In the earliest lasers, a flash tube surrounding the lasing medium would stimulate electrons in the atoms to jump up in energy. The invention of the laser is largely credited to physicists Arthur Schawlow and Charles Townes, who coined the name from its descriptive acronym: light amplification by stimulated emission of radiation.Ī laser's design centers on a "lasing medium"-a collection of atoms, usually embedded in glass or crystals. In studying the stability of oscillators, the researchers looked first to the laser-an optical oscillator that produces a wave-like beam of highly synchronized photons. Loughlin and Sudhir detail their work in an open-access paper published in the journal Nature Communications. "We hope that our recent theoretical developments and upcoming experiments will advance our fundamental ability to keep time accurately, and enable new revolutionary technologies." "We plan to demonstrate several instances of lasers with quantum-enhanced timekeeping ability over the next several years," says Hudson Loughlin, a graduate student in MIT's Department of Physics. These systems could then be used to track infinitesimally small differences in time, such as the fluctuations of a single qubit in a quantum computer or the presence of a dark matter particle flitting between detectors. If they can demonstrate that they can manipulate the quantum states in an oscillating system, the researchers envision that clocks, lasers, and other oscillators could be tuned to super-quantum precision. The team is working on an experimental test of their theory. You have to play with the quantum states themselves." But you have to be more clever than just isolating the thing from its environment. "Then, we've shown that there are ways you can even get around this quantum mechanical shaking. "What we've shown is, there's actually a limit to how stable oscillators like lasers and clocks can be, that's set not just by their environment, but by the fact that quantum mechanics forces them to shake around a little bit," says Vivishek Sudhir, assistant professor of mechanical engineering at MIT. ![]() In their study, the researchers also show that by manipulating, or "squeezing," the states that contribute to quantum noise, the stability of an oscillator could be improved, even past its quantum limit. ![]() The precision of oscillators would ultimately be limited by quantum noise.īut in theory, there's a way to push past this quantum limit. ![]() But only by so much.Ī new MIT study finds that even if all noise from the outside world is eliminated, the stability of clocks, laser beams, and other oscillators would still be vulnerable to quantum mechanical effects. Eliminating such environmental effects can improve a clock's precision. And heat can disrupt the oscillations of atoms in an atomic clock. A slight wind can throw a pendulum's swing out of sync. These smallest, most stable divisions of time set the timing for today's satellite communications, GPS systems, and financial markets.Ī clock's stability depends on the noise in its environment. And in atomic clocks, the world's state-of-the-art timekeepers, the oscillations of a laser beam stimulate atoms to vibrate at 9.2 billion times per second. In a digital watch, the vibrations of a quartz crystal mark much smaller fractions of time. In a grandfather clock, the length of a second is marked by a single swing of the pendulum. The practice of keeping time hinges on stable oscillations. Green shows the case where the in-loop amplifier is purely phase-sensitive. Light and darker blues depict the case where these modes are squeezed (light blue) and entangled (dark blue) (both with 12 dB of squeezing). Red shows the Schawlow-Townes spectrum of an oscillator with phase-insensitive amplifier and the in-coupled and ancillary modes in vacuum. Spectra of the output phase quadrature for four types of quantum noise-limited oscillators. Phase noise of quantum-enhanced feedback oscillators.
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