Tuesday, January 14, 2020

LIGO Interferometer Reduces Quantum Fluctuations of Light

LIGO interferometer for gravitational waves observations announces that it uses squeezed light to improve the measurement accuracy:

"The Heisenberg uncertainty principle states that we can't know both the position and the velocity of a quantum particle perfectly--the better we know the position, the worse we know the velocity, and vice versa. For light waves, the Heisenberg principle tells us that there are unavoidable uncertainties in amplitude and phase that are connected in a similar way. One of the stranger consequences of quantum theory is that there must be fluctuating electric and magnetic fields, even in a total vacuum. In a normal vacuum state, these "zero-point" fluctuations are completely random and the total uncertainty is distributed equally between the amplitude and the phase. However, by using a crystal with non-linear optical properties, it is possible to prepare a special state of light where most of the uncertainty is concentrated in only one of the two variables. Such a crystal can convert normal vacuum to "squeezed vacuum", which has phase fluctuations SMALLER than normal vacuum! At the same time, the amplitude fluctuations are larger, but phase noise is what really matters for LIGO."

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