seed pulse. This gas phase amplifies the seed pulse, shifting the peak and tilting forward so that it can exceed the speed of light. At the same time, there are photons from the incoming beam that interact with the gas phase to produce a second pulse called a conjugate because of its mathematical relationship with the seed pulse. The propagation of its peaks can also be accelerated or slowed down, depending on how the laser is tuned and the internal conditions of the laser.
In the experiment, the pulse peak arrived 50 nanoseconds faster, which is the contrast light propagating in vacuum.
There is a direct application, this group studies this system, which is intended for quantum discord. Quantum discord is a mathematically defined two related systems that share quantum information, in this case seed and conjugate pulses. By measuring the quantum discord between the fast beam and the reference beam, the team hopes to determine how this ultra-fast light is used to transmit and process quantum information.
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